Meaning
Resin degradation caused by moisture attack on ester or amide linkages during thermal processing defines a hydrolyzed polymer within compounding operations. Water molecules cleave the main chain at high melt temperatures, leading to molecular weight reduction and broad property drift across moulded lots. Such chemical cleavage alters melt flow rate beyond the tolerance window set for the mould.
Resin Specification
Material datasheets establish upper moisture limits for hydro-sensitive feedstocks prior to pellet entry into the barrel. Virgin grades arrive with specific drying requirements measured in parts per million of residual water content, whereas regrind introduces variable thermal history and unpredictable moisture affinity. Suppliers define mechanical property retentions based on controlled compounding and drying protocols executed before pellet plastication.
Processing windows narrow sharply when suppliers fail to declare regrind ratios mixed into prime resin shipments.
Moulding Parameter
Barrel temperature profiles and residence times dictate the extent of chain cleavage during injection or extrusion cycles. Technicians control screw speed and back pressure to minimize frictional heat generation that accelerates moisture driven scission. Feed throat starvation prevents premature melting of wet pellets in unvented barrel zones.
Melt temperature stability across production runs protects final part dimensions from unexpected shrinkage variations caused by lower molecular weight fractions.
Component Failure
Molecular weight degradation manifests as brittle part failure, surface silver streaking, and reduced impact strength under mechanical load. Low melt viscosity promotes flash formation around parting lines during high pressure injection phases. Component failure occurs when internal stresses exceed the tensile capacity of chain scission weakened structures.
Final part performance depends entirely on maintaining polymer chain integrity from feedstock hopper to finished article.
