The properties of polymer alloys and blends strongly depend on their phase structure. Morphological study is thus very important in the design and development of alloys and blends. Computer programs have been developed to predict the dependence of structure and properties on phase separation and shear flow. Phase structures of binary systems were calculated for various blend ratios by solving the phase separation equation using a finite difference method. Thermal conductivity, elastic modulus, and thermal expansion coefficient were predicted from the calculated phase structures by finite element heat, stress, and thermal stress analyses, respectively. The relationships between the structure and properties were numerically investigated. The predicted results for elastic modulus were verified by comparing with experimental data for PC/PS blends.

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Solid state viscoelastic properties of short glass fiber (GF) and carbon fiber (CF) filled liquid crystalline polymer (VA) composites, which were cut from injection molded specimens, were measured in the bending mode under forced vibration. These properties were compared with viscoelastic properties measured in the tensile mode using composite strands processed by a capillary type rheometer under various conditions. The temperature/frequency dependence of these properties was also measured.
Both storage modulus (E′) and loss modulus (E″) of the composites showed a rise with an increase of fiber content. E′ and E″ of CF-filled VA systems were higher than those of GF-filled systems at temperatures below 200°C, however, above this temperature, CF-filled systems showed lower E′ than GF-filled systems.
From a comparison of viscoelastic properties obtained in bending and tensile modes for unfilled and fiber filled VA systems, it was found that both E′ and E″ are dependent upon the processing conditions of the test samples. For example, E′ and E″ of composites prepared by injection molding were almost the same as those which were obtained by extrusion followed by natural cooling at room temperature, but were considerably lower than those obtained by extrusion followed by immersion in cold water for quick cooling.
The glass transition temperatures (Tg) of CF-filled and GF-filled systems determined from tan δ curves in bending mode experiments Were 103°C, which is the same as that obtained in the tensile mode. This may suggest that the viscosity (η) or E″ and storage modulus (E′) of VA polymers tends to increase in the vicinity of Tg with fibers (CF or GF).
The frequency dependence of E′ was generally higher than E″. E′ increased monotonically with increasing frequency, however, E″ showed a minimum at a critical frequency. Following the WLF equation, master curves of E′ for unfilled and filled VA systems were obtained in a wide frequency range from 10^-4 to 10⁷Hz. These curves may enable an estimation of the elastic properties at any temperature. The master curves of these systems, however, could not be obtained due to the abnormal frequency dependence of E″ vs. temperature between 60 and 130°C.
Experimental values for storage modulus of composites were compared with calculated ones by using “Law of Mixture” models for short fiber filled composites, and the influence of fiber orientation on modulus was discussed. As a result, it was found that the CF/VA system undergo change in fiber orientation from two-dimensional to three-dimensional random with an increase in its fiber content, while the GF/VA system assumes fiber orientation close to three-dimensional random, irrespective of its fiber content.

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PET and PE fishing net wastes were compression molded into sandwich-type boards, which were evaluated mechanically by three point bending test. The PET and PE fishing nets were knitted beforehand, then molded into PE/PET/PE laminates with three layers and PE/PET/PE/PET/PE laminates with five layers. The process was controlled so that only the PE layers were melted by the infrared heaters, and air was trapped in the non-melted core PET layers. As a result, a flexible, heat insulating board was achieved. The molding method described herein shows promise in contributing toward the recyclability of cord-type waste materials, such as fishing nets.

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