LC Polymer Blend

The amount of LC added, processing condition, viscosity ratio of the blend components and the rheological characteristics of the matrix decide the size, shape, and distribution of the LC polymer domains in the matrix. Appropriate shear forces are required to obtain good mixing and extensional flow to deform the dispersed LC domains into fibrillar shape. The orientation of LC polymer microfibrils can be increased by drawing, which in turn, improves the mechanical properties of the blend. Discussion of blends processing will follow with several examples. 

The blends of thermoplastics with LC polymers exhibit inferior properties due to lack of adequate compatibility between the two phases. However, application of common method of compatibiliza-tion, i.e., adding a third component in the form of a copolymer, having monomer unit of the two polymers, the properties of the blend can be enhanced. Thus, blends of Polyethylene (PE) with LCP can be compatibilized by adding PE-g-LC copolymers. The PE-g-LC copolymers can be produced by either of the two methods, i.e. melt polycondensation of LC monomers in the presence of a PE containing free carboxyl group and by reactive blending of the two. The blends can be prepared in an extruder fitted with internal mixer at high temperature ( 250°C). The mixture of PE and LC polymer 

A minor component LC polymer, in a polymer blend, can develop into fibrillar-type morphology. This morphology leads to enhanced mechanical properties in the draw direction, which is akin to unidirectional composites. The important microrheological parameter is the capillary number, k, which is defined as  

d is the particle diameter, v is the interfacial tension, and (T is the stress applied on the particle. The capillary number describes the balance between two simultaneous stresses such as the deforming and restoring stresses acting simultaneously on the droplet. However, this treatment is applicable to Newtonian liquids. Anyway, the general trend is expected to be applicable for viscoelastic material. In the case of viscoelastic polymer blend the deviation is expected as it is no more Newtonian fluid. The strategy for getting microfibrills is to have a elastomer as the matrix 

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