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In this study, high density polyethylene (PE) has been reinforced with a side chain LCP by graft copolymerization of p-benzophenoneoxycarbonylphenyl acrylate (BPOCPA). The mechanical and thermal behavior of the graft coproducts were investigated in relation to the structural changes (in unit cell parameters) of PE matrix. The crystalline melting temperature of PE, varying consistently with the poly(BPOCPA) content in the coproducts, significantly increased (from 131°C to 132-138°C). The unit cell dimensions, a and b, of the orthorhombic structure, the ab basal area and particle size of PE crystals initially expanded, and then consistently contracted with the graft content. The c parameter, however, remained relatively unchanged. Remarkable improvements were achieved in the tensile properties of the material; with the maxima of 38 % increase in tensile strength and 67 % increase in Young's modulus with the coproduct comprising 9.3 % poly(BPOCPA). These developments were found to be explained by the advances in the orientation and alignment of PE chains, conduced by greater chain mobility in the larger ab basal area and intensifying cohesive forces arising from the glassy nematic structured graft units.

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This present study centers sensitively on the determination of the effect of natural turkey feather fibers (TFFs) loading on fundamental features (thermal, mechanical, water-uptake, and micro-structural) of thermoplastic polyurethane (TPU). The composites with different TFFs contents (3, 6, 9, and 12 wt.%) were fabricated by the melt blending method using the twin screw extruder and micro-injection molder. The samples were characterized by means of differential scanning calorimeter (DSC), universal mechanical (tensile and hardness) tester, water-uptake, and scanning electron microscope (SEM) techniques. The thermal analysis depicted that the melting temperatures of the soft and hard segments as well as the crystallinity degree of TPU increased consistently with the increase of TFFs loading level thanks to the formation of better close-packed TPU chains in the matrices. As for the mechanical test results, when compared neat TPU, the tensile strengths were reinforced by 26.8% and 19.7%, and the modulus increased by 6.6% and 45.1% for the composite samples including 3% and 6% of TFFs, respectively. However, drastic diminishment were observed at further contents. Additionally, TFFs loadings brought about gradual increase in the water-uptake capacities of the composites due to the increasing of the number of voids and omnipresent flaws in TPU matrices. The taken SEM images also revealed that, at low contents, there existed the enrichment of interfacial adhesion between TFFs and TPU matrix, whereas the morphological appearance of the composites get worse at high contents accompanied by the formation of micro-structural defects.

The monomer, p-benzophenoneoxycarbonylphenyl methacrylate (BPOCPMA) the polymer of which exhibit mesomorphic behavior as side chain LCP has been graft copolymerized onto high density polyethylene (HDPE) in order to improve its properties. The PALS analysis of the products displayed that the graft copolymerization, while led to relatively small increase in the free volume size at low percentages of poly(BPOCPMA), resulted in decreases in the size and fraction of the free volume with the increase of poly(BPOCPMA) content. The graft copolymerization gave rise to remarkable improvements in the mechanical properties, especially in tensile strength and modulus, and the improvements were accompanied by the decreases in the free volume fraction. SEM analysis of the fracture surfaces of the mechanical test samples displayed a gradual transition from ductile fracture at low graft contents to brittle nature dominated at high percentages of poly(BPOCPMA). The XRD analysis showed significant expansions in the lateral dimensions (a and b parameters) of the orthorhombic unit cell in the crystalline domains of HDPE matrix, in consistence with poly(BPOCPMA) content. The grafting also gave rise to noteworthy increases in the crystalline melting temperature of the HDPE.

The monomers p-biphenyloxycarbonylphenyl acrylate (BPCPA) and p-biphenyloxycarbonylphenyl methacrylate (BPCPMA) were synthesized by the reaction of p-acryloyloxybenzoyl chloride and p-methacryloyloxybenzoyl chloride with 4-hydroxybiphenyl, respectively, and polymerized by bulk polymerization in vacuum by using dicumyl peroxide. The graft copolymerization of the monomers onto polypropylene were carried out by bulk melt polymerization at 170 • C with various concentration levels of the monomers and the initiator in reaction mixtures. The content of monomers in their graft coproducts increased with monomer-initiator percentage in the reaction medium. The graft coproducts were characterized by several available experimental techniques including differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and mechanical testing. Moreover, the crucial changes in the mechanical performances pertaining to the polypropylene product were investigated by theoretical computations performed based on the density functional theory (B3LYP) with the standard 6-311++G(d,p) level of theory. According to obtained results, the mechanical properties of the graft coproducts deteriorated significantly with the grafting of the homopolymers due to the damage of the rate-dependent viscoelastic deformation or yielding, leading to enhancement in the surface energy values. At the same time, experimental evidence confirmed that the poly(BPCPA) materials exhibited much weaker secondary Van der Waals bonds than those in the poly(BPCPMA) products.