vulcanization of polymers & biodegradable plastics
TRANSCRIPT
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Vulcanization of Vulcanization of Polymers & Polymers &
Biodegradable plasticsBiodegradable plastics
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Structure of natural rubberStructure of natural rubber
*Elastomer*Elastomer
*Derived from latex*Derived from latex
*Polymer of isoprene *Polymer of isoprene
*Molecular weight=100000-1000000*Molecular weight=100000-1000000
*Some include other materials*Some include other materials
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Chemical Properties of natural rubberChemical Properties of natural rubber
*Polyene
*C=C function e.g. addtion reactions
*Ozonolysis of rubber
*Pyrolysis of rubber
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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
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Process of VulcanizationProcess 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
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Methods of vulcanizationMethods of vulcanization
• vulcanization of tires- high pressure and temperature- compression molding
• Hot air vulcanization• Microwave heated vulcanization
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Physical Properties VS Structure
*Physical properties
-non-sticky, not easy to deform when warm, not brittle when cold , elastic
*Relationship with structure- crosslinkage
-polymer chains cannot move independently
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Uses of vulcanized rubberUses of vulcanized rubber*Industrial products
- tires and tubes
*General rubber goods (GRG)
-rubber boots
*Manufacturing
-belts, matting,flooring
*Textile applications
-rubber fiber
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Biodegradable plasticsBiodegradable plastics
• Decompose in natural aerobic and anaerobic environments
• Metabolism by microorganisms• Two forms of biodegradable plastics-injection molded, films
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Disposing of Non-degradable plasticsDisposing 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
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Degradable PlasticsDegradable PlasticsThe Three important categories:
1. biopolymers
2. synthetic biodegradable plastics
3. photodegradable plastics
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BiopolymersBiopolymers
*Input materials: renewable or synthetic
*Four main bases:
-sugar, starch, cellulose, synthetic materials (petroleum)
*Functional group to show biodegradability
- ester bonds
*Example: Polyhydroxyalkanoates
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Polyhydroxyalkanoates (PHAs)Polyhydroxyalkanoates (PHAs)
*Naturally occuring form of polyester
*More than a hundred PHA polymers
*Two examples:
-Polyhydroxybutyric ( PHB )
-Polyhydroxyoctanoate ( PHO )
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Example of PHAs: PHBExample 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
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Synthetic Biodegradable PlasticsSynthetic Biodegradable Plastics
• By synthetic biodegradable polymer• Funtional groups: esters, anhydrides,
orthoesters, amides,etc• Synthesized by ring opening polymerization
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Biodegradable polymersBiodegradable polymers
*Polyanhydrides
-functional group: anhydride group
-by melt condensation polymerization
-uses: short-term release of drugs, bioactive agent, controlled drug delivery devices.
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Biodegradable polymersBiodegradable polymers
• Graft polymers
-funtional group: carbonyl group-form by amino acid halide and polymers
with carbonyl group-uses: medical issues
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Decomposition of Biodegradable polymers by Decomposition of Biodegradable polymers by microbesmicrobes
• 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
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Advantages of using biodegradable polymersAdvantages of using biodegradable polymers
• Reduce the disposal of non-degradable products
• Reduce the cost of building up landfills• Reduce the problems of toxicity
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Photodegradable PlasticsPhotodegradable Plastics
• Decompose when exposed to sunlight• Functional group : Aromatic-based• Examples: Polyvinyl Chloride, Polyamides,
Polystyrene• Uses: Photodegradable plastic bags
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Limitation of Photodegradable plasticsLimitation 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
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ReferencesReferenceshttp://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