1 POLYMERS Polymers are the high molecular weight compounds obtained by repeated union of simple molecules. Question 7. The single most important factor in forming dioxin-like compounds is the temperature of the combustion gases. The contents of the reaction vessel are pressurized and continually mixed to maintain the suspension and ensure a uniform particle size of the PVC resin. A polymer is analogous to a necklace made from many small beads (monomers). About 90% of the plasticizer market, estimated to be millions of tons per year worldwide, is dedicated to PVC.. a. The reaction can take place between two similar or different monomers. Addition polymerisation needs one type of monomer and forms one product. PVC is a common, strong but lightweight plastic used in construction. 3. While di-2-ethylhexylphthalate (DEHP) has been medically approved for many years for use in medical devices, it was permanently banned for use in children's products in the US in 2008 by US Congress; the PVC-DEHP combination had proved to be very suitable for making blood bags because DEHP stabilizes red blood cells, minimizing hemolysis (red blood cell rupture). After 12 months of exposure, for example, there was a 34-fold difference in average total POPs amassed on LDPE compared to PET at one location. The unquenched polymer has been termed a living polymer, and if additional styrene or a different suitable monomer is added a block polymer will form. Once dehydrochlorination starts, it is autocatalytic.  The reported and audited mechanically recycled PVC tonnage in 2016 was 568,695 tonnes which in 2018 had increased to 739,525 tonnes. The linear expansion coefficient of rigid PVC is small and has good flame retardancy, the limiting oxygen index (LOI) being up to 45 or more. A polymerization in which the growth of polymer chains proceeds by condensation reactions between molecules of all degrees of polymerization. The Olympic Delivery Authority (ODA), for example, after initially rejecting PVC as material for different temporary venues of the London Olympics 2012, has reviewed its decision and developed a policy for its use. PVC produces HCl upon combustion almost quantitatively related to its chlorine content. As the volume is reduced during the reaction (PVC is denser than VCM), water is continually added to the mixture to maintain the suspension.. *Response times vary by subject and question complexity. Steiglitz, L., and Vogg, H. (February 1988) "Formation Decomposition of Polychlorodibenzodioxins and Furans in Municipal Waste" Report KFK4379, Laboratorium fur Isotopentechnik, Institut for Heize Chemi, Kerforschungszentrum Karlsruhe. the rate for recycling or reuse and the percentage of recycled content. This polymer can absorb 800 times it own weight of distilled water, but only 300 times its weight of tap water. A middle vinyl foam layer also gives a comfortable and safe feel. Polymer obtained by condensation polymerization is 1) Polythene 2) Teflon 3) Phenol-formaldehyde 4) Nitrile rubber 2. One of its earliest mass-market consumer applications was vinyl record production.  Various studies have been conducted that reach contradictory results. Plastic Applications. Some initiators start the reaction rapidly but decay quickly, and other initiators have the opposite effect.  In the private homeowner market, it accounts for 66% of the household market in the US, and in household sanitary sewer pipe applications, it accounts for 75%. Chlorinated polyvinyl chloride, (CPVC), as it is called, is produced by chlorination of aqueous solution of suspension PVC particles followed by exposure to UV light which initiates the free-radical chlorination. Higher levels of plasticizer result in softer PVC compounds and decrease tensile strength. Environmental Science & Technology, a peer-reviewed journal published by the American Chemical Society states that it is completely safe.. PVC fabric has a niche role in speciality clothing, either to create an artificial leather material or at times simply for its effect. Condensation Polymers Handbook of Plastics, Elastomers, and Composites, Fourth Edition, 2002 by The McGraw-Hill, Charles A. Harper Editor-in-Chief. About half of the world's PVC production capacity is in China, despite the closure of many Chinese PVC plants due to issues complying with environmental regulations and poor capacities of scale. Question 19.  The other major suppliers are based in North America and Western Europe. 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). , One approach to address the problem of waste PVC is also through the process called Vinyloop. In Europe, particularly Belgium, there has been a commitment to eliminate the use of cadmium (previously used as a part component of heat stabilizers in window profiles) and phase out lead-based heat stabilizers (as used in pipe and profile areas) such as liquid autodiachromate and calcium polyhydrocummate by 2015. , In November 2005 one of the largest hospital networks in the US, Catholic Healthcare West, signed a contract with B. Braun Melsungen for vinyl-free intravenous bags and tubing. 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