APP: see Atactic polypropylene
ASTM: American Society for Testing and Materials
Abrasion resistance: the ability to resist being worn away by contact with another moving, abrasive surface, such as foot traffic, mechanical, equipment, wind-blown particles, etc.
Absorption: the ability of a material to accept within its body, quantities of gases or liquid, such as moisture.
Accelerated weathering: the exposure of a specimen to a specified test environment for a specified time with the intent of producing in a shorter time period, effects similar to actual weathering.
Acrylic coating: a liquid coating system based on an acrylic resin. Generally, a latex-based coating system that cures by air drying.
Acrylic resin: polymers of acrylic or meth acrylic monomers. Often used as a latex base for coating systems.
Adhere: the clinging of one surface to another; either molecularly or otherwise.
Adhesion: steady or firm attachment.
Aggregate: (1) crushed stone, crushed slag or water-worn gravel used for surfacing a built-up roof system; (2) any granular material.
Algae: rooftop fungus that can leave dark stains on roofing.
Alligatoring: the cracking of the surfacing bitumen on a bituminous roof or coating on a SPF roof, producing a pattern of cracks similar to an alligator’s hide; the cracks may not extend completely through the surfacing bitumen or coating.
Aluminum: a non-rusting, malleable metal sometimes used for metal roofing and flashing.
Ambient temperature: the temperature of the air.
Application rate: the average quantity, (mass, volume or thickness) of material applied per unit area.
Asphalt: a substance left as a residue after evaporating or otherwise processing crude oil or petroleum. Asphalt can be refined to conform to various roofing grade specifications.
Asphalt emulsion: a mixture of asphalt particles and an emulsifying agent such as bentonite clay and water.
Atactic polypropylene: a group of high molecular weight polymers formed by the polymerization of propylene.