PERFORMANCE EVALUATION OF CORRUGATED PACKAGING - A KEY TO SUCCESS FOR PAPERMAKERS AND CORRUGATORS

Sanjay Tyagi, B. P. Thapliyal, R. D. Godiyal, Prachi Kaushik and Manoj Kumar

CENTRAL PULP AND PAPER RESEARCH INSTITUTE SAHARANPUR- 247001

• Pulp & Paper industry is one of the largest industrial sector in world producing 404 million MT of paper & paper board annually.

• Asia contributes highest production with 182 Mmt followed by Europe (106 Mmt) and North America (85Mmt)

Asia Europe North America

Latin America

Oceania Africa0

5

10

15

20

25

30

35

40

45

50

Pap

er a

nd

Pap

erB

oar

d P

rod

uct

ion

(%

)

Region-wise Production of Paper and Paperboard

(Source: Compendium of Census Survey of Indian Paper Industry, CPPRI (2015))

Global Production Trends

• Global Pulp & Paper industry shows positive growth despite a decline in production in graphic paper in North America and Europe.

• Positive growth of tissue and packaging grades has offset the retreat of graphic paper.

• According to FAO, paper and board packaging product will continue to represent industry’s largest segment with contribution of more than 50% of worldwide paper production.

37%

26%

14%

8% 8% 7%

0%

5%

10%

15%

20%

25%

30%

35%

40%

Corrugated Material

Printing and Writing

Paper

Paper Board for Packaging

Tissue Paper

Otherpaper Newsprint

Pape

r and

pap

er b

oard

Pr

oduc

tion

(%)

Grade-wise Global Production of Paper

(Source: Compendium of Census Survey of Indian Paper Industry, CPPRI (2015) )

Global Paper Consumption

• Highest consumption of paper is registered for Asia, Europe & North America

• China accounts for 25% of world demand against 26% of global production of paper and board.

• Europe consumes 24% of paper against the contribution of 27% of global paper production.

46%

24%20%

7%2% 1%

0%5%

10%15%

20%25%

30%35%

40%45%

50%

Asia Europe NorthAmerica

LatinAmerica

Africa Oceania

Con

sum

ptio

n of

Pap

er (%

)

Region- wise Global Consumption of Paper

(Source: Compendium of Census Survey of Indian Paper Industry, CPPRI, 2015)

221

156

50

215

75

159

23

126

47

13.2 8

0

50

100

150

200

250

Per

Cap

ita C

onsu

mpt

ion

Paper Consumption kg/capita

(Source: Compendium of Census Survey of Indian Paper Industry, CPPRI (2015))

Fact sheet of Indian Paper industryNumber of Mills 813

Total installed capacity, MMT 22.15

Operating Installed capacity, MMT 19.27

Production of Paper, board & newsprint, Mtpa 14.99

Capacity utilization, % 80

Per capita consumption (kg) 13.2

Contribution to exchequer, Rs. crores 4500

Employment Direct, million people 0.5

Indirect Employment, million people 1.5

Indian share in world’s production 3.7

(Source: Compendium of Census Survey of Indian Paper Industry, CPPRI (2015))

Variety Raw Material Production (Mtpa)

Total production Mtpa

% Contribution

Writing Printing Grade

Wood Based 2.675.21 35*Agro Based 0.54

Recycled Fibre Based

2.00

Packaging Grade

Wood Based 0.858.29 55*Agro Based 1.07

Recycled Fibre Based

6.37

Newsprint Grade

Wood Based 0.02`1.49 10*Agro Based Nil

Recycled Fibre Based

1.47

Total Production 14.99 100

Indian Paper Industry segment based on Products

(Source: Compendium of Census Survey of Indian Paper Industry, CPPRI (20150))

Projected requirement of different varieties of Paper

• It is estimated that production of paper will reach 21.94 million tons in 2025 against present production of 14.99 million tons.

• Industry requires an addition of 6.95 million ton production capacity over a period of 10 years i.e an addition of 0.69 million ton /annum.

Projected Growth of different varieties of Paper

Paper Grade Growth rate in %Writing/Printing Paper

• Coated Paper 10

• High grade maplitho 08

• Copier Paper 15

• Cream wove 05

Industrial Paper and Board

• Container and Corrugated board 10

• Carton Board 08

Newsprint 06

Specialty Paper 05

(Source: Compendium of Census Survey of Indian Paper Industry, CPPRI (2015))

Use of Paper and Paperboard for Packaging

• Bags, wrapping and infusible tissues e.g. Tea and coffee bags, sachets,

pouches, over wrap, sugar and flour bags, carrier bags

• Multiwall paper sacks

• Folding car tins and rigid boxes

• Corrugated and solid fiberboards boxes

• Paper based tubes, tubes and composite containers

• Fiber drums

• Liquid packaging

• Labels

• Sealing tapes

• Cap liners (sealing wads) and diaphragms (membranes)

• Contain the product.• Protect goods from mechanical damage• Preserve products from deterioration.• Information to customer / consumer.• Provide visual impact through graphical and

structural design.

Technical Requirement of Paper and Paper Board for Packaging

• All papers and paper board properties depend on the ingredients used e.g. type and amount of fiber and other materials, together with the manufacturing process.

• These related to the visual appearance and technical performance of packaging incorporating such materials.

• Appearance that relates to color, visual impression and the needs of any processes such as printing which have a major impact on the appearance of the packaging.

• Performance that relates to strength, product/consumer protection and the efficiency of all the production operations involved in making and using the packaging.

Corrugated fiber board packaging

• Corrugated fiber board packaging in terms of weight, is the commonest type of paper and paper board based packaging.

• It function is mainly the protection of products during distribution.

• Popularity of corrugated board as packaging material is primarily because of its high strength- to- weight ratio

Relative price verses relative strength of various packaging materials

Source: Alf dr Ruvo, “Development trends in packaging”, PRIMA supplement in Paper Europe, volume3, number 4, July 1991)

Structure of Corrugated Board

• Corrugated board has a sandwich material structure.

• It comprises a central paper (called the corrugating medium or simply the medium) which has been formed using heat, moisture and pressure in a corrugated i.e. fluted, shape on a corrugators and one or two flat papers (called liners) have been glued to the tips of the corrugations

Structure of Corrugated board

a Single Face

b Single wall

c Double wall

d Triple wall

Corrugating Flutes ProfilesFlutes Average

Number of flutes / m

Pitch (mm) Take up factor

D 75 14.96 1.48

K 95 1.70 1.50

A 110 8.60 1.53

C 129 7.95 1.42

B 154 6.50 1.31

E 295 3.50 1.24

F 310 2.40 1.22

G 350 1.80 1.21

O 360 1.25 1.14

(Sourse: ‘Technical Corrugating Roll Data’,BHS Corrugated brochure by Edmund Bradatsch and Lothar Jobst – July 2000)

Properties of corrugated paper board and their test procedure

• Weight per unit area (grammage) • Thickness (caliper)• Bursting Strength• Rigidly or bending stiffness• Edge Crush test• Flat crush test and hardness• Concora Medium Test• Puncture Test• Adhesion Test and Score cracking• Box Compression Test

Weight per unit area (grammage) and thickness (caliper)

• Grammage = L1 + (a x F) + L2

where L1 and L2 are the liners, F is the medium and ‘a’ is take-

up factor. • The take- up factor defines the length of the

medium (fluting) material used in a corrugated fiberboard structure compared with the length of the facings.

Thickness or Caliper• The thickness (caliper) is measured under 20 kPa pressure

Average value of thickness for different flutes in given below

Flute Caliper or Thickness (mm)

D 8.0

K 6.5

A 4.8

C 4.2

B 2.8

E 1.7

F 1.2

G 1.0

O 0.7

Why measuring the corrugated caliper is important?

• Caliper is an indirect measure of the compression stacking of corrugated boxes.

• Low caliper is usually the result of poorly formed flutes or crushed flutes and often results in poor corrugated box performance.

• Whenever the caliper of given grade of board is less than the target value, it failed to achieve the maximum strength potential.

How to maximize caliper?

• From the flutes to the maximum potential of the corrugated rolls

• Do not to crush the flutes after we have formed them.

Strength Properties

• The strength and durability of corrugated board lies in the strength of the components it made up of.

• A 20 x 20 x 20 – 200 lbs (976g/m2) test C- flute corrugated box can withstand almost 408 kg of weight before failing, yet it weighs only 1.02 kg.

• Reason lies in the fact that fluted medium separating two liners act as columns.

Bursting Strength

• It is indication of the character of the materials used in the manufacturer of the box.

• Depending on nature and grammage of the liners, large range of quantities from 800 to 8000 kPa is available.

• This test gives no direct information regarding the ultimate performance of the design or construction of a finished container.

• Burst strength test is of critical importance as a control test in the paper board mill.

• Triple wall corrugated board can not be tested suitably by the burst test method.

• Testing of double wall is of questionable accuracy since it is rarely possible to get sufficiently simultaneous burst of the multiple facing.

• For single wall corrugated board, the following equation is applied

Burst Strength = L1 + L2 + 100

Where L1 & L2 are the burst strength of the liners in kPa.

Rigidly or Flexural bending stiffness

• Relates the force required to deflect a flat specimen of corrugated board through a given angle.

• Capacity of structural members to resist bending. • Greater the flexural stiffness, greater is the load

required to produce a given deflection.• Combined board flexural stiffness in each direction

is summing the product of elastic modulus of each component.

• Combined board Stiffness S = EtH2/2 where E = Elastic modulus of liners t = liner thickness H = combined board caliper

• Combined board stiffness is sensitive to caliper of combined board, thus it is necessary to avoid crushing the board during conversion.

• C Flute has higher bending stiffness than B Flute

• Corrugated fiber board based on kraft liner has a higher bending stiffness than test liner of same grammage

• Bending stiffness increases with increasingly liner grammage.

Edge Crush test

• Evaluate the compression strength of the corrugated board as

per ISO 3037. Expressed as the breaking force divided by the

sample width (kN/m).

• Relates directly to the top to bottom compressive strength of

corrugated shipping container.

• Method is used for comparing the edge wise compression

strength of different lots of similar board or for comparing

different materials combinations

Maltenfort Equation

• ECT = k(σ CL1 + σ CL2 + α σ CF )

where σ C = compression strength of liners & flutting medium paper measured by any method SCT, RCT, CLT, CCT

α = take – up factor k = constant depending on manufacturing variables of

corrugated board

• 15 – 20% of ECT potential of corrugated board is lost during fluting process due to high bending and tension stresses induced in medium paper during fluting.

• Application of steaming operation though relieved stresses but it reduces elastic modulus and compressive strength of sheet by 5 – 15%.

Edge Crush Test piecesEdge Crush Test pieces

100 mm

25 mm

paraffin

Flat crush test and hardness

• Evaluate and classify the performance of the fluting in accordance with the type and basis weight.

• Measure of the resistance of the flutes in corrugated board to crushing force applied perpendicular to the surface of the board under prescribed conditions (ISO 3035)

• Measures the flute rigidity of the corrugated board.

• High FCT value indicates a good combination of the flute formation and at least adequate medium strength.

• A low flat crush value indicates a number of faulty conditions.

Flat Crush TestFlat Crush Test

• FCT test is satisfactory for single faced or single wall corrugated board but should not be used for double wall or triple wall board.

• This test gives the intrinsic performance of the flutes predicted by the Concora Medium Test (CMT) and by basis weight

• The FCT thus records how appropriate the fluting medium is for processing on the corrugators

Hardness

• In order to evaluate properly the performance of soft board, the hardness of corrugated board is other important criterion.

• Hardness is the resistance of the board in early stage of FCT. It relates to the real strength of the flutes whereas FCT is late yield point.

Effect of crushing force on flutes

3500

3000

2500

2000

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1000

500

01 2 3 mm

Compression

Force

23

45

6

1

leaning flutes

PUNCTURE TEST

• This test illustrates the energy required to penetrate the corrugated board.

• Conducted as per ISO 3036 standard. Values are reported in mJ/m.

• This test gives better performance of corrugated box as compared to Burst test.

Concora Medium Test

•It is a test of compression of the paper after fluting in fluting apparatus.

•The CMT value is the maximal force the sample can with stand before it breaks.

Concora Medium TestsConcora Medium Tests

Tape

Pin Adhesion Test (PAT) and Score cracking

• The Pin adhesion Test (PAT) is used to evaluate the bonding between the fluting and liner.

• Adhesion resistance is the maximum force required to separate the linerboard from the fluting with the help of special sample holder.

• In single face bonding, the adhesive is distributed on each side of the flute tip.

• In double backers, the adhesive deposit is placed on the top of the tip.

• Score cracking effect occurs during converting operation due to stress-strain occurring in folding & erecting.

How Box Collapse?

• In conventional vertical flute boards, with progressively increasing load, side & end panels become unstable & deflect laterally.

• Having become unstable, central region of each panel suffers appreciably reduction to accept further increase in load & box bow outward or inward.

• Edges carry greatest intensity of load & rupture of box at edges triggers failure of entire box.

• Box Compression test (BCT) is the best representation to practical stacking strength of corrugated board boxes.

Box Compression Test

• Stackability of corrugated boxes is best determined by box compression test (BCT) expressed as KN or kg.

• BCT is the top to bottom compression strength.• To conduct this test, the container is placed

between the platens of the test machine and compressed at a rate of 0.5 in/min. The maximum load and deflection at failure is recorded.

Box Compression Tester

• Box Compression strength = K x ECTa x FSb x Dc

where D is the dimension of box (perimeter), FS is the flexural stiffness of the board, ECT is the edge crush test of board and

K, a, b and c are empirical constants.

• ECT of combined box is a dominant factor in top load box compression strength.

• A % increase in ECT strength, contribute three times greater increase in BCT as compared to % increase in flexural stiffness & 1 – ½ times the same increase in box perimeter

Factors negatively affecting the top load Compression strength

Effect of relative humidity o compressive strength property of corrugated boards

Humidity

• Corrugated box looses half or more of its short term top load compression strength when relative humidity increased by 50%.

• BCT falls from 350±50 kg (at 23°C/50% RH) to 130±15 kg (at 20°C /90%RH)

• With increasing moisture content, ultimate paper strength properties reduced due to reduction in inter fiber bondings.

Age• With number of days the box is under

compression, compression strength of box began to loose at an alarming rate.

• This is due to creep within the cellulose fiber structure of the paper and the corrugated material itself.

• As a thumb rule, 50% of its stacking strength will be lost over six months period.

Misalignment

• Vibration disturb system stability. • BCT value of box from 300 kg falls by 40% (170 kg) due to vibration.

Column stack verse Interlock

Compression strength of corrugated box as a function of stackability

Pallet Overhang

Effect of pallet overhanging on compression strength of corrugated boxes

Rough Handling

• Mishandling including dented vertical edges on the container can result in as much as 50% decrease in the box compression strength when compared to the virgin container.

Conclusion

• Growing market has placed demands upon the corrugated case producers for better quality both in terms of strength and visual apperance.

• For achieving above points it become very essential to evaluate the performance parameters of corrugated boxes at every stage of production and converting.

• This should be done by adopting the correct procedure of testing of liner, medium and corrugated box with state of art equipments by following standard test methods.

THANKS