Transcript MicrowavePowerP

Plastics in the Microwave Oven
CE 435
Presented by:
Daniel Fulcher
Christopher Hunter
Martin Schaefer
April 17, 2001
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
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
Home Meal Replacement
Packaging
HMR Packaging
• Crystallized polyethylene terephthalate (CPET)
• Polyphenylene oxide, high impact polystyrene
blend (PPO/HIPS)
CPET Morphology
• Heterochain, modified homopolymer with ~30%
Crystallinity
• Step growth condensation polymerization reaction of
terephthalic acid and ethylene glycol
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
CPET Properties
• Good O2 and CO2 barrier properties
• Acceptable water barrier properties
• Easily colored with black carbon
CPET Processing
• In 2000, 84 million pounds produced at ~.52 $/lb
• Eastman Chemical Company produces CPET resin
under the product name of VersaTray®
• Thermoformed
• Vacuum Snap-Back Thermoforming
CPET Processing
PPO/HIPS Morphology
• Fully miscible blended amorphous polymer
• Noryl® manufactured by General Electric Plastics
• Noryl® PPO/HIPS blend is approximately 25% PPO
and 75% HIPS by weight
PPO Morphology
• Heterochain homopolymer
• Created by a free-radical, step-growth,
oxidative-coupling polymerization
HIPS Morphology
• Grafted copolymer of cis-1,4-poly(1,3-butadiene) and
styrene monomer
• Polystyrene chains are atactic
• 2% to 15% by weight of polybutadiene
HIPS Morphology
• Polystyrene (PS) and polybutadiene phase separate
creating compartmentalized regions
• Polybutadiene forms small, dispersed globules within
the polymer structure
PPO/HIPS Properties
• Improvements in final blend properties are in direct
proportion to the amount of PPO added
• PPO is added to HIPS to increase temperature
resistance from approximately 180°F to 230°F
• Blending with HIPS improves PPO’s low resin flow
characteristics
PPO/HIPS Properties
• Small, dispersed globules of polybutadiene elastomer
within the PS improves the blend impact strength
• PPO improves the poor gaseous and water vapor
barrier properties of HIPS
• Easily colored with black carbon
PPO/HIPS Processing
• High intensity mixer required to ensure accurate
blending during extrusion
• Thermoforming on equipment designed for PS
• Thermoform-Fill-Seal process
HMR Covers
• Heat-seal the food containers
• Most widely used film is multi-layer polypropylene
• Adhesives cause complications in migration testing
• PP is a low cost packaging film ~.53$/lb
Food Storage Containers
Polypropylene (PP) Morphology
• Zieglar-Natta polymerization
• Isotactic is crystalline, atactic is amorphous
PP Chain Structure
• PP is a blend of atactic and isotactic
PP Properties
• Properties and processability determined by isotacticity
PP Processing
• 1550 million pounds produced in 2000 at ~ .53 $/lb.
• Injected or blow molded
• INSPIRE® PP produced by Dow Plastics
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
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
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
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%
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
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
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
Questions?
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.