Polymer Degradation

Meaning

Irreversible breakdown of molecular structure in a plastic material resulting from heat, radiation or aggressive chemical environments. During the moulding cycle, polymer degradation occurs if melt temperatures rise too high or if the resin stays in the heated barrel for too long. This process permanently alters the performance of the plastic and usually results in part failure.

Molecular Breakdown

Shortening of the long molecular chains reduces the ability of the material to resist force without snapping. If polymer degradation is not controlled, the viscosity of the melt drops sharply and causes flashes of plastic to leak from tool seals. This loss of consistency disrupts automated monitoring sensors on the injection press.

Color Change

Appearance of dark spots or yellowing serves as an early warning that the plastic is burning or oxidizing inside the manifold. When severe polymer degradation sets in, the material may release volatile gases that create a safety hazard in the workplace. This chemical change makes the part brittle and unusable for structural loads.

Mechanical Loss

Recovery of strength is impossible once the chemical bonds have been severed by intense heat or UV rays. Preventing polymer degradation involves setting tight temperature limits and using correct amounts of thermal stabilizers during the initial compounding phase. It remains the primary reason why scrap levels are high in factories with poorly tuned processing parameters.