Search results
Results From The WOW.Com Content Network
One of the simplest repeat units is that of the addition polymer polyvinyl chloride, -[CH 2-CHCl] n-, whose repeat unit is -[CH 2-CHCl]-.In this case the repeat unit has the same atoms as the monomer vinyl chloride CH 2 =CHCl.
Polyvinyl chloride is formed in flat sheets in a variety of thicknesses and colors. As flat sheets, PVC is often expanded to create voids in the interior of the material, providing additional thickness without additional weight and minimal extra cost (see closed-cell PVC foamboard ).
Vinyl polymers are subject of several structural variations, which greatly expands the range of polymers and their applications. With the exception of polyethylene, vinyl polymers can arise from head-to-tail linking of monomers, head-to-head combined with tail-to-tail, or a mixture of those two patterns. Additionally the substituted carbon center in such polymers is stereogenic (a "chiral center")
Polymers that are formed by free-radical mechanisms, such as polyvinyl chloride are usually atactic. [citation needed] Due to their random nature atactic polymers are usually amorphous. [citation needed] In hemi-isotactic macromolecules every other repeat unit has a random substituent. [citation needed]
Vinyl chloride is an organochloride with the formula H 2 C=CHCl. It is also called vinyl chloride monomer (VCM) or chloroethene. It is an important industrial chemical chiefly used to produce the polymer polyvinyl chloride (PVC). Vinyl chloride is a colourless flammable gas that has a sweet odor and is carcinogenic.
A polymer which contains only a single type of repeat unit is known as a homopolymer, while a polymer containing two or more types of repeat units is known as a copolymer. [22] A terpolymer is a copolymer which contains three types of repeat units. [23] Polystyrene is composed only of styrene-based repeat units, and is classified as a homopolymer.
Polyvinyl fluoride (PVF) or –(CH 2 CHF) n – is a polymer material mainly used in the flammability-lowering coatings of airplane interiors and photovoltaic module backsheets. [2] It is also used in raincoats and metal sheeting.
In polymer chemistry, radical polymerization (RP) is a method of polymerization by which a polymer forms by the successive addition of a radical to building blocks (repeat units). Radicals can be formed by a number of different mechanisms, usually involving separate initiator molecules .