Dynamic mechanical behavior of ultradrawn polyethylene films produced by gelation/crystallization from solution

Abstract

This paper is concerned with the temperature dependence of mechanical properties of ultradrawn polyethylene in terms of storage modulus E' and loss factor tan 6 by the measurement of the complex dynamic tensile modulus over ranges of temperature from 20 to 140 ~ Interestingly, E' of a specimen with drawn ratio of 300 is about 120 GPa at 140 ~ when the measurement is carried out at a frequency of 100 Hz. This is a very high value. In addition, the drawn specimens were irradiated to try to produce ultradrawn polyethylene films with more excellent mechanical and thermal properties. However, the melting peak shifts to a lower temperature with increasing radiation dose. This result is probably attributed to the considerably radiation-induced scission of extended chains constructing crystals.

Ultradrawing of High Molecular Weight Polyethylene Films Produced by Gelation/Crystallization from Solution: Effect of the Number of Entanglements

“…This is due to the fact that drawability is dependent upon the softening of specimens as well as the suitable level of entanglements and 135oC is the temperature associated with rupt softening as indicated from DSC heating curves. 13 Actually, the achievement of high draw ratio could be realized under the condition that elongation was carried out immediately when the temperature in a hot oven became 135°C. In contrast, the draw ratio decreased with increasing annealing time and this tendency became considerable when the annealing time was beyond 15 min.…”

Ultradrawing of Isotactic Polypropylene Films Produced by Gelation/Crystallization from Solutions

“…18, No. 10,1986 polyethylene used at the same concentration in the previous work, 8 although the chain length of the former is about one-fifth that of the latter. Accordingly, this leads to the expecta-tion that the size or extension in space of polyethylene chains is much larger than that for polypropylene even if the molecular chain lengths for both the polymers are equal.…”

Cross-Linking Effect of Polyethylene-Polypropylene Blend Films Prepared by Gelation/Crystallization from Solution

“…This result was attributed to the considerable radiation-induced scission of extended chains forming the crystals. These results" - 13 indicate that cross-linking of ultradrawn polyethylene films by the irradiation is not appropriate for producing a net crosslinking effect occurring preferentially in the amorphous regions. This unfavorable finding is due to the high crystallinity of ultradrawn films.…”

“…12 A similar method was carried out by Sawatari and Matsuo using electron beam irradiation. 13 They exposed an electric beam to ultradrawn films, the draw ratios being greater than 50, under nitrogen. Unfortunately, the mechanical properties of the resultant specimens became much weaker with increasing radiation dose and the specimens with a dose of 200 Mrad were easily torn by hand.…”

“…19 The melting point of polypropylene increased with increasing draw ratio and approached the theoretical value. 20 The 25/75 blend film with a draw ratio of 60 could be kept at 160°C at a fixed dimension, which is higher than the apparent melting point ( 155°C) of polyethylene with a draw ratio of 300, 13 associated with the superheating effect. In order to pursue further improvement in high temperature resistance, the cross-linking of the blend films was performed with electron beam as well as with reaction of DCP.…”