Glossary of Terms

Agglomerate...
Gathering of small particles into a larger mass.

Air release...
A test for determining the relative ease of removing air from a plastisol.

Blister...
Irregular area of a surface in fused plastisols usually caused by water, solvent or air contamination.

Brookfield viscosity...
A measure of the low shear viscosity of a plastisol as determined with a Brookfield rheometer.

Cast molding...
Pouring plastisol into an open mold or injecting plastisol under low pressure into closed matching molds, then heating to achieve fusion.

Deaeration...
The removal of entrapped air from a plastisol compound. This is usually accomplished by subjecting the vinyl dispersion to a vacuum either during mixing or in a later operation.

Dilatant...
A liquid which increases in viscosity with increasing shear rate.

Diluent...
Additive used to lower the viscosity of a plastisol.

Dip coating...
A process by which plastisol becomes a functional part of the object dipped. Hot dip coating, the most common coating method, involves heating the object prior to immersing it in plastisol; the plastisol gels on the heated object, and final fusion takes place in a heated chamber. Cold dipping, used primarily for thin plastisol coatings, eliminates preheating the object before dipping, with fusion likewise taking place in a heated chamber. The plastisol's viscosity and other factors determine the thickness of the cold dip coating.

Dip molding...
A process similar to hot dip coating, in which the finished product is the fused plastisol stripped from the dipped mold. Dip molding is used to produce such articles as gloves, grips, and protective caps.

Dispersion...
Finely divided particles of a material in suspension in another substance.

Durometer...
(Hardness) - the hardness of a material measured by Shore Durometer.

Elongation...
A measure of how far a film of fused plastisol can be extended before breaking.

Emulsifier...
A chemical ingredient designed to produce an emulsion of two liquids which do not naturally mix, also called soap.

Flammability...
A material that is easily set afire or readily combustible.

Fillers...
Materials that are added to a system to reduce cost and/or modify the system or finished product properties.

Fusion...
The heating process by which the PVC resin and other components are transformed from their original form to a homogenous, new structure.

Gelation...
The time at which all liquids are absorbed by the resin, rendering the plastisol immobile.

Grind...
A test, which yields information on the size of particles within a plastisol.

Knife coating...
The use of a blade-like device to apply a coating of plastisol as thin as 2 mils or as thick as 3/16 inch, in a single pass, to paper, fabric, metal, or a release substrate. Knife coating paper adds strength and tear-resistance ¾ for durable wall coverings, for instance. With fabric the process can be used to add color, enhance durability and weather resistance, and create texture. Metal application increases corrosion resistance and can even be used for decorative effects. Applied to a release substrate, the fused plastisol can be stripped away to produce vinyl film.

Leaching...
Process by which plasticizer or other materials migrate out of a partially fused or fused vinyl film.

Newtonian...
A liquid, the viscosity of which is independent of shear rate.

Organosol...
A plastisol to which a solvent has been added.

Open cavity molding...
A cast molding process in which plastisol is formed into a finished article or cast in place as part of a composite article, such as a water filter or automotive air filter.

Organosol...
A plastisol to which a solvent has been added.

PVC dispersion resin...
Fine particle size PVC material which when mixed under moderate shear into an oil (plasticizer) base forms a plastisol.

Plasticizer...
High boiling organic liquids or low melting point solids that impart flexibility to PVC resin.

Plastisol...
A liquid composed of PVC dispersion resin dispersed in a plasticizer.

Pseudo-plastic...
A liquid which decreases in viscosity with increasing shear rate.

Rheology...
Incorporates viscosity measurements as well as how viscosity changes with shear rate.

Rotational molding...
Used to create hollow forms (flexible or rigid) with complex shapes and even varying wall thickness. The process involves introducing a precise amount of plastisol into a mold, then rotating the mold in two planes while heating it, to disperse, gel, and fuse the plastisol in a single step.

Saturation coating...
A method for totally impregnating a substrate with a plastisol compound.

Screen printing...
The application of plastisol through a fine screen, usually with a stencil in place to produce a specific design or portion thereof. Highly detailed, multi-colored images are possible with this process.

Severs viscosity...
A measure of the high shear viscosity of a plastisol as determined with a Severs rheometer.

Shear rate...
The velocity gradient applied to a liquid.

Shear Stress...
A shearing force per unit area expressed in dines cm².

Slush molding...
Used to create hollow, flexible items. A quantity of plastisol is poured into a heated female mold, causing gelling of the plastisol directly in contact with the heated surfaces. The excess plastisol is poured off and the gelled layer is allowed to fuse. After fusing, the finished item is removed from the mold.

Specific gravity...
Defined as mass per unit volume; expressed as the ratio of the weight of any volume of a substance to the
weight of an equal volume of water at 4ºC.

Specks...
Burnt resin or dark specs resulting from over heating in the drying process.

Spray coating...
A process involving the use of airless spray systems to coat large objects, vertical surfaces, irregular or shapes, often in-place. With spray coating, unlimited passes can be made in order to achieve the desired coating thickness. Decorative effects can be achieved using special spray heads.

Surfactant...
A surface-active agent used in plastisols to reduce viscosity and improve air release.

Tensile strength...
Breaking strength of a material when subjected to a breaking force - commonly expressed as pounds per square inch.

Thixotropic...
An decrease in viscosity of a liquid due to low shear force being applied continually.

Transfer coating...
Used for applications where the position, thickness, hardness, softness, or decorative effect must be tightly controlled.

UV resistance...
The ability of a substance to resist degradation from exposure to an ultra violet source.

Viscosity...
Result of shear force and the rate of shear applied to a liquid.

Viscosity aging...
The tendency for a plastisol to increase in viscosity during storage.

Yield value...
The force necessary to induce flow of liquid.