Plastisol expandable

A type of physical stabili2ation process, unique for poly(vinyl chloride) resias, is the fusion of a dispersion of plastisol resia ia a plastici2er. The viscosity of a resia—plastici2er dispersioa shows a sharp iacrease at the fusioa temperature. Ia such a system expansioa can take place at a temperature corresponding to the low viscosity the temperature can then be raised to iacrease viscosity and stabili2e the expanded state. 

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. 

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. 

A considerable range of plasticizers is available but those used most commonly are phthalate esters such as dioctyl or dinonyl phthalate (DOP or DNP). If it should be necessary to reduce the temperature of fusion, or to increase the rate of fusion (as with some expandable plastisols) a fast-solvating plasticizer such as butyl benzyl phthalate may be employed. Besides primary plasticizers such as these, less efficient secondary plasticizers (like chlorinated paraffins) can be included with a view to reducing costs and improving flame retardance. 

The technique is very versatile and adaptable. Plastisols may be applied overall or—by means of engraved screens—can be printed in selected areas, in weights that can be varied between 30 g m-2 and more than 500 g m-2. Suitable substrates include paper, other non-woven materials, glass-fibre webs, and textiles. Water-based inks can be employed as coatings or in printed designs. For relief effects, expandable aqueous polyacrylate dispersions offer an alternative to expandable plastisol inks. They are dried and then expanded at 120°C, a temperature much lower than is required for vinyls with a multi-station machine, a wide variety of products can be made. 

The general principles of formulation outlined earlier apply equally to compact and expandable plastisols for screen printing. Plastisols for compact products... 

Celogen SD dispersions eliminate dust, improve dispensability in PVC plastisols, and may be metered directly into the manufacturing process. May be found in sponge rubber and expanded plastics. 

Uses Blowing agent in printing inks, PU, PVC plastisols, fabrics, paper expanded microspheres as ultra-low density tillers tor use in engineered prods, in which other fillers would not be suitable, e.g., syn. marble and wood, coatings, sealants, explosives, auto, marine fillers, molding compds., composites, paint and crack fillers, cable fillings, elastomers Features Unexpanded microspheres Expancel 551 DE 20 [Expancel]... 

In recent years, the range of adhesive materials used in automotive manufacture has expanded to include polyurethanes, plastisols, phenolics, hot melts, anaerobics, cyanoacrylates, toughened acrylics and epoxies (see Structural and Hot melt adhesives). Selection criteria are based principally upon the nature of the adherends, the mechanical properties required under service conditions and application and curing characteristics. 

The Kleber-Colombes rigid PVC foam (265,266) is produced by compression molding vinyl plastisol to react and gel the compound, followed by steam expansion. The process involves mixing, molding, 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 Werner-Pfleiderer or a Baker Perkins type of mixer, and the resulting plastisol is molded under pressure. The initial temperature of the molds is 100-110°C, which increases to 180-200°C because of exothermic polymerization of the vinyl monomers and anhydride. The mold is cooled and the partially expanded PVC is removed and then further expanded by steam. After the water treatment, the foam is thermoset with a closed-celled structure and a relatively low thermal conductivity. 

Filler - Expanded perlite is used as a filler in textured paints and in auto imderbody plastisol coatings to reduce weight and improve soimd insulation. It is used in syntactic foams and in automotive polyester molding compounds and body fillers to reduce weight and improve sanding characteristies. Its spherieal shape allows more perlite to be incorporated, eompared to irregularly shaped fillers, because there is less effect on melt or plastisol viscosity. 

Expanded vinyl has been used as a pressure-sensitive tape backing for many years. Typically, a low-density foam is plastisol-coated on a casting liner that is used a number of times, or onto a continuous belt. After fusion and expansion, one or both sides are transfer-coated with adhesive that has been dried (and sometimes... 

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