Orientation of Films and Fibrillation

Schuur, G.; Vegt, A.K. van der

doi:10.1007/978-94-010-9803-8_12

Cited by 3 publications

(1 citation statement)

References 13 publications

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“…Orientation has been a widely used method to improve the mechanical properties of polymers. Several processing methods have generally been used to induce segmental orientation of polymer chains, ranging from drawing at elevated temperatures to spinning from liquid-crystalline solutions or gels. − Liquid-crystalline polymers are ideal candidates for such processing techniques and have been extensively studied for the last several decades. , There is a natural tendency for the rigid segments in these polymers to self-align into ordered domains; in melts or in solutions, this enables liquid-crystalline polymers to be processed into ordered materials having excellent high-performance properties. , One disadvantage of these existing orientation methods is that the degree of segmental orientation is difficult to control. Also, the inevitable relaxation of the chains when the external field is removed results in losing some or all of the induced anisotropy .…”

Section: Introductionmentioning

confidence: 99%

Main-Chain Lyotropic Liquid-Crystalline Elastomers. 2. Orientation and Mechanical Properties of Polyisocyanate Films

Zhao¹,

Kloczkowski²,

Mark³

et al. 1996

Macromolecules

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Novel types of main-chain, lyotropic liquid-crystalline polymer networks consisting of polyisocyanate chains were prepared by hydrosilation cross-linking. The characteristic liquid-crystalline band texture generated by shearing these networks in the swollen state was found to persist much longer than in the case of solutions of the same polymer in the un-cross-linked state, suggesting preservation of increased chain orientation. A series of these gels were deformed by application of suitable stresses and then dried in the strained state, in an orientation technique developed to improve the properties of networks consisting of such semiflexible polymers. The mechanical properties of the oriented films were then carefully examined as a function of their processing history: curing temperature, curing time, sol fraction, equilibrium swelling ratio, cross-link length, and polymer concentration during deformation. In the case of uniaxial extension, the tensile strengths and moduli of these oriented films increased 5−7 fold in the orientation direction. As expected, however, their mechanical properties in the perpendicular direction were diminished. Equibiaxial extension was found to have the advantage of giving mechanical properties that were uniform in the plane of the films and gave more than 2-fold increases in tensile strength and modulus at extension ratios during drying as small as 20%! The conclusion that these improvements were due to long-range ordering of the chains was verified by birefringence measurements.

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Section: Introductionmentioning

confidence: 99%

Main-Chain Lyotropic Liquid-Crystalline Elastomers. 2. Orientation and Mechanical Properties of Polyisocyanate Films

Zhao¹,

Kloczkowski²,

Mark³

et al. 1996

Macromolecules

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Biaxially stretched in comparison with conventionally blown coextruded composite plastic films

Siegmann

Nir

1987

Polymer Engineering & Sci

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Multilayer composite films consisting of polyolefins, either polypropylene, linear low density or medium density polyethylene, a thin adhesive layer, and a polyamide in various ratios were prepared using two basically different processes. The first, a conventional blown film process in which the extrudate is stretched while in the molten state; and the second, a two‐stage process in which the quenched extrudate is stretched at a temperature below the polymers' melting point. The films so prepared, having identical composition and similar extents of stretching, were compared on the basis of their tensile properties, thermoelastic shrinkage, oxygen transmission rate, and thermal behavior. The effects of stretching temperature, rate, and extent on the behavior of the composite films and control single layer films were investigated. The stretching temperature was found to be the dominating single process parameter in determining the films' behavior. The overall performance including tensile properties, barrier, and shrink properties of the “cold” stretched films was found markedly superior to that of the conventionally blown films. The stretched composite films possess physical properties that cannot be attained by the conventional process.

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Das Fibrillierungsverhalten von monoaxial verstreckten und unter Spannung getemperten Folien aus isotaktischem Polypropylen

Lenz

Wrentschur

1982

Colloid & Polymer Sci

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Uniaxial stretched polypropylene filmtapes were annealed under stretching tension during 20 seconds up to an annealing temperature of 210 ~ The splittabitity and the fibrillability were investigated as function of the annealing temperature. The splittability, measured as tearing force in transverse direction, remains constant up to 196 ~ and there upon drops abruptly as a result of a transformation of the fibrillar texture into a bimodal lamellatexture, which was visualised by TEM. At this annealing temperature the crystalline orientationfunction, the crystallinity, and the long identity period pass through a distinct maximum. Compared with this the fibrillability, measured as the number of fibrilruptureends, decreases constantly away from an annealing temperature of 165 ~ down to a complete disappearance. This phenomenon is explained by the diffusion of the originally irregularly in the microfibrils distributed defects to the crystallite boundaries, where they accumulate in lateral direction. For this reason the single microfibrils do not rupture anymore under tensile tension at the points of defect concentration but along the regular pattern of the uncrystallized regions. The decrease of the fibrillability correlates well with the drop of the tenacity as result of the weaker linkage of the crystallites in the longitudinal axis.

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Orientation of Films and Fibrillation

Cited by 3 publications

References 13 publications

Main-Chain Lyotropic Liquid-Crystalline Elastomers. 2. Orientation and Mechanical Properties of Polyisocyanate Films

Main-Chain Lyotropic Liquid-Crystalline Elastomers. 2. Orientation and Mechanical Properties of Polyisocyanate Films

Biaxially stretched in comparison with conventionally blown coextruded composite plastic films

Das Fibrillierungsverhalten von monoaxial verstreckten und unter Spannung getemperten Folien aus isotaktischem Polypropylen

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