Microstructure Of High-density Polyethylene Research Articles

Design and testing of high‐density polyethylene nanocomposites filled with lead oxide micro‐ and nano‐particles: Mechanical, thermal, and morphological properties

ABSTRACTThis research discusses the mechanical behavior and the microstructure of high‐density polyethylene (HDPE)‐based composites, manufactured using the melt‐mixing and thermal‐pressing techniques, where HDPE is mixed with various percentages of either bulk lead monoxide (bulk PbO) or PbO nanoparticles (PbO‐NPs) acting as fillers. The scanning electron microscope and the field emission transmission electron microscope were utilized to identify the morphology of polymeric composites. Both showed the proper dispersion of PbO in the HDPE matrix without substantial agglomerations. The effect of PbO on the thermal behavior of the HDPE was studied using the thermogravimetric analysis. Tensile tests were implemented to find out how the mechanical characteristics of the composites were affected. Yield stress, % elongation at break, stiffness, tensile energy (toughness), ultimate tensile strength, and ultimate tensile strain were elucidated in this work. The values of stiffness, ultimate tensile strength, and yield stress increased by increasing either the bulk PbO or PbO‐NPs' loading up to 40.0 wt % with reference to the hosting matrix. The values of ultimate tensile strain, tensile energy, and % elongation at break of the assembled composites diminished dramatically by increasing the filler's content from 10.0 to 50.0 wt %. Besides, composites with PbO‐NPs as a filler were identified as having higher mechanical characteristics than those with bulk PbO for the same wt %. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 47812.

Relating strain hardening moduli in high density polyethylene copolymers to anisotropic molecular deformation using infrared spectroscopic imaging

Understanding and establishing the relationship between the microstructure of high density polyethylene (HDPE) resins and their mechanical behavior is critical in designing new products and catalysts to produce these polymers. Recent advancement in the mid-infrared (IR) spectroscopic imaging techniques combined with intuitive mathematical modelling can provide a powerful tool in solving this industry-wide long-standing challenge. In this work, IR spectral anisotropy methods coupled with the Crystal Tie Mesh (CTM) model were used to examine the effects of various resin architectures (monomodal and bimodal) on the bulk strain hardening moduli in cold drawn HDPE samples. Using a polarized laser for IR imaging, the related stress strain profiles of local strain gradients (100% sample strain) were modelled using a modified Eyring algorithm. A clear correlating trend was found between a resulting structural parameter in this algorithm (β) and the bulk strain hardening moduli for all samples studied. Results show that the more stable the molecular network (e.g., the lamella segments connected via bridging entanglements and tie molecules), the less strain is observed (i.e. higher β values) when a load is applied. The observed structural effects on the β parameter are consistent with previous results obtained using the CTM model that views the system to be a type of cross linked network formed by multiple bridging and entangled tie chains through common crystalline lamella.

Effect of Microstructure of High Density Polyethylene on Catalytic Degradation: A Comparison Between Nano Clay and FCC

The effect of microstructure of high density polyethylene (HDPE) on catalytic degradation over fluid catalytic cracking (FCC) catalyst and Nano clay is investigated. An ethylene/1-hexene copolymer (HDPE) was fractionated based on 1-hexene content to different fractions using preparative temperature rising elution fractionation (P-TREF) method. The short chain branch (SCB) content of each fraction calculated based on 1H NMR results. The homogenous SCB content fractions were subsequently analyzed using TGA and thermal degradation behavior of samples were compared with catalytic degradation. The results showed that FCC, in contrast to nano clay, is more sensitive to microstructure of HDPE during catalytic degradation. Therefore, linear chains can start degradation sooner on FCC than the branched chains. In comparison of nano clay and FCC it was found that the nano clay, reduces temperature at maximum degradation rate (Tmax), but FCC reduces the T5% and Tmax significantly.

Influence of Titanium Dioxide Content on the Crystallization Behavior and Solar Reflectance of Polyethylene/Titanium Dioxide Composites

Titanium dioxide (TiO2) particles were introduced to improve the solar reflectance of high-density polyethylene (HDPE). The organic-inorganic hybrids were fabricated by melt blending. A series of characterizations were taken to study the crystallization behavior, morphology, solar reflectance, and real cooling property. TiO2 particles acted as nucleation agents in the HDPE matrix and made the HDPE form thick lamellar crystals. TiO2 particles could disperse well into the HDPE matrix under 2.5 wt.% loading but agglomerated with 3 wt.%. Solar reflectance was related to the reflective index of TiO2 and the microstructure of HDPE. The real cooling property depended on the solar reflectance and the dispersion of the TiO2 particles in the HDPE matrix.

The effect of shear on mechanical properties and orientation of HDPE/mica composites obtained via dynamic packing injection molding (DPIM)

AbstractThe interfacial interaction and orientation of filler play important roles in the enhancement of mechanical performances for polymer/inorganic filler composites. Shear has been found to be a very effective way for the enhancement of interfacial interaction and orientation. In this work, we will report our recent efforts on exploring the development of microstructure of high density polyethylene (HDPE)/mica composites in the injection‐molded bars obtained by so‐called dynamic packing injection molding (DPIM), which imposed oscillatory shear on the melt during the solidification stage. The mechanical properties were evaluated by tensile testing and dynamic mechanical analysis (DMA), and the crystal morphology, orientation, and the dispersion of mica were characterized by scanning electron microscopy and two‐dimensional wide‐angle X‐ray scattering. Compared with conventional injection molding, DPIM caused an obvious increase in orientation for both HDPE and mica. More importantly, better dispersion and epitaxial crystallization of HDPE was observed on the edge of the mica in the injection‐molded bar. As a result, increased tensile strength and modulus were obtained, accompanied with a decrease of elongation at break. The obtained data were treated by Halpin–Tsai model, and it turned out that this model could be also used to predict the stiffness of oriented polymer/filler composites. Copyright © 2009 John Wiley & Sons, Ltd.