Properties Of Ultra-high Molecular Weight Research Articles

Rheological, Mechanical, and Thermal Properties of Ultrahigh Molecular Weight Polypropylene/Low Molecular Weight Polypropylene Blends

Ultra-high molecular weight polypropylene (UHMWPP), with a molecular weight of more than 106 g/mol, is expected to have superior properties, such as high mechanical strength, high thermal properties, high chemical resistance and outstanding tribological properties. However, UHMWPP has a very poor processability due to its high melt viscosity. Therefore, we aimed to improve processability of UHMWPP by blending it with a low molecular weight polypropylene (LMWPP). We attempted to improve the interfacial miscibility and intermolecular entanglement of the UHMWPP/LMWPP system by using a kneader machine. The addition of LMWPP tended to change the mechanical, thermal, and rheological properties of the blend system.

Rheological and mechanical properties of ultrahigh molecular weight polyethylene/high density polyethylene/polyethylene glycol blends

Abstract Ultra-high molecular weight polyethylene (UHMWPE) possesses many excellent properties, but poor processability. There are many ways to improve the processability of UHMWPE, but most of which will compromise its other outstanding properties. The effect of polyethylene glycol (PEG) and high-density polyethylene (HDPE) on the rheological and mechanical properties of UHMWPE were investigated in this paper, and the UHMWPE blends were prepared by twin screw extruder. The addition of PEG can remarkably improve the processability of UHMWPE, so the UHMWPE/PEG (100/4) blends can be steadily extruded from the capillary. In addition, the apparent shear viscosity, storage modulus, loss modulus and the complex viscosity decrease with the increasing amount of PEG. However, the mechanical properties of UHMWPE/PEG blends decrease as the PEG content increase. The incorporation of HDPE can further improve the processability of the UHMWPE/PEG blends and reduce its apparent shear viscosity, storage modulus, loss modulus and complex viscosity. Mechanical properties test reveals that the best ratio of UHMWPE/HDPE is 60/40. Compared with UHMWPE/PEG (100/4), the tensile strength, flexural strength, and flexural modulus of UHMWPE/HDPE/PEG (60/40/4) increase by 13.8%, 25.7%, and 32.5%, respectively.

Ultradrawing properties of ultrahigh molecular weight polyethylenes/functionalized activated nanocarbon as-prepared fibers

Tensile strength and modulus values of UHMWPE, UHMWPE/ANC, UHMWPE/ATANC and UHMWPE/FANCmx fibers with varying draw ratios.

Ultradrawing properties of ultra-high molecular weight polyethylene/hydrochloric acid treated attapulgite fibers

Investigation of the influence of the purified and acid treated attapulgite (ATP) contents on the ultradrawing properties of ultrahigh molecular weight polyethylene/purified attapulgites (UHMWPE/ATP, F100Ay) and UHMWPE/acid treated ATP (F100AxM-y) as-prepared fibers is reported. In which, acid treated ATP nanofibers were treated with varying concentrations of hydrochloric solutions for various amounts of time. Similar to those found for the orientation factor values, the achievable draw ratios of the F100Ay and F100AxM-y as-prepared fibers and tensile strength values of their drawn fibers approach a maximal value as their purified ATP and/or acid treated ATP contents reach the optimal values at 0.05 and 0.025 wt%, respectively. In which, the maximal Dra values of F100AxM-0.025 as-prepared series fiber specimens and the tensile strengths and moduli of the drawn F100AxM-0.025 fiber specimens are significantly higher than those of the F100A0.05 drawn fiber specimens prepared at the same draw ratios and optimal ATP contents but without acid treatment. Moreover, it is worth noting that the maximal Dra values of the F100AxM-0.025 as-prepared fiber specimens and the tensile strengths and moduli of the drawn F100AxM-0.025 fiber specimens reached another maximal value as their ATP nanofibers were treated by 5 M HCl solutions for 60 min. To understand the interesting ultradrawing, orientation and tensile properties of F100Ay and F100AxM-y fiber specimens, Fourier transform infra-red, specific surface areas, scanning electron microcope and elemental analyses of the purified and acid treated ATP nanofibers, and/or morphological and thermal analyses of the F100Ay and F100AxM-y fiber specimens were performed in this study.

Thermal and mechanical properties of ultrahigh molecular weight polyethylene/high-density polyethylene/polyethylene glycol blends

Abstract Blends of ultrahigh molecular weight polyethylene (UHMWPE) with high-density polyethylene (HDPE) provide adequate mechanical properties for biomedical application. In this study, the mechanical and thermal properties of UHMWPE/HDPE blends with the addition of polyethylene glycol (PEG) prepared via single-screw extruder nanomixer were investigated. The UHMWPE/HDPE blends exhibit a gradual increase in strength, modulus, and impact strength over pure polymers, suggesting synergism in the polymer blends. The elastic and flexural modulus was increased at the expense of tensile, flexural, and impact strength for the blends containing PEG. The degradation temperature of UHMWPE was improved with the incorporation of HDPE due to good thermal stability of HDPE. HDPE improved the dispersibility of PEG in matrix, consequently reduced the surface area available for the kinetic effects, and reduced the degradation temperature. The morphology analysis confirmed the miscibility between UHMWPE and HDPE and the changes in polymer structure with the presence of PEG modify the thermal behavior of the blends. The mechanical properties of the blends that are underlying values for the design of implant material show the potential used as biomedical devices.

Synthesis and properties of ultrahigh molecular weight polyethylene/WS2 nanoparticle fiber for bullet-proof materials

Ultrahigh molecular weight polyethylene (UHMWPE)/WS2 nanoparticle fibers were prepared by adding WS2 nanoparticles treated by coupling agent in the precursor solution of UHMWPE. The influence of WS2 nanoparticles on the microstructure and properties of UHMWPE fibers was characterized by SEM, TGA, mechanical property measurement and bullet-shock test. The results showed that WS2 nanoparticles can be uniformly dispersed in the UHMWPE fiber. After incorporating of WS2 nanoparticles, UHMWPE fibers became stiffer and tougher than the pristine ones. Particularly, the modulus of the fiber increased from 1203 to 1326 cN/dtex. Furthermore, UHMWPE/WS2 fibers showed an improved thermal stability.

The Effects of Loading of Montmorillonite (MMT) on the Properties of the Ultra-High Molecular Weight Polyethylene (UHMWPE/Organo-MMT) Nanocomposite Sheets Prepared by Gel and Pressure Induced Flow (PIF) Processing

In this paper the effects of loading of montmorillonite (MMT) on the properties of ultra-high molecular weight polyethylene/montmorillonite (UHMWPE/MMT) nano-composites were reported. The UHMWPE gel sheet with nanoparticles of MMT clay was prepared by using paraffin oil as a non-volatile solvent. The paraffin oil was removed using two steps, i.e., mini-mold as PIF and extraction processes. The microstructure of the gel sheet shows good dispersion of MMT clay nanoparticles and hence intercalation and exfoliation between the layers of the microstructure gel sheet, i.e., MMT clay onto the layer surface by means of gel and PIF processes in the microstructure gel sheet shows that the layer spacing was increased significantly or even exfoliated. For intercalated nanocomposites, different layer spacing corresponds to different chain flexibility and the presence of multi-peaks is caused by the processing of these materials. The resulting exfoliated UHMWPE/organo-MMT nanocomposites were characterized by transmission electron microscopy and scanning electron microscope. The thermal properties of the nanocomposites were investigated by thermogravimetric analysis, dynamic mechanical analysis and differential scanning calorimetry. The results obtained provide a guide to the interfacial design of organic/inorganic materials.

Effect of ethylene–propylene copolymers on the phase morphologies and properties of ultrahigh molecular weight polyethylene: Dissipative particle dynamics simulations and experimental studies

Abstract This work aims to experimentally and theoretically study the effects of ethylene–propylene copolymers as compatibilizer on the phase morphologies, interfacial properties, rheological behaviors and mechanical properties of ultrahigh molecular weight polyethylene/homopolymerized polypropylene (UHMWPE/HPP) blends. The results indicate that the addition of ethylene–propylene block copolymer EPS30R or random copolymer DP3000 ranging within 1–3 parts per hundred parts (phr) of UHMWPE/HPP blends can remarkably reduce the sizes of the UHMWPE particles and significantly improve the mechanical property such as tensile strength and elongation at break. Moreover, the ternary blends still show two-phase morphologies, and the favorable melt flowability of the UHMWPE/HPP blends can be basically maintained. Besides, dissipative particle dynamics simulations on the ternary UHMWPE/HPP/ethylene–propylene copolymer blends indicate that with fixed mole number of the block copolymer, longer block chains have higher efficiency on reducing the interfacial tension than the shorter ones. But for the block copolymers with fixed volume fraction, interfacial tensions firstly decrease and then increase with increasing the chain length of block copolymer.

Ultradrawing properties of ultra-high molecular weight polyethylene/functionalized carbon nanotube fibers

Systemic investigation of the influence of the plain and functionalized carbon nanotube (CNT) contents on the ultradrawing properties of ultrahigh molecular weight polyethylene/carbon nanotubes (UHMWPE/CNTs, FCy) and UHMWPE/functionalized CNTs (FCfx-y) as-prepared fibers are reported. In a way similar to those found for the orientation factor values, the achievable draw ratios (Dra) of the FCy and FCfx-y as-prepared fibers approached a maximum value as their CNT and/or functionalized CNT contents reached their corresponding optimum values. The maximum Dra values obtained for FCfx-0.001 as-prepared fiber specimens prepared at varying maleic anhydride grafted polyethylene (PE-g-MAH)/modified CNTs weight ratios were significantly higher that of the FC0.0015 as-prepared fiber specimen prepared at the optimum plain CNT content. Tensile property analysis further suggested that excellent orientation and tensile properties of the drawn FCy and FCfx-y fibers can be obtained by ultradrawing the fibers prepared at their optimum plain CNT and/or functionalized CNT contents. To understand the interesting orientation, ultradrawing and tensile properties of FCy and FCfx-y fiber specimens, FTIR, specific surface area, and SEM morphology analysis of the plain and functionalized CNTs were performed in this study. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Mechanical, Thermal, and Surface Properties of Ultrahigh Molecular Weight Polyethylene/Polypropylene Blends

Various compositions of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blends were prepared in decalin, with the rheological, mechanical, thermal, and surface properties of the blends being determined using the solution cast film. Viscosity and mechanical properties of the blends decreased below the additivity value with increasing PP content implying that PP molecules disturb the entanglement of UHMWPE. Contact angle of the blend films with a water drop increased with increasing content of PP. The atomic force microscope (AFM) images showed that the surface of cast UHMWPE was very smooth whereas that of cast PP was very uneven. For blends, the surface became rough and uneven with increasing content of PP. The melting temperature of PP (T mP) decreased in the blends with increasing UHMWPE content while that of UHMWPE (T mU) remained almost constant in blends.

Effect of zone drawing accompanied with crosslinking on the structure and properties of ultrahigh molecular weight polyethylene gel film

To enhance the thermal properties of ultrahigh molecular weight (UHMW) (viscosity-average molecular weight of 6 × 106) polyethylene (PE) gel film, this was crosslinked by dicumyl peroxide (DCP) during a high-temperature zone drawing, which is effective to orient film. Through a series of experiments, it turned out that crosslinking actualized by an optimum amount of DCP and high-temperature zone drawing technique caused significant changes in the structure and properties of UHMW PE gel film. That is, crosslinking increased storage modulus of UHMW PE gel film at 25°C, resulting in improving thermal properties of the film. On the contrary, the crosslinking effect played a hindering role in raising the draw ratio of UHMW PE gel film. Maximum storage modulus of 165 GPa at 25°C could be obtained at the draw ratio of 324 of uncrosslinked homo-PE gel film. In the case of crosslinked PE gel film, the highest storage modulus at 25°C reached 65 GPa at maximum draw ratio of 150. Crosslinked film exhibited high modulus, even at 190°C, to some extent, while uncrosslinked homo-PE gel film was molten completely at 150°C. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1583–1590, 1997