Ultrahigh molecular weight polyethylene with improved crosslink density,oxidation stability,and microbial inhibition by chemical crosslinking and tea polyphenols for total joint replacements

Highly crosslinked ultrahigh molecular weight polyethylene (UHMWPE) stabilized by vitamin E (VE) is widely applied in artificial joints as the bearings. Despite the approval, there is a discord that VE lowers the crosslinking efficiency, limiting its use at high concentration. In this work, we aim to obtain highly crosslinked and oxidation resistant UHMWPE through the conjunction of tea polyphenol and chemical crosslinking. We hypothesized that highly incorporated tea polyphenol with multiple reactive sites can ameliorate crosslinking efficiency of chemical crosslinked UHMWPE in comparison to VE. Epigallocatechin gallate (EGCG) as representative tea polyphenol was incorporated into UHMWPE at high concentration (2–8 wt%), followed by chemical crosslinking with 2 wt% organic peroxide. Unlike VE/UHMWPE blends as the control, chemical crosslinking achieved an increasing trend in crosslink density of EGCG/UHMWPE blends with increasing antioxidant concentration. High concentration of EGCG also enhanced the oxidation stability of UHMWPE. Intriguingly, EGCG endowed UHMWPE with an excellent antimicrobial property, which was inefficient in VE/UHMWPE. Cell viability was hardly affected by the high loaded antioxidant and peroxide. The chemically crosslinked UHMWPE blended with EGCG is proved to be a reasonable, cost effective and realistic alternative for use in artificial joints.     

Effects of a mixture of stabilizers on the structure and mechanical properties of polyethylene during reprocessing

The properties of two polyethylenes [a high‐density polyethylene (HDPE) and a low‐density polyethylene (LDPE)] were studied after several extrusion cycles. To reduce the degradation effects during the reprocessing, a mixture of two stabilizers was added to the formulations. The predominant degradation mechanism was chain scission for the HDPE and chain branching and crosslinking for the LDPE. For both polyethylenes the FTIR spectra exhibited a growth in the number of carbonyl groups as a function of the number of extrusion cycles. Their tensile properties were degraded with the reprocessing but both polyethylenes maintained their nearly constant thermal behavior and crystallinity. The addition of a primary phenolic antioxidant and a secondary phosphite antioxidant preserved the melt behavior of virgin materials after the reprocessing and reduced the degradation effects. From the tensile tests, the efficiency of the antioxidants in the LDPE was very high and, after the reprocessing, the material retained the mechanical properties of virgin LDPE. The efficiency of the antioxidants for the HDPE was not significant. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3910–3916, 2004     

Rheological behaviors and foaming behaviors of crosslinked ethylene–vinyl acetate with polyfunctional monomers

To produce ethylene–vinyl acetate (EVA) foams with a higher foaming ratio and stable cell size, the efficiency of the crosslinking reaction is required to conduct simultaneously with the blowing reaction. Hence, the multifunctional monomer trimethylolpropane trimethacrylate (TMP) as a crosslinking promoter and a crosslinking agent dicumyl peroxide are used together as a crosslinking system to EVA foaming, when chemical blowing agent azodicarbonamide (ADC) is used. The TMP concentration of approximately 1.0 phr (per hundred resin) is most effective for balancing the expansion ratio and fine cell size. In the SEM diagram and expansion ratio results, it can be found that when the concentration of TMP ranges from 0 to 1.0 phr, the cell mean size is reduced from 360.3 to 140.5 μm and the expansion ratio is reduced from 13.6 to 9.1 at 170°C. The results of time-sweep experiment of thermogravimetric analysis (TGA) show that the foaming time of ADC in the melt increases with the addition of TMP. Capillary rheometer and rotational rheometer tests show that the viscosity and the crosslinking efficiency of the melt are improved with the TMP addition. The curing time has been reduced from 2.93 to 2.22 min for 170°C.     

Effect of mineral filler sepiolite on sulphur-free thiuram vulcanization of natural rubber

The effect of sepiolite on the sulphurless vulcanization of NR by tetramethylthiuram disulphide, with and without activator (triethanolamine) was studied. The influence on: a) kinetic vulcanization parameters, b) crosslinking density, c) crosslinking types, d) efficiency factor E and e) zinc sulphide formation was considered. The vulcanization rate increases with increasing sepiolite level but crosslinking density is reduced. Based on these results a vulcanization mechanism is proposed and discussed.     

高密度聚乙烯电子束辐射交联的研究

用高能电子束辐射技术研究了添加敏化剂季戊四醇三丙烯酸酯(PETA)和抗氧剂300的高密度聚乙烯(HDPE)体系的辐射交联效应.通过测定试样辐射后交联度、拉伸强度、直角撕裂强度等性能,考察了辐射剂量、w(PETA)和 w(300)对 HDPE辐射交联的影响;并用差示扫描量热法和热重分析研究了HDPE辐射后的结晶性和热稳定...     

Thermal insulation and antioxidation of vertical graphene oxide-grafted carbon nanofiber aerogels with ceramic coating

In this work, composite aerogels with low thermal conductivity and antioxidation were prepared by introducing graphene oxide (GO) on the carbon nanofibers (CNFs) surface, followed by ceramic coating. CNFs surface-grafted vertical morphology of GO was used as an enhancer to hinder the heat radiation transmission. The introduced shrinkage-resistant ceramic coating was used as an antioxidant barrier for carbon materials. The anti-shrinking ceramic coating was obtained by heat treatment of coating with wrinkle morphology to complete the ceramic transformation. The wrinkle morphology of the coating originated from the gradient crosslinking of the coating before its ceramic transformation. Among them, the gradient crosslinking of the coating could be done by irradiation crosslinking and crosslinker impregnation crosslinking. The thermal insulation and antioxidant of the composite aerogel were jointly investigated. Moreover, the mechanism of CNFs surface grafting GO and the anti-shrinkage mechanism of the coating were systematically discussed. The experimental results showed that the aerogel exhibited excellent thermal insulation and oxidation resistance in a wide range of temperatures. The structural design of the aerogel not only weakened the thermal radiation transmission to the CNFs aerogel but also significantly enhanced the antioxidant.     

Thermal oxidation of metallocene‐catalyzed poly(ethylene octene) by a rheological method

The thermal oxidation of a metallocene‐catalyzed poly(ethylene octene) (POE) melt was studied by a dynamic rheological method. Furthermore, to prove the effect of oxygen on the thermal oxidation of POE, cyclic samples, which consisted of virgin POE in the outer circle and POE with antioxidant inside, were made. The results showed that a thermal‐oxidation‐induced crosslinking reaction occurred in the POE melt at a high temperature. The amount of the antioxidant determined the thermal oxidation of POE when the antioxidant was added, and the diffusion of oxygen controlled the thermal oxidation of POE without the antioxidant. In addition, Fourier transform infrared and gel content characterization confirmed that the crosslinking occurred and that carbonyl groups formed in the reaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

铝盐混凝剂处理胜利油田聚合物驱采出水混凝机理研究

研究了铝盐混凝剂处理胜利油田聚合物驱采出水的效果和作用机理.结果发现:原油、部分水解聚丙烯酰胺(HPAM)和盐共存时,三者相互作用结果都导致混凝剂投加量增加,除油、除HPAM效果降低.在处理实际采出水时,混凝效果主要依靠Al~(3+)与水中残余HPAM的交联作用.采出水中油滴和盐都会阻碍铝盐与HPAM的交联反应.与HPAM交联能力较强的硫酸铝的除油效果和去除HPAM效果比聚合氯化铝(PAC)高.     

硅烷交联聚乙烯电力电缆绝缘料的研制

采用两步法制备了硅烷交联聚乙烯（PE）电力电缆绝缘料。以双螺杆挤出机为反应器,以低密度聚乙烯（LDPE）和线型低密度聚乙烯（LLDPE）为基础树脂,考察了影响PE接枝交联的主要因素（如基础树脂的配比,交联剂的用量及种类,引发剂、抗氧剂的用量等）,得出了具有良好性能的硅烷交联PE电力电缆绝缘料的配方（质量份数）：LDPE为85．00phr,LLDPE为15．0H0phr,硅烷W为0．60phr,硅烷Q为1．40phr,引发剂为0．12phr,抗氧剂为0．20phr。     

Irradiation crosslinking of PVC–ENR blend Effect of efficient radical scavenger

Abstract

The irradiation induced crosslinking of 50:50 poly (vinyl chloride)–epoxidised natural rubber (PVC–ENR) blend was studied in the presence of 0–1·5 pphr antioxidant Irganox 1010. The samples were irradiated using a 3·0 MeV electron beam machine at doses ranging from 20 to 200 kGy in air and room temperature. The gel fraction, tensile strength T _s, modulus at 100% elongation M ₁₀₀, elongation at break E _b, hardness, and resilience were used to follow the irradiation induced crosslinking of the blend. The decline in gel fraction, T _s, M ₁₀₀, hardness, and resilience and the concurrent increase in E _b with increasing antioxidant indicated the inhibition of irradiation induced crosslinking by the antioxidant used. The improvement in aging properties of the blend with the addition of the antioxidant is also reported. It was evident from FTIR that Irganox 1010 is involved in the stabilisation of the blend against irradiation induced degradation.     

新型光降解体系对光/生物降解薄膜光降解行为的影响

研究了由光敏剂硬脂酸铁和抗氧剂 10 76组成的光降解体系的光 /生物双降解聚乙烯薄膜在紫外灯辐照下的断裂伸长率保留率、分子量、脆化期、诱导期等的变化规律。结果表明 ,硬脂酸铁具有促进光降解和抑制交联的双重作用 ;抗氧剂 10 76对薄膜光降解作用的影响没有硬脂酸铁显著 ;由它们组成的光降解体系具有较好的时控光降解效应 ,能使薄膜诱导期在较大时间范围内调控     

光交联对HDPE凝胶量的影响

用安息香二甲醚和三(丙烯酰氧乙基)异氰尿酸酯(TAEIC)作为PE的光敏剂和助交联剂,研究了它们的用量、光照时间、交联温度,紫外光光强对PE交联度的影响。结果表明,安息香二甲醚是一种有效的光敏剂,引发效率较高;助交联剂可以提高交联效率;光照时间、紫外光光强和交联温度等对PE的交联度均有明显的影响。     

Mechanical characteristics of poly(2‐hydroxyethyl methacrylate) hydrogels crosslinked with various difunctional compounds

Poly(2‐hydroxyethyl methacrylate) hydrogels were prepared in the presence of 30 wt% water using two series of crosslinking agents including divinylic (ethyleneglycol dimethacrylate, 1,4‐butanediol dimethacrylate, 2,3‐dihydroxybutanediol 1,4‐dimethacrylate) and diallylic (1,5‐hexadiene‐3,4‐diol and 1,5‐hexadiene) compounds, over a concentration range between 0.1 and 5 mol%. The resulting polymers were swollen in water to yield homogeneous transparent hydrogels. These hydrogels were characterised in terms of equilibrium swelling in water, tensile properties and compression stress–strain measurements. The influences of the nature and the concentration of crosslinking agent on the swelling behaviour and the mechanical properties of these hydrogels were investigated. The crosslinking efficiency of two representative agents (ethyleneglycol dimethacrylate and 1,5‐hexadiene‐3,4‐diol) was quantified by compression experiments. A much lower crosslinking efficiency (0.013) was observed for 1,5‐hexadiene‐3,4‐diol than for ethyleneglycol dimethacrylate (0.336). It is suggested that the low crosslinking efficiency of diallylic agents is responsible for a trend in properties different from that displayed by the gels crosslinked with dimethacrylates. A comparison was made to the similar effect observed previously in heterogeneous PHEMA hydrogels. © 2001 Society of Chemical Industry     

The effectiveness of polymer additives as determined by torsional braid analysis

Torsional braid analysis has been explored as a means of providing a quantitative measure for the effectiveness of polymer additives. Quantitative determinations have been made of antioxidant activity of selected compounds when formulated with certain elastomers prone to oxidative crosslinking on heat aging. The torsional braid technique has been used to determine the time dependence of the sharp torsional modulus increase which corresponds to a change from a rubbery to a highly crosslinked state. This time dependence is taken as a measure of the rate of oxidative crosslinking in heat-aged elastomer films coated on a Fiberglas braid. In this manner an assessment of antioxidant activity can be made. The effect of concentration and aging temperature on antioxidant activity can be made also. It has been also possible to use this technique to study the effect of structural changes in an antioxidant on its resultant activity. Feasibility studies have also been made on antiozonants in natural rubber and cis-polybutadience at three temperatures. A value of 10.9 Kcal/mole was calculated for the activation energy for the oxidative crosslinking reaction of cis-polybutadiene.     

Effect of crosslinking density on the diffusion of antioxidant in XLPE matrices

A Fourier Transform Infrared spectrometer equipped with a microbeam accessary and a linear translation stage with a pinhole mask was used to monitor the diffusion of antioxidant in crosslinked polyethylene (XLPE) matrices crosslinked with controlled amounts of crosslinking agent. Integration of the peak area for a characteristic peak of the antioxidant at different positions along the sample indicated the changing concentration due to diffusion within 30 days. This technique allowed us to study an antioxidant with a molecular weight in the thousand range. The diffusion coefficients calculated were in the order of 10^?11 – 10^?10 cm²·s^?1. It was observed that the diffusion constants dramatically changed with the crosslinking density.     

Determination of the nature and content of antioxidant and antioxidant synergist in polyethylene and crosslinked polyethylene used in cables

It is shown that polyethylene and crossllnked polyethylene resins used for cable applications contain an antioxidant synergist in addition to an antioxidant. Their nature and content have been determined by a combination of ultraviolet and Fourier transform infrared spectroscopy and neutron activation analysis measurements. The results thus obtained suggest that part of the antioxidant compound is grafted to polymer chains during crosslinking.     

Radiation crosslinking of bisphenol-a polycarbonate in the presence of bisphenol-a dimethacrylate and triallyl cyanurate

Summary Radiation crosslinking of bisphenol-A polycarbonate (PC) was carried out by the γ-irradiation of the polymeric films containing 5 and 2 wt % of bisphenol-A dimethacrylate (BPDMA) or triallyl cyanurate, respectively, as well as by the BPDMA grafting from acetone solution onto PC preirradiated in air. The modified samples were analyzed for the sol/gel content, and the dependences of gel fraction yield of crosslinked polymer on monomers concentration and absorbed dose were found. The radiation-chemical yields of crosslinking and degradation as well as gelation doses were determined for the modified PC. Molecular weights of the starting and irradiated pure PC were detemined by the GPC method, and radiation-chemical yield of PC degradation was calculated. It has been found essential difference in efficiency of PC crosslinking depending on monomers and doses used as well as on methods of modification. Effects of crosslinking agents distribution in the PC matrix and simultaneous processes of crosslinking and degradation in the polymer-monomer compositions on efficiency of PC crosslinking have been discussed. Received: 22 March 2000/Revised version: 26 June 2000/Accepted: 26 June 2000     

EVM橡胶过氧化物交联体系的研究

研究了交联剂过氧化二异丙苯(DCP)、双叔丁基过氧异丙基苯(BIPB)、2,5-二甲基-双(叔丁基过氧基)己烷(DBPMH)以及助交联剂三烯丙基异氰脲酸酯(TAIC)、三烯丙基氰脲酸酯(TAC)、N,N′-间苯撑双马来酰亚胺(HVA-2)对乙烯-醋酸乙烯酯橡胶(EVM)硫化特性、交联密度以及力学性能的影响。通过测试硫化曲线、力学性能和交联密度还研究了无机阻燃填料氢氧化镁的隔离效应对EVM橡胶交联效率的影响。结果表明,EVM橡胶最优过氧化物交联体系为BIPB和TAIC,其最佳配比为2.3/2.5,此时EVM橡胶有较好交联效率、交联速率和力学性能。氢氧化镁对EVM橡胶的交联效率没有影响,但硅烷化氢氧化镁能够提高EVM橡胶的表观交联密度。使用高交联效率过氧化物交联体系BIPB和TAIC,并添加硅烷化氢氧化镁,可平衡EVM橡胶阻燃性能和力学性能。     

Effect of copolymers modifying PVC on its physical and mechanical properties and its UV-radiation resistance. VI. Photodegradation and crosslinking of PVC films containing MMA/MA,VC/VAC,MBS or ABS

The degradation and crosslinking induced by 253.7 nm wavelength radiation was investigated in pure PVC films and in films containing 1–10 wt.-% of modifying copolymers (ABS, MMA/MA, VC/VAC or MBS). It has been found that these copolymers decrease the efficiency of PVC crosslinking. Especially ABS and 3–10 wt.-% MBS clearly hamper this reaction. The induced changes of the limiting viscosity number (LVN) and solubility observed in samples containing MBS and VC/VAC suggest that these copolymers increase or decrease the efficiency of photodegradative or crosslinking processes, depending on the concentration of the copolymers in the samples.     

Durable press finishing of cotton with polycarboxylic acids. II. Ester crosslinking of cotton with dithiosuccinic acid derivative of S-triazine

The preparation of an alternative polycarboxylic acid to replace the most promising but expensive crosslinking reagent butanetetracarboxylic acid (BTCA) was reported in Part I.¹ Part II studies the efficiency of the crosslinking of cotton with the dithiosuccinic acid derivative of s-triazine (HDTST). Diffuse Reflectance infrared (DR FTIR) spectroscopy in combination with wrinkle recovery angle measurements (WRA) were used to analyse the efficiency of cotton cellulose crosslinking. Energy Dispersive X-ray analysis (EDX) of the polycarboxylic acid-finished cotton fabric was performed to study sulphur distribution. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 171–177, 1997