1. Vulcanization of Polymers & Biodegradable plastics

2. Structure of natural rubber
*Elastomer
*Derived from latex
*Polymer of isoprene
*Molecular weight=
*Some include other materials

3. Chemical Properties of natural rubber
*Polyene
*C=C function e.g. addtion reactions
*Ozonolysis of rubber
*Pyrolysis of rubber

4. Vulcanization *Charles Goodyear (1800-1860)
*Chemical process -convert rubber,polymers into durable material
*Irreversible
*Cross-linkage -between polymer chains with sulphur
*Benefit the industrial world

5. Process of Vulcanization
Cure sites -attractive to sulphur atoms
Break down of 8-membered ring of sulphur
Attachment of sulphur atoms to rubber molecule -one or more suphur atoms can be attached
Reach the cure site of another rubber molecule

6. Methods of vulcanization
vulcanization of tires - high pressure and temperature - compression molding
Hot air vulcanization
Microwave heated vulcanization

7. Physical Properties VS Structure
-non-sticky, not easy to deform when warm, not brittle when cold , elastic
*Relationship with structure - crosslinkage
-polymer chains cannot move independently

8. Uses of vulcanized rubber
*Industrial products
- tires and tubes
*General rubber goods (GRG)
-rubber boots
*Manufacturing
-belts, matting,flooring
*Textile applications
-rubber fiber

9. Biodegradable plastics
Decompose in natural aerobic and anaerobic environments
Metabolism by microorganisms
Two forms of biodegradable plastics
-injection molded, films

10. Disposing of Non-degradable plastics
*Problems raising:
- vegetation - blighting heritage areas - blocking drains - destroying natural habitat
*Problems solving
- mixing dirty polymers - crafts with plastic bags - replace by degradable plastic products

11. Degradable Plastics 1. biopolymers 2. synthetic biodegradable plastics
The Three important categories:
1. biopolymers
2. synthetic biodegradable plastics
3. photodegradable plastics

12. Biopolymers *Input materials: renewable or synthetic *Four main bases:
-sugar, starch, cellulose, synthetic materials (petroleum)
*Functional group to show biodegradability
- ester bonds
*Example: Polyhydroxyalkanoates

13. Polyhydroxyalkanoates (PHAs)
*Naturally occuring form of polyester
*More than a hundred PHA polymers
*Two examples:
-Polyhydroxybutyric ( PHB )
-Polyhydroxyoctanoate ( PHO )

14. Example of PHAs: PHB
*Produced by microorganisms - Ralstonia Eutrophus, Bacillus Megaterium
*Stiff, highly crystalline polymer
*Limitation in the production
- brittleness
- high cost
*Uses
- packaging
-beverage containers

15. Synthetic Biodegradable Plastics
By synthetic biodegradable polymer
Funtional groups: esters, anhydrides, orthoesters, amides,etc
Synthesized by ring opening polymerization

16. Biodegradable polymers
*Polyanhydrides
-functional group: anhydride group
-by melt condensation polymerization
-uses: short-term release of drugs, bioactive agent, controlled drug delivery devices.

17. Biodegradable polymers
Graft polymers
-funtional group: carbonyl group
-form by amino acid halide and polymers with carbonyl group
-uses: medical issues

18. Decomposition of Biodegradable polymers by microbes
Break down into simpler compound
Aerobic conditions
- consume oxygen
- into carbon dioxide and water
Anaerobic conditions
-do not consume oxygen
- into methane and carbon dioxide

19. Advantages of using biodegradable polymers
Reduce the disposal of non-degradable products
Reduce the cost of building up landfills
Reduce the problems of toxicity

20. Photodegradable Plastics
Decompose when exposed to sunlight
Functional group : Aromatic-based
Examples: Polyvinyl Chloride, Polyamides, Polystyrene
Uses: Photodegradable plastic bags

21. Limitation of Photodegradable plastics
Not easy to expose under sunlight in landfill
- cover by other waste products
Possible byproducts
- toxic, harmful environmental problems
Takes long time to decay
- pose hazard to wild life
- contribute to solid waste volume

22. References
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