Effects of Nano-Scale Core-Shell Rubber on the Volume Shrinkage for Unsaturated Polyester
Y-J Huang, T-J Guo, Y-H Yang, M-C Chen, M-C Tsai and Y. Andriani
National Taiwan University of Science and Technology, TW
unsaturated polyester resin (UP), nano-scale core-shell rubbers (CSR), low-profile additive (LPA), curing, volume shrinkage, internal pigmentability
The effects of nano-scale core-shell rubbers (CSR) as low-profile additives (LPA) on the volume shrinkage characteristics and internal pigmentability of unsaturated polyester resins (UP) during the cure at 110oC were investigated. These CSRs were synthesized by two-stage emulsion polymerizations, where the soft core was made from rubbery poly(n-butyl acrylate) (PBA), while the hard shell was made from methyl methacrylate (MMA) with and without ethylene glycol dimethacrylate (EGDMA) as a crosslinking agent. For ST/UP/CSR systems, adding a higher content of CSR may generally result in a lower volume shrinkage, or even an expansion, after the cure. At a fixed CSR content, employing the MA-PG type of UP, with a higher molecular polarity than the MA-PA-PG type of UP, may generally lead to a lower volume shrinkage after the cure. It is inferred that the microvoid formation, which can compensate the volume shrinkage during the cure, and the relief of the polymerization shrinkage force caused by the rubbery core of the CSR, which can lead to the less compact microgel structures and a decrease of intrinsic polymerization shrinkage, are more favorable for the MA-PG system. The experimental results have been explained by an integrated approach of measurements for the static phase characteristics of the ST/UP/CSR system, reaction kinetics, cured sample morphology, and microvoid formation by using differential scanning calorimetry (DSC), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical microscopy (OM), and image analysis.
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