AD-A016 127 DEVELOPMENT OF A WATER SOLUBLE FOAM …'.i.'^ I - FEASIBILITY DEMONSTRATION Ihe...
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AD-A016 127
DEVELOPMENT OF A WATER SOLUBLE FOAM PACKAGING MATERIAL
T. J. McCown, et al
McDonnell Douglas Astronautics Company
^
Prepared for:
Army Natick Development Center
January 1975
DISTRIBUTED BY:
KUT National Technical Information Service U. S. DEPARTMENT OF COMMERCE
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TECHNICAL REPORT
DEVELOPMENT OF
A WATER SOLUBLE FOAM PACKAGING MATERIAL
McDonnell Douglas Astronautics Company I
St. Louis, Missouri 63166
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Contract No. DAAKO3-/4-C-0185 ; ;>
Approved for public release; distribution unlimited.
; UNITED.STATES ARMY .NATICK* DEVELOPMENT CENTER
NATICK, MASSACHUSETTS 01760
January 1975
I
Reproduced by
NATIONAL TECHNICAL INFORMATION SERVICE
US D«p«r1m«f>t of Commvrt« SpHr.glidd, VA. 2315!
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REPORT DOCUMENTATION PAGE I. REPORT NUMBER
75 - 88 FEL 2. OOVT ACCESSION NO.
4. TITLE fand Suitll/.J
DEVELOPMENT OF A WATER SOLUBLE FOAM PACKAGING MATERIAL
7. AIJTHORf.J
T. J. McCown and G. E. Wahlmann
t. PERFORMING ORGANIZATION NAME AND ADDRESS
McDoiinell Douglas Astronautics Company St. LouiSf Missouri 63166
II. CONTROLLING OFFICE NAME AND ADDRESS
US Army Natick Development Center Natick, Massachusetts 01760 ATTN: AMXNM-WM 14. MONITORING AGENCY NAME ft ADDRESS?/? df/feronf from Controlling Olllcm)
READ mSTRUCTICrtS BEFORE COMPLETED PwRM
J. RECIPIENT'S CATALOG NUMBER
S. TYPE OF REPORT 4 PERIOD COVERED
Final Pet 71 - Jan 75 6. PERFORMING ORG. REPORT NUMBER
FF,Tr26 rr.ir«:? ,_ S. CONTRACT OR GRANT NUMBER)«)
DAAK03-74-C-0185
10. PROGRAM ELEMENT, PROJECT, TASK AREA S WORK UNIT NUMBERS
6.2 1T762720D048
02-020 12. REPORT DATE
January 1975 13. NUMBER OF PAGES
13 IS. SECURITY CLASS, (at Oil» npott)
UNCLASSIFIED
is., OECLASSIF:CATION/DOWNGRADING SCHEDULE
IS. DISTRIBUTION STATEMENT (ol tnfe Report;
Approved for public release; disti-ibution unlimited.
17. DISTRIBUTION STATEMENT (ol Ihm mbtlracl entered In Block 20, II dtltmnt from Report)
IS. SUPPLEMENTARY NOTES
19. KEY WORDS (Continue on revert« »Id» II neceetar/ and Idtntlty by block numb*r)
KLUGEL HTDROXYPROPYL CELLULOoE DEVELOPMENT FEASIBILITY STUDIES CELLULOSIC RESINS
SOLUBILITY (WATER) THERMOPLASTICS RESINS FOAM PACKAGING FOAM PACKAGING MATERIALS
EXPOSURE HUMIDITY FRESH WATER SALT WATER DISSOLUTION
20. ABSTRACT fConMnue an revere. »Id» II mctnir/ and Identify by Mock number)
The purpose of this program was to investigate the feasibility of developing and reliably reproducing a water soluble foam from hydroxypropyl cellulose re3in (KLucel) and to establish product parameters.
The program was divided int two phases. In Phase I. the feasibility of extruding the water solubl; thermoplastic resin into a candidate packaging material was successfully demonstrated. Hydroxypropyl cellulose was extruded
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/ SECURITY CLASSIFICATION OF THIS PAGE fWlen Ball Entered)
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by conventional m*»ans into a loose-fill packaging foam having a compre3sive stiffness conforming to Federal Sepcification FPP-C-Q50, Cushioning Material, Polystyrene Expanded, Eesilient, Class 4 (Extra Firm). In Phase II, the loose-fill foam product produced from this resin was tested using ehe methods detailed in federal Specification PPP-C-I683. Cushioning Material, Expanded Polystyrene, Looae-Fill Bulk and standard properties were established. Additional investigations conducted on the loose-fill samples were:
0 Effects of long and short term relative humidity exposure, o Solubility and dissolution rates in fresh and salt «rater.
long term humidity exposure caused the material to deteriorate and lose all foam cushioning properties.
Complete dissolution of the Klucel foam floating and submerged in fresh and prepared sea water was demonstrated.
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FOHEWORD
As a result of extensive use of foam plastics for cushioning materials by the various DOD agenciesf disposal of the material after use is an ecological problen, particularly at depots and aboard ships at sea. A water soluble, nontoxic cushioning material, hydroxypropyl cellulose, was proposed by McDonnell Douglas Corporation as a solution to this problem. Subsequently, the US Army Natick Development Center contracted with McDonnell Dc glas to determine whether hydroxypropyl cellulose could be reliably fabricated into a foamed pioduct using conventional foam- ing processes; and to establish the standard product parameters on the material produced.
The project was carried out by the McDonnell Douglas Astronautics Company - East, Saint Louis, Missouri. The Program Manager was Mr. Thomas J. McCown and the Principal Investigator was Mr. Gilbert E. Wahlmannf The extrusion process work was done under subcontract by Mr. Donald Murray of Gloucester, Massachusetts. Project Officer for the US Army Natick Development Center was Mr. Raymond T. Mansur of the Food Packaging Division, Food Engineering Laboratory and the Alternate Project Officer was Mr. Charles F. Macy of the Pollution Abatement Division, Food Sciences Laboratory.
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TABLE OF CONTENTS
SECTION
FOREWORD FIGURES TABLES
PARE
1 3 5
1. INTRODUCTION
1.1 Background 1.2 'urpose 1.3 Objectives 1.4 Organization
2. PHASE I - FEASIBILITY DEMONSTRATION
2.1 Resin Material 2.2 Processing Methods 2.3 Formulation 2.4 Equipment and Process Description 2.5 Material and Process Development 2.6 Problems Encountered and Recommended Solutions 2.7 Compresslve Stiffness Testing 2.8 Manufacturing Reliability
3. PHASE II - PROPERTY DETERMINATION
3.1 PPP-C-1683 Testing 3.1.1 Dynamic Test 3.1.2 FlowabilUy Test 3.1.3 Vibratlonal Settling Test 3.1.4 Loaded Bulk Density Test 3.1.5 Compresslve Creep Test 3.1.6 Compresslve Set Test 3.1.7 Flammabllity Test 3.1.8 Electrostatic Adhesion Test 3.1.9 Miscellaneous Examinations 3.2 Supplemental Testing 3.2.1 31 Day Humidity Test 3.2.2 Moisture Absorption 3.2.3 Solubility/Dissolution Rate Testing
4. SUMMARY AND CONCLUSIONS
REFERENCES
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FIGURES
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Water Soluble Foam Loose-Fill Packaging Material
Two-Stage Pilot Production Extruder Used for Phase I Development Work
Extruder Stage 1 and Feed riopper
Extruder Stage 1 (Rear) and Fee<i Hopper
Pumping Units
Control Panel
Coupling Between Extruder Stages
Extruder Stage 2 (Rear)
Extrusion Die
Instron Test Machine for Compressive Stiffness Testing
Instron Test Machine Platens with Compres- sive Stiffness Specimen in Position
Stress-Strain Curve (Compressive Stiffness)
Prototype Load with Accelerometer and One Ballast Weight Installed
Dynamic Drop Test
Average Acceleration vs. Static Stress Level Curve
Flowability Test Funnel
Flowability Test Funnel (Interior)
Funnel Loaded with Foam Prior to Flowability Test
Gravity Flow of Loose-Fill Material from Flowability Test Funnel
1 ibrational Settling Test
Cleated Box, Leveling Board and 50 Pound Weight for Loaded Bulk Density Test
Loose-Fill Undergoing Loaded Bulk Density Test
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Interior and Exterior Modified Kerstner Box with Loose-Fill and Weight for Compresslve Creep/Set Test
Loose-Fill Material Undergoing Compressive Creep/Set Test
Compresr 've Creep Curve
Flammabinty Test
Five Gallon, All Fiber Drum with Telescop- ing Lid for Electrostatic Adhesion Test
Electrostatic Adhesion Test Drum 1/3 Full of Test Material
Electrostatic Adhesion Test Drum Rolled per PPP-C-1683 Test Method
Electrostatic Adhesion Test Drum Rolled per McDonnell Douglas Test Method
Emptying of Looss-Fill Material After Electrostatic Adhesion Test
Loose-Fill Specimens Prior to 31 Day Humidity Test
Humidity Test Cabinet
Loose-Fill Specimens After 31 Day Humidity Test
PAGE
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TABLES
Npj_ TITLE PAGE
1 Loose-Fill Formulation 18
2 Extrusion Press Data and Control Settings 20
3 Federal Specification PPP-C-850D Compressive 26 Stiffness Requirements
4 Compressive Stiffness Values of Foamed 26 Hydroxypropyl Cellulose Resin (Development Specimens)
5 Compressive Stiffness Values of Foamed 29 Hydroxypropyl Cellulose Resin (Reliability Specimens)
6 Peak Accelerations (G's) 35
7 Flowability 40
3 Vibrational Settling 40
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1 9 Loaded Bulk Density
; io Test Load Determination
ii Compressive Creep
12 < Comnrescive Set
f 13 Flammability
14 Miscellaneous Examinations
I • 31 Day Humidity Exposure
16 Moisture Absorption - Short T°rm
17 Dissolution Rate
lei ■ Federal Specification PPP-C-1683 Test Summary
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1nI Background
Current packaging techniques for ordnancef hardware, electronics and other supplies used by the various Department of Defense agencies employ plastic foams extensively for foam-in-place, loose-fill» and preformed shape protective materials.
Although plastic foams provide lightweight, low cost packaging naterials, disposing of the foam after uncrating and unpacking can be an ecological problem. Consequently, methods are needed to effectively dispose of the discarded packaging materials without causing an adverse el feet on the environment. A potential solution to this disposal problem would be to develop a packaging material which dissolves in water without leaving undesirable by-products. Hydroxypropyl celluJose resin (Klucel-*), which has been used in foodstuffs for many years, is a candidate material which might be used for such a product application. This resin is water soluble, nontoxic, and has an inherently low equilibrium moisture content. Foamed products have previously been molded from various types of hydroxypropyl cellulose but the manufac- turing feasibility hed not been determined.
1.2 Purpose
The purpose of this project was to determine the feasibility of pro- ducing a water soluble packaging foam from hydroxypropyl cellulose resin and to establish standard product parameters on the material produced.
1.3 Objectives
The objectives were:
o Evaluate conventional methods for producing a packaging foam material using hydroxypropyl cellulose resin,
o Establish manufacturing reliability, o Produce representative samples of hydroxypropyl cellulose foam
to comply withfClass 3 (Firm) or Class 4 (Extra Firm) of Federal Specification PPP-C-£ j>OD; Cushioning m ' <?rial, Polystyrene Expanded, Resilient
o Test to establish standard properties for hydroxypropyl cellulose foam material including effects of humidity and water solubility characteristics,
o Provide samples of finished product.
^Registered trademark of Hercules, Inc.
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1.4 Organization
The project was divided into two phases:
o Phase I - Feasibility Demonstration o Phase II - Property Determination
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?. '.i.'^ I - FEASIBILITY DEMONSTRATION
Ihe feasibility to produce a water soluble, loose-filJ foam packaging material was demonstrated in the following manner»
2.1 Re* sin Material
The basic resin used to make the water soluble foam product (Figure l) was a hydroxypropyl cellulose manufactured by Hercules, Incorporated, called KLucel. This resin is prepared by reacting alkali cellulose with propylene oxide at elevated temperatures and pressures. Tie propylene oxide can be substituted through an ether linkage at the chree reactive hydroxyle present on each anhydroglucose monomer uni^ of the cellulose chain (Reference l). Published information suggests that the etherification takes place in such a way that the hydroxypropyl substituent groups contain almost entirely secondary hydroxyls* The secondary hydroxyl present in the side chain is available for further reaction with the oxide and chaining out may take place.
Since hydroxypropyl cellulose is water soluble, the effect rx' rela- tive humidity on packaging stability is important. Despite being readily soluble in water, items foamed from hydroxypropyl cellulose are nontacky and do not readily fingerprint during handling (Reference 2)„ Equilibrium moisture, or the maximum amount of moisture which ..he material will absorb at a given relative humidity, is the key to this performance. At 73 P and 50 percent relatire tumidity, hydroxypropyl cellulose has an equilibrium moisture contenL. of four percent* It should be noted that hydroxypropyl cellulose is far less hygroscopic than other water soluble polymers.
With regard to toxicity, hydroxypropyl cellulose is physiologically inert. The results of repeat insult patch tests on humans have not. disclosed any evidence that it is either a primary skin irritant or a skin sensitizing agent (Reference 3). Ihis resin is nonnutrient, ^eing nutritionally equivalent to purified cellulose (Reference 4).
2.2 Processing Methods
The extrusion process was selected as Jie conventional fabricating technique to demonstrate the feasibility of producing a loose-fill fcam material from hydroxypropyl cellulose resin. Pilot plant and laboratory size extruders normally used to manufacture polystyrene, polyethylene and polypropylene foams were employed to produce the KLucel foam samples«. In general, the equipment melts and mixes the resin formulation, provides access for ir^ectior of the foaming agent, and forces the product througn "he ex- truder die to form the desired shape.
1. A. Jo Desmarais, "Hydroxyalkyl Derivaties of Cellulose", Industrial Gurrs, 2nd Edition (1973)» Pg» 650.
2. Ibid, pg 665.
3. Ibid, pg. 666.
4« Hercules, Incorporated, "Klucel-Hydroxypropyl Cellulose; Chemical and Physical Properties", Brochure (1971), pg» 4»
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The material and processing characteristics of hydroxypropyl cellu- lose resm were examined and beginning formulations were determined In addition to the resin, ingredients included an anticake agent, p'asticizer, lubricant, stabilizers, nucleating agent and foaming component.
2 3.1 Hydroxypropyl Cellulose (Resin) - As stipulated by contract, Klucel was used äs the thermoplastic resin, Klucel 13 available m several grades which vary in molecular weiqht (\%) from 50,000 to 1,250,000 (Reference 5?. Grade J (Mw = 150,000) was chosen from other Klucel grades because it has the best flow characteristics, which is beneficial in an extrusion process. A change to a higher molecular weight grade of Klucel results in a softer polymer but reduces the melt flow characteristics (Reference 6). A decrease in polymer moiecula» weight increases both the product stiffness and melt flow
2.3.2 Silicon Dioxide (Anticake Agent) - Compression of the resin by its own weight causes compaction and fusion into a lumpy solid To prevent this, a small auantity of silicon dioxide was deluded n the formulation to serve as an anticaking agent.
2.3.3 Polyethylene Glycol (Plasticizer) - To impart flexibility and workability into the plastic melt and to reduce *!ie fibrous behavior and del ami nation tendency of the thermoplastic resin, a low molecu'ar weight (400 +20), water soluble polymer of ethylene oxide was used as a plasticizer." It has good heat stability and is not a skin irritant
In the initial runs, propylene glycol was used as the plasticizer but was found to be less suitable due to its low boiling point and tendency to flash off at the die.
2.3.4 Polyethylene Glycol (Lubricant) - A high molecular weight (3350 +350?, water soluble polymer of ethylene oxide was used as a lubricant. A waxy solid, this material was added to provide good anti- stick and antiblocking properties to the formulation during its passage through the extruder die. This was a replacement lubricant 'or g'.ycerol monostearate which tended to exude to the surface of the product and produce a waxy or sticky feel.
2,3 5 Butylated Hydrpxytoluene (BHT) - Hydroxypropyl cellulose resin is a cellulose ether whose molecular weight can be significantly reduced by cleavage of glucose units when severe conditions of heat and oxida- tion prevail. Without the BHT to act as a stabilizer, the mo'ecula' weight would be degraded and constant variations in the melt viscosity of the formulation would result, producing erratic behavor du'mg extrusion.
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2.3.6 L aury1th i odi propi on ale (LTDP) - LTDP functions as a stabilizer by decomposing peroxides"to" make them less effective as degradation agents.
2.3.7 Magnesium Silicate (Talc) - Ultra fine (17 in1" surface area/g) and highly pure (98 percentTmagnesium silicate powder was added as a processing aid and as a nucleating agent to provide sites for the forma- tion of bubbles in the same manner as a cloud is seeded to produce rain. Only enough talc was used to lightly d\ist the outside of the formulation pellet. Talc has also been used effectively with polystyrene and polyethylene foaming operations to produce a smooth, flat surface effect.
2.3.8 Freon 11/Freon 12 (Foaming Agent) - The foaming agent used throughout this investigation was duPont Freon*. It was chosen because it is one of the easiest, safest and most efficient materials available for foaming operations. Also, it has the ability to produce fine cell structure in polystyrene and polyethylene foam products. Freon 12 was very satisfactory but it was found 'hat a 70% Freon 12 and 30% Freon 11 blend minimized occasional popping at the die and was used to produce the Phase II test specimens.
2.4 Equipment and Process Description
2.4.1 Blender - The nucleating agent (talc) was blended with the rest of the formulation ingredients, previously pelletized into one- eighth inch diameter spheres, in a small cement mixer type blender. Blending was continued for approximately ten minutes to provide a dust coating over the pellet exterior. The blended batch was then loaded by hand into the feed hopper of the extruder.
2.4.2 Extruder - Foaming feasibility was determined using a two- stage Extro extrusion press manufactured by Gloucester Engineering Com- pany of Gloucester, Massachusetts. The extruder features tandem screws in series with one another (Stage 1 and Stage 2). A schematic of the floor plan for the extruder complex is shown in Figure 2. The circled figure numbers indicate the location and direction of the figures which follow.
The ingredients are delivered into the barrel of the primary extruder, Stage 1 (Figures 3 and 4), which contains a 2-1/2 inch diame- ter blending screw. The barrel housing has five heater stages and the ingredients are mixed and heated until a uniform molten state is attained. Near the end cf the barrel, the Freon liquid roaming agent is injectjd into the molten plastic under pressure supplied by the pumping units (Figure 5) and controlled by settings on the control panel (Figure 6).
The two extruder stages are joined by a coupling (Figure 7). The temperature of the plastic melt is continually monitored at this interface location.
*Registered trademark of duPont.
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During the latter part of the Phase I feasibility study, a scaled- down version of the Extro extruder (M^ni Extro) was used. The screw size of this extruder was 1-1/4 and 1-1/2 Inches diameter for the Stage 1 and Stage 2 screws, respectively, and it was operated at its maximum throughput capacity of approximately 24 pounds per hour. The Extro extruder was operated at approximately 40 percent of its 150 pound per hour maximum capacity.
2.5 Material and Process Development
During the course of this investigation it became apparent that certain processing conditions must be present in critical combinations if a foam material with the required physical and mechanical properties was to be produced and reproduced reliably. These are:
o Mixing ratio o Barrel temperature o Barrel pressure o Extrusion rate.
All are interrelated. Changing one will modify each of the others and variations 1n material densities, cell structure, cell uniformity, surface conditions and mechanical properties will result. In addition, altering the molecular weight of the resin, the amount of the foai.ilng agent or the amcint of the nucleating agent as well as the moisturt content of the starting resin will also contribute to modifications in the end product. The final foam product resulted from a series of adjustments to both formulation and processing parameters. The final formulation chosen to produce the foamed loose-fill samples, which complied with Federal Specification PPP-C-850, Class 4 (Extra Firm) compressive stiffness requirements, is shown in Table 1. Typical extruder control settings utilized in the extrusion process to produce the above samples are shown in Table 2.,
2.6 Problems Encountered and Recommended Solutions
2.6.1 Moisture - Hydroxypropyl cellulose resin which has not been predried will contain approximately 3-4 percent moisture at 50 percent relative humidity conditions. Some of this moisture will vaporize into steam in the extruder barrel and vent back to the feed hopper where it Condenses, causing entering feed material to agglomerate and choke the
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flow. The material which goes through the extruder also contains some steam which causes surging and popping as the mixture is forced through the die. The resulting material is also very soft and has a tendency to colliirse as the water contained serves as additional plasticizer. Higher humidity operating conditions were found to aggravate this problem as the feed material tends to stick to the sides of the feed hopper.
An attempt was made to remove this moisture from the resin in the first stage barrel during extrusion by a process called starve feeding. In this method, sometimes used successfully with other plastic resins, the feed rate to the extruder is decreased to create a void space in the barrel for heat accumulation to dry t.,e resin. This effort was not suc- cessful as the extruded foam product varied from dry to sporadic slugs of wet material. So it was necessary to dry the resin prior to use by passing 60-70°F desiccant dried air over it and storing it in moisture proof cans as polyethylene bags will not protect the dried resin against moisture for mote than 24 hours.
It is recommended that the exposure time during blending be mir:.ii1zed and the feed hopper be covered or that a hopper drier be utilized, especially during lengthy production runs, to ensure feed material of sufficient dryness.
2.6.2 Foam Collapse - Some foam specimens experienced structural collapse during initial extrusion runs. The collapse was due partly to the moisture in the resin, as previously stated, and partly to the temperature of the extruded material. If the temperature in the final extrusion stage is too hot, the extruded material will not have the time to cool sufficiently to provide the cohesive strength necessary to contain individual gas pockets. The gas bubbles can migrate together and form large gas masses within the extrusion which cannot support themselves and the walls eventually collapse.,
This problem was corrected by operating the final extrusion chamber at a lower temperature to allow the foam cells to harden more quickly and achieve the necessary strength.
2.6.3 High Density - Although it is necessary to lower the tempera- ture in the final extrusion stage tö avoid foam collapse, too low an extrusion temperature is also a critical variable in production of the water soluble foam. If the temperature of the extruded material is too cold, foaming is inhibited because the material is too hard to allow the gas to expand properly and a high density material results. The density of developmental specimens averaged 5„08 lbs per cu. ft. with a range of 3.58 to 10.0 lbs per cu„ ft. (80% were less than 6.0 lbs per cu. ft.). Production specimens averaged 5.19 lbs per cu. ft. ranging from 4.61 to 5.70 lbs p?r cu. ft.
The proper extruded material temperature for the subject formulation, extrusion equipment and conditions of this investigation are shown in Table 2.. However, the temperature variable is critical enough to
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2.7 CompressIve Stiffness Testing
This test was used to screen likely candidate samples extruded during the material and processing development stage
2.7.1 Test Description - The compressive stiffness of the loose-fill material was determined during Phase I using an Instror. test machine (Figure 10) in accordance with Federal Specificaton PPP-C-850D, Amend- ment 1 and Interim Amendment 2. The height of al1 spec* ons tested was 1.0C0 +0,040 inches after machining flat to assure even contact with the platens of the test machine. The- other dimensions of the specimen were dependent on the most convenient size which could be obtained from the samples produced by the extruder. These dimensions varied from approx*- mately 1/2 to 1-1/4 inches in diameter, AH dimensions were taken with a standard caliper graduated in 0002 inch increments. The specimen size was an exception taken to the 4 x 4 x 1 inch requirement of Federal Specification PPP-r.-850D,
After conditioning at room ambient conditions for a minimum of 24 hours, the specimens were weighed on an enclosed beam balance
Each specimen was placed in the Instron with the machined surfaces parallel to the platens and aligned along their vertical centerline. The platens were then brought togethe • ti just touch the specimen's upper surface with an application of approximately 0.025 psi load (Figure 11) With the test machine adjusted to apply load at a rate of 0.5 inch per minute per inch of specimen thickness and a recorciii g chart set to traverse 10 inches per minute, the'specimens were compressed through loads equivalent to 50 psi.
To determine the effect of the more dense outer coating (skin) of the extruded specimens on compressive stiffness, both cutout cubes having no skin as we1! 6S right cylinder specimens with skin mtact were tested. In addition, groups of four specimens held ■ightly together with a rubber band to provide greater total surface area were tested for the correlation of compressive stiffness values of individua' specimens when specimen diameters were less than one inch.
2.7.2 Test Results - The resulting compression charts taken from the test machine recorder were used to determine the strain values for ascertaining compliance with Federal Specification PPP-C-850D, Class 4 compressive stiffness requirements The strain values required for stresses of 20, 40 and 50 psi are shown m Table 3j ndud-ng the fifteen percent allowable tolerance. The experimental sUan va'ues were obtained by calculating the actual load required on the specimen face area to attain the 20, 40 and 50 psi stress values using the following relationship:
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2.7.3 Discussion - A hydroxypropyl cellulose formulation and process control settings were developed which yielded compressive stiff- ness values conforming to Federal Specification PPP-C-850D, Class 4 requirements. In most cases, the specimens were found to also meet Class 3 stiffness requirements, which is not unusual due to the 5C-85 percent overlap in requirement valuta, including tolerance (Table 3)v However, the tested specimens often were too stiff for the Class 3, 20 psi stress requirement and usually were more centrr.lly positioned within the Class 4 stiffness range for 40 and 50 psi stress applications. For these reasons the loose-fill packaging foam preserted for reliability determination and further testing was designated is Class 4 material (Table 4)..
The reproducibility of strain values determined fcr sister specimens was excellent, varying by no more than six percent.
A typical stress/strain curve, as shown in Figure 12, reflects the initial resistance of the loose-fill material to compression. Continued application of pressure resulted in a relaxation or "give" in the material prior to an asymptotic rise in strain. Compression data obtained in this study is not sufficient to explain the portion of the curve in which the strain decreased. This phenomenon was present regardless of the configuration (cube o" cylinder) or size of the specimens investigated,
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The effect of the more dense outer coating (skin) of the specimens on compressive stiffness values was also determined. Both cutout cubed specimens without skin and cylindrical specimens with skin intact were taken from the same sample section and tested. The results indicated that the presence of the outer skin increased the compressive stiffness value by no more than eight percent, which was not significant enough to cause a specific specimen to change considerably from one stiffness class to another. As a direct result of this test, future compression specimens were tested as right cylinders with skin intact.
The effect of extrusion flow on compressive stiffness was also investigated. Of the skinless cubed specimens tested, some were com- pressed with the axis of the Instron tester in the machine (extrusion) direction while identical specimens were compressed with the axis in the transverse (right angle to the extrusion) direction. Th results indicated a negligible (less than five percent) increase 1n m sured stiffness in the transverse direction.
Because of the comparatively small (approximately 9/16 inch) diam- eters of the specimens tested, a group of four specimens held together by a rubber band were tested for comprebsive stiffness as a group. The excellent correlation between the group specimen anJ individual speci- mens from the same extrusion run (reliability run) indicates the validity of using single specimens for stiffness tests (see Table 5).
2.8 Manufacturing Reliability
The ability to reproduce foamed specimens at will, using a pre- established formula end processing parameters to the compressive stiff- ness requirements of Federal Specification PPP-C-850D, Class 4, was satisfactorily demonstrated. The work was performed using a smaller scale extruder built by the same equipment manufacturer, having the same design features but of lesser throughput capacity than that utilized to obtain the developmental sampl» data. The fact that previous machine settings found to be satisfactory for earlier work, could be scaled down for the smaller capacity extruder to provide the desired compressive stiffnesses, demonstrated the flexibility of the production process used (see Table 2)..
The compressive stiffnesses of the reliability specimens produced, as shown in Table 5, meet the contractual compressive stiffness requirements of Federal Specification PPP-C-850D, Class 4 in Its mid- range and very nearly (except for 20 psi stress values) satisfies the PPP-C-850D, Class 3 values as well,
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3. PHASE II - PROPERTY DETERMINATION
3.1 PPP-O-1683 Testing
In Phase II, tests were conducted on the loose-fill foam material to determine the physical and mechanical properties when tested as described in Federal Specification PPP-O-1683; Cushioning Material, Expanded Polystyrene, Loose-Fill Bulk. The following procedural test descriptions are in accordance with that specification unless stated otherwise.
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3.1.1 Dynamic Test
3.1.1.1 Test Description - A cleated plywood box (Federal Specification PPP-B-601, Style A; Boxes, Wood, Cleated-plywood) was drop tested using the loose-fill packaging material to protect an interior prototype load against shock. The l/2-inch thick walls of the box were reinforced with 1-inch thJck pine cleats at all exterior edges. There were no projections. The interior dimensions of the box were 12 x 12 x 12 inches. A prototype load consisted of a rigid aluminum box with a length, width, and depth of six inches to provide a 36 square inch bearing area on the packaging material. The aluminum box was constructed to allow the installation of ballast weights, which wer* bolted to the bottom of the box (Figure 13). A triaxial accelerometer, mounted on a rigid post, was located at the geometric center of the prototype load. The ballast weights were designed to provide static stress levels on the packaging material of O.lOif to 0.624 pounds per square inch (psi) in 0.104 psi increments. The inside bottom surface of the plywood box was covered wi«n a three inch layer of the packaging material. The box was briskly rocked from side to side for 30 seconds to provide a uniform layer. Additional material was added, as required, to obtain a three inch depth« The prototype test load was placed on the layer of packaging material and centered. In accordance with the test method (PPP-C-I683), the box was filled to the top with the packaging material and then over-filled with an extra amount of material so that when a 50 pound weight wa-5 placed on the cover, a gap of approximately one-eight inch existed between the cover and the box. The cover was then secured with four carriage bolts. An adjustable sling assembly, attached to eye-bolts in the ply- wood box cover, was used to raise and level the pack assembly. The sling assembly was attached to an electrically operated quick release mechanism which was hung on a chain hoist. The mechanism and box attachment were arranged so that no rotational or sidewise forces were imparted when the box was dropped to the floor.
30
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r ? .
The outputs of the triaxial acceleror.ieter were electrically connected to charge amplifiers which provided signal conditioning, filtering and current amplification for driving recording galvanometers. The charge amplifier outputs were connected to a recording oscillograph. Low-pass filters in the charge amplifiers were set for a cut-off (-3 dB) fre- quency of 330 Hertz. This frequency response was proved to be adequate when the filtered data was compared to unfiltered data during prelimi- nary tests.
A pack assembly for each of the six static stress levels was sub- jected to ten successive drops (Figure 14). After each drop, the bottom of the cleated plywood box was leveled with the concrete flour, raised to a height of 30 inches and dropped. After the ten drops at each static stress level, the loose-fill was removed and replaced with fresh mate- rial for testing at the next static stress level. A new plywood box was used for each series of six bearing loads and ten drops (60 drops total per box used).
During each drop test, the outputs from the triaxial accelerometer were recorded on the oscillograph and the peak acceleration levels were tabulated.
3.1.1.2 Test Results - When the box cover was removed after each series of ten drop tests, 1t was observed that a space of approximately one Inch in depth existed due to settling of the packing material. It was also observed that following each series of drop tests where the static stress level was 0.208 psi or above, noticeable compaction of the packaging material occurred. The packaging material was compacted to the point that it would not fall from the box when the box was inverted.
The acceleration data from the last eight of each series of ten drops tests were averaged and plotted vs. static stress level for each of the three accelerometer axes. Absolute values of the cross-axes (X and Y axes) data were used for averaging since the direction of the acceleration pulses varied among the drop tests. The plots of average acceleration vs. static stress levels are presented in Figure 15 for each series of drop tests conducted. The average of the peak accelera- tions in the X, Y and Z-axes are as shown in Table VI.
3.1.2 FlowabiHty Test
3.1.2.1 Test Description - An aluminum funnel (Figures 16 & 17) having a three cubic foot capacity was fabricated for measuring the flowability of tha loose-fill material. The upper and lower inside diameters of the funnel were 33-1/2 inches and 6 Inches respectively and the slope of the wall was 45 degrees. The six inch diameter bottom neck was 12 Inches long and was fitted with a nonrestricting, quick opening slide gate. After the funnel was filled with loose-fill
32
1lmtit.*lm*—iLgKk»**.-un\rtmim,- .. ... ...^....■^^„-..„-,., .-, r|||...-.,.-,-.- ,. a T, ,,,.,;, , nMMi^rÜI
3P9PRMHU. p!^J»^l^f^WP■!|l■WWW*ly!|SPWJ(^^*=^-^-w^,«*^M, "»■*■ tw«' ,.,^^^--^-1?--,-"^™—'-^w-.-^-^..— ■ ^ . -1 * m - ™^>w-■■ ■ '^-»Ar'.^p'^^*. M|
FIGURE 14 - DYNAMIC DROP TEST
33
■ ■II Mil.Ill« -■—■■■■--- wwmi .ii-i^MBal—IMiMMnM.i>M«. ■■
mumm "WWÜPI m rßWi>mwimmMwmmm%wmmwiwm&m'mmi>mwv M« « «IM ----
30
20
10
l
I 1 a ü
1
~t:-;t-:-;->V^--l^ Requirement 170
160
150
340
130
120
110
100
90
GO
e---i^ Limits of PPP-C-1683 i
■f-::--'l"
■\
■ ('■ :;
otÖ 0.1 0.2 0.3 0.4 0.5 Static Stress Level - pol
FIGURE 15 - AVERAGE ACCELERATION VS STATIC STRESS LEVEL
0."6
34
mmääämtmuit, ■^^.M-^--»^ti^.......,-.........,-_...^ ^ ., - :-*-|iiiiiiilii i- i .i »J-MJ.*-» ■»,■.■■ Uli, ^.i ,L i.
mm "•*"-«— , L iii.iuwi.l^w.p.ii,!■ H.H.)... isniMfinp L>,,■*,.'i IM
TABLE 6 PEAK ACCELERATIONS (G'S)*
RUN NO.
_____
AXIS
STATIC STRESS LEVEL (PSI)
0.104 0.208 0.312 0.416 0.520 0.624
1 X Y Z
23.3 18.1 178
17.3 10.8 112
17.5 14.4 95.7
7.3 11.7 80.6
8.4 12.1 69.4
10.9 /.2
63.8
2 X Y Z
24.5 19.7 170
14.6 9.5
no
10.6 12.9 92.6
9.2 13.1 74.6
11.1 10.5 74.5
11.2 9.7
71.5
3 X Y Z
17.0 22.8 150
20.9 17.4 115
13.2 17.4 91.6
8.8 24.7 77.8
14.3 14.9 81.5
8.0 10.6 70.2
♦Values are averages of drops No. 3 through No. 10.
35
«-a— III-—1—■
CpipriHUppiPWpwg .w.m .wimir »i tjup«ji m i iiu. iuuf i i. *T;- .. u!ii.p.ii!flifij.i,i.,u.,i..«i'i .»WIIWI.JWII 1u»,~a-.3PJMi^»"Tr!^-'- ■'»c'™' «■*««■
FIGURE 16 - FLOWABILITY TEST FUNNEL
FIGURE 17 - FLOWABILITY TEST FUNNEL (INTERIOR)
36
■Um .umm^attM^,—„ja»»»!»«^ .«. ■-■•-. i .in'MijatMIMIIililhill.alt Hill ■ I i im n Mmaan^Kiaii...
mmm mm UIJ ,..]|iJii|.Uaaiv ^pntlNi.m, i- cHnm e^iww',-" "^s
foam material and leveled off (Figure 18), the slide gate was opened and the m? '.rial allowed to flow freely (Figure 19). The time required tor the funnel to become empty was determined. Three tests were performed.
3.1.2.2 Test Results - The elapsed times for the funnel to become empty are shown •'. '"able 7. No loose-fill material was retained in the funnel.
3.1.3 vibrational Settling Test
3.1.3.1 lest Description - A test assembly as prepared for the dynamic test previously described in 3.1.1.1 was used fjr the vibra- tional setting test except that the prototype loads tested were 0.156 and 0.468 psi due to equipment limitations. The completed pack was placed on the head of an electrodynamic force exciter for excita- tion in the vertical (Z) axis. Fences were bolted to the exciter head to biock the lateral motion of the pack assembly without restricting its vertical movement. A calibrated piezoelectric accelerometer was bonded to the exciter head adjacent to the fence to monitor the applied excitation (Figure 20). The average vartical distance from the top face of the four corners of the prototype load to the top of the box was determined and recorded.
Sinusoidal vibratory excitation was applied to each pack assembly for a period of 30 minutes. An excitation level of 1.1 gpk (0.93 inch, double-oi.iplitude) was applied at 4.8 Hz. Six 30-minute tests were conducted; three tests with pack assemblies having the prototype load ballasted to provide a static stress level of 0.156 psi and three tests with a 0.468 psi static stress level. The pack assemblies were removed from the exciter i/ter each test and the packaging material above the test load was carefully removed. The vertical distance from each of the four upper corners of "the prototype load to the top of the box was remeasured and recorded.
3.1.3.2 Test Results - The average of the four corner measurements was used to calculate the vertical displacement (vibrational settling) as a percentage of the initial distance measured. A summary of the • ibration settling tests is tabulated in Table 8.
It was noted that voids due tc packaging material settling and compaction similar to that observed during free fall drop testing occurred during the vibrational settling tests.
37
--—■■- - inn ■■•"« --■m J
I ■pBMP*»*^l»^^^!WW"lfl|S^I!!IP^PW^WW*W^ .1. —^«^" v--l^Miti.Ui..»PMWH.lJ^.'.»-*-^J,J.«ff,w"^l?»^,.,>-- *■*> mm'-'- "^ww"™" ^w.v,.v jm. • vnwvr*rr-- - *°m
i
FIGURE 18 - FUNNEL LOADED WITH FOAM PRIOR TO FLOWABILITY TFST
FIGURE 19 - GRAVITY FLOW OF LOOSE-FILL MATERIAL FROM FLOWABILITY
TEST FUNNEL
38
ll iHJl'i«ÜillliH'lllllll 1* IKI i !-■ ■- -—"a—»—
»*• mm |PP I »_'f:iv»lfW.WJWIIWI|'l!!J>l>im»NLW-»''«™*l«.'»»«PM*'^BP«.«.*«W,"' I".'I.»««1H>-:.PJ'^—T.-ÜT-.T - 1»»W»W I*»"
FIGURE 20 - VIBRATIONAL SETTLING TEST
39
■*■"■-üBaHtanü*« i -- ..-->— -i , ,, . , ■ I iHJM—.■■III
PP^PipflpipPipMipppVlPP^ ,ryyyjw»BVPittfi?rrpwjWgjpyjT^ ■-. g^y ■nwr'-g-j ^.n.wg^'Nrw^fyw "»W ■iTpiTni .TCr^v-.-rrrwr.-^-^i-r.'^
TABLE 7* FLOWABILITY
RUN NO.
ELAPSED FLOW TIME
(SEC/3 CU.FT.) FLOWABILITY
CU.FT7MIN
1 13.5 13.3
2 13.4 13.4
3 13.3 13.5
AVG. 13.4 13.4
TABLE 8 VIBRATIONAL SETTLING
TEST NO.
TEST TIME (M1n)
EXCITATION FREQUENCY
(Hz)
EXCITATION LEVEL
STATIC STRESS (ps1)
VIBRATIONAL SETTLING (%) (1npk-pk) <9pk>
1 30 4.8 0.9.1 1.10 0.156 8.0
2 30 4.8 C.93 1.10 0.156 8.0
3 30 4.8 0.93 1.10 0.156 5.0
4 30 4.8 0.93 1.10 0.468 14.0
5 30 4.8 0.93 1.10 0.468 16.0
6 30 4.8 0.93 1.10 0.468 13.7
'I n
40
**M I im n "ini'-"**"*' ■ - : -
wmm UPPPUPP .1 !Lijip^w_pji»—i"T- - nrp»v-«,in.p.".i.jii!i i«r»jwj «<^vo wqi—v.«n<nnn>! msBmji P «5
Tne vlbrational settling tests were conducted per Federal Specifica- tion PPP-C-1683 with the following exceptions:
(1) The static stress levels employed (0.156 and 0.468 psi) were four percent above those specified due to equipment limitations.
(2) The excitation frequency of 4.8 hz employed versus the 4.5 Hz specified for the vibrational settling tests caused the appli- cation of an additional 540 cycles of excitation during each 30 minute test period. This amounted to a 6.7 percent increase in the number of test cycles applied.
3.1.4 Loaded Bulk Density Test
3.1.4.1 Test Description - A cleated, plywood box (Figure 21) as described for the dynamic test was used to contain the loose-fill material for the determination of loaded bulk density. After filling the box with the loose-fill material, it was leveled and a 11-7/8 x 11-7/8 x 3/4 inch plywood leveling board placed on top of it. The leveling board was then loaded with 50 pounds of weight at the center (Figure 22). The corner depths from the top of the box to the under- side of the leveling board was measured and the average distance determined. The net weight of the loose-fill was measured and the bulk density calculated to the nearest 0.05 pounds per cubic foot. Three runs were made, each using fresh loose-fill material.
3.1.4.2 Test Results - The bulk densities (Table 9) were deter- mined from the following equation:
Bulk density (lbs/cu ft) 0.0265 W 11.25 +D
where: W = net weight (gms) of loose-fill
D = average corner depth from top of box to underside of leveling board (inches)
3.1.5 Compressive Creep Test
3.1.5.1 Test Description - Compressive creep characteristics of the loose-fill material was determined by maintaining a constant com- pressive load and measuring the deformation periodically. Two modified Kerstner boxes (Figure 23) each consisting of an inner and outer box of 3/4 inch thick plywood was fabricated for this test.
The inner box, with exterior dimensions of 6-3/8 x 6-3/8 inches by 8 inches deep, served as a movable, guided platen into which the necessary weights were placed to achieve 0.4, 0.8 and 1.2 psi (nominal) loadings. The outer box, serving as a base plate for the testing
U
- IM «im mam *,— ■,-
im™ |i i«iiiipniWi. iwm ipiii i ii ij i MM, mepmrm ifß *SPpwm9|P^lpq!P
FIGURE 21 - CLEATED BOX, LEVELING BuARD AND 50 POUND WEIGHT FOR LOADED BULK DENSITY TEST
FIGURE 22 - LOOSE-FILL UNDERGOINC LOADED BULK DENSITY TEST
42
BUM ...■.--.~......— mdtimt ... .^ ^i»«.
WpiipiPpigl^PPPWgpBBipjPpipjP » IB-M t»'lill.lL,l.i»l»ipjJWUWJ.J-K" i.«""''—*"» . i.,v ■>, .-...,.,, — -
TABLE 9 LOADED BULK DENSITY
RUN NO. BULK DENSITY (LBS/CU FT)
1 2.80
2 2.80
3 2.85
AVG. 2.80
h'3
fcilMlf IlifililMUUii^lHiiiii ii i a ■- - ■" - "—»., , ■ooAntftt i' iiiiliiHiii" ■
»*w '■■' myipiuii pmnrngp ■''.■ '•' '"'»"mm*****pwiw-»' >" y ■'im^ii'w.g
device, had Inside dimensions of 6-1/2 x 6-1/2 inches by 9-1/4 inches deep. As required by Federal Specification PPP-C-1683, the wood from the back panels were replaced with translucent plastic. The coefficient of friction between the inner and outer boxes was measured and found to be 0.3. An exception was taken to the loose-fill dimensional require- ment of PPP-C-1683 for the specimen size. The production material produced for testing was right cylinders approximately one inch high by 9/16 Inch diameter rather than the specified "at least 2x2 inches along the length and width and one Inch 1n thickness." This change was dictated by the size of the foam extruder available for our use.
The loose-fill material was placed evenly in the outer box to a depth of about 3-1/2 inches and the unloaded inner box gently placed upon it. One of the required loads was then placed into the inner box so as to avoid wedging within the outer box (Figure 24). The average distance between loading surfaces was then measured and recorded as T-j, the Initial thickness under load. Subsequent measurements were made after 6 minutes, 1 hour, 24 hours, 96 hours (4 days) and 168 hours (7 days) of load duration. Three test: for each of the three loadings were made.
3.1.5.1 Test Results - The static stress (Table 10))for each load and the compressive creep values (Table XI) were calculated as shown below. The amount of creep observed was less than four percent and is plotted in Figure 25.
W Static Stress, psi = ^
where: W = Weight of load applied to inner box in pounds
A = Area of inner box bearing surface in square inches
Compressive Creep, percent = —Z—- x 100
where: T = Thickness of original material placed in box in inches
Tn = Thickness of material under load at any particular time interval, n, in inches
3.1.6 Compressive Set Test
3.1.6.1 Test Description - The compressive set characteristics of the loose-fill material was determined by measuring the recovery rt^porse of the material upon removal of the loads applied for the Compressive Creep Test after the 168 hour (7 day) period. The thick- ness of the material after three recovery time intervals, 30 seconds, 30 minutes and 24 hours, were measured.
44
i . ---natUtMMt rijflmaa -am.i»'..-,|l^.l(.■, ^...^tdU
PHP i iHBapigjQngnfnpigpi ■WPWWPMWSPJMil'
FIGURE 23 - INTERIOR AND EXTERIOR MODIFIED KERSTNER BOX
WITH LOOSE-FILL AND WEIGHT FOR COMPRESSIVE CREEP/SET TEST
FIGURE 24 - LOOSE-FILL MATERIAL UNDERGOING COMPRESSIVE
CREEP/SET TEST
45
■ ■ —
mp i! pnpunmMpimnp >lll|ll||*Wp|lft»|l!tpU.ip^ljp».>i^i)!Hpwi. ■
TABLE 10 TEST LOAD DETERMINATION
PPP-C-1683 REQUIREMENT
(psi) WEIGHT (lbs)
SURFACE AREA
(sq 1n.)
CALCULATED STATIC STRESS
(psi)
0.4 18.0 40.64 0.44
0.8 34.0 40.64 0.84
1.2 | 52 0 40.64 1.28
46
uai —"■*^""
jammmmgmmmagmiMMgifiprt^TfM^^
TABLE 11 COMPRESSIVE CREEP
I
ACTUAL STATIC STRESS, LOAD
(psD TIME
INTERVAL
ORIGINAL THICKNESS, T (INCHES)
LOADED THICKNESS,
Tn (INCHES) COf'DRESSIVE CREEP (%)
0.44
1 min. 6 min. 1 hr.
24 hrs. 96 hrs. 168 hrs.
3.30
3.30 3.30 3.29 3.27 3.25 3.25
0.00 0.00 0.30 0.91 1.52 1.52
1 min. 6 min. 1 hr.
24 hrs. 96 hrs. 168 hrs.
3.13
3.13 3.13 3.11 3.10 3.09 3.09
Ö.ÖÖ 0.00 0.64 0.96 1.28 1.28
1 min. 6 min. 1 hr.
24 hrs. 96 hrs. 168 hrs.
3.25
3.25 3.25 3.23 3.20 3.20 3.20
0.00 0.00 0.62 1.54 1.54 1.54
0.84
1 min. 6 min. 1 hr.
24 hrs. 96 hrs. 168 hrs.
3.19
3.19 3.19 3.15 3.13 3.13 3.13
0.00 0.00 1.25 1.88 1.88 1.88
1 min. 6 min. 1 hr.
24 hrs. 96 hrs. 168 hrs.
3.38
3.38 3.38 3.34 3.31 3.31 3.31
Ö.00 0.00 1.18 2.07 2.07 2.07
1 min. 6 mir. 1 hr.
24 hrs. 96 hrs. 168 hrs.
3.23
3.23 3.23 3.19 3.16 3.16 3.16
0.00 0.00 1.24 2.17 2.17 2.17
47
I. inline—■« i i iHMUMMi« .»Mf
r qipBfrwf" 11. giffwwpwB^eywggBiaBgww^ npn^i pmmivH -si HWII'WP«» ■'. f»v-'.ir <~zrprr
TABLE It COMPRESSIVE CREEP (CONT'D)
[
ACTUAL STATIC ORIGINAL LOADED STRESS, LOAD TIME THICKNESS, THICKNESS, COMPRESSIVE
(psl) INTERVAL T (INCHES) Tn (INCHES) CREEP {%)
1 m1n. 3.25 0.00 6 m1n. 3.25 0.00 1 hr. 3.25 3.19 1.85
24 hrs. 3.15 3.08 96 hrs. 3.13 3.69 168 hrs. 3.13 3.69
1 min. 3.50 0.00 6 min. 3.50 0.00
1.28 1 hr. 24 hrs. 3.50 3.39
3.38 3.14 3.43
96 hrs. 3.38 3.43 168 hrs. 3.38 3.43
1 mil. 3.38 0.00 6 m1n. 3.38 0.00 1 hr. 3.38
3.31 2.07 24 hrs. 3.29 2.66 96 hrs. 3.25 3.84
i 168 hrs. 3.25 3.84
1
MÜfÜÜHIIilÜ
rm •"^mmmmmmmmm- mmmmmmm
a: 3Z
LU
LU
cn
a. LU
0£
CO oo LU ac G. •z. o o
LT> CM
XL
(%) d33cJD
49
■ — ■ - ■"»■..— ■■■■■■■-■ ^-jajuätttMjiiM^^^.^- .. . -■■'-■ ■■■■•»-MM^''' ihlfei
MI' i uJiJi.miJuiiii ■ . i,wu wiiunmiiii rffMW^.wBW*7^y!PTqy^.< ^iy^.Pj»if»y^ .',i;y^!iiiw;p^F'^^.^J.i.,ni!W.y.ii--
3.1.6.2 Test Results - Upon removal of the load applied to the loose-fill material on completion of the 168 hour Ccmpressive Creep Test, no measurable thickness change (recovery) of the compressed material took place during the 24 hour test period. Consequently, the percentage compressive set after the 30 second, ?0 minute and 24 hour test intervals was the same value as that obtained at the end of the 168 hour Compressive Creep Test as shown in Table 12.
3.1.7 Flammability Test
3.1.7.1 Test Description - A tared basket, 8 inches long by 6 inches wide by 8 inches tall was fabricated of 1/4 inch stainless steel wire mesh for testing the flammability of the loose-fill material. After filling the basket with loose-fill material, a oi e foot length of MIL-F-I8405? Fuse, Firecracker, 30-second was threaded through the center of the six inch basket width and allowed to protrude from each side (Figure 26). Additional loose-fill was then added to the basket until level with the top. The filled basket was then weighed and the net weight of the contents, less one gram for tne fuse, was determined. The filled basket was then placed in a draft free environment and the fuse ignited. After the fuse had been consumed, the br.sket and contents were reweighed. Seven tests were performed.
3.1.7.2 Test Results - The flammability cf the loose-fill material, based on the percentage of net loose-fill remtMng after the test, was calculated as follows:
Percentage material remaining Final net weight, gms x JQQ Original net weight, gms
The results are shown in Table 13«
3.1.8 Electrostatic Adhesion Test (Figures 27 thru 31)
3.1.8.1 Test Description - The loose-fill material was tested for electrostatic adhesion properties by filling a five gallon, 11 inch diameter fiberboard drum with telescoping cover, one-third full of material. While lying on its side, the drum was rolled back and forth across a ten foot span of floor for three minutes at a rate of approximately 60 revolutions per minute. Within 30 seconds after the final revolution, the drum was opened and the looae-fill allowed to empty out by gravity (without shaking).
In addition to the preceding PPP-C-I683 test procedure, the same drum, again filled to one-third capacity, was placed on a power driven roller and rotated at the 60 rpm rate for the three minute test.
Test Results - Three tests were performed for each of the above test procedures. In each test no loose-fill material vis retained in the emptied drum.
50
mm atf^H WW 11 ii—rn ,...,... 1 magjflflft^M,,^:.*,....
wmmm mwinrnj» ^mmmm*J* •>"" "."•»■■«»..,!n<w-*m* |lW.kl|J'l|UP!ipl|i"^"«-i»'l!WI.J*'»lH>-ll-'irw!i!!iJ »wm-r.mmvr'r-^mm
TABLE C0MPRESS1VE SET
f
ACTüAL STATIC
STRESS, LOAD (psO
DURATION OF LOAD
THICKNESS CHANGE (inches)
RECOVERY TiME
OPPRESSIVE SET (%)
0.44 • 68 0 00 30 sec, 30 mm & 24 hrs.
i) 1.52 2) 1.28 3) ! 54
0.84 168 0.00 30 :C , 30 mm. & 24 hrs
M 1.88 2) 2.07 3) 2.17
1.28 '68 0 00 30 sec, 30 mir. & 24 hrs
1) 3=69 2) 3.43 3) 3.84
TABLE 13 FLAMMAB1LITY
TEST NO
NET WEIGHT OF LOOSE-FILL (GRAMS) MATERIAL
REMAINING (%) INITIAL FINAL
i 28 i 280 99.6
2 285 284 99.7
3 283 282 99.7
4 285 284 99.7
5 283 283 100.0
6 283 281 99.3
7 285 284 99.7
AVERAGE 99.7
■ -- ■ — - -■■ n Ba^JMwy -:■■■■
jgHP^UPWfflpmpipp ii« i mnwit-iwiinmwf»iHpnBw»^~--i.i uiiumgpmw^npni.wuu ■""—"-
• " --*i
■ •
"|F ; -^P-''
WIRE BASKET AND LOOSE-FILL MATERIAL
WITH FUSE PROTRUDING
STEP 1
IGNITION OF FUSE
STEP 2
-;.-*ikVy^-.* 'i'<*V'*V'
FUSE BURNING THROUGH LOOSE-FILL MATERIAL
STEP 3
COMPLETED TEST WITH BURNED CENTRAL AREA
STEP 4
FIGURE 26 - FLAMMARILITY TEST
52
bMM MÜ ■Mau« JiBMIi>GiaiMMHB^ —■-——«»—— — — ■''—* ■ • ■■ -'■• ■
w***^m*mmi™m ...,..(W.« ""s^'Y'i'?"-"''"-
FIGURE 27 - FIVE GALLON. ALL FIBER DRUM WITH TELESCOPING LID
FOR ELECTROSTATIC ADHESION TEST
FIGURE 28 - ELECTROSTATIC ADHESION TEST DRUM 1/3 FULL OF TEST MATERIAL
53
u— i ——»——-■ ■- ——"-^iiniii i mull in i - ^ — -
mm/mm* sw {pHfppppwjippp üP ... .^.i,--^, i i.«,..— • ..J.P... i i ■pn I««
MCA*
FIGURE 29 - ELECTROSTATIC ADHESION TEST DRUM ROLLED PER PPP-C-168S
TEST METHOD
FIGURE 30 - ELECTROSTATIC ADHESION TEST DRUM ROLLED PER MCDONNELL DOUGLAS
TEST METHOD
54
--—^J^I—****.— . — ■■■ i mm1——"—"*,—i—— ■— ■
mmmmmm mm* mp . wwwpwwisiwjwpp^ ppp
i .
FIGURE 31 - EMPTYING OF LOOSE-FILL MATERIAL AFTER ELECTROSTATIC
ADHESION TEST
55
—- l«MMäl ..I.. a^MMMMaai—MMttaM—i» tf— - ■ - ■■ ■ --^- -~ -J
■■BWWflllllWWBPPg^W^ IBBBIISPIBBPaP^WWPBff^ ■*ri!sisvii<<Fw?ipmmw*K^w>'m!S'^r™!m~™
3.1.9 Miscellaneous Examinations - The loose-fill material was examined for color, configuration, dimensions, tolerances and workmanship. The results are as shown in Table 14..
TABLE 14 MISCELLANEOUS EXAMINATIONS
PROPERTY RESULT
Color White
Configuration Homogeneous right cylinders
Dimensions Approximately 9/16 inch diameter by 1 inch long
Dimensional Tolerance
+6.6% on diameter (21 random production samples)
Workmanship Clean, dustless, no visible foreign matter, imperfections or fragmented particles
3.2 Supplemental Testing
The effects of 24 hour and 31 day humidity exposures on product properties were determined and the dissolution rates in salt and fresh water were established.
3.2.1 31 Day Humidity Test
3.2.1.1 Test Description - Twenty one specimens of loose-fill foam measuring approximately 9/16 inch diameter by one inch long, each weigh- ing about 0.3 grams (Figure 32), were put into individual aluminum dishes and placed in a humidity cabinet (Figure 33) for 31 days. The environment in the cabinet was controlled at 100 +2°F and 95 +3% relative humidity. The wet and dry bulb temperatures were continuously monitored by a recorder.
3.2.1.2 Test Results - At the termination of the 31 day test period, the specimens were removed from the cabinet and reweighed. Each speci- men increased 1n weight an average of 16 percent (Table 15). The appearance of the specimens had changed from an opaque white to a clear, translucent color. The cylindrical cross-section had collapsed and became ellipsoidal and the material was soggy but had not flowed freely (Figure 34).
56
MMMI ..-■■ - 'Ml - ■-•■-■ ' ii in i- '■ • — MFt^m«- ■ J-- ■
VWWPffW i iiijinji.p■ tunji u u,n ui...,,H.iiti*,!j«m^,^!^K-,,mmi*mi<mvrimr*w >mmmmr*Fm^™*°r^'' 5W!
LÜ t-
>■ I- I—i Q
< O
on
o f-
Q£ O
a.
on z Ul zc t—4
o Ul
to
to o o
<M CO
57
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RUN NO.
1
SPEC MEN WEIGHT (6MS)* WEIGHT CHANGE* ORIGINAL FINAL CHANGE
0.3322 0.3856 0.0534 +16.07
2 0.3387 0.3928 0.0541 +15.97
3 0.3336 0.3869 0.0533 +15.97
AVG. 0.3348 0.3884 0.0536 +16.01
♦Average of seven specimens
60
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3.2.2 Moisture Absorption
3.2.2.1 Test Description - Twenty-four hour temperature/humidity exposures were run on foam specimens at 73°F and 50% RH, 73°F and 95% RH, 165°F and 50% RH and 165°F and 95% RH conditions. The weight for each specimen was determined prior to its placement in the environ- mental chamber.
3.2.2.2 Test Results - As shown in Table 16 , specimens exposed to an environment of 73°F and 50% RH for 24 hours experienced an increase in weight of 2-3 percent with slight dimensional changes. Exposure to 73°F and 95% RH resulted in a 7-8 percent increase in weight with more significant dimensional changes in length but not diameter. After exposure to 165°F and 50% RH for 24 hours,spe:imens had a loss in weight of 3-4 percent, a slight increase in diameter and approxinately a 15-20 percent increase in length. On the otner hand, after exposure to 165°F and 95% RH, the specimens experienced a 6-7 percent weight gain, had become translucent and had flattened out to an ellipsoidal shape.
3.2.3 Solubility/Dissolution Rate Testing
3.2.3.1 Test Description - Solubility tests were conducted to determine the relative rate of dissolution of a given mass of foam ma'ärial in given quantities of fresh and prepared sea water. Tests were run on seven sets of specimens in each test group. Specimens in one group were separately placed in glass jars containing 100 ml of fresh (tap) water and were allowed to float freely on the surface. Another group of specimens was individually placed in 100 ml of fresh water and maintained in a submerged state by enclosure in an outer wrap of stainless steel wire mesh. These same procedures were used for two other groups of seven specimens which were floated and submerged in glass jars filled with laboratory prepared sea water containing 2.7 percent sodium chloride (Reference 7).
The pH and temperature of the water solutions in which each speci- men was placed were taKen before and after dissolution. All specimens were weighed before testing. Lids were used to cover the containers of all floating specimens in order to prevent the specimens from stick- ing to the wall of the container due to evaporation of the water during the 24 hour test period.
2 Test Results - Twenty-eight hours were required to com- issölve all floating specimens in fresh water and 32 hours pecimens exposed to the sea water. Submerged specimen? more rapidly due to the greater contact area which allowed dissolution of the gel type outer coating formed during the
on process (Reference 8). All of the specimens submerged in er were in solution after ten hours. Twelve hours were to completely dissolve submerged sea water specimens.
3.2.3. pletely d for the s dissolved continual dissoluti fresh wat required
7o Reinhold Publishing Corporation, New Yorkp Condensed Chemical Dictionary,, (7th Edition), pg. 23?.
8. J. B. Titus.; "Environmentally Degrada^le Plastics/' Materials Engineering, April 19745 pg« 20.
61
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TABLE 17 DISSOLUTION RATE
FLUID MEDIA
SOLUTION PH BEFORE DISSOLUTION AFTER DISSOLUTION
FLOATING SUBMERGED FLOATING SUBMERGED
Fresh Water 9.85 9.85 8.8 8.4
Sea Water 9.30 9.30 8.1 7.5
63
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4. SUMMARY AND CONCLUSIONS
The results of the feasibility study for Phase I show that hydroxy- propyl ceVulose resin can be satisfactorily formulated and processed into a loose-fill foam material using a r nventional extrusion process. A candidate packaging foam was produced which met the compYessive stiifness requirements of Federal Specification PPP-C-850D for Class 4 (Extra Firm) material. During development, foamed products in all other specification classes were also produced using small variations in formulation and machine settings to effect the changes.
The density of the loose-fill produced was relatively high for a plastic foam material used in packaging applications. In addition to higher costs due to greater resin content, the effect of high -ensity was reflected in loaded bulk density and certain peak acceleration properties which did not comply to the requirements of Federal Speci- fication PPP-C-1683.
The 9/16 inch diameter by one inch long loose-fill material was extremely floweble, had excellent vibrational settling characteristics and exhibited no residual electrostatic charge.
Although the material possessed strong resistance to compressive creep for loadings up to 1.2 psi, when the loads were removed no measurable recovery took place withir the 24 hour test period. Still, the compressive set values were well within the Federal Specirication PPP-C-1683 requirements due to the small amount of compression that occured during the creep test.
Flammabi 11ty tests showed that the foamed hydroxypropyl cellulose did not support combustion, experiencing only a minute amount of weight loss due to consumed material. During the burning process, the resin in contact with the fuse was degraded from a normal white, fiberous condition to a fused brown mass.
The water soluble characteristic of the resin was not adversely affected by either the formulation or the extrusion process. Complete dissolution in both fresh water and prepared sea water was demonstrated 1n both the floating and submerged states. Complete solubility in sea water took a slightly longer time than in fresh water exposures.
Long term conditions of 100°F and 95 percent RH caused the specimen surfaces to become tacky and to enlarge an appreciable amount as moisture was absorbed. Specimens that were exposed to shorter term moisture absorption tests behaved in a similiar manner provided the temperature was not elevated. At a temperature of 165°F and 50 percent
64
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relative humidity, the specimens experienced a weight loss as the surrounding heat drove out moisture. However, at 165°F and 95 percent relative humidity, the specimens again absorbed moisture in spite of the hot environment due to the greater amount of moisture present at the higher humidity.
Table 18 compares the physical and mechanical property require- ments of Federal Specification PPP-C-1683 with the average values obtained from the loose-f^ll production material when tested in accor- dance with the subject specification.
TABLE 1* FEDERAL SPECIFICATION
PPP-C-1683 TEST SUMMARY
NAME OF TEST PPP-C-1683 REQUIREMENT TEST RESULT
1. Dynamic Type I: 60g maximum peak accelerations within 0.15-0.45 psi static stress range.
X-axis = 20.5 g's, max. Y-axis = 16.5 g's, max. Z-axis = 133 g's, max.
i
Type II: 90g maxi- mum peak accelera- tions within 0.15- 0.45 psi static stress range.
2. Flowability Class 1: 6.0 cu ft per minute or greater. Class 2: Less than 6.0 cu ft per minute
13.4 cu ft per minute (Class 1)
3. Color Type I: White only Type II: Other than white
White (Type I)
4. Configuration Supplier's option but homogeneous
Homogeneous right cylinders
65
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I TABLE 18 FEDERAL SPECIFICATION
OPP-C-1683 TEST SUMMARY (Continued)
NAME OF TEST PPP-C-1683 REQUIREMENT TEST RESULT
5. Dimensions No overall outside dimension greater than 2 inches (1f other than strand configuration)
Approximately 9/16 inches diameter by 1 inch long
6. Tolerance (dimensional)
+20% (If other than strand configuration)
+6.6% on diameter of 21 random production samples
7. Vibrational Settling
30% maximum displacement
7% avg. max. displacement at 1.56 ps1 static stress. 14.6% avg. max. displacement at 4.68 psi static stress.
8. Loaded Bulk Density
0.40-1.5 lbs per cu ft
2.80 lbs per cu ft
9. Compress1ve Creep
Load (psi) % Creep
0.4 10 max. 0.8 15 max. 1.2 18 max.
Load (psi) % Creep
0.44 1.45 0.84 2.06 1.28 3.65
10. Compressive Set Load (psi) % Creep
0.4 5 max. 0.8 10 max. 1.2 13 max.
Load (psi) % Creep
0.44 1.45 0.84 2.06 1.28 3.65
No recovery within 24 hour test period
66
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TABLE 18 FEDERAL SPECIFICATION
PPP-C-1683 TEST SUMMARY (Continued)
NAME OF TEST PPP-C-1683 REQUIREMENT TEST RESULT
11. Flammability Not less than 50% of original weight retained
99.7% of original weight retained
12. Electrostatic Nonstatic Nonstatic
13. Workmanship Clean, free of foreign matter and imperfections. Less than 10% deformed or frag- mented particles.
Clean, dustless, no visible foreign matter, imperfections or frag- mented particles.
When comparing the results obtained in Phase II to the requirements of PPP-C-1683 (Table XVili), it is evident that the hydroxypropyl cellulose fo? exceeds the allowable property values for high peak acceleration and loaded bulk density. This departure from the standard property requirements for foams currently in use for cushioning purposes can be directly attributed to the relatively high density (5.19 lb/cu ft) of the individual p-'T.es of Klucel foam.
The effects of the 31 day, long term humidity exposure was damaging. The amount of moisture absorbed caused material deterioration which completely altered the pnysical properties and appearance of the specimens. However, from a water solubility standpoint, hydroxypropyl cellulose foam appears promising as a loose-fill packaging material which could provide an acceptable ecological solution to a disposal problem.
The present cost of Klucel Grade J resin is $2.18/lb. This compares unfavorably with the price of polyethylene and polystyrene polymers used to produce the conventional foamed loose-fill packaging materials presently on the market. The current prices of polyethylene and polystyrene are $C.25-$0,30/lb *nd $0.305-$0.33/lb respectively (Reference 9). The effect of this price differential is even more noticeable when it is realized that the density of the current loose-fill foam products is approximately one-half that of the product produced in this project.
67
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REFERENCES
1. A. J. Desmarals, "Hydroxyalkyl Derivatives of Cellulose," Industrial Gums, 2nd Edition (1973), pg. 650.
2. Ibid, pg. 665.
3. Ibid, pg. 666.
4. Hercules, Incorporated, "Klucel-Hyi oxypropyl Cellulose; Chemical and Physical Properties," Brochure 0971), pg. 4.
5. James Rossman and A. J. Desmarals, "The Case of the Disappearing Comb," Hercules Chemist, No. 61 (1970), pg. 10.
6. Ibid, pg. 10.
7. Reinhold Publishing Corporation, New York, Condensed Chemical Dictionary (7th Edition), pg. 837.
8. J. B. Titus, "Environmentally Degradable Plastics," Materials Engineering, April 1974, pg. 20.
9. Special Report, "The Economics of Materials," Materials Engineerinq, January 1975, pg. 21 (table).
68
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