Vulcanization of Polymers & Biodegradable plastics

Structure of natural rubber *Elastomer *Derived from latex *Polymer of isoprene *Molecular weight=100000-1000000 *Some include other materials

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

References http://www.ideaconnection.com/solutions/4349-Non-biodegradable-plastic-waste.html http://www.o2.org/ideas/cases/biopolymers.html http://www1.eere.energy.gov/biomass/pdfs/production_polymers.pdf http://www.firstscience.com/home/articles/technology/plastics-you-could-eat-recyling-page-2- 1_1528.html http://www.bookrags.com/research/photodegradable-plastic-enve-02/ http://www.bionomicfuel.com/7-applications-for-synthetic-biodegradable-polymers/#more-320 http://www.globe-net.com/articles/2011/april/4/disposal-options-for-biodegradable-plastics.aspx http://www.pharmainfo.net/pharma-student-magazine/controlled-drug-delivery-biodegradable