Reinforcement of high density polyethylene with a side chain LCP by graft copolymerization—thermal, mechanical and morphological properties

Abstract

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.

Detailed analysis on thermal, microstructural, mechanical, and morphological features of side chain liquid crystalline polymer/isotactic polypropylene graft copolymers: Effect of grafted and ungrafted polymer units

“…The monomer, BPOCPA was synthesized in the three steps; (I) p-acryloyloxybenzoic acid, ABA, (II) acryloyloxybenzoyl chloride, ABC and (III) the monomer, BPOCPA as reported in our previous study. 22 At first step, 69.0 g of HBA (0.5 mol) were added to 0.5 M of NaOH solution and the prepared solution were cooled at the temperature of 0-5 C. Then, equivalent mol of AC (0.5 mol) was added to this solution drop by drop by stirring about 1 h. The solution was precipitated with the addition of diluted HCl, then filtered and washed excessively with water to get rid of the formed salts. The obtained intermediated product, ABA was purified 3-4 times via the recrystallization techniques from acetone.…”

“…20 On the other hand, it could be emphasized that poly(p-benzophenoneoxycarbonylphenyl acrylate), poly(BPOCPA) bearing the pendant aromatic mesogenic groups in the polymeric backbone possessed the mesophase properties of according to the papers announced previously. 21,22 They founded that poly(BPOCPA) exhibited liquid crystalline behavior by forming the glassy nematic order phase observed at the range from 144 to 199 C.…”

Experimental and theoretical approaches for structural and mechanical properties of novel side chain LCP-PP graft coproducts

“…The graft copolymerizations of the monomers onto the PP material were expected to result in the improvements of the mechanical characteristics (especially tensile strength) due to the regular and organized structure of side chain LCPs. 28 In other words, the grafted monomers led to development of the orientation and alignment in the polymers (chain disentanglement) besides the probable fiber reinforcement effect noted. 14 Hence, the mechanical performances belonging to the coproducts enhanced considerably, similar to the significant improvements in our previous work.…”

“…With the same line of reasoning, high density polyethylene has been previously reinforced by graft copolymerization of p-benzophenoneoxycarbonylphenyl acrylate. 28 Besides the remarkable improvements in the tensile properties (38% in tensile strength and 67% in Young modulus), the grafting also led to significant increases in the crystalline melting temperature of the material (from 131 • C to 132-138 • C), in consistence with the graft content in the coproducts. The developments were explained by the advances in the orientation and alignment of PE chains, conduced by greater chain mobility in the larger ab basal area of the orthorhombic unit cell and intensifying cohesive forces arising from the glassy nematic structured graft units.…”

Investigation on two modification strategies for the reinforcement of biodegradable lignin/poly(lactic acid) blends

“…Meanwhile, even though the tensile modulus was only 3.5 GPa, the tensile strength of PLA 96 LIG 4 -0.4MA reached 71.6 MPa, which was higher than all the other samples. As we discussed above in the reaction mechanisms, MA was grafted onto PLA with the initiation of BPO, [43,44] which could also reacted with lignin. By this way, lignin and PLA were chemically bonded with strong interaction, contributing to the high tensile strength of PLA 96 LIG 4 -0.4MA.…”