As today its the first day ,I will be explaining just the basics of "Plastics" As its a wide term and sky is the limit for plastics , there an endless number of resin and granual bases but we will get familier with the basics ,so Today will provide a basic review of polymer chemistry, with emphasis on the distinctions between various structures and their influence on the Engineering of Plastics
The "Chemistry of Polymer " The chemical structure and the nature of plastics materials have a significant relationship not only to the properties of the "Plastic" but to the ways in which it can be processed, designed,or otherwise translated into an end-product.
Basically, all polymers are formed by the creation of chemical linkages between relatively small molecules monomers to form very large molecules or polymers; the same idea as connecting boxes on a train track to form a train,the boxes being monomers and the train a polymer. Like boxes, the molecules must have the ability to be coupled at either end .
Actually, in polymer formation, the process is more like forming many, many trains in a rail road yard simultaneously from the boxes available in the yard in a competitive fashion,so that the switching engine that moved the fastest would form the longest train while the slowest switching engine would form the shortest train, due to depletion of the available rolling stock by the concurrent train-forming process ,The train-forming process of polymerization comes to a stowhen factors prevent any additional boxcars from beingadded to any of the trains being assembled.Thus, we ultimately end up with trains having a variety of lengths, yet all composed of the same kinds of boxes. The rail road analogy described above is basically what happens in an “addition” type of polymerization.
The above process is characterized by the simple combination of molecules without the generation of any by- products formed as a result of the combination. The molecules that combine do not decompose to produce fission products which then remain as part of the reaction debris or need to be removed from the reaction to either allow it to continue the molecule- building process or to ensure the formation of a pure polymer
In reality the addition-type process can occur in several ways
First way simply involves the external chemical activation of molecules that causes them to start combining with each other in a chain-reaction-type fashion (by the bonding of atoms directly within the reacting molecule).
second Another way for an addition polymerization to occur is through a rearrangement ofatoms within both reacting molecules, but still without the net loss of any atoms from the polymer molecule
third way for addition polymerization to occur is for a molecule composed of a ring of atoms to open up and connect with other ring-type molecules being opened up under the influence of the proper catalytic activators, once again with no net loss of any atoms from the polymer structure
fourth In another type of polymerization reaction, which has been called “condensation” poly-merization, the chemical union of two molecules can be achieved only by the splitting out of a molecule (usually small) formed by the atoms, which must be removed from the two molecules being joined to allow the couplingprocess or polymerization to continue. This is the type of polymerization involved in the formation of some nylons, phenolics, amino resins, and polyester pre-polymers.
There is yet another method by which polymers
may be formed, but it is in reality simply
a sequential combination of the previous two
processes. Such a process is used in the formation
of plastics such as the polyesters and
the polyurethanes.
There are many process techniques of polymerisations but as a conclusion we can say there are 4 main types of process polymerising
WE will discuss about then tomm.on our blog . .
any suggestions in regard to the blog are always welcome ,
we are always available to the plastic engg and other people who need help or suggetions to their current and new plastic projects.
you can write me bu visiting the site described below or could write in the inquire for . i will get that straight and reply back asap.
Er.G P Singh.
www.deekayengg.com
www.blowmoulds.info
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