Abstract
In this study, Polydimethylsiloxanes (hydroxyl group terminated) are used to toughen 3-Glycidoxypropyltrimethoxysilane (GPTS) modified novolac type phenolic resin / SiO2 organic/inorganic nanocomposite material via sol-gel method. Effects of polydimethylsiloxane on the physical, chemical, mechanical and thermal properties of nanocomposite material were discussed. The polydimethylsiloxanes with various molecular weights (MW = 400~700) were used. Moreover, due to the incompatibility of polydimethylsiloxane and GPTS modified novolac type phenolic resin, three coupling agents (3-Glycidoxypropyl trimethoxysilane, GPTS, 3-Isocyanatopropyl triethoxysilane, IPTS, Tetraethoxysilan, TEOS) were used to modify polydimethylsiloxane and the properties were investigated.From FT-IR spectra studies, it was found that the peak of hydroxyl group at the ends of PDMS is disappear at 3312 cm-1 and produced a new peak of C-O stretching at 1100 cm-1. It was also found that the peak of isocyanato group of IPTS disappeared at 2272 cm-1 and peaks of urethane group at 1680~1630 cm-1 and 1640~1550 cm-1 were shown. The peak of hydroxyl group at the ends of PDMS disappeared at 3312 cm-1 and split peaks at 1100 cm-1~1080 cm-1 can be seen. The split peaks are the absorption of C-O stretching and Si-O-Si antisymmetric stretching. It is confirmed that the three coupling agents (GPTS, IPTS and TEOS) are successfully modified PDMS.29Si solid-state NMR spectra revealed that Q3, Q4 and T3 are the major environments for GPTS modified phenolic resin nanocomposite condensed with modified PDMS (less than 10 phr), i.e., it formed the network structure of Si-O-Si bonding. From thermal property study, the Td5 (Temperature of 5% weight loss) of GPTS modified phenolic resin nanocomposite condensing with GPTS modified PDMS decreased from 381℃ to 369℃, decreased from 381℃ to 362℃ for IPTS modified PDMS and increased from 381℃ to 401℃ for TEOS modified PDMS. From mechanical property study, the impact strength of GPTS modified phenolic resin nanocomposite which condensed with GPTS modified PDMS increased from 8.4kJ/m2 to 10.8 kJ/m2, increased from 8.4 kJ/m2 to 8.9 kJ/m2 for IPTS modified PDMS and increased from 8.4 kJ/m2 to 10.1 kJ/m2 for TEOS modified PDMS. The flexural strength of GPTS modified phenolic resin nanocomposite which condensed with GPTS modified PDMS increased from 77.2 MPa to 85.1 MPa, decreased from 77.2 MPa to 69.1 MPa for IPTS modified PDMS and decreased from 77.2 MPa to 72.4 MPa for TEOS modified PDMS. The L. O. I. values of all nanocomposite reached 35~38 and the U. L. values are 94V-0.