Properties of epoxy molding compound according to the pretreatment method of an amino-silane coupling agent on epoxy or phenol resin

Abstract

An amino-functional silane coupling agent, which is an important component for epoxy molding compound (EMC), has been used by diverse methods, such as integral addition into a mixed powder and pretreatment on silica or on resin. However, the homogeneous dispersion of the amino-functional silane coupling agent in mixed powder is limited with integral addition, and the possibility of white gel formation, sometimes causing gate blocking during the transfer-molding process, due to the aggregation of silica with the coupling agent cannot be completely removed by it. The pretreatment of the amino-functional silane coupling agent on silica has been adopted as an alternative process, but the process is expensive and limited in mass production. Although the pretreatment of the coupling agent on resin as another method has also been used by some EMC manufacturing companies, it has hardly been known in which resin phase, the epoxy or hardener, the silane coupling agent should be pretreated for better mechanical properties of EMC. In this study, the pretreatment of the amino-functional silane coupling agent on epoxy or phenol resin, essential components of EMC, has been investigated with respect to the reaction during the pretreatment and the properties of EMC according to the different pretreatment methods. In the case of the pretreatment on epoxy, the amino-functional silane coupling agent rapidly forms an adduct with epoxy via a ring-opening reaction, whereas its alkoxy groups are well preserved. The glass-transition temperature and flexural strength of the EMC by the application of the pretreatment method on epoxy are lower than those by the pretreatment on phenol. It is thought that the degree of linkage between the resin matrix and silica becomes lower because of the confinement of aminopropyltriethoxy silane (APTS) within the epoxy matrix through an irreversible reaction with epoxy in advance. In the case of the pretreatment on phenol, most of the alkoxy groups in the coupling agent are assumed to be replaced with protonic nucleophiles such as phenol, generating an equivalent amount of alcohol. Because the adduct between the phenol and amino-functional silane coupling agent can be easily regenerated during the manufacturing process, it is thought that the pretreatment method of APTS on phenol helps APTS disperse well within EMC. Actually, the glass-transition temperature and flexural strength of EMC by the application of the pretreatment method on phenol are higher than those by the integral addition method and the pretreatment on epoxy. However, they become lower as the degree of reaction of silane with phenol increases. The pretreatment of the amino-functional silane coupling agent on phenol shows lots of advantages over the previous methods. From the viewpoint of the process, the homogeneous dispersion of the coupling agent can be obtained with consistency, and the possibility of white gel formation can also be completely removed by it. From the perspective of properties, through a controlled pretreatment on phenol resin, better mechanical properties of EMC can be obtained than those through the pretreatment on epoxy. In addition, the pretreatment process on phenol is simple and feasible for mass production. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2171–2179, 2006