PVC, rigid

The Kleber-Colombes rigid PVC foam (253,254) is produced by compression mol ding vinyl plastisol to react and gel the compound, followed by steam expansion. The process involves mixing, mol ding, and expansion. The formulation consists of PVC, isocyanate, vinyl monomers such as styrene, anhydrides such as maleic anhydride, polymerization initiators, FC-11, and nucleators. The ingredients are mixed in a Wemer-Pfleiderer or a Baker Perkins... 

By far the most common lead salt used for PVC stabilization is tribasic lead sulfate. It can be found either alone or combined with another lead salt in almost every lead-stabilized PVC formulation. Many of the combinations are actually coprecipitated hybrid products, ie, basic lead sulfophthalates. Dibasic lead stearate and lead stearate are generally used as costabilizers combined with other primary lead salts, particularly in rigid PVC formulations where they contribute lubrication properties dibasic lead stearate provides internal lubrication and lead stearate is a good external lubricant. Basic lead carbonate is slowly being replaced by tribasic lead sulfate in most appHcations due the relatively low heat stabiHty of the carbonate salt which releases CO2 at about 180°C during PVC processing. 

Rigid Applications. The use of the lead stabilizers is very limited in the United States but, they are stiU used in several rigid PVC appHcations in Europe and Asia. The highest use of lead stabilizers in rigid PVC is for pipe and conduit appHcations. Tribasic lead sulfate is the primary heat stabilizer with lead stearates included to provide lubrication. The lead products are typically fully formulated, usually including lubricants and pigments for pipe extmsion appHcations. These lead one-packs, when used at about 1.8—2.5 phr, provide all of the stabilizer and lubrication needed to process the polymer. A lead one-pack contains tribasic lead sulfate, dibasic lead stearate calcium stearate, polyethylene wax, paraffin wax, ester wax, and pigments. 

Current manufacturers of these products are the Polymer Additives Group of Witco Corp. (New York), with the trade name Mark, and Synthetic Products Co. (Cleveland), with the trade name Synpron. The antimony-based stabilizers are typicaHy used for rigid PVC extmsion appHcations at about 0.4 to about 0.8 phr, priced at about 3.80— 4.50/kg. 

Calcium—zinc stabilizers are used in both plasticized PVC and rigid PVC for food contact where it is desired to minimize taste and odor characteristics. AppHcations include meat wrap, water botdes, and medical uses. 

Injection-Molded Products. Numerous housings, electrical enclosures, and cabinets are injection-molded from rigid PVC. These take advantage of PVC s outstanding UL flammabiUty ratings and easy mol ding into thin-waHed parts. PVC has developed melt flow capabiUties to the point where it competes with essentially any other flame-retarded engineering thermoplastic and molds easier than most. 

Siding. The resin most used for siding is poly(vinyl chloride) homopolymer, compounded with modifiers, stabilizers, and pigments. Modifiers are most often acryhc esters, followed by chlorinated polyethylene or ethylene—vinyl acetate, used at 6—8 phr (parts per hundred resin). The modifier increases the impact strength of the rigid PVC. 

Door and Window Frames and Sashes. The first successflil application of rigid PVC for windows was as a cladding over a wood core to avoid the need for painting and repainting the sash and the exterior of the frame. Since then, extmded profiles of rigid PVC have been developed to allow... 

Use only apparatus strong enough to withstand the considerable force which may arise due to movements of mercury (e. rigid pvc or polythene)... 

These compounds are particularly advantageous for equipment exposed to low temperatures. This plastic containing chlorinated ethylene does not differ significantly in chemical resistance from rigid PVC, but does have a slightly lower creep strength. 

The materials of construction, from the cupboard to the fan, should be inorganic and resistant to attack by perchloric acid. For the cupboard itself suitable materials include stainless steel of types, 316 or 317, solid epoxy resin, and rigid PVC. Stainless steel has been popular for this application as it is easy to form, weld, and polish. It is, however, attacked by the acid, which causes discoloration of the metal surface and the formation of iron(III) perchlorate, which can be explosive. Ductwork, separate from other extract systems, is usually made from stainless steel or plastic materials. Fire regulations may preclude the use of plastic ductwork or require it to be sheathed in an outer casing of metal or GRP. The fan casing and impeller can both be made of plastic. 

Since 2-hydroxy-4-alkoxybenzophenones are widely used to stabilize polystyrene, flexible and rigid PVC, celluloses, acrylics, and polyolefins such as PE and PP, the polymeric UV stabilizers shown in Table 1 are used with polystyrene, polymethylmethacrylate, and cellulose triacetate (CTA). The polymeric-HALS are used in polyolefins. 

By permission, Norton Chemical Process Products Corp., Bull. SI-72 and Bull. PTP-1 other manufacturer s data are equivalent, f Also available in polypropylene (including glass reinforced) high density polyethylene, rigid PVC, fluorinated vinyls. 

Rigid PVC is used in many items such as pipes, fittings roofing, automobile parts, siding, and bottles. 

ABS has a specific gravity of 1.03 to 1.06 and a tensile strength in the range of 6 to 7.5 X 10 psi. These polymers are tough plastics with outstanding mechanical properties. A wide variety of ABS modifications are available with heat resistance comparable to or better than polysulfones and polycarbonates (noted later in this section). Another outstanding property of ABS is its ability to be alloyed with other thermoplastics for improved properties. For example, ABS is alloyed with rigid PVC for a product with better flame resistance. 

Over 90% of organotin stabilizers are used in rigid PVC. Table 3 provides details of the estimated quantities of methyl-, butyl-, and octyltin stabilizers used in rigid and flexible PVC applications, whereas Table 4 details the types of applications in which the PVC products are used. 

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