Thermoset/Thermoplastic Interphases: The Role of Initiator Concentration in Polymer Interdiffusion.

Area of Science:

• Polymer Science and Engineering
• Materials Science
• Adhesion Science

Background:

• Co-bonding of thermoset and thermoplastic polymers creates an interphase due to polymer interdiffusion.
• Optimizing interphase properties is critical for enhancing the mechanical performance of polymer composites and adhesive joints.
• Factors influencing interdiffusion and interphase formation require thorough investigation for advanced material design.

Purpose of the Study:

• To investigate the effect of initiator concentration on the interphase thickness in co-bonded thermoset-thermoplastic polymers.
• To establish a correlation between initiator concentration, gelation time, cure speed, and interphase characteristics.
• To provide insights for optimizing the co-bonding process for improved mechanical properties.

Main Methods:

• Rheometer measurements to determine the dependence of gelation time on initiator concentration.
• Differential scanning calorimetry (DSC) to assess the cure speed of the thermoset resin.
• Optical microscopy to measure the interphase thickness in co-bonded polymer samples.

Main Results:

• A direct correlation was found between increased initiator concentration and decreased gelation time.
• Higher initiator concentrations led to a significant reduction in interphase thickness and polymer diffusivity.
• Increasing the initiator/resin weight ratio from 1% to 3% reduced gelation time by 74% and interphase thickness by 63%.

Conclusions:

• Initiator concentration is a key factor controlling interphase formation and thickness in co-bonded thermoset-thermoplastic systems.
• Reduced gelation times, achieved by higher initiator concentrations, effectively minimize interdiffusion and interphase development.
• This study offers a method for controlling interphase thickness to enhance the mechanical integrity of co-bonded polymer structures.