Polyacrylonitrile is used for very few products an average consumer would be familiar with, except to make another polymer, carbon fiber. Homopolymers of polyacrylonitrile have been uses as fibers in hot gas filtration systems, outdoor awnings, sails for yachts, and even fiber reinforced concrete. But mostly copolymers containing polyacrylonitrile are used as fibers to make knitted clothing, like socks and sweaters, as well as outdoor products like tents and such. If the label of some piece of clothing says "acrylic", then it's made out of some copolymer of polyacrylonitrile. Usually they're copolymers of acrylonitrile and methyl acrylate, or acrylonitrile and methyl methacrylate:

Also, sometimes we make copolymers of acrylonitrile and vinyl chloride. These copolymers are flame-retardant, and the fibers made from them are called modacrylic fibers.

But the slew of copolymers of acrylonitrile doesn't stop there. Poly(styrene-co-acrylonitrile) (SAN) and poly(acrylonitrile-co-butadiene-co--styrene) (ABS), are used as plastics.

SAN is a simple random copolymer of styrene and acrylonitrile. But ABS is more complicated. It's made by polymerizing styrene and acrylonitrile in the presence of polybutadiene. Polybutadiene has carbon-carbon double bonds in it, which can polymerize, too. So we end up with a polybutadiene chain with SAN chains grafted onto it, like you see below.

ABS is very strong and lightweight. It is strong enough to be used to make automobile body parts, but it is so light that Wassana can lift this front bumper fascia over her head with only hand! Using plastics like ABS makes automobiles lighter, so they use less fuel, and therefore they pollute less.

ABS is a stronger plastic than polystyrene because of the nitrile groups of its acrylonitrile units. The nitrile groups are very polar, so they are attracted to each other. This allows opposite charges on the nitrile groups to stabilize each other like you see in the picture on the left. This strong attraction holds ABS chains together tightly, making the material stronger. Also the rubbery polybutadiene makes ABS tougher than polystyrene.

Polyacrylonitrile is a vinyl polymer, and a derivative of the acrylate family of polymers. It is made from the monomer acrylonitrile by free radical vinyl polymerization.

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Ammar Ghasemian Azizi ; e-mail: ammar5ghasemian@yahoo.com or azizi@fmplastics.nl ; Tel : +98 912 386 2365

پلی آکریلو نیتریل

Polyurethanes are the single most versatile family of polymers there is. Polyurethanes can be elastomers, and they can be paints. They can be fibers, and they can be adhesives. They just pop up everywhere. A wonderfully bizarre polyurethane is spandex.

Of course, polyurethanes are called polyurethanes because in their backbones they have a urethane linkage.

The picture shows the a simple polyurethane, but a polyurethane can be any polymer containing the urethane linkage in its backbone chain. More sophisticated polyurethanes are possible, for example:

Polyurethanes are made by reacting diisocyanates with di-alcohols. To find out how, click here.

Sometimes, the dialcohol is replaced with a diamine, and the polymer we get is a polyurea, because it contains a urea linkage, rather than a urethane linkage. But these are usually called polyurethanes, because they probably wouldn't sell well with a name like polyurea.

Polyurethanes can hydrogen bond very well, and thus can be very crystalline. For this reason they are often used to make block copolymers with soft rubbery polymers. These block copolymers have properties of thermoplastic elastomers.

Spandex

One unusual polyurethane thermoplastic elastomer is spandex, which DuPont sells under the trade name Lycra. It has both urea and urethane linkages in its backbone. What gives spandex its special properties is the fact that it has hard and soft blocks in its repeat structure. The short polymeric chain of a polyglycol, usually about forty or so repeats units long, is soft and rubbery. The rest of the repeat unit, you know, the stretch with the urethane linkages, the urea linkages, and the aromatic groups, is extremely rigid. This section is stiff enough that the rigid sections from different chains clump together and align to form fibers. Of course, they are unusual fibers, as the fibrous domains formed by the stiff blocks are linked together by the rubbery soft sections. The result is a fiber that acts like an elastomer! This allows us to make fabric that stretches for exercise clothing and the like.

this page sponsored by BAYER MATERIAL SCIENCE for http://pslc.ws/

Ammar Ghasemian Azizi ;

the reference of this text is : http://pslc.ws/

e-mail : azizi@fmplastics.nl or ammar5ghasemian@yahoo.com

Tel : +98 912 386 2365

Polycarbonate, or specifically polycarbonate of bisphenol A, is a clear plastic used to make shatterproof windows, lightweight eyeglass lenses, and such. General Electric makes this stuff and sells it as Lexan.

Polydicyclopentadiene is a polymer used to make really, really big things in one piece. And by big, I mean BIG. With polydicyclopentadiene you can make a whole tractor cab in one piece, or a whole satellite dish antenna. That's not good enough for you? Then how about a 1500 gallon storage tank for dangerous chemicals? With polydicyclopentadiene that's no problem. But the very first use for it was the cowlings of snowmobiles, again molded in one piece. This was because it has very good impact resistance at low temperatures, where a lot of other polymers become brittle.

Polydicyclopentadiene is made by a nifty reaction called ring-opening metathesis polymerization (ROMP) from the monomer endo-dicyclopentadiene. Click here if you want to see the monomer in 3-D.

But it's not done yet! There's a double bond left in the bottom ring, as you can see in the picture of polydicyclopentadiene. These can undergo vinyl polymerization, to give us a crosslinked thermoset material.

This thermoset is good stuff, but you can't mold a thermoset. So how do we make anything from it? The answer is to make it in chunks that are already shaped like we want them. The fancy name for this is called reaction injection molding or RIM for short. Put simply, we fill a mold full of the monomer, and polymerize it in the mold. That's how we can make products from thermosets.

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Ammar Ghasemian Azizi ; the reference of this text is : http://pslc.ws/

e-mail : azizi@fmplastics.nl or ammar5ghasemian@yahoo.com

Tel : +98 912 386 2365

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Poly(ether sulfones get their name because they have ether groups and sulfone groups in their backbone chains. PES polymers have high glass transition temperatures, or T_g's, because the sulfone groups are so stiff. In fact, poly(phenyl sulfone) is so stiff that it doesn't have a glass transition temperature! It stays hard as a rock right up until it decomposes at around 500 ^oC.

This is bad. This means that it can't be processed. In order to make it processable, we have to make that chain a little more flexible so the polymer will soften at a reasonable temperature. We do this by putting flexible groups in the backbone chain, namely ether linkages.

Udel^TM uses a bisphenol A derived linkage to make the chain flexible. You'll notice that this polymer has two ether linkages in the repeat unit. For this reason Udel^TM is more properly called a poly(ether ether sulfone).

We call this a bisphenol A linkage because it's based on the monomer bisphenol A, but more about that later.

This brings the Tg down to 190^oC. By playing around and using different kinds of flexible groups we can alter the Tg further. If we use a less flexible linkage, the Tg jumps to 230 ^oC.

This PES is made by Imperial Chemical Industries (ICI), and they call it by the romantic name of Polyether Sulfone 200 P^TM. You'll notice that unlike Udel^TM, this polymer has only one ether linkage between sulfone groups. This makes the chain stiffer and the Tg higher.

But you ask, "How do we make a wonderful poly(ether sulfone)?" Like this: One reacts the sodium salt of bisphenol A (remember bisphenol A?) and reacts it with di-para-fluorophenylsulfone in a solvent like dimethylsulfoxide (DMSO) at between 130 and 160 ^oC.

And that gets us a poly(ether sulfone)!

Referece of tihs text is : http://pslc.ws/

for more info. you can see this site :

 http://www.tangram.co.uk/TI-Polymer-PES.html ( good info. about PES )