改性纳米碳酸钙对天然胶乳胶膜热性能的影响

探讨改性纳米碳酸钙对天然胶乳胶膜耐热老化性能和热降解性能的影响。结果表明，加入改性纳米碳酸钙可以改善天然胶乳胶膜的耐热老化性能和热降解性能；改性纳米碳酸钙用量为3份的天然胶乳胶膜耐热老化性能和热降解性能与防老剂264用量为1份的天然胶乳胶膜相当，而生产成本较低。     

天然胶乳中蛋白质的结构及对其应用性能的影响研究

天然胶乳是一种生物合成的高分子聚合物水基型胶体体系,主要以聚顺-1,4-异戊二烯为主体,具有优异的综合性能,主要成分为橡胶烃、水、非胶物质,非胶物质主要由蛋白质、类脂物、丙酮溶物、水溶物、无机盐等组成.其中蛋白质对天然胶的应用性能影响最为重要,本文对天然胶乳中蛋白质的结构进行分析,并对低蛋白质天然胶的研究,蛋白质对其力学性能的影响进行综述.     

胶料热老化性能试验

对以天然橡胶和顺丁橡胶并用的胶料,在无防老剂和有防老剂状态下分别进行热老化和热氧老化对比试验,试验表明,试片在无氧热老化条件下胶料的性能下降很少,而且经较长时间硫化的试片对胶料热氧老化性能略有提高.配方中增用防老剂后,明显提高了胶料的耐热氧老化性能,特别是经较长时间硫化的试片热氧老化性能更进一步提高.     

天然橡胶的热氧老化研究

为了改善天然橡胶的热氧老化性能，试验了防老剂D提纯品和工业品对天然橡胶热氧老化性能的影响，调试了其热氧化诱导期、热失重、热老化的性能变化。结果表明：含杂少纯度高的防老剂D使天然橡胶的抗热氧老化得到改善。     

CR硫化胶老化过程中热性能和动态力学性能变化的研究

探讨CR硫化胶老化过程中交联密度、热性能和动态力学性能的变化。结果表明，随着老化时间延长，CR硫化胶的交联密度先减小后增大，结晶度和结晶速率先增大后减小，初始降解温度降低，最大降解速率增大，玻璃化温度先降低后升高，0℃附近的tanδ值先减小后增大，60℃附近的tanδ值减小。     

不同金属离子催化剂制备氢化天然橡胶的热氧老化性能对比

采用不同金属离子催化剂,通过乳液氢化方法制备了氢化天然橡胶（HNR）,研究了生胶的等温氧化诱导时间（OIT）和硫化胶热氧老化前后的拉伸性能变化,考察了金属离子催化剂对HNR热氧老化性能的影响。结果表明,过氧化氢/水合肼/铜离子催化体系中的铜离子对材料的热氧老化性能影响较大,采用铜离子制备的HNR热氧老化后拉伸性能变化率高于天然胶乳,OIT缩短至2.5 min。将铜离子替换为锌离子后制备的HNR,100 ℃热氧老化72 h后拉伸强度变化率减小至23.91%,扯断伸长率变化率为32.12%,150 ℃ OIT延长至32.4 min,具有更好的热氧老化性能。     

天然脂质和蛋白质在纯天然橡胶热老化行为中的作用

三叶橡胶是制备橡胶的天然胶乳的主要商业来源之一。除了主要成分聚异戊二烯外,NR中还含有碳水化合物、蛋白质、脂质、重金属等其他物质。这些成分完全取决于橡胶的品种、季节、成熟程度和种植过程。对非橡胶成分的化学和物理性质的影响已有深入研究。聚异戊二烯链的断裂引起NR     

老化对NR硫化胶的影响

研究了热空气老化和真空老化对ＮＲ硫化胶结构和性能的影响,采用化学探测剂脱硫的方法测定了老化过程中ＮＲ硫化胶交联密度及交联键分布变化的情况,同时测定了硫化胶的力学性能和动态性能随时间变化的情况。结果显示,热空气老化使硫化胶的交联密度增加,但力学性能损失严重,原因是主链氧化断裂。真空老化使ＮＲ硫化胶交联密度略微降低,但力学性能保持良好,类似于硫化返原。热空气老化使ＮＲ硫化胶的动态性能改善,而真空老化后     

新工艺环保型防老剂264对天然橡胶热氧老化性能的影响

对比普通防老剂264,研究新工艺环保型防老剂264（简称新型防老剂264）对天然橡胶（NR）胶料的硫化特性、热氧老化性能及其耐水抽出性能的影响。结果表明,与普通防老剂相比,新型防老剂264对NR胶料的硫化特性影响不明显,其耐水抽出性能及胶料的耐热氧老化性能较好,更适合在潮湿的环境下使用。新型防老剂264在NR胶料中的用量以1～2份为宜。     

蛋白质对天然橡胶及其性能影响的研究

天然橡胶(NR)的主要成分为橡胶烃、水、非胶物质,其中非胶物质中蛋白质的含量对其性能的影响最大.本文分析了天然胶乳中的蛋白质的结构,介绍了低蛋白天然胶乳的制备及其性能的研究概况、蛋白质对其硫化及力学性能影响研究现状,并对低蛋白天然胶市场前景进行了分析与展望.     

不同天然胶乳含量乳胶海绵的热氧老化行为

采用加速热空气老化的方法将2种不同天然胶乳含量的乳胶海绵（80 NR和0 NR）置于100℃条件下,通过黄度指数、白度指数、交联密度和压陷硬度等性能指标考察了其热氧老化行为,探讨了材料的热空气老化规律。结果表明,在老化过程中乳胶海绵80 NR的黄度指数始终大于0 NR,而白度指数始终小于后者。80 NR的交联密度始终要大于0 NR,所以该乳胶海绵更容易发生分子链的断裂和交联反应。80 NR的压陷硬度受老化时间的影响较明显,且会出现在较短时间内压陷硬度急剧增大的现象;0 NR的压陷硬度与老化时间呈线性相关且增幅较小。乳胶海绵0 NR的耐老化性能要优于80 NR。     

Study on preparation of chlorinated natural rubber from latex and its thermal stability

The effects of pH value of reaction system, reaction time, and reaction temperature on the chlorination reaction in the preparation of chlorinated natural rubber (CNR) from natural rubber latex were discussed. It has been found from the thermal analysis that the thermal degradation of CNR in nitrogen is a one-step reaction, and 30% carbonide with a stable structure remained at 360 to 700°C; whereas the thermo-oxidative degradation of CNR in air is a multistep reaction, and the thermal degradation ratio reaches to 100% at 560°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2863–2867, 1999     

生物酶法催化天然乳胶中过敏蛋白质交联的研究

利用谷氨酰胺转氨酶催化天然乳胶(NRL)水溶性蛋白质(WSP)发生交联,减少天然乳胶中水溶性蛋白质的含量.利用粒径分析、结构表征、十二烷基硫酸钠凝胶电泳实验证明了交联反应的发生.采用这一新技术可以降低天然乳胶制品的过敏性,拓展了其在医疗卫生领域、食品加工等领域的应用空间.     

Study on hot air aging and thermooxidative degradation of peroxide prevulcanized natural rubber latex film

The air‐aging process at 120°C and the thermooxidative degradation of peroxide prevulcanized natural rubber latex (PPVL) film were studied with FTIR and thermal gravity (TG) and differential thermal gravity (DTG) analysis, respectively. The result of FTIR shows that the ? OH and ? COOH absorption of the rubber molecules at IR spectrum 3600–3200 cm^?1, the ? C?O absorption at 1708 cm^?1, and the ? C? OH absorption of alcohol at 1105 and 1060 cm^?1 increased continuously with extension of the aging time, but the ? CH₃ absorption of saturated hydrocarbon at 2966 and 2868 cm^?1, the ? CH₃ absorption at 1447 and 1378 cm^?1, and the C?C absorption at 835 cm^?1 decreased gradually. The result of TG‐DTG shows that the thermal degradation reaction of PPVL film in air atmosphere is a two‐stage reaction. The reaction order (n) of the first stage of thermooxidation reaction is 1.5; the activation energy of reaction (E) increases linearly with the increment of the heating rate, and the apparent activation energy (E₀) is 191.6 kJ mol^?1. The temperature at 5% weight loss (T_0.05), the temperature at maximum rate of weight loss (T_p), and the temperature at final weight loss (T_f) in the first stage of degradation reaction move toward the high temperature side as the heating rate quickened. The weight loss rate increases significantly with increment of heating rate; the correlation between the weight loss rate (α_p) of DTG peak and the heating rate is not obvious. The weight loss rate in the first stage (α_f1) rises as the heating rate increases. The final weight loss rate in second stage (α_f2) has no reference to heating rate; the weight loss rate of the rubber film is 99.9% at that time. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3196–3200, 2004     

淀粉纳米晶对天然胶乳性能的影响

将淀粉纳米晶作为天然胶乳的补强剂,研究其对天然胶乳的胶体性能及硫化胶膜的物机性能、耐水性和耐溶剂的影响。研究结果表明:将淀粉纳米晶加入天然胶乳后,胶乳的粘度变化不大,机械稳定度提高;硫化胶膜的物机性能明显提高,耐溶剂性提高,而耐水性降低。     

表面活性剂对天然胶乳蛋白质含量影响的研究

采用表面活性剂直接处理鲜胶乳离心浓缩法制备浓缩胶乳,先用尿素预处理新鲜胶乳后加入表面活性剂处理,再离心浓缩法制备浓缩胶乳。研究表面活性剂种类、尿素预处理时间和预处理温度及新鲜胶乳的pH值对处理所得浓缩胶乳蛋白质含量的影响。同时用傅立叶红外吸收光谱对2种处理方法制备的浓缩胶乳胶膜进行了表征。实验结果表明,鲜胶乳先经尿素预处理一定时间后加入阴离子表面活性剂处理,再离心浓缩制备浓缩胶乳,蛋白质含量显著降低。适宜条件下,浓缩胶乳的氮含量从质量分数0．430％下降至0．089％。红外光谱分析表明,先用尿素预处理新鲜胶乳,然后加入阴离子表面活性剂处理,再离心浓缩制备浓缩胶乳,胶膜在1546cm。处蛋白质的酰胺Ⅱ谱带几乎消失,在3295cm。处N—H的伸缩振动峰明显减弱。     

Effects of Sm3+/PMAA on mechanical and thermal properties of natural rubber latex film

Samarium carbonate [Sm₂(CO₃)₃] was taken as the source of Sm³⁺, and methyl acrylic acid (MAA) was employed as the precursor to prepare polymethacrylic acid (PMAA). The mixture of Sm₂(CO₃)₃ and PMAA was marked as “SmP.” The SmP prepared under different conditions was added to natural rubber (NR) latex to prepare NR/SmP films. The influence of the polymerization temperature of MAA and the amount of SmP on the mechanical properties and structure of NR/SmP films were analyzed. The results show that polymerization temperature has significant effect on the mechanical properties of NR/SmP film; lower temperature is benefit to improve modulus and rigidity, whereas higher temperature helps maintain good elasticity. Compared with neat NR, addition of 5-phr Sm₂(CO₃)₃ results in a 30%–37% increase of tensile strength. Furthermore, the glass transition temperature (T_g) can also be increased by the addition of SmP; and the tan δ curves of all samples exhibit only one transition peak and indicate no phase separation between SmP and NR matrix. The influence of SmP on the structure and morphology of NR was explored by Fourier transform infrared, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy analysis; and the results show that SmP can be dispersed uniformly in the NR latex when loading of Sm₂(CO₃)₃ is lower than 20 phr.     

天然胶乳/炭黑复合材料的动态力学性能研究

通过添加阴离子表面活性剂,制备了稳定性能优异的炭黑分散液;然后将其添加到天然胶乳(NRL)中,采用胶乳共沉法制备NRL/炭黑复合材料,并对其物理性能、动态力学性能和内生热等进行了探讨。研究结果表明:当炭黑类型相同时,由胶乳共沉法制备的硫化胶之力学性能普遍优于由机械法制备的硫化胶;当采用炭黑N375补强时,由胶乳共沉法制备的硫化胶之力学性能相对最佳,其拉伸强度、撕裂强度和硬度分别比由机械法制备的硫化胶提高了6.5%、4.6%和8.8%;由胶乳共沉法制备的硫化胶之损耗因子(tanδ)小于由机械法制备的硫化胶,故前者的滞后损失更小、内生热更少且温升更低。     

Preparation and thermal stability of brominated natural rubber from latex

The effects of pH value of reaction system, reaction time, reaction temperature, bromine concentration, and amount of potassium persulfate on the bromination reaction in the preparation of brominated natural rubber (BNR) from natural rubber latex were discussed. It has been found from the thermal analysis, that is, the thermal degradation of BNR in nitrogen is a two‐step reaction, and 16% carbonide with a stable structure remained at 470–650°C. The thermo‐oxidative degradation of BNR in air is also a two‐step reaction, and the percentage of degraded BNR reaches to nearly 100% at 600°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of atmosphere on the thermal decomposition of chlorinated natural rubber from latex

The kinetics of the thermal decompositions of chlorinated natural rubber (CNR) from latex under both air and nitrogen atmospheres were studied with thermogravimetric analysis (TGA). The thermooxidative decomposition of CNR had two weight-loss step changes in the TGA curves, which occurred at the two distinct temperature ranges of about 160–390 and 390–850°C, respectively. The gaseous products of the first step change were mainly HCl with a little CO₂, and the apparent reaction order (n) was 1.1. The reaction activation energy (E) increased linearly with the increment of heating rate (B), and the apparent activation energy (E₀), calculated by extrapolation back to zero B, was 101.7 kJ/mol. Bs ranging from 5 to 30°C/min were used. The initial temperature of weight loss (T₀) was 1.31B + 252°C, where B is in degrees Celsius per minute. The final temperature of weight loss (T_f) was 0.93B + 310°C, and the temperature of maximum weight-loss rate (T_p) was 1.03B + 287°C. The decomposition weight-loss percentage at T_p (C_p) and that at T_f (C_f) were not affected by B, and the average values were 38 and 60%, respectively. The second weight-loss step change was an oxidative decomposition of the molecular main chain. The value of n was 1.1. E increased linearly with the increment of B, and E₀ was 125.0 kJ/mol. C_f after the second step approached 100%, which indicated complete decomposition. The thermal decomposition of CNR in a N₂ atmosphere had only one weight-loss step change with an n of 1.1. E increased linearly with the increment of B, and E₀ was 98.6 kJ/mol. T₀ was 1.25B + 251°C, T_f was 0.91B + 315°C, and T_p was 1.09B + 286°C. C_p and C_f were not affected by B, and the average values were 37 and 68%, respectively. The weight percentage of more stable, nonthermal decomposed residue was about 30%. The thermal decompositions of CNR in both atmospheres were similar, mainly by dehydrochlorination, at the low temperature range (160–390°C) but were different at the high temperature range (390–850°C). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2590–2598, 2001