低蛋白天然橡胶在空气和氮气气氛中的热降解行为

采用热重分析法研究了低蛋白天然橡胶(LPNR)在氮气和空气气氛下的热降解和热氧降解行为,并与天然橡胶(NR)在同样条件下的降解行为进行了比较.结果表明,在氮气气氛下,LPNR和NR的热降解都是1步进行,LPNR的起始降解温度(T0)、最大降解温度(Tp)和反应活化能都比NR高,说明其耐热性比NR好;在空气气氛下,LPN...     

蒙脱土接枝插层改性胶乳与天然胶乳热降解动力学的研究

采用胶乳接枝插层法制备了蒙脱土接枝插层改性胶乳；采用热重分析法对天然胶乳（NRL）和蒙脱土接枝插层改性胶乳进行了等速升温热降解动力学研究。结果表明。NRL和蒙脱土接枝插层改性胶乳在氮气中的热降解过程相似。2者的热降解率（C）不受升温速率的影响；NRL和蒙脱土接枝插层改性胶乳的平衡起始降解温度相近，而后者的平衡最大降解率开始温度和终止温度均高于前者；NRL的反应级数为2．4，表观反应活化能为218kJ／mol,而蒙脱土接枝插层改性胶乳的反应级数为1．8，表观反应活化能为151．7kJ／mol。     

低蛋白天然橡胶的性能研究

分析了LPNR(低蛋白天然橡胶)和NR(天然橡胶)中的C、H、N和S元素的含量。结果表明，两者N元素的含量差异显著。而其它元素的含量差异不大；研究了LPNR和NR的弹性模量(G′)随频率变化和应变变化的响应曲线。结果表明，LPNR和NR的弹性模量随频率的增大而增大，随应变的增大而减小，在整个变化过程中LPNR的弹性模量比NR的弹性模量大；研究了LPNR和NR在N2中的热降解性能，发现LPNR的耐热性较NR的差。     

霉化对天然橡胶组分及其热降解过程的影响

采用红外光谱仪分析了微波干燥未霉化天然橡胶(NR)和霉化天然橡胶(NR—m)的组分。图谱显示,NR在1541.20cm-1处有酰胺Ⅱ吸收峰,而NR—m没有。采用热重分析法分别在氮气和空气气氛中测试了微波干燥的NR和NR—m热降解和热氧降解。TG和DTG曲线显示,NR和NR—m的热降解均为1步反应,热氧降解均为2步反应。在等速升温条件下,NR的热降解温度和热氧降解温度均高于NR—m,NR降解时的活化能明显低于NR—m;2试样的反应级数为:在热降解中n2,在热氧降解中n2;在热降解中NR的相关系数r均大于NR—m;随升温速率的增大,2试样的A值和A1值均增大。     

石油发酵尼龙1313热降解性能的研究

利用热重分析和差示热重分析法研究了石油发酵尼龙1313在N2气流中以不同速率升温时的热降解过程及其动力学，发现尼龙1313的热降解过程为一步反应；随着升温速率的增大，降解温度线性升高，降解率则变化不大；分别用Coats-Redfem方法、Ozawa方法和Friedman方法进行了反应动力学处理，确定尼龙1313的表观降解反应级数为1．0,反应活化能为277．8kJ／mol左右。     

胶乳法溴化天然橡胶的热降解研究

采用胶乳法分别制备了溴质量分数为0.28和0.41的溴化天然橡胶(BNR),并采用傅里叶变换红外光谱法和热重分析法研究其热降解和热氧降解过程.结果表明:胶乳法BNR热降解为2步反应,第1步发生脱溴化氢反应,试样的质量损失率近似等于其溴质量分数;第2步BNR在475℃降解时仍有6.9%～8.8%的残留物存在,且较稳定.胶乳法BNR热氧降解分3步进行,第1步反应的温度及质量损失率与热降解相近,产物主要是溴化氢,此外还有少量二氧化碳;第2步和第3步产物为二氧化碳,且分解彻底.     

SIS-g-AN热降解性能的研究

采用热重分析法和差示热重分析法研究丙烯腈(AN)接枝热塑性弹性体SIS(SIS g AN)的热降解性能。结果得出,SIS g AN的平衡起始降解温度、平衡最大降解速率温度和平衡终止降解温度分别为659. 17, 713. 94 和740.05 K;热降解反应活化能为195.2 kJ·mol-1;热降解机理是Deceleration中的D3 降解机理;不同质量损失率下的热寿命与温度呈线性关系。     

不同硫化体系天然胶乳胶膜的热氧降解过程及差异

用热重法，微商法重法和差热分析研究了不同硫化体系天胶乳胶膜的热氧降解过程。试验结果表明，胶乳胶膜的降解反应均分三步进行，但降解过程存在较大差异，过氧化物预硫化胶乳胶膜的热氧降解最为彻底，而硫黄／促进剂ＴＭＴＤ＝氧化锌体系硫化胶乳胶膜的热氧稳定性最好。     

丁腈橡胶热降解的影响因素分析

采用热重分析法对丁腈橡胶(NBR)热降解的影响因素进行分析。结果表明:交联可加快NBR热降解,降低热降解温度;生胶门尼粘度对NBR热降解无影响;随着丙烯腈质量分数的增大,NBR最大降解速率温度降低,最大质量损失速率减小;升温速率较小时,丙烯腈质量分数对最大质量损失速率和最大降解速率温度的影响较大;升温速率增大,最大降解速率温度升高,丙烯腈质量分数越大,最大降解速率温度受升温速率的影响越大,升温速率对最大质量损失速率的影响恰好相反;与氮气气氛相比,空气气氛下炭黑/NBR硫化胶的降解温度升高,降解速率减小。     

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。     

Comparison and evaluation of the thermooxidative stability of medical natural rubber latex products prepared with a sulfur vulcanization system and a peroxide vulcanization system

This article deals with our study of the thermooxidative degradation of medical natural rubber latex tubes prepared with sulfur‐prevulcanized latex (sample I) and peroxide‐prevulcanized latex (sample II) in a dynamic air atmosphere by the use of the thermogravimetry/differential thermogravimetry method as well as the evaluation of the thermooxidative stability of these two samples. The test results showed that an oxygen‐absorption mass‐gain process occurred after a slight mass loss; the mass‐gain rate decreased with an increase in the temperature rising rate (β), and this was more prominent in sample II than in sample I. The maximum mass‐gain rate of sample II was 1.43% when β was 5°C/min, which was 5.02 times that of sample I; the thermooxidative stability of sample II was also lower than that of sample I. Because the oxygen absorption of sample II clearly caused serious oxidation, the balanced initial temperature, the temperature of the balanced degradation peak, and the balanced final temperature of sample II in the first reaction stage were obviously lower than those of sample I. The apparent activation energy (E_o = 143.6 kJ/mol) of sample I was significantly higher than that of sample II, and the stability of sample I was also higher than that of sample II. The temperature of the balanced degradation peak of sample II in the second reaction stage was higher than that of sample I, and E_o (154.0 kJ/mol) of sample II was significantly higher than that of sample I; the stability of sample II was also higher. Thermogravimetry curves of the two samples at various β values intercrossed each other, and the temperature at the crosspoint and the degradation rate increased linearly as β increased. On the temperature segment from the initial temperature to the crosspoint, the degradation rate of sample II was higher than that of sample I when the temperature of the two samples was the same, but on the segment from the crosspoint to the final temperature, the degradation rate of sample II was lower than that of sample I when the temperature of the two samples was the same. The degradation rate of the samples at 600°C was 99.2–99.5%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 591–597, 2005     

三氯溴甲烷改性天然胶乳的力学性能与阻燃性分析

对单用三氯溴甲烷改性天然胶乳和并用三氧化二锑改性胶乳的硫化胶膜的力学性能和阻燃性能进行了研究,并采用TG和DTG进行了热性能的分析。结果表明:三氯溴甲烷与三氧化二锑改性天然胶乳比单用三氯溴甲烷改性胶乳的阻燃性要好;三氯溴甲烷用量增加,改性天然胶乳硫化胶膜的阻燃性提高,而力学性能下降;三氯溴甲烷改性胶乳的起始热降解温度提前,改性胶乳热降解为二步反应。     

Cationic cyclization of purified natural rubber in latex form with a trimethylsilyl triflate as a novel catalyst

Cyclization of deproteinized natural rubber (DPNR) or purified natural rubber latex was effectively performed in latex phase by using trimethylsilyl‐trifluoromethane sulfonate or trimethylsilyl triflate (TMSOTF) as a novel catalyst, which is still not reported in the case of natural rubber latex. Various cyclization conditions affecting the degree of cyclization were studied, such as dry rubber contents, temperature, TMSOTF concentrations, and time. The cyclized products were characterized by FTIR, Raman, ¹H‐, and ¹³C‐NMR spectroscopies, as well as DSC and TGA. The degree of cyclization was estimated by ¹H‐NMR spectrum. It was found that the degree of cyclization in NR was a function of cyclization conditions. The thermal stability of cyclized DPNR increased with the degree of cyclization. Solubility of the obtained rubber was good in chloroform, toluene, cyclohexanone, and cyclohexane, and bad in tetrahydrofuran. The average number molecular weight of cyclized DPNR with 76% degree of cyclization was about 4.2 × 10⁴ g/mol. On the basis of FTIR, Raman, ¹H‐, and ¹³C‐NMR, the C?C of cyclized DPNR dramatically decreased after prolonged reaction time. In addition, the topology of cyclization DPNR particles was rough on its rubber particle as analyzed by TEM. The mechanism for this reaction will also be discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007.     

蛋白质对天然橡胶硫化动力学的影响

选用与天然胶乳中的d球朊结构类似的牛白蛋白,将其加入到经Alcalase蛋白酶处理得到的低蛋白天然橡胶中,通过硫化仪法研究了蛋白质对胶料硫化动力学的影响。结果表明：各胶样的硫化反应可按一级反应处理;在相同温度条件下,随着蛋白质用量的增加,焦烧时间（t10）和正硫化时间（t90）缩短,硫化反应速率提高,说明牛白蛋白能够提高天然橡胶的硫化速度;硫化速率随着温度的升高而显著提高,且都能很好地符合阿伦尼乌斯方程;反应活化能随着蛋白质用量的增加而提高。     

Composite natural rubber based latex particles: a novel approach

The oil resistance of natural rubber (NR) film could be effectively improved by using the heterocoagulation of large NR particle with small polychloroprene (CR) particles. In the preparation of NR/CR composite particle with a core-shell structure, a nonionic surfactant whose molecule bears poly(ethylene oxide) (PEO) was adsorbed on CR particles and allowed to form complexes between PEO and indigenous surfactant (protein-lipid) on the NR particle surface. Composite latex particle obtained was characterised by particle size, zeta potential and glass transition temperature measurements and the data indicated the presence of CR on the outer layer of composite particle. Better oil resistance of film casted from heterocoagulated latex when compared to that of NR film confirmed the NR/CR core-shell structure. The epoxidised natural rubber (ENR), crosslinked ENR and/or skim latex particles were investigated in order to replace the use of CR in the heterocoagulation process.     

Natural rubber-based nanocomposites by latex compounding with layered silicates

Natural rubber (NR) based nanocomposites with 10 wt% natural and synthetic layered silicates were produced via the latex compounding method. As layered silicates, sodium bentonite (natural) and sodium fluorohectorite (synthetic) were selected in addition to a non-layered inert filler (English India clay or commercial clay) as reference material. The nanocomposites were prepared by compounding the dispersions of clays and other latex chemicals necessary for vulcanization. The vulcanized nanocomposites were subjected to mechanical, thermal and swelling tests. The silicate dispersion was studied by transmission electron microscopy. Layered silicates outperformed the reference material (commercial clay) in all aspects. This was attributed to the intercalation/exfoliation of the silicates and to the formation of a skeleton ‘(house of cards)’ silicate network in the NR matrix.     

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。     

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.     

Structure and performance of hydrogenated natural rubber prepared by the latex method

Hydrogenated natural rubber (HNR) with different degrees of hydrogenation was prepared by the latex method. The hydrazine hydrate/hydrogen peroxide/boric acid catalytic system could result in the hydrogenation of natural rubber (NR) under the latex state. The NR without hydrogenation contained around 13% of gel, when the hydrogenation degree reached 66.9%, the gel content was 34.4%. The decomposition temperature of HNR kept on increasing, which was all higher than that of NR and the glass transition temperature increased slightly. The cross-linking density of vulcanised rubber rose along with the increasing degree of hydrogenation, the NR cross-linking density was 0.114 mmol cm^?3, when the hydrogenation degree was 34.6%, 42.7% and 66.9%, the cross-linking density was 0.182, 185 and 221 mmol cm^?3, respectively. This further proved decreasing flexibility of the HNR after hydrogenation and weakening crystallisation of HNR along with increasing degree of hydrogenation.