Incoming Resin Lot Qualification and Certificate Validation
Incoming resin qualification mandates physical sampling, melt rheology auditing, and CoA validation to prevent off-spec polymer from entering production.
Polymer Delamination
Meaning
Structural surface separation defects manifest as physical peeling of discrete resin layers along high-shear flow lines within molded plastic parts. Polymer delamination occurs when incompatible polymer blends or severe shear stresses prevent inter-chain entanglement during cavity filling. The boundary of this condition covers physical layer separation and excludes surface discoloration or minor sink marks.
Shear Disruption
High velocity melt fronts flowing through restrictive gate geometry create extreme shear stress along cavity walls. Excessive shear stress induces mechanical polymer delamination by fracturing cold material layers as fresh melt flows underneath. Lowering injection speed reduces shear stress and promotes uniform layer bonding across the flow front.
Material Incompatibility
Processing raw material contaminated with foreign resin types prevents chemical bonding across molecular interfaces. Blending regrind stock containing secondary polymers creates localized weak zones where physical separation occurs under light mechanical loads. Virgin polymer purity specifications restrict cross-contamination to preserve structural integrity.
Moisture Scission
Unbound water within hydroscopic resins undergoes rapid vaporization inside heated barrel assemblies. Superheated steam generates internal gas pockets that rupture as resin passes through the mold gate, creating skin-core separation. Thorough desiccant drying lowers moisture content below critical thresholds, preventing steam expansion and preserving mechanical layer cohesion throughout the part structure.
Extended residence time in humid hoppers reintroduces water vapor, requiring sealed material handling systems to prevent defect recurrence.