Fracture Mechanism Change at a Heterogeneous Polymer-Polymer Interface Reinforced with in Situ Graft Copolymers

Area of Science:

• Materials Science
• Polymer Science
• Surface Science

Background:

• Heterogeneous polymer-polymer interfaces often exhibit complex failure mechanisms.
• In situ graft copolymers can enhance interfacial properties but require detailed investigation of their failure modes.
• Understanding failure mechanisms is crucial for designing robust polymer composites.

Purpose of the Study:

• To investigate the failure mechanisms at a polystyrene (PS)/polyamide (nylon 6, Ny6) interface reinforced with in situ graft copolymers.
• To determine the influence of bonding time and temperature on fracture toughness and failure modes.
• To provide experimental evidence for molecular diffusion effects at the interface.

Main Methods:

• Dynamic secondary-ion mass spectroscopy (DSIMS) was employed to analyze the chemical composition and diffusion at the interface.
• Fracture toughness tests were conducted to evaluate the mechanical performance under varying conditions.
• In situ graft copolymerization was utilized to modify the polymer interface.

Main Results:

• A transition in failure mechanism from adhesive to cohesive was observed with increasing bonding time and temperature.
• DSIMS confirmed diffusion of nonreactive polystyrene (PS) away from the interface at longer annealing times.
• Fracture toughness varied significantly, correlating with the identified failure mechanisms.

Conclusions:

• The study elucidates the dual failure mechanisms (adhesive and cohesive) at reinforced heterogeneous polymer interfaces.
• Molecular diffusion of nonreactive polymer chains is a key factor driving the shift towards cohesive failure.
• The findings are applicable to polymer interfaces reinforced with in situ graft copolymers, irrespective of polymer crystallinity.