Glossary

Alfa Chemistry's glossary serves as a quick reference guide for customers and is designed to provide comprehensive definitions of plastics industry terms.

A

C

D

E

F

G

I

P

S

T

A

Abrasion Resistance
It is the ability to withstand wear and tear caused by the friction of mechanical parts as well as repeated scraping or rubbing.

C

Compression Molding
It is a relatively simple process involving pressing or squeezing a deformable material charge between two halves of a heated mold and its subsequent transformation into a molded part after cooling or curing.

Cavity
In a plastic injection mold, the cavity is an impression in the front, stationary half of the mold.

Crazing
Crazing is also called hairline craze. It refers to small, hair-like cracks beneath the surface of a plastic part.

D

Deflashing
Covers the range of finishing techniques used to remove the flash (excess, unwanted material) on a plastic molding.

Degree of Polymerization
The degree of polymerization (DP) is defined as the number of monomer units in the polymer. In most plastics the DP must reach several thousand if worthwhile physical properties are to be had.

Decoration
Plastic injection molded parts can be decorated using a variety of methods, the most common of which include pad printing, hot stamping, thermal transfer, and in-mold decoration.

Dimensional Stability
It is a measure of the ability of a plastic part to retain its fit, form and functional properties throughout its life cycle.

Drape Forming
It is a process whereby a plastic sheet is heated to the state where it can be pressed, bent or formed into or over a mandrel or form.

E

Extrusion
Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section.

F

Finish
It refers to the final surface appearance, texture and characteristics of a plastic product or component.

Flexible Molds
Molds made of rubber or elastomeric plastics used for casting plastics. They can be stretched to remove cured pieces with undercuts.

Flexural Modulus
It is defined as the tendency of a material to bend or is described in terms of flexural deformation, the ratio of stress to strain.

Flexural Strength
It is defined as the material's ability to resist deformation under load.

G

Gate
The orifice through which the melt enters the cavity in injection and transfer molding.

I

Injection Ram
In injection molding, the ram that applies pressure to the feed plunger in the process of either injection or transfer molding.

Izod Impact Test
It is a standard test that measures the impact energy needed to fracture a material.

P

Plastic Deformation
It is the permanent deformation that occurs when a material is subjected to tensile, compressive, bending, or torsion stresses that exceed its yield strength and cause it to elongate, compress, buckle, bend, or twist.

Plastic Memory
It refers to the tendency of certain plastics to return to their original form when heated after deformation.

Plasticity
It refers to the property of being able to be shaped by plastic flow.

Plasticize
To soften a material and make it plastic or moldable, either by means of a plasticizer or the application of heat.

S

Surface Finish
Surface Finish is a measure of the overall texture of a surface that is characterized by the lay, surface roughness, and waviness of the surface.

T

Tolerances
Tolerances for specified dimensions of a molded part are ranges of acceptable deviation from too small to too large.