polymers - chemistry of he environment

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