Crystal modulus of a new semiaromatic polyamide 9‐T

The elastic modulus (El) of crystalline regions in the direction parallel to the chain axis in a new semiaromatic polyamide 9-T (PA9-T) containing a long aliphatic chain unit was measured by X-ray diffraction and the derived El value was discussed in terms of its molecular conformation and mechanical properties. For low and high molecular weight PA9-Ts, the El value of 40 GPa was obtained. The low El value for PA9-T is due to the presence of aromatic groups with long crankshaft arms, which result in a greater moment of force during deformation compared with those polymers with planner zigzag molecular conformation like polyethylene and nylon 6 α-form. Another factor for the low El is due to the contraction of its molecular chains that is likely originated from the existence of a torsional conformation. The presence of contraction causes some internal rotation in the polymer chain during extensional deformation, which results in low El. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers