There are three types of stress cracking: 1. Thermal stress cracking is caused by prolonged exposure of the part to elevated temperatures or sunlight. 2. Physical stress cracking occurs between crystalline and amorphous portions of the part when the part is under an internally or externally induced strain. 3. Chemical stress cracking occurs when a liquid or gas permeates the partís surface. All of these types of stress cracking have the same end result: the splitting or fracturing of the molding.
Cracking that occurs as a result of mechanical stress. In most cases, tiny cracks caused from exposure of the plastic to chemicals or ultraviolet radiation are already present.
Cracking of the laminate due to dimensional movement.
The development of cracks which are frequently accelerated by the environment to which the plastic is exposed.
A crack, either external / internal, in a plastic part caused by tensile stress less than its short time mechanical strength. The moulded-in stress left in the moulded part - due to unbalanced filling, over packing or non uniform freezing – can fail in service condition. The service environment can have objectionable temperature or contact with aggressive chemicals causing the plastic part to fail. Avoiding or minimising moulded-in stress in plastic part can increase the performance of part even under adverse condition.
The fracturing of parts which have retained residual stresses from cold forming, heat treating, or rapid cooling.
Also referred to as crazing. Fine cracking which appears in the surface of paint, porcelain, etc.
