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Thermal, rheological, and fiber spinning behavior of poly(ethylene terephthalate-co-4,4‘-bibenzoate) random copolymers containing 5−65 mol % bibenzoate (BB) units have been studied. Copolymer randomness was determined by 13C solution NMR. Copolymers with >40 mol % BB units spin like thermotropic liquid crystals and have mechanical properties approaching those of liquid crystals; however, no evidence of liquid crystallinity was observed in these fibers based on thermal, optical, and rheological studies. Thus, we believe these polymers are frustrated liquid crystalline polymers. The α-relaxation attributed to the glass transition temperature is completely suppressed in the fully drawn and heat-treated PETBB55 fibers. Structure development during fiber spinning as well as fiber mechanical properties have been studied. Fibers containing more than 40 mol % bibenzoate show the development of a new crystal structure and exhibit much higher tensile modulus than the copolymers containing a lower bibenzoate percentage. Copolymers containing more than 40 mol % bibenzoate also exhibit high melt relaxation times compared to the lower bibenzoate copolymers.

The number, type, strength, lifetime, and the exchange of hydrogen bonds in the self-healing process at different temperatures were investigated by molecular dynamics simulation using a micro-crack model.

Several compositionally different poly(ethylene terephthalate-co-1,4-phenylene bisacrylate) (PETPBA) copolymers were melt spun into fibers. The resulting fibers were subjected to UV irradiation to induce crosslinking. Evidence of crosslinking was obtained from FTIR, solid-state 13 C-NMR, thermal analysis, and solubility. Irradiation of the fiber results in an increased glass-transition temperature, reduced thermal shrinkage, and enhanced modulus retention at elevated temperature.

In this paper, a synthesis method of epoxy resin toughening agent was presented, then the chemical composition and molecular number were studied, which include the DSC curves analysis, the fracture surface morphology and bonding strength. In addition, the mechanism of epoxy resin toughening agent and the effect of toughening agent’s content to bonding strength were studied. The testing results reveal that this toughening agent can form a micro two-phase structure in epoxy-amine system, which results in the stable chemical properties and excellent physical properties.