Ultradrawing of films of high‐molecular‐weight polyethylene (M̄w = 1.5 × 106) produced by gelation crystallization from solution is discussed. The influence of the initial polymer volume fraction (ϕ) on the maximum draw ratio (λmax) of the dried films is examined in the temperature region from 90–130°C. The results can be described very well by the relation λmax = λ max1 ϕ−1/2 where λ max1 is the (temperature‐dependent) maximum draw ratio of the melt‐crystallized film. An attempt is made to discuss the marked influence of the initial polymer volume fraction on λmax in terms of the deformation of a network with entanglements acting as semipermanent crosslinks.

No abstract

No abstract

215by the slight scatter of experimental points, but the amplitude of motion appeared to have no sensible effect.The attenuating properties of the two transducer circuits are shown in figs. 7 and 8. There is a distinct difference in the atten-Variable sine wave generator setting l~ig. 9. Calibration of the variable sine wave generator uation of the two signals for each cut-off frequency, the difference increases with increasing frequency over the 0-25 c.p.s. frequency range, for the 50 and 150 cut-off frequencies. In the case of the 20 c.p.s. cut-off frequency the curves cross at a frequency of about 18.4 e.p.s, and the attenuation of both signals reaches a much higher value than those for the 50 and 150 cut-off frequencies.The amplitude of motion cannot be found directly from the resolved components indicator and this was found independently using an optical system in which there could be no internal attenuation. The results of this test are shown in fig. 9.The results show the importance of proper characterisation of the transducer circuits and it is likely that because of manufacturing variations each instrument should warrant individual analysis for the most accurate work. A dcnowledgement The authors wish to thank Mr. D. R. Hall and Mr. R, D. Wall of Solarton Electronics Ltd. for several helpful discussions, Mr. I. Urquhart for technical assistance and the Ministry of Aviation for financial support. SummaryA method is described of analysing the frequency response of the transducer circuits of the Weissenberg rheogoniometer. Results are presented of a comprehensive analysis of an 1%.16 model and it appears that considerable phase shifting between the signals from the input motion transducer and the torsion head transducer arises in the network and persists in varying degrees over the working range of the instrument. There is also an attenuation of both signals which is generally not the same for both transducer signals and likewise persists over the whole of the instrument range. Errors will arise in evaluating rheological properties in oscillatory shearing motion if the experimental results are not corrected for these effects.

No abstract