Synthesis And Characterization Of PA6-b-PPG Block Copolymer

Thermoplastic polyamide elastomers(TPAs) consist of polyamide hard segments and polyether or polyester soft segments. They own elasticity as the rubber, they also can be reprocessed like thermoplastics. TPAs have relatively excellent wear resistance,elasticity, dimensional stability and processability. They also have outstanding resistance high and low temperature, heat aging resistance and chemical resistance.TPAs have been widely studied and applied because of these advantages.In this paper, a kind of TPA based on PA6-b-PPG was synthesized by one-step method and two-step method. Considering the actual situation in industrial production, one-step method was chosen to synthesize TPAs by comparing the viscosity and the content of extractable matter of products synthesized by different methods. Optimum reaction conditions were obtained from a series of experiments.The temperature of ring-opening reaction was set as 220 oC, the time of ring-opening reaction was set as 2 hours, the amount of water added was set as 6 wt%. The temperature of post polymerization was set as 260 oC, the time of post polymerization was set as 2 hours, the pressure of reaction system was set as 1000 Pa.A series of TPAs with different content of PPG was synthesized by one-step method. Chemical structure of TPAs were characterized by FT-IR and1H-NMR,thermal properties were measured by DSC and TG, crystallization properties were analyzed by DSC, WAXD and PLM, dynamic mechanical thermal properties and mechanical properties were also tested. The results show that block copolymerization between PA6 hard segments and PPG soft segments occurs. Melting points of TPAs vary from 209 oC to 225 oC, initial thermal decomposition temperature is over 380 oC and maximum weight loss rate point temperature is over 400 oC. It indicates that TPAs own good thermal stability. The crystallinity declines and the crystalline type of TPAs transforms from γ-crystalline to α-crystalline with the content of PPG increasing. When the content of PPG were 5%, 10%, 20%, the glass transition temperature of TPAs were 35 oC, 24 oC, 15 oC. It shows that the glass transition temperature decline with the content of PPG increasing. The α-relaxation peak andβ-relaxation peak of TPAs get close to each other, it indicates that the compatibility of PA6 hard segmenst and PPG soft segments improved with the content of PPG increasing. The series of TPAs show good mechanical properties. When the content ofPPG increase from 5% to 35%, the shore hardness of TPAs decrease from 73.6D to40.6D, the tensile strength of TPAs decrease from 51 MPa to 32 MPa, the elongation at break of TPAs increase from 210% to 460%, the flexural strength of TPAs decrease from 27.1 MPa to 11.6 MPa, The impact strength reached maximum 75 KJ/m2 when the content of PPG arrives at 30%.In this paper, synthesis methods and reaction conditions were studied systematically. A series of TPAs with good mechanical properties was synthesized and the relationship between structure and properties were analyzed by various test methods. This work provides theoretical support for the continuous industrial production of TPAs.