Molecular Weight Dependence on the Morphological Properties of Polyethylene Gels

Sawatari, Chie; Okumura, Tomoko; Matsuo, Masaru

doi:10.1295/polymj.18.741

Cited by 72 publications

(58 citation statements)

References 35 publications

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“…Sawatari et al [14] showed that for ultra-high molecular weight polyethylene gel films the optimal concentration, i.e. the concentration at which just enough realized at this concentration.…”

Section: Resultsmentioning

confidence: 99%

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Gel-spun polyethylene fibres

et al. 1988

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In addition to spinning temperature, spinline stretching and spinning speed, the properties of gel-spun polyethylene fibres hot-drawn to the maximum draw ratio also depend on the polymer concentration, molecular weight and molecular weight distribution. Reducing the polymer concentration reduces the number of entanglements, and fibres with better properties are obtained. However, a minimum number of entanglements is necessary to ensure sufficient coherence of the entanglement network and avoid premature breakage of the spinline. Therefore, an optimal concentration exists which is shown to shift to a lower value for polyethylene with a smaller molecular weight distribution. Fibres with a tensile strength exceeding 6 GPa and a modulus of about 160GPa can be prepared as long as spinline stretching is avoided. A smaller molecular weight distribution enhances the deteriorating effect of spinline stretching. The difference in morphologies for as-spun fibres prepared from different gel compositions and under different spinning conditions also strongly affects the cold-drawing behaviour of the extracted as-spun fibres.

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Section: Resultsmentioning

confidence: 99%

“…On the other hand, some entanglements are necessary to warrant sufficient coherence of the starting structure to allow drawing without premature breakage [12,13]. For this reason there is an optimal concentration [14].…”

Section: Introductionmentioning

confidence: 99%

Gel-spun polyethylene fibres

et al. 1988

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“…17 • 18 As for low molecular weight polyethylene, the dried gel cannot form a film and within the film there exist spherulitic textures. 19 Judging from the relationship between the morphology of the superstructure and molecular weight for polyethylene dry gels, it may be postulated that the existence of rodlike textures within dry gel polypropylene films is also due to the ultra-high molecular weight used in the present work.…”

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confidence: 86%

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

Matsuo

Sawatari

Nakano

1986

Polym J

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ABSTRACT:Films of ultra-high molecular weight isotactic polypropylene (4.4 x 10 6 ) were produced by gelation/crystallization from dilute solutions according to the method of Smith and Lemstra. The dried gel films could be readily stretched to a maximum draw ratio of 100 in a hot oven at 165-170°C. For a draw ratio of 100, tensile strength and the Young's modulus attained the maximum values of 1.56 and 40.4GPa, respectively, at 20oC. These values are among the highest reported for polypropylene. The tensile strength was beyond the theoretical value reported by Samuels and the Young's modulus is close to the theoretical value measured by X-ray diffraction.KEY WORDS Ultra-High Molecular Weight Polypropylene / Dried Gel Film I Tensile Strength I Young's Modulus / In recent years, research on the preparation of fibers and films with high modulus and high strength has become a topic of increasing interest and this problem has been concentrated on polyethylene. 1 -u In attempt to produce such fibers (films), gel deformation is one of excellent methods. This method was first proposed by Smith et a/. 5 -6 Gels were prepared by gelation/crystallization from dilute solutions of ultra-high molecular weight polyethylene and decalin used as the solvent was allowed to evaporate from the gels under ambient conditions. The dry gels were elongated at 130-l35°C. Recently, Matsuo and Sawatari succeeded in producing ultradrawn films whose Young's modulus attained 216 GPa corresponding to almost theoretical values measured by X-ray diffraction technique. 11 The drawn ratio attained to about 400 times and the second order orientational factor of the crystal c-axes was 0.99999 indicating almost complete orienta-

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“…The key element in obtaining high-strength UHMWPE fibers is to find a way to draw the as-prepared gel specimens to an ultrahigh draw ratio after the gel spinning process. The drawability of the as-prepared gel specimens was found to depend significantly on the compositions of solutions from which gels were made [12][13][14][15][16][17]. Several authors [16,[18][19][20][21][22] reported that the drawing temperature and rate could markedly affect the maximal achievable draw ratio and tensile properties of solution-grown UHMWPE samples.…”

Section: Introductionmentioning

confidence: 99%