Melt Spinning of Poly-xylyleneadipamide

Drawn poly-m-xylyleneadipamide filament was dry-heat-treated under free tension at the temperature ranging from 50 to 230°C, and thermal shrinkage (S), birefrigence (Δn), degree of crystallinity (x), degree of crystalline orientation (fc) and degree of amorphous orientation (fa) of the specimens were measured . Relation between transition points observed by Arrhenius plot of 'thermal shrinkage vs. temperature of the thermal treatment and structural quantities, namely thermal retraction mechanism was investigated.The results are as follows : 1) Transition points are observed at 75, 110 and 190°Cin Arrhenius plot, that is, the plot of the logarithm of the thermal shrinkage (log S) vs. reciprocal of the absolute temperature (1/T). In the plots of Δn, x, fc and fa vs. 1/T, transition points are also observed at 50, 70, 110 and 180°C. There is a good relationship between thermal shrinkage and structural quantities.2) The transition point at 50°C is assumed to prior glass transition temperature in the slightly wet state and the thermal retraction caused at the temperature ranging from 50 to 75°Cis due to the disorientation of amorphous chains in the same state.3) The transition point at 75°Cis glass transition temperature, and the retraction caused at the temperature between 75 and 110°C is deduced from the disorientation of amorphous chains and the retraction of amorphous chains under tension induced by folded chain crystallization.4) The transition point at 110°Ccorresponds to the crystal grain boundary relaxation, designated as ai, and the thermal retraction caused at the temperature ranging from 110 to 190°Cis assumed to be mainly the retraction of amorphous chains under tension induced by folding.5) The transition at 190°C is assigned to the crystal disordering relaxation, designated as ct2, and the retraction in the range of 190 to 235°C is due to the rearrangement of molecular chains and partial melt. Melting point of this polymer is 235°C.