chemassignment2 ppt

Manufacturing PVC(Polyvinyl chloride) product

Processes

PetroleumVCM(Vinyl

chloride monomer)

PVC(Polyvinyl chloride) Products

Cracking and Chlorination Polymerization Molding

Cracking and Chlorination

• Petroleum heated with catalyst, high pressure and without air

• Produce Ethene and “light” hydrocarbons• Chlorination to ethene • Thermal cracking • ChloroetheneVinyl chloride monomer

Polymerization of PVC

• Condition : UV light or heat and pressure• Organic peroxide compounds(initiator)• Monomer(VCM)Addition polymerizationFree radical addition

Mechanism

• Chain initiation :

• Chain propagation :

• Chain termination :

Polymerization of PVC

• Molecule masses vary with the temperature• Exothermic reaction• Strong intermolecular forceDipole-dipole between polymer chains

Adding additive

• Plasticizer(塑化劑 )DEHP(di-2-ethyl hexyl phthalate)• Filler• Stabilizer• Dyes or coloring

C6H4(C8H17COO)2 Bis(2-ethylhexyl)phthalate(BEHP)

Molding

• Using heat to soft the plastic, pressure to squeeze and place to a mold, then cool down

Injection molding(a)Compression molding(b)

a b