Plastisol fused

Molded Vinyl Foam With other materials such as urethanes and elastomers, most foam products are molded. They are either allowed to expand under low pressure to fill the mold, yielding an open cell stmcture, often with a skin (as in, e.g., crutch pads) or molded and thermoset under pressure and subsequently expanded in an oven, yielding a closed cell structure (as with foam rubber shoe soles or mattress components). The products of oven expansion, referred to as buns, can be skived and die cut to gaskets or seals. The latter process is also carried out with vinyl. Molds are filled with plastisol, fused and cooled under pressure, and then expanded in an oven at 100-120 °C, softening the polymer and enabling the trapped gas to expand. For highly defined shapes, this step can be carried out in a second mold. 

Another type of extmsion process iavolves the pressuri2ation of a fluid plastisol at low temperatures with an iaert gas. This mixture is subsequently extmded onto a belt or iato molds, where it expands (109,110). The expanded dispersion is then heated to fuse it iato a dimensionally stable form. 

There are two principal PVC resins for producing vinyl foams suspension resin and dispersion resin. The suspension resin is prepared by suspension polymerization with a relatively large particle size in the 30—250 p.m range and the dispersion resin is prepared by emulsion polymerization with a fine particle size in the 0.2—2 p.m range (245). The latter is used in the manufacture of vinyl plastisols which can be fused without the appHcation of pressure. In addition, plastisol blending resins, which are fine particle size suspension resins, can be used as a partial replacement for the dispersion resin in a plastisol system to reduce the resin costs. 

The elastomer process is very similar to the Dennis process. It involves a number of steps in which a gas, formerly carbon dioxide and now fluorocarbon, is mixed with a plastisol under pressure. When released to atmospheric pressure, the gas expands the vinyl compounds into a low density, open-ceUed foam which is then fused with heat. 

The Vanderbilt process involves the mechanical frothing of air into a plastisol containing proprietary surfactants by means of an Oakes foamer or a Hobart-type batch whip. The resulting stable froth is spread or molded in its final form, then gelled and fused under controlled heat. The fused product is open-ceUed with fine cell size and density as low as 160 kg/m (10 lbs/fT). 

The term plastisol is used to describe a vinyl dispersion that contains no volatile thin-ners or diluents. Plastisols often contain stabilizers, fillers, and pigments, along with the essential dispersion plastics and the liquid plasticizer. All ingredients exhibit very low volatility under processing and use conditions. Plastisols can be made into thick fused sections with no concern for solvent or water blistering, as with solution or latex systems, so they are described as being 100 percent solids. 

Polyvinyl chloride is also widely used. Rigid polyvinyl chloride is introduced to the mold in powder form. The material is chosen for durable constructions because of its chemical resistance and ease of processing. It incorporates functional additives and demolds easily. Plasticized polyvinyl chloride can be used to produce flexible parts such as balls and soft toy parts. The polyvinyl chloride is introduced to the mold as either a plastisol or powder. A plastisol is a suspension of granules in a plasticizing agent. When heated, the polymer granules absorb the plasticizer and fuse to form a cohesive, flexible material. 

Plastisols are dispersions of powdered PVC resin in plasticizer. A typical composition would consist of 100 parts of PVC nesin dispersed in 50 parts of DOP. The resultant paste when heated to 300"F (149"C) fuses or fluxes into a solid plastic mass. Stability of this plastisol at room temperature may range from several weeks to several months depending on the plasticizers and resins employed. 

Commercial Plastisols, Accdg to definition given in Ref 2, a plastisol is a liquid dispersion of finely divided resin in a plasticizer. It is usually 100% solid with no volatiles when volatile content exceeds 5% of the total wt it is called organosol. When the plastisol is heated, the plasticizer solvates the resin particles, and the mass gels. With continued application of heat the mass fuses to become a conventional thermoplastic material... 

Effect of Atomizer Speed. Four different atomizer tip speeds, 79, 98, 118, and 138 M/sec., were studied. Increasing the atomizer speed increased the agglomeration present in the plastisols (Table I and Figure II). Increasing atomizer speed is known to produce smaller spray droplets. This should result in more highly fused resin agglomerates, (Figure IV,... 

The pastes used are plastisols—finely divided polymer dispersed in plasticizer. They are mobile mixtures which may range in viscosity from liquids that can be poured readily to thick pastes—the viscosity depending essentially on the type of resin and the amount and type of plasticizer involved. Such mixtures can be applied to substrates by coating or by techniques akin to printing after application they are converted into homogeneous flexible vinyls by heating to temperatures in the range 175 to 200 °C, when the dispersed particles of resin dissolve in the plasticizer and are fused into a continuous structure.1... 

So that the temperature of the web can be increased in stages the oven should be zoned in a minimum of three sections. Most pastes contain a volatile diluent and it is essential that the temperature in the first zone should be relatively low so that volatiles can be driven off before fusion occurs. Too rapid an application of heat leads to blistering of the coating as residual solvent escapes from the fused areas. In each of the zones careful control of the air temperature, velocity, and distribution is essential for uniform fusion across the full width and throughout the coating. Operating conditions for ovens for PVC plastisols were considered by A. C. Poppe.5... 

The 121 sample films were formulated into a replicate series. Those utilizing emulsion polymerized PVC were cast from plastisol onto glass plates and fused in a circulating hot air oven. Those incorporating suspension polymerized PVC were fluxed via a Banbury and two-roll compounding mill and finished on an inverted L 8-inch X 16-inch four-roll calender. Plastisol films were of nominal 8-mil thickness calendered film was 4 mils. 

Plastisol is a specialized technique for making flexible vinyl products. It is also sometimes called paste or dispersion technology. Basically, powdered PVC is stirred into liquid plasticizer at room temperature to form a viscous liquid or spreadable paste. This can be poured or spread into the shape of the final product, heated to fuse, and cooled to gel into the final solid product. Simple pouring or gentle spreading require no heavy equipment, and do not damage delicate substrates such as... 

Dip Coating. A product is preheated and dipped into the plastisol. The plastisol gels onto the surface of the product. It is withdrawn from the liquid, allowed to drain off excess liquid, and then placed in a 191-204°C oven to heat it in a few seconds to about 177°C and fuse the gel to a homogeneous solution. This is then cooled in air or water to solidify it to the final rubbery coating. Typical... 

Rotational Casting. Like rotomolding, the plastisol is poured into a cold mold, which is rotated and heated to gel the plastisol onto the walls of the mold. It is then heated to fuse, cooled to solidify, opened, and the product removed. Typical products are volley balls, basketballs, dolls, and auto parts. 

Open Molding. Plastisol is poured into an open mold, heated to gel and fuse, cooled to solidify, and stripped out from the mold. Typical products are auto air filters, oil filters, truck flaps, and place mats. 

Some high-flow plastics, such as nylon, have been used in small pellet form. Ethylene vinyl acetate and PEs are also used in specialized applications as are PVC, PC, TP polyester, nylon, and PP. RM vinyl plastisols produce different products such as beach balls, floating animals, and toys as well as industrial products. The liquid or powdered plastic used in this method flows freely into comers or other deep draws upon the mold s being rotated and is then fused by heat passing through the mold s wall. 

Most of the plastisols are used in open molding. It is a very simple process to use. A measured amount of plastisol is poured into an open mold cavity. The mold and plastic are heated to gel and fuse the plastisol. The mold is then cooled so that it solidifies. It is stripped from the mold. Inserts can be placed in the liquid plastic before it is fused inserts can also be inserted in the mold before pouring. Two or more colors can be placed in different parts of the mold. 

This process resembles the open molding process except it is closed like a two-part compression mold (Chapter 14). A measured amount of plastisol is poured or pumped into the closed mold cavity, similar to close molding except that a slight pressure of about 5 psi (34.5 kPa) is applied. The mold is heated to fuse the plastisol then cooled. Later the mold is opened and the product stripped out. This process can provide for accurate thickness control, filling very complex shaped parts, and so on. 

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