NCloeter Final Presentation ENMA499 Final

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Maximizing Ceramic Filler in a Composite with a Polymer

MatrixNathan Cloeter

Materials Science and EngineeringSenior Laboratory Project

Fall 2014

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Overview

Overview Background Goals Procedure Results Conclusions Summary

1. Background0 Why0 How

2. Goals3. Procedure4. Results

0 Mixing0 Testing

5. Conclusions6. Project Summary

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Background

0Cavities form in our teeth0Different Materials have been

developed to fix this.0 Each has a weakness.

0Current composites0 Ceramic filler with polymer

matrix.0 Current ceramic is silica0 Lack of durability (10 years)


Image Courtesy of studiodentaire.com

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Titania FillerSilica (SiO2)0 Commercial composites use agglomerated silica.

0 Nanosilica and microsilica (~0.2 micron) are easier to mix.

New Material needs to be selected0 Titania (TiO2) and alumina (Al2O3) have more favorable

properties.0 E Alumina (340 MPa)>E Titania (240 MPa)>E Silica (70 MPa)

0 Alumina is the strongest, but samples turn gray.0 Titania, silica do not have this issue.

0 Percentage of filler volume needs to be high enough for modulus that compares with enamel.

0 After certain amount of filler is added to the matrix, it becomes too difficult to add more.


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MatrixBisGMA0 2,2-Bis [4-(2-Hydroxy-3-Methacryloxypropoxy) Phenyl] Propane0 Monomer that is commonly used as a polymer matrix in dental

composite research due to it being able to adhere to enamel.TEGDMA0 tri(ethylene-glycol) dimethacrylate0 Added to BisGMA matrix to lower viscosity of the matrix.BPO0 Benzoyl Peroxide0 Used as a heat initiator for polymerization.Matrix is a 50/50 mixture of BisGMA-TEGMA with 1% BPO added as an initiator.


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Silane0 MPTMS

0 Methacryloxypropyltrimethoxysilane0 Previously used: (3-

Mercaptopropyl)trimethoxysilane0 New Silane has a higher amount of

agglomeration compared to the previous type.

0 Covalent Crosslinking across surface of filler.0 Siloxane surface is created.0 Surface becomes hydrophilic.0 Increases surface hardness.0 Downside: causes agglomeration.

0 One gram of MPTMS added for every ten of Titania.


Image Courtesy of Cornell.edu

Image Courtesy of UCDavis.edu

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Solvents

0Protic Solvents0 Solvent that has a hydrogen

atom bound to an oxygen (hydroxyl) or nitrogen (amine).0Acetic Acid0 Isopropyl Alcohol


0Change from previous semester of aprotic solvents.0 New MPTMS as silane requires

acetone in control to give a base reading.

Solvent Chemical Formula

Boiling Point ( C)ᵒ

pKa Polarity FDA Limit

Acetic Acid 118.1 20 6.2 5000 ppm

Isopropyl Alcohol

82.5 16.5 3.9 5000 ppm

Acetone 56 20 5.1 5000 ppm

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Goals1. Overall Goal: Reach high enough volume percent

of filler where mechanical properties are favorable to replace the current commercial model.0 Should be attainable with volume percent of titania > 60%.0 Through density calculations, this means weight percent of

titania > 80%.

2. Evaluate effect of diluents on mixing mechanical properties after curing.0 See if any are capable of being used to raise filler% more

effectively than any of the others.0 Test effectiveness of polar protic solvents to see if effective.

Introduction Background Goals Procedure Results Conclusions Summary

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Procedure0 Silanize nanopowder with MPTMS0 Washed powder with ethanol to remove MPTMS.0 Add BPO as an initiator to Pre-mixed BisGMA-TEGMA matrix0 Add 3 mL of solvent for every two grams of matrix.0 Add powder in stepwise process to matrix, mechanically stirring

each time until uniform.0 Store in vacuum to let solvent evaporate from mixture.0 Pack into molds.0 Cure in an oven at 80 degrees Fahrenheit.0 Polish the samples.0 Perform mechanical tests.


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Result of adding diluent


Diluent Added

Behavior During Sample Prep?

Weight Percent Achieved (60/70)

Notes after curing

No Diluent Stiff and hard to mix

55 wt% Is polishable. Some porosity.

Acetic Acid Unable to fully remove solvent.

(Yes, No) Extremely porous. Difficult to polish.

Isopropyl Alcohol

Had difficulty mixing.

(Yes, No) Some pores. Not as bad as acetic acid.

Acetone Behaved Normally

(Yes, Yes*) Came out the best.

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Modulus/Flexural Strength


o Despite having the same weight percent of filler, Fall 2 doesn’t perform as well.o High porosity affected results.o Only one sample survived

o Isopropyl alcohol had samples that had the potential to work the best.o Extremely sporadic.

o Flexural Strength is the highest due to dependence on max load that is applied.

Sample Average Flexural Modulus

Standard Deviation

Average Flexural Strength

Standard Deviation

Fall 2 2.55 GPa N/A 31.5 Mpa N/A

Fall 3 4.87 GPa 0.208 62.9 MPa 11.47

Fall 4 6.36 GPa 0.133 55.0 MPa 0.67

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Toughness/Hardness

o Similar trend of results compared to last slide.o Isopropyl alcohol has much higher levels of toughness, with yet again a

high deviation.o The hardness levels seem to be constant with each sample.


Sample Average Toughness

Standard Deviation

Average Hardness

Standard Deviation

Fall 2 204.4 MPa N/A 42.5 HV 9.70

Fall 3 422.9 MPa 140.8 58.3 HV 9.55

Fall 4 244.1 MPa 13.09 63.1 HV 8.46

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Conclusions


• Acetone was the most promising diluent.• Still haven’t reached the 80 weight percent goal.• None of the solvents could be used to reach levels

already achieved in earlier semesters.• Includes control.• May be a result of new silane.

• Directions for future research:• Reduce amount of silane used.• 50-50 mixture of different solvent types.• Find a protic solvent that evaporates more effectively.• Change ratio of polymer matrix.

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Project Summary

Introduction Approach Design Experimental Prototype Conclusions Summary

• Goal is to reach eighty weight percent filler for sample.• Attempted to add diluent to the sample to increase filler

percent.• Unable to reach levels from previous semester.• Due to combination of new silane, as well as the new solvents being

ineffective.

• Could not get samples above 60 weight %. • Potential is there to raise weight percent, as well as change other

areas to raise results.

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References

Introduction Approach Design Experimental Prototype Conclusions Summary

0 Wang Y, James J. Lee, Lloyd IK, Wilson OC, Rosenblum M, and Thompson V. "High Modulus Nanopowder Reinforced Dimethacrylate Matrix Composites for Dental Cement Applications." Journal of Biomedical Materials Research Part A 82A.3 (2003): 651-57.

0 Chen Q, Zhao Y, Wu W, Xu T, Fong H. "Fabrication and Evaluation of Bis-GMA/TEGDMA Dental Resins/ Composites Containing Halloysite Nanotubes." Dent Mater 28.10 (2007): 1071-079.

0 Chen YH, Lloyd IK. "Mechanical Properties of Dental Composites with Mixed Alumina and Silica Fillers." Thesis. University of Maryland, n.d. Print.

0 Chan, K. S., Y. -D. Lee, D. P. Nicolella, B. R. Furman, S. Wellingho , and R. Rawls. ff"Improving Fracture Toughness of Dental Nanocomposites by Interface Engineering and Micromechanics." Engineering Fracture Mechancis 74 (2007): 1857-871.

0 Ferracane JL. "Resin Composite—State of the Art." Dental Materials 27 (2011): 29-38.

0 Udomphol, T. "Laboratory 7: Bend Testing." Suranaree University of Technology.0 England G. "Vickers Hardness Test." GordonEngland. Surface Engineering Forum

NCloeter Final Presentation ENMA499 Final

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