Enhancement on ultimate tensile properties of ultrahigh molecular weight polyethylene composite fibers filled with activated nanocarbon particles with varying specific surface areas

This investigation aims to improve the ultradrawing and ultimate tensile properties of ultrahigh molecular weight polyethylene (UHMWPE) fibers by incorporating small amounts of functionalized activated nanocarbon particles with a wide range of specific surface areas (ca. 100–1,400 m²/g) during gel spinning processes of UHMWPE fibers. The ultradrawing, ultimate tensile, orientation properties, and “microfibril” characteristics of UHMWPE/functionalized activated nanocarbon fibers was discovered to improve considerably with the increase in specific surface areas of functionalized activated nanocarbon. An extraordinary high ultimate tensile strength at 95.8 g/d was obtained for the best prepared UHMWPE/functionalized activated nanocarbon drawn fiber. This value is the highest value ever reported for one‐stage drawn UHMWPE fibers and is about 2.9 times that of the UHMWPE drawn fiber prepared in this study. In addition to thermal, ultimate tensile, and orientation factor properties of as‐prepared and/or drawn UHMWPE/functionalized activated nanocarbon fibers, specific surface area, Fourier transform infrared, and morphological analyses of original and functionalized activated nanocarbons were performed to comprehend the considerably improved ultradrawing, ultimate tensile properties, and microfibril characteristics of the UHMWPE/functionalized activated nanocarbon fibers. POLYM. ENG. SCI., 58:980–990, 2018. © 2017 Society of Plastics Engineers     

Study on processing of ultrahigh molecular weight polyethylene/polypropylene blends

The processing of ultrahigh molecular weight polyethylene (UHMWPE) by the addition of polypropylene (PP) and high‐density polyethylene (HDPE) was investigated. The results show that the addition of PP improves the processability of UHMWPE more effectively than does the addition of HDPE. UHMWPE/PP blends can be effectively processed with a twin‐roller and general single‐screw extruder. In the extrusion of UHMWPE/PP blends, PP is enriched at the surface of the blend adjacent to the barrel wall, thus increasing the frictional force on the wall; the conveyance of the solid down to the channel can then be carried out. The melt pool against the active flight flank exerts a considerable pressure on the UHMWPE powder in the passive flight flank, which overcomes the hard compaction of UHMWPE. The PP penetrates into the gaps between the particles, acting as a heat‐transfer agent and adhesive, thus enhancing the heat‐transfer ability in the material. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 977–985, 2004     

凝胶纺丝法制备超高分子量聚乙烯/高分子量聚乙烯纤维延伸性能的研究

用凝胶纺丝法制备了超高分子量聚乙烯(UHMWPE)/高分子量聚乙烯(HDPE)纤维,探讨了添加不同种类高分子量聚乙烯对凝胶初生纤维在后续延伸过程中延伸性能的影响。结果表明在固定制备条件时,当超高分子量聚乙烯(UHMWPE)/高分子量聚乙烯(HDPE)的质量比在最适当质量比时,高分子量聚乙烯的分子量为1.5～2.0×104时,所制备的凝胶初生纤维的可延伸比达最大值。     

Ultradrawing and ultimate tensile properties of ultrahigh molecular weight polyethylene composite fibers filled with functionalized nanoalumina fillers

Ultradrawing and ultimate tensile properties of ultrahigh molecular weight polyethylene (UHMWPE) composite fibers were successfully improved by the addition of nanoalumina (NAL), acid treated nanoalumina (ATNAL), and/or functionalized nanoalumina (FNAL). As evidenced by FTIR and TEM analyses, maleic anhydride grafted polyethylene (PE_g‐MAH) molecules were successfully grafted onto ATNAL fillers. The specific surface areas of FNAL fillers reached a maximal value at 516 m²/g, as they were modified using an optimal weight ratio of PE_g‐MAH to ATNAL at 8. Achievable draw ratio (D_ra) values of UHMWPE/NAL (F₁₀₀A_y), UHMWPE/ATNAL (F₁₀₀A_x%‐8‐y) and/or UHMWPE/FNAL (F₁₀₀A_x%‐8FPE^z_y) as‐prepared fibers approached a maximal value as NAL, ATNAL, and/or FNAL contents reached an optimal value at 0.1, 0.1, and 0.075 phr, respectively. The maximal D_ra values of F₁₀₀A_x%‐8FPE^z_0.075 as‐prepared fiber specimens were significantly higher than those of F₁₀₀A_0.1 and F₁₀₀A_x%‐8‐0.1 as‐prepared fiber specimens. In which, the maximal D_ra values obtained for F₁₀₀A_x%‐8FPE^z_0.075 as‐prepared fibers reached another maximal value as FNAL fillers were modified using an optimal weight ratio of PE_g‐MAH to ATNAL at 8. The ultimate tensile strength value of F₁₀₀A_2%‐8FPE⁸_0.075 drawn fiber reached 6.4 GPa, which was about 2.4 times of that of the UHMWPE drawn fibers prepared at the same optimal UHMWPE concentration and drawing condition. POLYM. ENG. SCI., 55:2205–2214, 2015. © 2015 Society of Plastics Engineers     

Toughness enhancement of poly(ethylene terephthalate) with functionalized ultrahigh molecular weight polyethylene

Ultrahigh molecular weight polyethylene (UHMWPE) is available commercially in the form of powder, consisting of fine primary particles, 1–5 μm in diameter, agglomerated into secondary “free‐flowing” particles with overall dimensions in the region of 50 to 150 μm. These are normally sufficiently coherent and retain their conglomerated particulate structure when blended with other polymers because of the extremely high viscosity of UHMWPE. In this study the surface of the agglomerated primary particles was acid functionalized by reactions with aqueous solutions of acrylic acid, after being irradiated with γ‐radiation at 15–45 kGy. The acid groups were used to introduce a glycidoxyl functionality through reactions with a difunctional cycloaliphatic epoxy resin and also to a “partial” metal carboxylate functionality through reactions with zinc acetyl acetonate. When blended with polyethylene terephthalate (PET) in either a small‐batch mixer or in a twin‐screw extruder all the treated powders, except those functionalized with acrylic acid, were broken down to their primary size and were uniformly dispersed and strongly bonded to the surrounding matrix. The blends containing the deglomerated particles were found to have much greater ductility and toughness than those produced from both untreated and acid functionalized powder. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2972–2986, 2001     

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, FC_y) and UHMWPE/functionalized CNTs (FC_fx‐y) as‐prepared fibers are reported. In a way similar to those found for the orientation factor values, the achievable draw ratios (D_ra) of the FC_y and FC_fx‐y as‐prepared fibers approached a maximum value as their CNT and/or functionalized CNT contents reached their corresponding optimum values. The maximum D_ra values obtained for FC_fx‐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 FC_0.0015 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 FC_y and FC_fx‐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 FC_y and FC_fx‐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     

Effects of stearic acid on the tensile properties of ultrahigh molecular weight polyethylene fibers

For the purpose of the development of ultrahigh molecular weight polyethylene (UHMWPE) fibers with improved tensile properties, the stearic acid (SA) was added to the gel spinning of UHMWPE and acted as a lubricant film. SA addition was intended to be 0.2, 0.4, 0.6, 0.8, and 1.0 wt% of UHMWPE for forming the SA modified UHMWPE fibers. The tensile properties, thermal properties, crystallization properties, and orientation properties of the prepared UHMWPE fibers were systematically investigated. Results show that there is a more significant tensile property for UHMWPE fibers as SA addition is 0.6 wt%. Their tensile strength and tensile modulus reach 32.86 and 1580.89 cN/dtex, which are raised to an extent of 12.0% and 7.7%, respectively, compared with UHMWPE fibers alone. Moreover, the thermal properties, crystallization properties, and orientation properties of the prepared UHMWPE fibers are enhanced observably when the SA addition is 0.6 wt%.     

Properties of bamboo flour/high-density polyethylene composites reinforced with ultrahigh molecular weight polyethylene

In order to improve the properties of bamboo-plastic composites (BPCs), bamboo flour/high-density polyethylene (HDPE) composites were reinforced with ultrahigh molecular weight polyethylene (UHMWPE). The effects of UHMWPE on properties of composites were studied. The crystallinity of composites decreased slightly. Compared with non-UHMWPE added bamboo powder/HDPE composite, the composite with 6 wt % UHMWPE, showed decrease in water absorption to 0.41%, whereas its tensile strength and flexural strength increased to 34.51 and 25.88 MPa, respectively, a corresponding increase of 34.59 and 12.87%. The temperatures corresponding to initial degradation temperature (T_initial) and maximum degradation temperature (T_max) of the composite increased from 282.7 and 467.4 °C to 288.5 and 474.7 °C respectively. Scanning electron microscopic images showed that UHMWPE was well dispersed and fully extended as long fibers in the composite, forming a “three-dimensional physically cross-linked network structure,” which contributed to the improved properties of the composites. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48971.     

Study on processing of ultrahigh molecular weight polyethylene/polypropylene blends: Capillary flow properties and microstructure

The capillary flow properties and morphologies of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blends were studied. The results show that UHMWPE is difficult to process. The melts flowed unsteadily at lower shear rate. With 10 wt % PP contained in the UHMWPE/PP blends, the apparent melt viscosity was much lower than that of UHMWPE. When the PP content increased to 20 and 30 wt %, no pressure vibration occurred throughout the whole shear rate range. Microstructure analysis showed that PP prefers to locate in the amorphous or low crystallinity zones of the UHMWPE matrix. The flowability of UHMWPE increased substantially with the addition of PP. The addition of PE could not effectively reduce the chain entanglement density of UHMWPE. The improvement of processability of UHMWPE by the addition of PE was rather limited. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3894–3900, 2004     

Effects of phenolic antioxidants on ultrahigh molecular weight polyethylene/decalin solution

The degradation of ultrahigh molecular weight polyethylene (UHMW‐PE) during its dissolution into decalin is discussed. The stabilization of the solution by three phenolic antioxidants, octadecyl β‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate (1076), tetrakis[methylene‐β‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate]methane (1010), and 1,1,3‐tris(2‐methyl‐4‐hydroxy‐5‐tert‐butylphenyl)butane (CA), and an auxiliary antioxidant, dilaurylthiodipropionate (DLTP) is also discussed. Among the three phenolic antioxidants, 1076 had the greatest effect. The auxiliary antioxidant was effective in stabilizing the solution when combined with one of the three phenolic antioxidants. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2877–2881, 2000     

Investigation on dry spinning process of ultrahigh molecular weight polyethylene/decalin solution

The relationship between the draw‐down ratio in the dry spinning process of ultrahigh molecular weight polyethylene/decalin solution and the fiber performance through maximized after‐drawing was investigated. The structural development during the after‐drawing process was analyzed by scanning electron microscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction, sonic velocity, and FTIR measurements. An optimum draw‐down ratio was found in the multihole dry spinning process, which may be explained by molecular disentanglement and the composite effect of entropy and the viscosity component. The as‐spun fiber by draw‐down had an obvious shish kebab morphology, lower crystallinity, and a higher melting temperature compared with a free extrusion sample, and higher crystallinity and melting temperature compared with the fiber by first‐stage after‐drawing. During the subsequent after‐drawing process, the crystallinity, melting temperature, X‐ray diffraction, and sonic velocity orientation factors increased slowly in the higher after‐drawing ratio region, which was not consistent with the rising tendency of the tensile properties. The polarized and unpolarized IR spectra reflected the variations of the orientation and the content of the folded chains. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 474–483, 2005     

Supercritical CO2 as an exfoliating aid for nanocomposite preparation: Comparison of different processing methodologies

This article examines several new methods for compounding nanocomposite materials by twin screw extrusion that use supercritical CO₂ as a processing aid to produce more highly exfoliated polyolefin‐layered silicate nanocomposites than conventional melt intercalation. These methods varied the manner in which the plasticizing behavior of CO₂ influences the surfactant of an organoclay, the compatibilizer, and the matrix during preparation of a polyolefin nanocomposite. The results have shown that targeting CO₂ to the organoclay‐compatibilizer interface can improve the extent of intercalation. However, reduced performance was observed when CO₂ was introduced predominantly to the matrix or neat organoclay. In general, the different techniques of addition for CO₂ did bring about greater structural changes to the organoclay, but the stiffness of the resulting materials was lower than simply following a conventional melt intercalation approach. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

A study on sliding wear of ultrahigh molecular weight polyethylene/polypropylene blends

The wear and friction behavior of ultrahigh molecular weight polyethylene (UHMWPE)/ polypropylene (PP) blends was studied. The addition of PP improves processability and the anti‐wear properties of UHMWPE. The friction coefficient and wear rate of pure UHMWPE are much higher than those of UHMWPE/PP blends under the same conditions, and the wear rate of UHMWPE is more sensitive to load and wear time than that of the UHMWPE/PP blend. Long scratch grooves and cracks occurred in the worn surface of UHMWPE, while no such serious damage was observed in the worn surface of the UHMWPE/PP blend. Atomic Force Micrograph using the contact mode indicated that the friction force between pure UHMWPE and Si₃N₄ tip is much higher than that for the UHMWPE/PP blend, which is consistent with the results from macro‐friction testing.     

Surface modification of ultrahigh molecular weight polyethylene fibers by plasma treatment. I. Improving surface adhesion

The fiber/epoxy resin adhesion increases after plasma treatment on ultrahigh molecular weight polyethylene (UHMW-PE) fibers. The surface modification of UHMW-PE monofilaments was studied using a combination of techniques: contact-angle measurements, SEM, and pullout tests. The results may be summarized as follows: Infiuenced by different plasma parameters and draw ratios of the monofilaments, the adhesion increases by at least four times by plasma treatment. Failure in the pullout tests involve rupture within a treated monofilament and the skin of it was peeled off; the degree of peeling-off is affected by different plasma treatment conditions and draw ratios of the monofilaments. There is only a slight decrease in the surface energy of the treated monofilaments with aging time. Ways of combining plasma etching with other chemical treatments to further improve the fiber/resin adhesion have also been studied. © 1993 John Wiley & Sons, Inc.     

Investigation on the thermal behaviors and mechanical properties of ultrahigh molecular weight polyethylene (UHMW-PE) fibers

Fibers of ultrahigh molecular weight polyethylene (UHMW-PE) were prepared with the gel fiber drawing method, and the solvent and extraction solvent used were a general kerosene and gasoline, respectively. The thermal behaviors and mechanical properties of the fiber were studied using thermal analysis, a wide-angle X-ray diffractiometer, density, the sound orientation factor, as well as mechanical property measurement. The results showed that the morphology of macromolecular chains was changed from the folded state to an extendedcain structure with increasing of the drawing ratio. In addition, the crystal form of the fiber also changed. These changes were more evident while the drawing ratio exceeded 20. The tensile strength, similar to the modulus of the fibers, increases with an increasing draw ratio in the range that we researched, whereas the sonic velocity orientation factor and the degree of crystallinity increase slowly when the draw ratio is over 30. © 1996 John Wiley & Sons, Inc.     

Preparation and electrical conductivity of graphene/ultrahigh molecular weight polyethylene composites with a segregated structure

Graphene-coated ultrahigh molecular weight polyethylene (UHMWPE) powders were prepared by a two-step process. The first step is to coat UHMWPE polymers with graphene oxide (GO) sheets. The second step is to reduce GO on the powders to graphene. The two-step process can effectively prevent the aggregation of graphene during reduction. The resultant graphene/UHMWPE mixtures were hot pressed at 200 °C to obtain the composites with a segregated structure. The composites exhibit high electrical conductivity at a very low percolation threshold (0.028 vol.%). Our method provides a new route for preparing electrical conductive graphene/polymer composites with low percolation threshold.     

Surface modification of ultrahigh molecular weight polyethylene fibers by plasma treatment. II. Mechanism of surface modification

A detailed examination has been undertaken of the influence of surface treatment on the adhesion of ultrahigh molecular weight polyethylene (UHMW-PE) fibers to epoxy resin. XPS, SEM, FTIR–ATR, LRS, and contact-angle measurements have been used to characterize the chemical and physical changes of the fibers. The results, taken together, suggest that the adhesion depends on three factors: (i) chemical bonding effects, after plasma treatment, with the introduction of various kinds of oxygen-containing groups into the surface of the nonpolar polyethylene, which greatly improve the surface energy of the fibers; (ii) mechanical keying effects; and (iii) the nonpolar dispersion force. It is concluded that these three factors can be regarded as additive and the contributions from each of them to fiber/resin adhesion are different and change with increasing treatment time. The optimum results are obtained when their respective contribution reaches about 60%, 30%, and 10%. © 1993 John Wiley & Sons, Inc.     

Photochromic films prepared by solid state processing of disentangled ultrahigh molecular weight polyethylene and photochromic dyes composites

Disentangled ultrahigh molecular weight polyethylene (DPE) is a special grade of polyethylene (molecular weight, >10⁶ Da) which can be processed by an environment friendly solid state process on counter rotating two roll mill (TRM) below the melt temperature of the polymer. This unique processing property of DPE was utilized to develop smart DPE photochromic films. Photochromic dye like 'Spirooxazine' or 'Spiropyran' has been mixed with DPE resin powder prior to film formation without altering the DPE properties. These films could change their optical appearances on exposure to UV-light of wavelength 365 nm and the color change phenomenon of the films could also be replicated by sunlight. The color change observed is found to be reversible, that is, films could return to colorless form either spontaneously in dark or by thermal stimuli. Such smart property was imparted to DPE even at very low concentration (2,000 ppm) of photochromic dyes. Spectrophotometric studies were used to measure the rate of forward reaction with UV radiation and the rate of backward reaction in dark. In fact, DPE powder and photochromic dye composite was used to produce the compression molded disc to understand the color change phenomena. Moreover, it was observed that the photo-degradation rate of dye, could be retarded ~30% by using amphoteric Zinc phthalate salt. TGA and DSC studies confirmed that the characteristics of DPE film remained almost unaltered even after with preparation of film photochromic dyes.     

Effect of polyalphaolefin oils as a solvent in gel-spinning of ultra-high molecular weight polyethylene fibers

In this work, lubricants based on polyalphaolefin with different viscosities were evaluated in the processing of UHMWPE fibers. All fibers were obtained by extrusion with 0.04 to 60 wt% of polyalphaolefin oils with different kinematic viscosities and densities (in ascending order: PAO8, PAO40, and PAO100), under screw speed of 20 to 60 rpm with a nozzle of 1.82 mm diameter. Also, n-hexane was used to extracting the oils from UHMWPE fibers. The fibers did not undergo the drawing process. It was observed that the fibers that underwent process with PAO40 showed the highest linear density, achieving 3273 tex, indicating the orientation of the crystals in a compact morphology inside the extruder and the higher relaxation after leaving the nozzle, increasing die-swell. Microscopic analysis revealed roughness in fiber as the insertion of PAO100 oil increased, while fibers with PAO40 proved to be more densified. In addition, the fibers processed with PAO40 have an increase in thermal stability after n-hexane extraction, with degradation temperature T_max of 482°C in comparison with 476°C for the neat UHMWPE.