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Acto Polymcriu 35 ( 1 9 W Nr. 9 580 SUJAK, WLOCHOWICZ and WYSOCKI: IR spectroscopic analysis of changes in the molecular structure of pitch carbon fibre motion of chains is realized, apparently, only in the interior of their coordinate surrounding and performs by rotations of some portions of the macromolecule around its axis, atomic displacements along and transverse the axis accompanying this process. In this case the contactwhere 8 is the maximal rotation angle of the chain portion, r is the maximal atomic displacement along the axis, z = 4 to 6 is the coordination number of the linear macromolecules stacking. Substituting ST = 5 s , , for instance, in this relation one obtains the following equation: 8/n = (1.25 dB/rz)'12.Probability of displacements r > dB m 0.3 nm a t thermal motion in polymer a t T < T g is negligibly small.Then it follows from the plot 8 ( r ) , Fig. 7, t h a t the @relaxation in copolymers, PVB and polyamide 6 takes place by means of rotation of the main chain portions around the macromolecule axis by angles 8 2 n/2 (accompanying displacements of main chain atoms have the magnitude r = 0.05 to 0.2 nm). This result together with the experimental data shown in Fig. 5 is a n evidence in favour of operating the conformational transitions in the temperature region of @-relaxation in glassy polymers4). 4 , I t should be noted that the results obtained are not in contradiction with the activation analysis data [8, 161, indicating that the length of rotating main chain portions is commensurable with that of KUHN'S segment.Changes occurring during the process of oxidation of precursor pitch carbon fibres have been analyzed by means of I R spectroscopy. It has been established that a crosslinking process takes place, when the fibres are heated to temperatures above 553 K. Oxidation of the fibres depends on kind of oxidizing medium (oxygen, ozone, air) as well as on duration of oxidation. Infrarotspektroskopische Analyse der bei der Oxidation von Precursoren fur Kohlenstoff-Fasern aus Pech auftretenden Anderungen der MolekiilstrukturDie beim OxidationsprozeS der Precursoren fur Kohlenstoff-Fasern aus Erdolpech auftretenden Anderungen wurden mit Hilfe der Infrarotspektroskopie analysiert. Es wurde festgestellt, daB ein VernetzungsprozeB auftritt, wenn die Fasern auf Temperaturen oberhalb 553 K erhitzt werden. Die Oxidation der Fasern hangt vom Oxidationsrnedium (Sauerstoff, Ozon, Luft) sowie von der Dauer der Oxidation ab. Anafiua u3&enenuB 8 &owetcympnoB cmpyxmype npedulecm8ennutcoe nexoebzx eofioEon npu npoyecce otcuc*Zenua aemo6'oa ung6patcpacnoii cnetcmpocxonuuHa OCHOBe MIC-CneKTpOCHOnllreCK~X mcnenoBaaai nposegeH a~a~1113 m~e r~e~n i i B npoqecce OKacneHm npen-IIIeCTBeHHHKOB YrOJIbHblX BOJIOKOH E13 neKa. YcTaHOBneHO, 'iTO IlpOqeCC CTPYHTYPUPOBaHHJ3 BOJIOKOH npOE1CXOgllT T o r g a , K o r~a~o n o H~a~a r p e s a r o i w i~o~e~n e p a~y p u s b~I u e 553 I C . O K H~~~H E~~B~~~K~H~~B I I C H T O TWei cpegH (~acnopog, 030H, B03AYX), a TaHxe OT npogonxmenbHocTH npoqecca.