Polymerisation Polyvinyl chloride

Examples of important commercial products obtained by free radical polymerisation of substituted ethenes are polypropene (polypropylene). Polyphenylethene (polystyrene), poly-1 chloroethene (polyvinyl chloride) and poly 1-methoxy carbonyl-1 methylethene (polymethalmethacrylate). 

Polyvinyl chloride-montmorillonite nanocomposites were prepared either by in-situ suspension polymerisation using initiator- and comonomer-modified montmorillonite in the presence of free-radical initiators, such as AIBN, and compared. It was found that monomer conversion was low when the nanocomposites were prepared using initiator-modified montmorillonite. Exfoliated nanocomposites... 

Vinyl chloride can be polymerised to form polyvinyl chloride (PVC) which is fairly brittle and unsuitable for food contact applications, so it is mixed with plasticisers to soften the polymer and impart flexibility. Plasticised PVC may contain about 30% of plasticisers and is used to make stretch films and flexible PVC. Flexible PVC used for tubing and gaskets may contain di(2-ethylhexyl)phthalate, and stretch films will probably contain di(2-ethylhexyl)adipate and a polymeric adipate plasticiser. Rigid PVC may... 

In order to determine the sources of contamination, some water samples, including wastewaters and effluents from different industries, were also taken. Along the Cinca River and in the industrial area of Monzon, industrial effluents from two different industries were selected the first one produced EPS (expandable polystyrene) treated with flame retardants and ABS (acrylonitrile-butadiene-styrene), and the second one produced PVC (polyvinyl chloride). As regards the Vero River, three industries were sampled the first one was a textile industry which produced polyester fibres treated with flame retardants, the second produced epoxy resins, and the third focused on polyamide polymerisation. 

PVC may be formed by the polymerisation of vinyl chloride emulsion under pressure, using a peroxide catalyst. Polyvinyl chloride is found as UPVC (unplasticised PVC), plasticised PVC or as an impact modified PVC. 

The production and applications of polymers have gradually developed, gaining ground in many fields. The main classes of polymers, namely polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene and polyethylene terephthalate are produced in millions of tonnes annually [1]. There are many methods of polymer synthesis free-radical polymerisation (bulk, solution, emulsion and suspension), condensation polymerisation, ethoxylation, polymer compounding and formulations involving solvents, fillers, pigments and so on. Besides the high volume consumption of these common plastics, the demand for polymers with specific end-use properties has increased. 

The suspension polymerisation approach is often used in the production of polyvinyl chloride dispersions for use in plastic pipes. Polystyrene and styrenic copolymers are also produced by suspension polymerisation. The polystyrene beads are often prepared by suspension polymerisation for use as packing material in gel permeation chromatography (GPC) columns. Ion exchange resin beads are also commonly produced by suspension polymerisation. Because suspension beads are relatively large, it is easier to separate the polymer by coagulation than in the case of emulsion polymerisation. 

Polyvinyl chloride (PVC) is often produced by suspension or emulsion polymerisation. It is used extensively in producing PVC pipes for construction. Impact modifiers are often added to strengthen the material. PVC is also used in plastisols for dipped coatings, in shower curtains, and in vinyl leather. Nonvolatile plasticisers are necessary in such applications where the material must remain flexible. Because PVC is a very hydrophobic polymer with good barrier properties, it makes an effective obstacle to oxygen and water vapour in packaging films. 

Gaseous vinyl chloride monomer is polymerised under high pressure conditions. Since polyvinyl chloride polymer is insoluble in its own monomer, the reaction kinetics do not follow the classical emulsion polymerisation kinetics. During polymerisation, chain transfer to monomer is extensive, and molecular weight development depends upon the reaction temperature rather than the initiator concentration. Consequently, lower reaction temperatures are needed to reach higher molecular weights. A typical formulation for the suspension polymerisation of polyvinyl chloride is given in Table 5. 

Table 5 Recipe for the preparation of polyvinyl chloride (PVC) dispersion by suspension polymerisation at 60 °C ...

Polyvinyl chloride (PVC) was first observed as long ago as 1838 by Regnault [7] and first patented in 1912 when Klatte used sunlight to initiate the photo polymerisation of vinyl chloride (VC). In 1926, Ostromislensky patented flexible film cast from a solution containing the polymer and a plasticiser. The phthalate plasticisers were introduced in 1920 and 1922. The first patent on a mouldable plasticised PVC (PVC-P) was granted to BFGoodrich in 1932. Later on the Carbide Company patented copolymers of VC with vinyl acetate (VAc) that are still in use today [1]. 

Amongst the polymers based on crude oil, seven groups of polymers - polyolefins (PE and PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), emulsion polymerised styrene butadiene rubber (ESBR), polyamides (PA) and unsaturated polyester resins (UP) constitute approximately 80 % of the total consumption of polymers. 

Polymerisation is the most important reaction process and produces amongst others the plastics polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS). The reaction principle includes the opening of the double bond of a monomer (Figure 2.2) and linking many monomeric molecules together forming a saturated long chain macromolecule. 

This document focuses on the main products of the European polymer industry both in production figures and in environmental impact, mainly produced in dedicated installations for the production of one specific polymer. The list of products covered is not conclusive but includes polyolefins, polystyrene, polyvinyl chloride, unsatuiated polyesters, emulsion polymerised styrene butadiene rubbers, solution polymerised rubbers containing butadiene, polyamides, polyethylene terephthalate fibres and viscose fibres. 

A free radical catalyst or initiator is dissolved in the monomer which is then heated and stirred in a suitable vessel. The polymerisation is exothermic and dissipation of heat through cooling may be required. As the reaction progresses, tlie system becomes viscous making stirring difficult. The method is economical and the product is of high purity. The technique is used for preparing polyvinyl chloride. (PVC), polystyrene (PS) and polymethymethacrylate (PMMA). 

A suspension of droplets of vinyl chloride monomer (VCM) in water, of size 30-150 iJim, is formed by agitation with a stirrer. It is stabilised by a colloidal layer of partially hydrolysed polyvinyl acetate or other water-soluble polymer. When the suspension is polymerised at a temperature in the range 50-70 °C, PVC molecules form in the VCM droplets. As PVC is insoluble in VCM, it precipitates in the form of primary particles, initially... 

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