Plastic molding and plastic Granual polymerisation. " Polymer Chemistry"

  Hello all, 

                       So as I said  in my last topic that we will countinue .further i am starting . 

There are many process techniques  of polymerisations but as a conclusion we can say there are 4 main types of  process polymerising

In actual practice there are many different techniques  used to carry out polymerization reactions.

                                                   

                                                   However, most involve one of four  

general methods of polymerization: The 

polymerization of the monomer or reactants in 

bulk, in solution, in suspension, and in emulsion 

forms. The bulk and solution methods are 

used for the formation of both addition and 

condensation type polymers, whereas suspension 

and emulsion techniques are used largely 

for addition polymerizations.                                                                     

                                                                     

1.Bulk Polymerization. This type of polymerization 

involves the reaction of monomers 

or reactants among themselves without placing 

Catalyst activated bond opening (ethylene 

polymerization)

them in some form of extraneous media such 

as is done in the other types of polymerizations.

                                                                    

Two types of behavior are observed in bulk

 polymerizations. 

               first  The polymer is    

soluble in the monomer during all stages of the

 polymerization, and a monomer-soluble initiator  

is used. As polymerization progresses, viscosity 

increases significantly, and chain growth 

takes place in the monomer or polymers dissolved

 in the monomer until all of the monomer 

is consumed.

            In the second case  The polymer is insoluble

 in the monomer system. In such systems, the po

lymerization is believed to occur within the

 growing polymer chains because very high molecular 

weights are formed even though the 

polymer chain drops out of the monomer solution

2.Solution Polymerization. Solution polymerization is similar to bulk polymerization except

that the solvent for the forming polymer in bulk polymerization is the monomer, whereas the solvent in solution polymerization is usually a chemically inert medium. The solvents used may be complete, partial, or non solvents for the growing polymer chain. When the monomer and the polymer are both

soluble in the solvent, initiation and propagation of the growing polymer chains take place

in the oil or organic phase. Because of the mass action law, rates of polymerization in solvents

are slower than in bulk polymerizations, and the molecular weight of the polymers formed

is decreased.

          

3. Suspension Polymerization. Often called  “pearl” polymerization,"pearl” polymerization, this technique normally is used only for catalyst-initiated or free radical addition polymerizations. The monomer is mechanically dispersed in a liquid, usually water, which is a non solvent for the monomer

as well as for all sizes of polymer molecules  that form during the reaction.

4.Emulsion Polymerization. This is a technique in which addition polymerizations are camed out in a water medium containing an emulsifier (a soap) and a water-soluble initiator. It is used because emulsion polymerization is much more rapid than bulk or solution ipe, and reaction conditions provides additionalcontrols over the reaction. Polymerization techniques can have a significant

effect on the number, size, and characteristics of the polymer molecules formed and thus

will have a significant effect on the properties of the polymer. Thus, batches of a polymer

such as polystyrene, which can be made by any of the four polymerization techniques described

above, will differ, depending on which type of polymerization method was used to

make the material.

As I initially said thte polymers and plastic is a very very broad and sky is the limit so ,not even a part of it can ge coverd in the topic of mine , But I think that every plastic injection  molder shoul know and be aware with. the  the basic of polymer 

Its ok for today  and I will be here tommorow again with some new information and basic relevant  to all the people  who provide these PLASTIC ENGG SERVICES ,to the people of world , plastic ,plastic moulding,injection moulding , injection moulds  and blow Molds 

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Plastic molding and plastic resin basic " Polymer Chemistry"

Hi,
      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
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