Meaning
Polymer blend microstructure consists of elastomer particles distributed within a rigid thermoplastic matrix to improve impact resistance. This composite structure arises from core-shell morphology, where an inner polymer domain is encapsulated by an outer polymer layer. The outer shell ensures compatibility with the matrix, while the inner core absorbs mechanical energy during impact.
Toughness Enhancement
Impact modification of brittle polymers relies on the spacing and size of these distributed rubbery particles. High-rate mechanical stresses are dissipated by the core-shell morphology, which prevents crack propagation through the moulded component. The ductile shell deforms under load and transfers stresses to the energy-absorbing elastomer core.
Processing Influence
Melt temperature and shear rate during extrusion affect the dispersion of these multi-component particles. High shear forces during compounding can disrupt the core-shell morphology, leading to localized agglomeration and reduced toughness in the final part. Maintaining optimal melt viscosity is necessary to preserve the encapsulated boundary layers.
If the extrusion temperature is too high, the core and shell phases may interdiffuse and lose their distinct boundaries.
Property Preservation
Recycling processes often degrade the interface between the core and the shell. Such thermal degradation alters the core-shell morphology and diminishes the impact performance of the regrind blend. Tool designers must adjust runner profiles to avoid high-shear regions that could tear the shell from the core.
