Plastics in the Microwave Oven CE 435

2. Plastics in the Microwave OvenCE 435 Presented by: Daniel Fulcher Christopher Hunter Martin Schaefer April 17, 2001

3. Introduction • U.S. households owning a microwave oven increased from 15% in 1980 to 78% by 1989 • Gorman’s New Product News reported the number of new microwave product introductions increased from 278 in 1986 to almost 1000 in 1988 • Microwave frequency of ~2.45 GHz ensures effective penetration into the food and even food heating • Annual revenues of 3 billion dollars

4. Scope • Max temperatures of 230oF for microwave ovens and 400oF for dual oven applications • Containers should be sturdy, rigid in shape and capable of supporting its contents • Limited migration of additives, colorants, or fillers • Federal Food and Drug Administrative approval

5. Home Meal Replacement Packaging

6. HMR Packaging • Crystallized polyethylene terephthalate (CPET) • Polyphenylene oxide, high impact polystyrene blend (PPO/HIPS)

7. CPET Morphology • Heterochain, modified homopolymer with ~30% Crystallinity • Step growth condensation polymerization reaction of terephthalic acid and ethylene glycol

8. CPET Properties • Crystallization of PET increases the upper temperature resistance from 230°F to 400°F • Balance between strength properties and temperature resistance • Crystallinity of 28%-32% and an intrinsic viscosity of .85 to .95 • Two-layer structure of CPET and APET

9. CPET Properties • Good O2 and CO2barrier properties • Acceptable water barrier properties • Easily colored with black carbon

10. CPET Processing • In 2000, 84 million pounds produced at ~.52 $/lb • Eastman Chemical Company produces CPET resin under the product name of VersaTray® • Thermoformed • Vacuum Snap-Back Thermoforming

11. CPET Processing

12. PPO/HIPS Morphology • Fully miscible blended amorphous polymer • Noryl® manufactured by General Electric Plastics • Noryl® PPO/HIPS blend is approximately 25% PPO and 75% HIPS by weight

13. PPO Morphology • Heterochain homopolymer • Created by a free-radical, step-growth, oxidative-coupling polymerization

14. HIPS Morphology • Grafted copolymer of cis-1,4-poly(1,3-butadiene) and styrene monomer • Polystyrene chains are atactic • 2% to 15% by weight of polybutadiene

15. HIPS Morphology • Polystyrene (PS) and polybutadiene phase separate creating compartmentalized regions • Polybutadiene forms small, dispersed globules within the polymer structure

16. PPO/HIPS Properties • Improvements in final blend properties are in direct proportion to the amount of PPO added • PPO is added to HIPS to increase temperature resistance from approximately 180°F to 230°F • Blending with HIPS improves PPO’s low resin flow characteristics

17. PPO/HIPS Properties • Small, dispersed globules of polybutadiene elastomer within the PS improves the blend impact strength • PPO improves the poor gaseous and water vapor barrier properties of HIPS • Easily colored with black carbon

18. PPO/HIPS Processing • High intensity mixer required to ensure accurate blending during extrusion • Thermoforming on equipment designed for PS • Thermoform-Fill-Seal process

19. HMR Covers • Heat-seal the food containers • Most widely used film is multi-layer polypropylene • Adhesives cause complications in migration testing • PP is a low cost packaging film ~.53$/lb

20. Food Storage Containers

21. Polypropylene (PP) Morphology • Zieglar-Natta polymerization • Isotactic is crystalline, atactic is amorphous

22. PP Chain Structure • PP is a blend of atactic and isotactic

23. PP Properties • Properties and processability determined by isotacticity

24. PP Processing • 1550 million pounds produced in 2000 at ~ .53 $/lb. • Injected or blow molded • INSPIRE® PP produced by Dow Plastics

25. Regulations • The code of federal regulations provides guidance on polymers allowed in the direct contact of food. • Article 177 presents data specific to each polymer • Composition specifications, allowable coatings, modifiers, emulsifiers, and testing criteria

26. CPET Regulations • Article 177.1630 • Emulsifier < 2.0 percent of the dry weight • Additional substances allowed must be generally recognized as safe by the FDA • < 0.02 mg/in2 of chloroform-soluble extractives for heptane and distilled water migration tests

27. PPO/HIPS Regulations • Articles 177.1810 and 177.2460 • PS: molecular weight > 29,000 and soluble in toluene • Maximum extractable fractions of chloroform in distilled water and 50% ethanol are 0.0039 mg/cm2 • PPO: intrinsic viscosity > 0.30 deciliter/gram • < 0.02 weight percent extractable with n-heptane

28. PP Regulations • Article 177.1520 • Density of 0.880 -0.913 and m.p. 160 C - 180 C • Maximum extractable fraction of n-hexane is 6.4% • Maximum soluble fraction of xylene is 9.8%

29. Testing and Health Issues • No specific requirements for microwave food containers • FDA provides guidance for proper microwave migration testing protocols • Migration tests using food simulants (e.g. cooking oil) • Migration testing at the highest cooking temperature

30. Testing and Health Issues • Size and type of food, cooking time, and food geometry play part in the maximum temperature • Consult with FDA before deciding on a migration testing protocol for microwave only containers • Plasticizers have been linked to endocrine disorders • Further study needed to determine possible health risks due to migration of polymer additives

31. Conclusion • Primary polymer materials: CPET, PPO/HIPS, PP • Applications ranging from single use HMR to repeated use food storage containers • Essentially no health risks • Cost effective containers

32. Questions?

33. References annotated in the Polymers in the Microwave written report. 1.Rubbright, H.A., Davis N.O., The Microwave Decade, Packaging Strategies, West Chester, PA, 1989. 2.Becker, R. “As a Matter of Fact.” Chem Matters April 2000: Volume 18 Number 2. Online. Available HTTP: www.acs.org/education/curriculum/chemmatt.html 3.Dow Plastics, Polypropylene Resins Molding Guide. The Dow Chemical Company, 1998. 4.Brady, A.L., Marsh, K.S., The Wiley Encyclopedia of Packaging Technology. New York: John Wiley and Sons, Inc., 1997. 5.Hanlon, J.F., Kelsey, R.J., Forcinio, H.E., Handbook of Package Engineering. Technomic Publishing Company, Inc., 1998. 6.Selke, S.E., Understanding Plastics Packaging Technology. Cincinnati: Hanser/Gardner Publications, Inc., 1997. 7.1999 CFR Title 21 Food and Drugs, Volume 3. Part 177 Indirect Food Additives: Polymers. Online. Available HTTP: www.access.gpo.gov/nara/cfr/waisidx_99/21cfr177_99.html 8.Eastman Chemical Company. Online. Available HTTP: www.eastman.com/productfiles/prod0018.html 9.General Electric Company. Plastics Division. Online. Available HTTP: www.geplastics.com/resins/techsolution/technifacts.html 10.Department of Polymer Science, University of Southern Mississippi, Macrogalleria, 1996. Online. Available HTTP: www.psrc.usm.edu/macrog/floor2.html 11.Modern Plastics Encyclopedia. New York: McGraw-Hill Companies, Inc., 2001. 12.U.S. Food and Drug Administration. Online. Available HTTP: vm.cfsan.fda.gov/~dms/opa-pmnc.html 13.U.S. Food and Drug Administration. FDA Consumer Magazine, Volume 97, Number 11. Maryland; FDA, 1998.