Effect of poly(ether imide) blends on the physical properties of thermoplastic glass mat composites

Glass mat thermoplastic composites (GMTs) were prepared from poly(ether imide/poly(ethylene naphthalate) (PEI/PEN) and PEI/poly(ethylene terephthalate) (PET) blends using compression molding. The thermal stability, surface hardness, rheological, mechanical, and gas barrier properties and the coefficient of thermal expansion (CTE) for various composites were analyzed. Differential scanning calorimetric and thermogravimetric analysis showed that PEI blends with 30% PEN or PET retained 80% of the thermal stability of virgin PEI. PEI melt viscosity significantly decreased with addition of PEN and PET, which greatly improved impregnation during GMT manufacture. The tensile strength and CTE of GMTs containing up to 30% PEN or PET remained similar to that of PEI/GM, while the flexural modulus increased and the gas barrier properties improved two fold. Scanning electron microscopy confirmed that interfacial adhesion improved for surface-modified GMs. We demonstrated that inexpensive GMTs could be prepared while retaining the superior properties of PEI.