Shear modulus liquid crystalline polymers

Shear modulus, polyamide, 138 Sheet molding compounds (SMCs), 30 Shoe sole products, 205 Shore hardness gauge, 243 Side-chain liquid crystalline polymers, 49 Side reactions, in transition metal coupling, 477... 

Some unexpectedly complex liquid solid interactions have been detected and studied by ultrasonic impedance measurements (ultrasonic impedometry). Small amounts of water and alcohols have pronounced effects on the physical state of hydrophilic polymers specifically, the high frequency shear modulus and crystallinity index of a poly (vinyl alcohol) film increases with water content to a maximum before normal solution phenomena occur. These effects are attributed to the increased molecular order owing to water hydrogen bonded between polymer chains. The unusual effects of moisture on a novel poly(vinyl chloride)/plasticizer system and on hydrophilic polymers other than poly (vinyl alcohol) are also described. 

Although as-spun fiber of Me-HQ/Cl-PEC showed high modulus of 72 GPa,the modulus of the injection molded test pieces of Me-HQ/Cl-PEC was only 26 GPa.Ph-HQ/Cl-PEC and tBu-HQ/Cl-PEC showed no liquid crystallinity,but the moduli of the injection molded test were 7.5 and 15.1 GPa,respectively,which were 2-5 times higher than that of isotropic polymers.tBu-HQ/Cl-PEC showed many fibrils on the cross section of the flexural fractured test pieces as shown in Fig. 6(2).We assumed that tBu-HQ/Cl-PEC was a quasi liquid crystalline polymer which could orient at the high shear rate.Although W.B.Black reported a lyotropic quasi liquid crystalline polymer which could orient at the high shear rate,tBu-HQ/Cl-PEC is the first example of the thermotropic quasi liquid crystalline polymer(6). 

The aggregate model also has been used with success to describe the mechanical anisoti opy of several liquid crystalline polymers. Ward and co-workers [56] examined the dynamic mechanical behaviour of several thermotropic polyesters in tension and shear over a wide temperature range, and used the single-phase aggregate model to relate quantitatively the fall in tensile modulus with temperature to the corresponding fall in shear modulus. 

Yi XS, Shi F, Michaeli W (1996) The modulus of shear-induced fibers from a thermotropic liquid crystalline polymer in a thermoplastic matrix. Polym Compos 17 423... 

As shown by Eq. (15) and (17), the tensile elastic behaviom of fibers made from lyotropic polymers is determined by the chain modulus e the shear modulus go and the orientation parameter . As has been discussed in Sect. 2 and 3, the latter is determined by the persistence length, the molecular weight, the polymer concentration and the temperature of the liquid crystalline solution, and furthermore by the spinning and coagulation conditions. 

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