polymers - chemistry of he environment

celluloid

celluloid

one of the earliest synthetic polymers

plasticizers

• added to provide flexibility

• earliest were PCBs

phthalate

environmentally persistent, resistant to treatment processes, prone to undergo bioaccumulation

polyethylene

• simplest, cheapest, most common synthetic polymer

• monomer has double bonded carbons; polymer has single bonded carbons

high density polyethylene (HDPE)

• mostly linear molecules that pack closely together

• used for milk jugs, bottle caps, toys, etc.

low density polyethylene (LDPE)

• more highly branched form of polyethylene

• used to make plastic bags, plastic films, electric wire insulation, etc.

thermoplastic polymers

• softened by heat and pressure

• Can be repeatedly melted down and remolded

• Molecules can slide past one another under heat and pressure

thermosetting polymers

• Heated to harden permanently when they were formed

• Strong heating causes them to discolor and decompose

addition polymerization

monomers add to one another in such a way that the resulting molecule contains all atoms that are present in the monomers

pendant groups

groups attached to carbon chain backbone

elastomers

• polymers that will elongate when subjected to a tensile force

• often used as binders in paints

vulcanization

Natural rubber is soft and tacky when hot. Reacting it with sulfur cross-links the polyisoprene and makes the rubber harder

polybutadiene

• common example of synthetic rubber

neoprene

• very similar to polybutadiene, but contains chlorine in the place of the methyl group

• used to make gasoline hoses

styrene-butadiene rubber (SBR)

• copolymer of styrene and butadiene

• tougher and more resistant to oxidation than natural rubber

• used to make tires

condensation polymerization

small molecules such as water, alcohols, ammonia, or HCl are released as by-products

nylon

• polyamide

• mostly manufactured as fibers

polyesters

condensation polymers made from molecules containing alcohol and carboxylic acid functional groups with ester linkage

Polyurethanes

• similar to nylons

• may be elastomers or tough and rigid, depending on the monomers used

• used in foam rubber, skate wheels, and tough furniture finishes

silicones

polymers that contain silicon rather than carbon

properties of polymers

• high molar masses

• very strong IMFs

• strong fibers

• viscous liquids

crystalline polymers

• molecules of the polymer line up in neat rows forming fibers of great strength

• tend to be very rigid

Amorphous polymers

• molecules that are randomly tangled

• tend to be soft and rubbery

glass transition temperature (Tg)

temperature above which the polymer is tough and rubbery, and below which it is like glass―hard, brittle, and stiff