示差走査熱量測定による短繊維強化熱可塑性プラスチック射出成形品の固化温度の同定と冷却速度との相関関係

抄録

Short fiber-reinforced thermoplastics (SFRTPs) have a strength and elastic modulus superior to those of other materials. In injection molding, these thermoplastics continually transition between the solid and liquid phases. The temperatures at which these phase transition behaviors occur are called the crystallization temperature (T_c) and glass transition temperature (T_g). In previous research, we proposed a short beam method for determining the interfacial shear strength (IFSS) of SFRTP injection-molded products. By analysis of the IFSS and weld strength, the solidification temperature (T_solid) could be quantified. However, the relationship between T_solid, T_c, and T_g has not been specified. In this study, T_solid was calculated for three kinds of glass fiber-reinforced thermoplastics in a matrix of polypropylene (PP), polystyrene (PS), and polylactic acid (PLA). Heat flow analysis by differential scanning calorimetry (DSC) was then performed and the heat flow curve in the cooling process was compared with the T_solid value. It was shown that when crystalline plastic was used as the matrix, T_solid equated to T_c, but when amorphous plastic and semi-crystalline plastic were used, T_solid corresponded to T_g.