Study on Preparation and Properties of PAI Materials Containing Trifluoromethyl in Side Chain

Polyamide-imide (PAI) materials with good heat resistance, excellent friction, wear properties, and low water absorption were prepared by acyl chloride process with diamine monomer containing trifluoromethyl in the side chain. The results showed that PAI prepared from 2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diamine without flexible hinge group had the best heat resistance, with Tg as high as 302.6 °C and Td5% as 490.1 °C. With the increase of the proportion of flexible hinge groups in diamine monomer, the thermal properties of PAI materials would decrease. The wear mechanism of PAI prepared from 2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diamine was mainly adhesive wear. With the increase of the proportion of flexible hinge groups in diamine monomer, the wear mechanism would change from abrasive wear, slight adhesive wear to severe adhesive wear. The friction coefficient and wear loss of PAI prepared by 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene were the smallest, which were 0.4706 and 3.5, respectively. PAI synthesized by diamine monomer containing trifluoromethyl had low water absorption and high water contact angle. With the increasing flexibility of monomer containing trifluoromethyl diamine, the elongation at break and tensile strength of the material increased gradually.