新型无氨保存剂HY对鲜天然胶乳及橡胶性能的影响

以不挥发水溶性广谱抗菌剂三嗪衍生物(HY)为鲜天然胶乳(NRL)的保存剂,研究保存剂HY对NRL保存效果及天然橡胶(NR)生胶和硫化胶性能的影响。结果表明:采用保存剂HY的NRL保存120h后,其粘度、pH值变化不大,且后期凝固用酸量显著减小,保存效果较好;NR生胶的各项指标均符合5#标准胶标准要求,且塑性保持率比氨保存生胶高10个单位值;NR硫化胶的物理性能明显优于氨保存剂硫化胶,尤其是拉伸强度提高了26%。     

金属离子钝化剂添加工艺对胶清橡胶性能的影响研究

通过不同的添加工艺将乙二胺四乙酸二钠(EDTA-2Na)、柠檬酸钠(NaCA)、三聚磷酸钠(STPP)三种金属离子钝化剂加入胶清橡胶,研究金属离子钝化剂对胶清橡胶硫化性能,物理机械性能及热氧老化性能的影响。结果表明,加入金属离子钝化剂,对胶清橡胶的硫化性能和物理机械性能的影响较小,但是能够明显提高胶清橡胶的热氧老化性能。NaCA和EDTA-2Na在凝固前加入胶清对提高胶清橡胶的热氧老化性能和热稳定性效果更好,而STPP则是在混炼过程中添加效果更好。     

金属离子钝化剂添加工艺对胶清橡胶性能的影响

通过3种添加工艺将乙二胺四乙酸二钠(EDTA-2Na)、柠檬酸钠(Na CA)和三聚磷酸钠(STPP)3种金属离子钝化剂加入胶清橡胶,研究金属离子钝化剂对胶清橡胶硫化特性、物理性能和热氧老化性能的影响。结果表明:加入金属离子钝化剂对胶清橡胶硫化特性和物理性能影响较小,但能明显提高胶清橡胶的热氧老化性能;Na CA和EDTA-2Na在凝固前加入胶清对提高胶清橡胶热氧老化性能和热稳定性效果更好,STPP则在混炼过程中添加效果更好。     

凝固方法对胶清橡胶力学性能的影响

研究了3种不凝固方法对胶清橡胶性能和碳黑或CaCO3/胶清橡胶硫化胶力学性能的影响.结果表明,采用十二烷基硫酸钠和CaCl2凝固胶清制得胶清橡胶具有较好的性能.     

新型天然胶乳生物保存剂在标准胶制备中的应用研究

研究新型天然胶乳生物保存剂(简称生物保存剂)在标准胶制备中的应用,并与传统保存剂氨进行对比。结果表明:随着生物保存剂和氨质量分数的增大,天然胶乳的保存时间延长,当生物保存剂的质量分数大于0.010(按干胶计)时,天然胶乳的保存时间超过10 h;与采用氨保存的天然胶乳制备的标准胶相比,采用生物保存剂保存的天然胶乳制备的标准胶凝固用酸(甲酸)量大幅度减小,回收率较高,灰分含量、杂质含量、挥发分含量和塑性初值较大,塑性保持率和门尼粘度较低,胶料物理性能无明显差异,生产成本较低,生产环境改善。     

天然橡胶和胶清橡胶的热氧降解特性研究

采用热重分析法(TGA)研究了胶清胶(NR-s)和天然橡胶(NR)在空气气氛中的热氧降解行为。结果表明:(1)NR-s和NR的TG图中均出现多个平台,对应的DTG图中均出现多个峰,因此其热氧降解均属于多步反应。(2)NR-s的T0.05(质量损失率为5%时的温度)为283℃,NR的T0.05为316℃,说明NR-s的热稳定性较NR有一定的下降。     

胶清凝固工艺的研究

研究了表面活性剂和氯化钙作为胶清的凝固体系,对胶清凝固效果和胶清橡胶性能的影响。结果表明,在胶清中加入十二烷基硫酸钠和氯化钙,可在36 h内使胶清完全凝固。当十二烷基硫酸钠为0.2%、氯化钙为3.0%时,胶清的凝固效果较好,胶清橡胶具有良好的综合性能。     

生产工艺对胶清胶拉维邦颜色指数的影响

研究生产工艺对胶清胶拉维邦颜色指数的影响。结果表明:在胶清池中增加除氨装置、控制酸质量分数为0.15~0.25、喷洒质量分数为0.05的抗氧剂(焦亚硫酸钠)溶液、压绉工艺增加2台绉片机机组,制备的胶清胶拉维邦颜色指数小于11,生产成本显著降低。     

配方因素对CM/EPDM并用胶性能的影响

研究氯化聚乙烯橡胶(CM)和EPDM用量及硫化体系对CM/EPDM并用胶性能的影响.结果表明,随着CM用量的增大,并用胶交联密度降低,拉伸强度增大;随着EPDM用量的增大,并用胶t90缩短,撕裂强度减小;硫黄硫化体系的硫化效率较低,并用胶撕裂强度和拉断伸长率较大;过氧化物硫化体系硫化效率适中,并用胶综合物理性能最好;噻唑类硫化体系的硫化效率最高,并用胶拉伸性能和耐热空气老化性能良好.     

微波降解胶清橡胶的制备及表征

采用微波研究其对离心浓缩胶乳副产物胶清橡胶的降解过程,着重探讨其降解程度与胶清用量、微波作用时间、微波功率等因素的关系,结果表明:在微波作用下,胶清橡胶能够实现降解,且在一定程度上,降解程度随着微波作用时间的延长而增大,其降解产物甚至可以达到液体天然橡胶所需分子量的范围。     

Characterization of enzyme‐deproteinized skim rubber

Skim natural rubber latex is a protein‐rich byproduct obtained during the centrifugal concentration of natural rubber latex. Skim latex has a very low dry rubber content (4–8%), and the rubber particles are smaller in size. It has a higher proportion of nonrubber solids, which are mostly proteinaceous in nature. It is difficult to coagulate, and it takes more processing time. The proteins in skim latex can be decomposed by proteolytic enzymes. This article discusses the use of stabilized liquid papain from the papaya plant (Carica papaya) for deproteinization followed by creaming for quick and easy coagulation of skim latex. The technological properties and aging characteristics of the deproteinized skim rubber are compared with those of conventionally prepared skim rubber and block rubber. The deproteinized skim rubber showed enhanced quality parameters. Particle size analysis revealed that deproteinization and creaming of the skim latex did not markedly change the particle size. Gel permeation chromatography showed a reduction in the quantity of fatty acids after deproteinization and creaming, which was reflected in the improvement of the aging characteristics in comparison with the control sample. Vulcanizates prepared with the deproteinized skim rubber had higher resilience, lower heat buildup, lower compression set, and good tensile strength and elongation at break in comparison with conventionally prepared skim rubber, and the properties were almost comparable to those of block rubber. The improvement in the mechanical properties and aging characteristics could be attributed to the reduction of the protein content, the partial removal of unsaturated fatty acids, and the removal of metal ions that were pro‐oxidants during the deproteinization and creaming process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Comparative study of the elasticity and permeability of vulcanized films made with skim and cream natural rubber latex

The purpose of this study was to gain a clearer picture of the structure and properties of vulcanized films made with skim and cream latex from Hevea brasiliensis. The two properties targeted for this study were the elasticity of the films and their permeability to acetone. Surface characterization by atomic force microscopy revealed that vulcanization substantially modified the structure of the films compared to unvulcanized films. Unlike unvulcanized films, particle identity was retained in the vulcanized films made with cream latex, even after 4 weeks of aging. In addition, skim latex gave vulcanized films with greater elasticity than those obtained with cream latex. On the basis of the structural characterization carried out on the latex and films and information from the literature, the greater elasticity of the skim films arose from more entanglements between polyisoprene chains and associations between proteins. Despite differences in the structure, the acetone permeability was very similar for skim and cream vulcanized films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

氯化石蜡共混改性天然胶乳的研究

分别采用氯化石蜡、氯化石蜡／Sb2O3共混改性天然胶乳．考察了改性胶乳硫化胶膜的力学性能及阻燃性能．并进行了TG·DTG和DSC分析。结果表明：改性胶乳的阻燃效果比未改性天然胶乳的高．且氯化石蜡／Sb2O3共混改性天然胶乳可产生协同阻燃效果；随Sb2O3用量的增加．硫化胶膜撕裂强度增加．而拉伸强度下降。氯化石蜡／Sb2O3改性胶乳的热降解过程为二步反应．且起始热降解温度比天然胶乳的低．玻璃化转变温度提高。     

Preparation and characterization of organoclay‐rubber nanocomposites via a new route with skim natural rubber latex

Skim natural rubber latex (SNRL) is a protein rich by‐product obtained during the centrifugal concentration of natural rubber (NR) latex. A new method to recover rubber hydrocarbon and to obtain nanocomposites with organoclay (OC) was investigated. The approach involved treatment of SNRL with alkali and surfactant, leading to creaming of skim latex and removal of clear aqueous phase before addition of OC dispersion. Clay mixed latex was then coagulated to a consolidated mass by formic acid, followed by drying and vulcanization like a conventional rubber vulcanizate. X‐ray diffraction (XRD) studies revealed that NR nanocomposites exhibited a highly intercalated structure up to a loading of 15 phr (parts per hundred rubber) of OC. Transmission electron microscopy studies showed a highly exfoliated and intercalated structure for the NR nanocomposites at loadings of 3–5 phr organically modified montmorillonite (OMMT). The presence of clay resulted in a faster onset of cure and higher rheometric torque. The rubber recovered from skim latex had a high gum strength, and a low amount of OC (5 phr) improved the modulus and tensile strength of NR. The high tensile strength was supported by the tensile fractography from scanning electron microscopy. Thermal ageing at 70°C for 6 days resulted in an improvement in the modulus of the samples; the effect was greater for unfilled NR vulcanizate. The maximum degradation temperature was found to be independent of the presence and concentration of OC. The increased restriction to swelling with the loading of OC suggested a higher level of crosslinking and reinforcement in its presence. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3277–3285, 2006     

Creaming skim natural rubber latex for encapsulation of urea fertiliser

Abstract

Skim natural rubber latex has been characterised before crosslinking with γ-radiation. Micrographs of γ-vulcanised skim particles embedded in polystyrene revealed a semi-interpenetrating polymer network morphology of fine rubber–polystyrene particles surrounded by membrane layer. Creamed skim latex was prepared by addition of 15–45 phr sodium alginate and further used for encapsulation of urea fertiliser. Non-spherical capsules containing an homogeneous urea dispersion were obtained.     

硫黄用量对天然胶乳膜性能的影响

采用凝固剂浸渍法制备天然胶乳硫化胶膜,并对其结构和性能进行研究。结果表明：天然胶乳预硫化程度随硫黄用量的增加而增大;胶膜硫化后的交联程度随硫黄用量的增加先增大后减小,在硫黄用量为1.25份时达到最大值;拉伸强度随硫黄用量的增加先增大后减小,在硫黄用量为1份时达到最大值,而拉断伸长率呈下降趋势;当硫黄用量为1份时达到最佳致密性。     

Novel nonammonia preservative for concentrated natural rubber latex

A derivative of sym‐triazine (HTT) was chosen as a new nonammonia preservative for concentrated natural rubber latex (CNRL) in place of NH₃–TT/zinc oxide (ZnO). The preservation effects of the HTT for CNRL, drying characteristics, mechanical properties, and cytotoxicity of the vulcanized natural rubber (NR) film were investigated. The results show that the CNRL was preserved steadily for more than 6 months with 0.3% HTT, and the volatile fatty acid number, viscosity, and mechanical stability of CNRL all met the requirements of ISO 2004:2010(E). The drying characteristics of the vulcanized NR film preserved by HTT retained no change compared with those of the film preserved by NH₃–TT/ZnO. The tensile strength and elongation at break of the vulcanized NR film preserved by HTT were 32.17 MPa and 853.80%, respectively; these were very similar to those of the film preserved by NH₃–TT/ZnO, whereas the tear strength reached 68.43 kN/m, and this was much higher than that by NH₃–TT/ZnO. The results of the cytotoxicity and dermal irritation tests prove that HTT is not especially harmful to humans. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41749.     

Preparation of high-performance deproteinized natural rubber/chitosan composite films via a green and sulfur-free method

To solve the environment and health issues arose from the sulfur vulcanization, a facile and completely eco-friendly method of latex-assembly and in situ cross-linking is developed to prepare fully bio-based and high-performance rubber films. The films are featured by a “reinforced concrete” structure composed of dynamically cross-linked chitosan framework and unvulcanized deproteinized natural rubber (DPNR) matrix. The self-assembly of DPNR latex particles and chitosan, as well as the in situ cross-linking of chitosan in the film forming process are confirmed by transmission electron microscope and dynamic light scattering. As green rubbers without vulcanization, the as-designed composite films possess excellent mechanic properties comparable to those of the sulfur vulcanized DPNR film, whose tensile strength and toughness reach 15.2 MPa and 77.6 MJ m⁻³ respectively. Moreover, the films exhibited appropriate permeability to moisture and achievable reprocessing, which have potential applications in wearable devices.     

The Role of Coagulants on the Preparation of Dipped film from Radiation Vulcanized Natural Rubber Latex

The effect of coagulants on the preparation of dipped film with good physical properties was studied. In order to optimize various parameters like coagulant concentration, latex concentration, and former dipping time in latex and coagulant, the effect of coagulant on the physical properties of radiation vulcanized natural rubber latex film was evaluated. Calcium nitrate, calcium chloride, and ammonium nitrate were used as the coagulant by dissolving either in water or ethanol. Calcium nitrate solution was found to be the best one among the coagulants used.     

杜仲粗胶对NR共混性能的研究

本文通过采用生物酶预处理的方法对杜仲叶子进行处理,得到杜仲粗胶,研究了杜仲粗胶的用量对NR共混性能的影响。结果表明：杜仲粗胶的用量对于硫化胶的焦烧时间,工艺正硫化时间影响不大;用量超过15份后门尼粘度明显增加;随着杜仲粗胶用量的增加,硫化胶的物理机械性能提高,老化后整体的拉伸强度升高,扯断伸长率降低;硫化胶的弹性模量降低,损耗因子升高。