Glossary

Plastics Glossary - G

Gardner Impact and Dynatup Impact .. See Instrumented impact testing.

Gardner Mobilemeter Instrument used to determine the thixotrophy of a material.

Gate Blush A blemish or disturbance in the gate area of an injection molded article.

Gate freeze In injection molding, gate freeze is the point at which polymer flows into or out of the cavity stops caused by the solidification of polymer in the gate.

Gate mark Blemish on the molded part left by the mold gate.

Gate In injection molding, the channel through which the molten resin flows from the runner into the cavity. Generally, it is small and solidifies first. The restricted opening through which the plastic enters the mold cavity.

Gel Semisolid system that consists of a solid held in a liquid; a more solid form than a sol.

Gelometer Instrument used to measure the time required for a fluid to gel.

Gibbs Absorption Law When the concentration of a substance in the interfacial layers between two phases exceeds that in the bulk of either phase the substance is absorbed at the interface.

Glass fiber See fiberglass reinforcement.

Glass Fibers A family of reinforcing materials for reinforced plastics based on single filaments of glass.

Glass filament A form of glass that has been drawn to a small diameter and extreme length. (Most filaments are less than 0.005 inch in diameter).

Glass finish A material applied to the surface of a glass reinforcement to enhance the bond between the glass and the plastic binder.

Glass transition temperature The approximate midpoint of the temperature range at which a non-crystalline (amorphous) polymer changes from brittle (glass) to rubbery.

Glass transition The change in an amorphous polymer or the amorphous regions of a partially crystalline polymer from (or to) a viscous or rubbery condition to (or from) a hard and relatively brittle one. The glass transition occurs in a relatively narrow temperature range and is similar to the solidification of a liquid to a glassy state.

Glass, percent by volume The product of the specific gravity of a laminate and the percent glass by weight, divided by the specific gravity of the glass.

Gouy Diffuse Double Layer The gradual, exponential electrical potential drip from the interface of an emulsion into the bulk of the phase.

Green strength The ability of the material, while not completely cured, to undergo removal from the mold and handling without tearing or permanent distortion.

Guide pin bushing The bushing into which the guide pin mates upon closing of the mold or during the ejection stroke.

Guide pin A pin which guides mold halves into alignment on closing. Also called a leader pin. Also used to guide ejector plate movement so that the ejector plates remain perpendicular to the direction of the applied ejector force.

Gum Class of colloidal substances that is exuded by plants.

Gussets Reinforcement structures used to reinforce the part wall and structural supports without increasing wall thickness.