A novel itaconic acid (IA) based epoxy resin with curable double bonds (EIA) was synthesized by the esterification reaction between IA and epichlorohydrin (ECH). Its chemical structure was confirmed in detail by FT-IR, 1 H-NMR and ESI-ION TRAP MS before being cured by methyl hexahydrophthalic anhydride (MHHPA). In order to manipulate the properties of the cured resin, divinyl benzene (DVB) and acrylated epoxidized soybean oil (AESO) were employed here to act as comonomers. The results demonstrated that EIA showed a higher epoxy value of 0.625 and higher curing reactivity toward MHHPA compared with the commonly used diglycidyl ether of bisphenol A (DGEBA). The glass transition temperature, tensile strength, flexural strength and modulus of the cured EIA without comonomers were 130.4 °C, 87.5 MPa, 152.4 MPa and 3400 MPa, respectively, which were comparable or better than those of DGEBA cured by the same curing agent. After being copolymerized with DVB or AESO, the properties of the cured EIA could be regulated further. The results indicated that EIA has great potential to replace the petroleum-based thermosetting resin, such as DGEBA.
The crystallization behavior of polylactic acid (PLA) was studied in the presence of a crystal nucleating agent, ethylenebishydroxystearamide (EBH). The crystallization rate and crystallinity were significantly increased with addition of EBH. The isothermal crystallization halftime at 105 C was decreased from 18.8 minutes for neat PLA to 2.8 minutes for PLA with 1.0 wt % of EBH. The crystallinity of PLA with 1.0 wt % EBH was about 35% after 5-minute annealing at 105 C. Like neat PLA, the double melting peaks were also observed for nucleated PLA. The changes of the double melt peaks were investigated with various crystallization temperatures, heating rates, and annealing times. The heat deflection temperature (HDT) of nucleated PLA was up to 93 C after annealing. The correlation between crystallinity and HDT was demonstrated. A percolation threshold of crystallinity was found corresponding to HDT. The crystal size of nucleated PLA was significantly decreased with addition of EBH. The mechanical properties of annealed PLA blends simultaneously; showed improved modulus and impact strength.
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