Preparation And Properties Of PPO Modified Epoxy Resin Composite Materials Applied In High Requency Copper Clad Laminates

Epoxy resin is an important class of thermosetting material with good mechanical and electrical properties, and has been widely used as the materials of copper clad laminates (CCLs). However, the applications of epoxy resin in the high requency CCLs that request fast transportation speed and high circuit density are restrained because of their inferior thermal and dielectric properties. Polymer blending has been a feasible and convenient way to improve the physical properties of epoxy resin. Poly(phenylene oxide)(PPO) has the low water uptake, high dimensional stability, good heat-resistant and dielectric properties. Therefore, the epoxy/PPO composite material has been considered as an excellent candidate for the the high requency CCLs.The phenol-formaldehyde epoxy-novolac resin (EPN) has greatly improved chemical and heat resistance compared to the much more common bisphenol-A epoxy resin, and would be more suitable for the applications as high requency CCLs. Besides, PPO is thermodynamically immiscible with epoxy resin, and therefore the phase separation occurs in their blends, which is more significant for PPO with high molecular weight. Reactive blending of immiscible polymers is a useful strategy to produce the polymeric materials with controlled phase morphology and high physical performances. Therefore, the epoxide-terminated low-molecular-weight PPO was synthesized by modifying the terminal hydroxyl group of PPO and it was reactively blended with EPN. The curing kinetics, phase morphology, thermal stability, dielectric property, and water absorption behavior of the cured EPN/epoxide-terminated PPO composite materials were investigated and compared to EPN/PPO.As revealed by the FTIR and DSC analysis, epoxide-terminated PPOs take part in the curing reaction and form a reactive blend with EPN. The curing rate of both EPN/PPO and EPN/epoxide-terminated PPO blends first increases and then decreases with increasing the PPO or epoxide-terminated PPO fraction. The blends have lower degree of curing than neat EPN, due to the steric hindrance effects of PPO or epoxide-terminated PPO. Because of the reaction between blend components, EPN/epoxide-terminated PPO blends show faster curing rate and higher degree of curing than the corresponding EPN/PPO blends. As revealed by the SEM and TEM analysis, the reactive blending improves the dispersion of epoxide-terminated PPO in EPN matrix and the EPN/epoxide-terminated PPO blends form a co-continuous morphology even at a low epoxide-terminated PPO content, compared to the typical sea-island morphology of EPN/PPO blends. The compatibility of blends is improved remarkablely by reactive blending due to epoxide at the end of epoxide-terminated PPO. Besides, all the EPN/PPO and EPN/epoxide-terminated PPO composite materials have remarkable smaller dielectric constant, dissipation factor, and water absorption than neat EPN.