Vulcanization of Vulcanization of Polymers & Polymers &

Biodegradable plasticsBiodegradable plastics

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

Chemical Properties of natural rubberChemical 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 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

Methods of vulcanizationMethods of vulcanization

• vulcanization of tires- high pressure and temperature- compression molding

• Hot air vulcanization• Microwave heated vulcanization

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

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

Biodegradable plasticsBiodegradable plastics

• Decompose in natural aerobic and anaerobic environments

• Metabolism by microorganisms• Two forms of biodegradable plastics-injection molded, films

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

Degradable PlasticsDegradable PlasticsThe Three important categories:

1. biopolymers

2. synthetic biodegradable plastics

3. photodegradable plastics

BiopolymersBiopolymers

*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)Polyhydroxyalkanoates (PHAs)

*Naturally occuring form of polyester

*More than a hundred PHA polymers

*Two examples:

-Polyhydroxybutyric ( PHB )

-Polyhydroxyoctanoate ( PHO )

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

Synthetic Biodegradable PlasticsSynthetic Biodegradable Plastics

• By synthetic biodegradable polymer• Funtional groups: esters, anhydrides,

orthoesters, amides,etc• Synthesized by ring opening polymerization

Biodegradable polymersBiodegradable polymers

*Polyanhydrides

-functional group: anhydride group

-by melt condensation polymerization

-uses: short-term release of drugs, bioactive agent, controlled drug delivery devices.

Biodegradable polymersBiodegradable 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 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

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

Photodegradable PlasticsPhotodegradable Plastics

• Decompose when exposed to sunlight• Functional group : Aromatic-based• Examples: Polyvinyl Chloride, Polyamides,

Polystyrene• Uses: Photodegradable plastic bags

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

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