High-Density Polyethylene (HDPE)/linear low-Density Polyethylene (LLDPE) blends have been designed by varying the HDPE: LLDPE ratio. The ratio of 70: 30 showed the best combination of tensile properties (19. 53 MPa), melt flow index (MFI) (1. 75 g/10 min) and hardness properties (Shore D 46. 5), and its tensile strength and hardness was greater than those of plain LLDPE, whereas its MFI was greater than that of a plain HDPE. Hence, with the same composition, the composites were made by addition of silica with a ratio of 10–, 40%. Incorporation of silica acts as a reinforcement into the system and improves the structural rigidity and 30% incorporation showed the best performance in terms of tensile (23. 69 MPa), and hardness (Shore D 48) but slightly less MFI (0. 85 g/10 min) of the composites. Incorporating coconut shell charcoal (CSC) not only improves the system’, s performance but also utilizes its waste and properties are measured as tensile strength (22. 33 MPa), maintaining the hardness properties and slight reduction in MFI (0. 77 g/10 min). All blends and composites were processed through extrusion and palletization followed by compression molding. Plain silica, CSC as well as the selected blends and composites were evaluated by FTIR, XRD, and SEM analyses. Hence, the synergistic effect of silica and CSC in the HDPE-LLDPE blend is studied and such a composite can be suitable in automotive applications.

In the present study, the thermal oxidation behaviour of High-Density Polyethylene (HDPE) containing each of two types of oxidized Polyethylene (OPE), one prepared using 500 ppm of iron (III) stearate as pro-oxidant and the other without the pro-oxidant, was investigated. Fourier-transform infrared spectroscopy (FTIR) showed that the carbonyl index of the HDPE increased from 1.03 to 6.37 upon the addition of 5.0 wt.% of OPE containing the pro-oxidant after 100 h of thermo-oxidative aging at 90°C. Moreover, it was observed that the rate of changes in retained tensile strength and retained elongation-at-break of the HDPE during the thermal oxidation increased in the presence of 5.0 wt.% of each type of OPE, especially, the one containing iron (III) stearate, which was consistent with the obtained data from gel content measurements. Lastly, the evolution in crystallinity of the film samples was monitored by Density measurements as well as differential scanning calorimetry (DSC). It was revealed that the crystallinity of the tested films during thermo-oxidative degradation grows faster in the presence of OPE. Overall, the findings indicated that the utilization of OPE containing trace amounts of iron (III) stearate can accelerate the thermal oxidation of HDPE films and facilitate entering the final biodegradation stage, while resolving the need to use High concentrations of harmful heavy metal salts.

Immobilization of Lipase produced from Rhizomucor miehei on HDPE fine powder was investigated. As compared to an aqueous system, immobilization in a non-aquous organic medium such as n-hexane was not successful and caused enzyme denaturation. Prewetting the support with ethanol increased the immobilized protein and enzyme activity as much as 31% and 34%, respectively. The maximum immobilized activity was obtained at the isoelectric pH of 4-5. The enzyme was suspected to have competition and/or interaction with other protein entities on the surface. Immobilization of the enzyme onto the support seems to be via shear sensitive weak physical adsorption. Proper duration of mixing was found to be around 6 minutes. Longer periods of shaking led to enzyme desorption, thereby reducing the immobilized activity. Neither efficiency nor stability was improved using glutaraldehyde as a crosslinking agent despite the fact that in some occasions, protein loading of the support was improved. This suggests the possible effect of glutaraldehyde on enzyme denaturation in these conditions. At optimum conditions, immobilized enzyme activity was enhanced almost 6- folds increasing from 8 units (per 0.5 ml of the enzyme liquor) to about 45.8 units (when 0.5 ml was immobilized on one gram of support).

Morphologically distinct binary polymer blends have been prepared by melt mitring of High-Density Polyethylene (HDPE) and various linear low-Density Polyethylene (LLDPEs) for the entire range of blend composition under identical processing conditions.The morphology of the tensile fracture surfaces of the parent polymers and their blends are quite interesting and show good correlation with thermal and mechanical properties. The HOPE forms linear and interpenetrating fibrils with large interfibrillar separation, whereas, octene containing LLDPE (OLLDPE) with almost equal number of branching to that of HDPE shows nicely formed twisted fibrils. On the other hand, pentene containing LLDPE (PLLDPE) manifests a straight fibrillar morphology with well defined boundary comprising many thin fibrils with alternative thick and thin regimes and perfection, whilst butene containing LLDPE (SLLDPE) shows thick comparatively smooth and well defined and imperfect boundary of tensile fracture. The blends morphology is quite distinct to that of parent polymers. The physical properties, melting and crystallization behaviour show good correlation to the fineness, twisting and discontinuity of the fibrils.

Chemical resistance of natural fiber (wood flour- rice hulls- kenaf fiber and newsprint)- High Density Polyethylene composite was studied in terms of their weight loss after seven days immersion in different chemicals. Composite containing 25% and 50% of varios natural fiber and High Density Polyethylene were prepared and immersed in NaOH(10%), NaClO(13%), HCl(10%), H2O2(3%), soap solution(1%) and acetone. Results indicated that H2O2, soap solution and acetone had very negligible effects on all composites. On the other hand, the effects of NaClO and HCl were found to be statistically significant. Different fibers exhibited different behaviors regarding their chemical resistance. Generally it was concluded that NaClO and HCl had the Highest impact on natural fiber- High Density Polyethylene composites.

The effect of a High-Density Polyethylene grafted amine alcohol (HDPE-g-DMAE) as compatibilizer on the mechanical, rheological and morphological characteristics of Polyethylene/Polyethylene post-consumer recycled blends (HDPE/rHDPE) reinforced with nanoclay was studied. Blends of HDPE with High rHDPE contents, more than 60% (wt) of rHDPE, were evaluated. HDPE bottles were manually separated from municipal solid waste, washed, grinded, and finally compounded at various concentrations with virgin HDPE and nanoclay. The effect of this HDPE-g-DMAE was compared with conventional Polyethylene maleic anhydride (HDPE-g-MA) compatibilizer. FTIR characterization confirmed the formation of this HDPE-g-DMAE compatibilizer. The mechanical properties of uncompatibilized blends decreased with increasing rHDPE content, whereas these properties were significantly enhanced when HDPE-g-DMAE was used compared with HDPE-g-MA compatibilizer and with uncompatibilized blends. Scanning electron (SEM) micrographs of the fractured surfaces when using HDPE-g-DMAE showed improvement in the interfacial adhesion and interaction between recycled and virgin Polyethylene. The nanocomposites compatibilized with PE-g-DMAE had better clay exfoliation–, intercalated structure compared to PE-g-MA-compatibilized nanocomposites. The novelty of this work is based on the use of PE-g-DMAE as a compatibilizer in HDPE/rHDPE/nanoclay composites with improved mechanical properties. This compatibilizer promoted the adhesion between recycled and virgin polymer phases in the blend and increased the interactions between compatibilizer and hydroxyl groups on the clay surface, as well as oxidized groups in the recycled polymer. This indicates that recycled postconsumer HDPE could replace, in larger proportions, part of the virgin HDPE for certain applications with better mechanical performance than uncompatibilized blends. This is an option to bring recycled plastics back into the market and increase the versatility of products manufactured with recycled polymers.

Drawn tapes were manufactured by mechanical drawing on a hot plate maintained at 82°C from as- extrudates with different crystallinities from HighDensity Polyethylene (HDPE) to small quantity of linear low-Density Polyethylene (LLDPE). The process of drawing was analyzed to understand the effects of the percentage crystallinity of as-extrudates on the mechanical properties of the drawn tapes. Incorporation of LLDPE up to 15 % LLDPE systematically decreases the percentage crystallinity of as-extrudate by 25 % . It was also noticed that the initial differences in crystallinity were not reflected in the drawn tapes. However, the as-extrudate with Higher initial percentage crystallinity produced a tape with better mechanical properties than the asextrudate with lower crystallinity. The coarse fibril formation is seen in the flakelike crystalline bodies of the as-extrudates. This fibrillar formation is quite distinct with HDPE as-extrudate. On drawing, the flake-like crystalline bodies disintegrate to fibrils. The Higher inter-planar spacing helps in the formation of uniform and finer fibrils. Finer and uniform fibrils free of branching and discontinuity perhaps are imperative for better mechanical properties. The HDPE as-extrudate with High percentage crystallinity and good fibrillar formation provides a better precursor for the High tenacity and modulus tape.

Method of inverse gas chromatography (IGC) has been used for the physico-chemical characterization of polymers for more than two decades. In this method the polymeric stationary phase could be characterized by using probe molecules. The retention volume of probe is a measure of the polymer-probe interaction and show changes in the polymer structure at melting point or glass transition temperature. Crystallinity of High-Density Polyethylenes (HDPE) of Poliran and Irapol from Iranian petrochemical companies was studied. The effects of the flow rates and the sample size on peak retention volume were investigated. Modified techniques for measurement of flow rate and coating were used. Retention diagram and degree of crystallinity were determined for a sample of low-Density Polyethylene and the results were compared with those obtained for HDPE. Experimental data of crystallinity and melting points showed that the Iranian HDPE is a polymer with suitable engineering properties.