The effect of shrinkage on the structure and properties of ultra-high molecular weight polyethylene fibers with different concentration

Interface variation in the extraction and drying process of ultra-high molecular weight polyethylene (UHMWPE) gel fiber results in different shrinkage at different direction. The essence of shrinkage lies in the crystallization of UHMWPE chains under the effect of interface tension. However, UHMWPE gel fiber prepared with different solution concentration has different chain entanglement points density that can hinder the regular stacking for UHMWPE chains. The restriction for axis shrinkage of UHMWPE gel fiber facilitates the orientation of UHMWPE chains that is beneficial to improve the tensile strength of UHMWPE drawn fiber. Combined with multiple methods of Wide angle X-ray diffraction, Small-angle X-ray scattering, Differential scanning calorimetry and sonic orientation, the structural evolution of UHMWPE fiber with different shrinkage ratio and different concentration was investigated. Meanwhile, the suitability for UHMWPE fibers in production was evaluated by final tensile strength of the fibers. Here, a structural evolution model is proposed to elucidate the correlation between the shrinkage and the structure and properties of UHMWPE fibers prepared with different solution concentration.     

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     

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%.     

Utilization of rice husk ash in green natural fiber-reinforced cement composites: Mitigating degradation of sisal fiber

This study aims to explore a novel approach to improve the durability of sisal fiber in cement composites by using by-products of biomass power plant: rice husk ash (RHA). The effects of two RHAs on the fiber's degradation were investigated indirectly by testing flexural behavior of sisal fiber-cement composite beams and directly by means of uniaxial tensile properties, thermal decomposition, crystallinity indices and microstructures of embedded fibers, after exploring up to 30 wetting and drying cycles. Allowing the distinction between pozzolanic activities, the efficiency of RHA was compared with two fly ashes and combinations of two clay minerals (metakaolin and nanoclay) with a cement substitution level of 30 wt.%. The durability of composites was improved considerably by incorporating RHA owing to the mitigation of fiber's degradation: the ultimate tensile strength and cellulose fraction of embedded fibers were improved by 384% and 45%, respectively. Fine RHA and the combination of metakaolin and nanoclay yield similar efficiency in mitigating degradation of sisal fiber, and are better than the coarse RHA and fly ashes. The correlations between cement hydration and sisal fiber degradation were analyzed. The results indicate that degree of hydration, calcium hydroxide content and alkalinity of the cement matrix play decisive roles in alkali attacks and mineralization of fiber's cell walls.     

A new and simple way of preparing polycation‐grafted fibrous cellulose

A new way of producing polycation‐grafted fibrous cellulose for its use as a retention aid in the papermaking process was conceived. It consists of adding, under intense stirring, to a cellulose fibers suspension at a basic pH a cationic polyacrylamide dissolved in water. As the cellulose fiber's surface is negatively charged because of its more or less acid groups, the cationic polymer adsorbs on it. The cationic‐grafted cellulose fibers are very similar to the cellulose fibers used in papermaking, since the polymer is (on a micrometer scale) homogeneously grafted on them as a film. It could so be used to increase the retention of the negatively charged fillers, fibers, and pigments during the process, without altering the properties of the resulting sheet of paper. The amount of polymeric grafts depends on the quantity of anionic groups on fiber's surface and varies monotonically with the grafting temperature and polyacrylamide's concentration in the blend. The grafted fibrous cellulose is well stable, even in drastic media and for lower M_w grafts, and the amount of grafted polymer also depends on the concentration and characteristics of fiber's suspension. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3149–3157, 2006     

Mechanical properties of surface‐modified ultra‐high molecular weight polyethylene fiber reinforced natural rubber composites

The mechanical properties of ultra‐high molecular weight polyethylene (UHMWPE) fibers reinforced natural rubber (NR) composites were determined, and the effects of fiber surface treatment and fiber mass fraction on the mechanical properties of the composites were investigated. Chromic acid was used to modify the UHMWPE fibers, and the results showed that the surface roughness and the oxygen‐containing groups on the surface of the fibers could be effectively increased. The NR matrix composites were prepared with as‐received and chromic acid treated UHMWPE fibers added 0–6 wt%. The treated UHMWPE fibers increased the elongation at break, tear strength, and hardness of the NR composites, especially the tensile stress at a given elongation, but reduced the tensile strength. The elongation at break increased markedly with increasing fiber mass fraction, attained maximum values at 3.0 wt%, and then decreased. The tear strength and hardness exhibited continuous increase with increasing the fiber content. Several microfibrillations between the fiber and NR matrix were observed from SEM images of the fractured surfaces of the treated UHMWPE fibers/NR composites, which meant that the interfacial adhesion strength was improved. POLYM. COMPOS., 38:1215–1220, 2017. © 2015 Society of Plastics Engineers     

Surface modification of ultra-high molecular weight polyethylene fibers by γ-radiation-induced grafting

A technique for grafting acrylic polymers on the surface of ultra-high molecular weight polyethylene (UHMWPE) fibers utilizing ⁶⁰Co gamma radiation at low dose rates and low total dose has been developed. Unlike some of the more prevalent surface modification schemes, this technique achieves surface grafting with complete retention of the exceptional UHMWPE fiber mechanical properties. In particular, poly(butyl acrylate) and poly(cyclohexyl methacrylate) were successfully grafted onto UHMWPE fibers with no loss in tensile properties. The surface and tensile properties of the fibers were evaluated using Fourier transform infrared/photoacoustic spectroscopy (FTIR/PAS), X-ray photoelectron spectroscopy (XPS), and tensile tests. The reinforcement efficiency of untreated, polymer-grafted, and plasma-treated UHMWPE fibers in polystyrene and a poly(styrene-co-butyl acrylate-co-cyclohexyl methacrylate) statistical terpolymer was characterized using mechanical tensile tests. The thermoplastic matrix composites were prepared with 4 wt% discontinuous (10 mm), randomly distributed UHMWPE fibers. An approximate 30% increase in composite strength and modulus was observed for poly(cyclohexyl methacrylate)-grafted fibers in the terpolymer and polystyrene matrices. A comparable improvement was realized with the plasma-treated fibers. On the other hand, poly(butyl acrylate) grafts induced void formation, i.e. energy dissipation through plastic deformation and volume expansion at the fiber/matrix interface in terpolymer composites. The latter resulted in a 75% increase in the elongation to failure. The effect of polymer grafts on fiber/matrix adhesion is discussed in terms of the graft and matrix chain interactions and solubility, graft chain mobility, and fracture surface characteristics as determined by scanning electron microscopy (SEM).     

Development of UHMWPE modified PP/PET blends and their mechanical and abrasive wear behavior

In this study, polypropylene and polyethylene terephthalate blend were modified by incorporating different percentages of ultrahigh molecular weight polyethylene (UHMWPE) ranging from 1 to 5 phr. Modified blends were prepared by melt mixing the PP/PET blend and UHMWPE. Ultimate tensile strength of UHMWPE filled blend was determined at 10, 20, 50, and 100 mm/min cross head speeds of testing. It was found that increase of cross head speed from 10 to 100 mm/min increases the tensile strength of PP/PET/UHMWPE blends. Maximum ultimate tensile strength is exhibited by the blend containing 2 phr UHMWPE. Breaking strain of the UHMWPE modified and unmodified PP/PET blend increased with the increase of cross head speed due to the highly entangled chain structure of UHMWPE. Shore A hardness of the filled blends also increased from 341 to 356, which is highest for 2 phr UHMWPE. High stress abrasive wear of UHMWPE modified blend was determined by using Suga abrasion tester, model NUS‐1 Japan. Wear rate of the PP/PET(90/10) blends having 1, 2, and 5 phr of UHMWPE was determined at different loads such as 1, 3, 5, and 7 N and sliding distances from 6.4 m to 25.6 m. Wear rate values show that UHMWPE has prominent effect on abrasive wear of PP/PET blends. Addition of 2 and 5 phr UHMWPE improved the wear resistance of PP/PET blends at different loads, which has been explained on the basis of improved bonding as compared with pure PP/PET blend and increased hardness. Maximum abrasive wear rate reduction was achieved by adding 2 phr UHMWPE in PP/PET(90/10) blend. POLYM. COMPOS. 28:267–272, 2007. © 2007 Society of Plastics Engineers     

高强度聚乙烯纤维绳索的制备研究

研究了纤维的捻度及浸胶处理对超高相对分子质量聚乙烯 (UHMWPE)纤维力学性能及摩擦磨损性能的影响。结果表明 ,UHMWPE纤维的断裂强力随着纤维捻度的增加而减小 ,纤维浸胶处理后的断裂强力增大 ;当UHMWPE纤维中改性氯丁胶粘剂或聚氨酯胶粘剂的含量为 6%时 ,其断裂强力分别增加 17.2 %或 13 .9% ,聚氨酯胶粘剂处理过的UHMWPE纤维的耐摩擦磨损性能最好。     

Multiple-step drawing innovative ultrahigh-molecular-weight polyethylene fibers modified with bacterial cellulose and scCO2-aid

Innovative supercritical carbon dioxide (scCO₂)-assisted ultrahigh-molecular-weight-polyethylene (UHMWPE)/modified bacterial cellulose (MBC) as-spun fibers were found to display substantially lower dynamic transition temperatures than those acquired for scCO₂-assisted UHMWPE or UHMWPE/MBC as-spun fibers prepared without scCO₂-assistance or incorporation of MBC nanofibers. Multiple-step drawing methods were first-time applied to these finely ''relaxed'' scCO₂-assisted UHMWPE/MBC fibers and considerably improved their achievable draw ratios (D_ras), orientation factor (f_os), and tensile tenacities (σ_tts). The best five-step drawn scCO₂UHMWPE/MBC fiber displayed a particularly high σ_tt of 135 g d⁻¹, which was ~35, ~3.75, and ~1.7 fold of σ_tts acquired for good steel fiber and the most appropriate single-step drawn scCO₂-assisted UHMWPE and UHMWPE/MBC fibers, respectively. The particularly high D_ras, f_o, and σ_tts acquired for the best multiple-step drawn scCO₂-assisted UHMWPE/MBC fibers is ascribed to their more ''relaxed'' UHMWPE structures, thinner lamellae, and successive increased drawing temperature in the multiple-step drawing processes.     

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     

不同材料填充超高摩尔质量聚乙烯复合材料的力学性能分析

对纳米Al2O3、玻纤粉、石墨、微珠粉等材料填充的UHMWPE复合材料进行了拉伸、强度和磨损性能试验。结果表明：不同填料对UHMWPE性能的影响不一样，几种填料填充UHMWPE后，其硬度及耐磨性有不同的改善，而拉伸强度和断裂伸长率有不同程度的下降；其中以质量分数为10％的纳米Al2O3填充UHMWPE综合性能最佳；石墨填充材料的加入会使UHMWPE拉伸强度和断裂伸长率下降较大，脆性增大，但可较好地改善UHMWPE的耐磨性。     

Zirconia-alumina multiphase ceramic fibers with exceptional thermal stability by melt-spinning from solid ceramic precursor

Zirconia-alumina multiphase ceramic fibers with 80 wt% (Z80A20 fiber) and 10 wt% (Z10A90 fiber) proportions of zirconia were prepared via melt-spinning and calcination from solid ceramic precursors synthesized by controllable hydrolysis of metallorganics. The zirconia-alumina multiphase fibers had a diameter of about 10 µm and were evenly distributed with alumina and zirconia grains. The Z80A20 and Z10A90 ceramic fibers had the highest filament tensile strength of 1.78 GPa and 1.87 GPa, respectively, with a peak value of 2.62 GPa and 2.71 GPa. The Z80A20 ceramic fiber has superior thermal stability compared to the Z10A90 ceramic fiber and a higher rate of filament strength retention due to the stability in grain size. After heat treatment at 1100 °C, 1200 °C, and 1300 °C for 1 h respectively, the filament tensile strength retention rate of Z80A20 ceramic fibers was 87 %, 80 %, and 40 %. While Z10A90 ceramic fiber was fragile after being heated at 1300 °C. The results showed that the high zirconia content facilitated the fiber's thermal stability.     

低温等离子体改性UHMWPE纤维的表面性能

采用空气低温等离子体改善超高相对分子质量聚乙烯(UHMWPE)短纤维的黏着性,设计正交试验对改性后纤维的黏着性进行测试与分析,确定出较优试验方案;然后对未处理和经较优方案改性后的UHMWPE短纤维的表面形貌、表面化学成分、表面润湿性和强伸性进行测试分析。结果表明:空气低温等离子体改性UHMWPE短纤维黏着性的较优处理条件为功率50 W、压强15 Pa、反应时间120 s,此时,纤维的剥离功是未处理的4.14倍,黏着性得到了大幅度的提升,且单纤维强力损失率仅为3.29%;经较优方案处理后,纤维表面的粗糙程度有所增加,表面润湿性有明显改善,纤维表面的C元素含量明显减少,O、N元素含量有所增加,且出现了相对含量为22.2%的C=O官能团,有利于UHMWPE短纤维黏着性的改善。     

Ultradrawing properties of ultrahigh‐ molecular‐weight polyethylene/carbon nanotube fibers prepared at various formation temperatures

The influence of formation temperature on the ultradrawing properties of ultrahigh‐molecular‐weight polyethylene/carbon nanotube (UHMWPE/CNT) fiber specimens is investigated. Gel solutions of UHMWPE/CNT with various CNT contents were gel‐spun at the optimum concentration and temperature but were cooled at varying formation temperatures in order to improve the ultradrawing and tensile properties of the UHMWPE/CNT composite fibers. The achievable draw ratio (D_ra) values of UHMWPE/CNT as‐prepared fibers reach a maximum when they are prepared with the optimum CNT content and formation temperature. The D_ra value of UHMWPE/CNT as‐prepared fibers produced using the optimum CNT content and formation temperature is about 33% higher than that of UHMWPE as‐prepared fibers produced using the optimum concentration and formation temperature. The percentage crystallinity (W_c) and melting temperature (T_m) of UHMWPE/CNT as‐prepared fiber specimens increase significantly as the formation temperature increases. In contrast, W_c increases but T_m decreases significantly as the CNT content increases. Dynamic mechanical analysis of UHMWPE and UHMWPE/CNT fiber specimens exhibits particularly high α‐transition and low β‐transition, wherein the peak temperatures of α‐transition and β‐transition increase dramatically as the formation temperature increases and/or CNT content decreases. In order to understand these interesting drawing, thermal and dynamic mechanical properties of the UHMWPE and UHMWPE/CNT as‐prepared fiber specimens, birefringence, morphological and tensile studies of as‐prepared and drawn fibers were carried out. Possible mechanisms accounting for these interesting properties are proposed. Copyright © 2010 Society of Chemical Industry     

Development and physico‐mechanical behavior of LDPE–sisal prepreg‐based composites

Low‐density polyethylene (LDPE)‐coated sisal fiber prepreg was prepared by using solution coating process. These coated fiber prepregs were consolidated to make composites having different weight fraction of sisal fibers in a hot compression‐molding machine. This experimental study reveals that higher loading of sisal fiber up to 57wt% in LDPE–sisal composites is possible by this technique. Mechanical and abrasive wear characteristics of these composites were determined. The tensile strength of composites increased with the increase in sisal fiber concentration. Coating thickness of LDPE was varied by changing the viscosity of LDPE–xylene solution that manifested to different weight fraction of fiber in sisal–LDPE composites. Mechanical, dynamic mechanical, and abrasive wear characteristics of these composites were determined. The tensile strength and modulus of sisal composites reached to 17.4 and 265 MPa, respectively, as compared to 7.1 and 33MPa of LDPE. Storage modulus of sisal composites LD57 reached to 2.7 × 10⁹ MPa at 40°C as compared to 8.1 × 10⁸ MPa of LDPE. Abrasive wear properties of LDPE and its composites were determined under multi‐pass mode; pure LDPE showed minimum specific wear rate. The specific wear rate of composites decreased with the sliding distance. Increase of coated sisal fiber content increased the specific wear rate at all the sliding distances, which has been explained on the basis of worn surface microstructures observed by using SEM. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

UHMWPE/CNTs复合体系及其纤维的研究进展

综述了超高分子量聚乙烯(UHMWPE)、碳纳米管(CNTs)、UHMWPE/CNTs复合体系及其纤维的研究现状,以及CNTs的添加对UHMWPE/CNTs复合体系及其纤维性能的影响;添加CNTs可有效提高UHM-WPE的耐磨性、电学性能、力学性能以及UHMWPE纤维的抗蠕变性能和热稳定性能;指出CNTs对UHM-WPE改性过程中存在的主要问题是CNTs分散性差,CNTs的生产成本高,UHMWPE/CNTs的改性机理有待进一步深入,并进一步拓宽UHMWPE/CNTs复合体系及其纤维的应用领域。     

Surface modification and physical properties of various UHMWPE‐fiber‐reinforced modified epoxy composites

Two surface modification methods—plasma surface treatment and chemical agent treatment—were used to investigate their effects on the surface properties of ultrahigh‐molecular‐weight polyethylene (UHMWPE) fibers. In the analyses, performed using electron spectroscopy for chemical analysis, changes in weight, and scanning electron microscope observations, demonstrated that the two fiber‐surface‐modified composites formed between UHMWPE fiber and epoxy matrix exhibited improved interfacial adhesion and slight improvements in tensile strengths, but notable decreases in elongation, relative to those properties of the composites reinforced with the untreated UHMWPE fibers. In addition, three kinds of epoxy resins—neat DGEBA, polyurethane‐crosslinked DGEBA, and BHHBP‐DGEBA—were used as resin matrices to examine the tensile and elongation properties of their UHMWPE fiber‐reinforced composites. From stress/strain measurements and scanning electron microscope observations, the resin matrix improved the tensile strength apparently, but did not affect the elongation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 655–665, 2007     

Effect of fiber-matrix adhesion on the properties of short fiber reinforced ABS

The tensile strength, fracture energy, and impact strength of ABS reinforced with discontinuous crystalline fibers such as Fybex

1 Du Pont trademark.

can be controlled by manipulating fiber-matrix interfacial adhesion. In “good bonding” situations composite tensile strength, thermal expansion coefficient, and elastic moduli are significantly improved over the unfilled resin. The excellent impact strength of unreinforced ABS can be retained by lowering the fiber-matrix interfacial adhesion. This results in a corresponding reduction in the improvements in tensile and flexural strength. However, the elastic moduli and thermal expansion coefficients are relatively insensitive to changes in adhesion. Consequently, a material with high modulus (>500,000 psi), high Izod impact resistance (7.0 ft-lb/in.), and low expansion coefficient (3.0 × 10^?5 in./in./°F) can be obtained. A material with this unique combination of properties should find use in large parts such as camper tops, truck grilles, and snowmobile bodies. Fiber-matrix adhesion was measured directly by an x-ray analysis technique which could be employed because of the fiber's crystallinity and unique growth habit. This independent measurement allowed a correlation between bonding and composite properties. The interfacial bond strength was manipulated by a variety of fiber coatings and resin additions.     

Short aramid-fiber reinforced ultra-high molecular weight polyethylene

Summary Ultra-High Molecular Weight Polyethylene (UHMWPE) is frequently used in artificial joints because of its high wear resistance. To extend the lifetime of these joints even further, it is necessary to decrease the wear rate. The wear rate may be decreased by blending UHMWPE with short aramid fibers. On account of the extremely high viscosity of UHMWPE mixing was accomplished by swirling the UHMWPE powder and the chopped fibers with compressed dry nitrogen, and a composite with fairly uniformly distributed and randomly oriented fibers was obtained by compression moulding. The failure behaviour of the composite changes from ductile for low fiber content to brittle failure for higher fiber content. The deviation of the experimental Young's modulus from the theoretical value can be explained by, among others, the void content. Preliminary results show that the wear rate of UHMWPE indeed decreases with incorporation of the aramid fibers.