STRUCTURAL-ANALYSIS OF POLYAMIDE-6,6 REINFORCED WITH GLASS-FIBER BY THE USE OF FOURIER-TRANSFORM INFRARED-SPECTROSCOPY WITH PHOTOACOUSTIC DETECTION AND DIFFERENTIAL SCANNING CALORIMETRY

The effect of fibre reinforcement, industrial processing and subsequen t annealing on the structure of polyamide-6,6 was analysed in this pap er from the correlation between photoacoustic Fourier transform infra- red (PA FTi.r.) spectroscopic and differential scanning calorimetry (d .s.c.) thermal measurements. Using the band situated at 1650 cm(-1) as an internal reference band, no spectral change was detected in the ba nds at 936 and 1146 cm(-1). Furthermore, the bands centred at 1335 and 1224 cm(-1), which are related to chain-folding, appear in the unanne aled composite, whereas in the matrix these were only detected at the highest annealing temperatures. It seems that the manufacturing proces s used for the composite determines its microstructure and the subsequ ent annealing does not produce further conformational changes. On the other hand, the composite satisfies a two-phase conformational model, different from that of the matrix, which can be related to the strong interactions between the polymer and the glass fibres with surface tre atment. In the thermal analysis, in contrast to the spectroscopic resu lts, substantial changes in the endothermic melting peaks and in the d egree of crystallinity can be noted. Up to an annealing temperature of similar to 120-150 degrees C, the composite crystallinity is constant and lower than the matrix crystallinity, but above this temperature t he value rises and tends towards the values of the matrix. Furthermore , there was a more homogeneous crystalline distribution detected in th e unannealed matrix, along with a greater size and perfection of the c rystals than that seen in those of the unannealed composite. We sugges t that the d.s.c. variation in the crystallinity can be attributed to an improvement in the fibre-matrix interface, in which the crystals of the interfacial phase change to more perfect ones as a result of the annealing treatment.