氯化钙凝固天然橡胶的热分析研究

用热分析法(TGA/DTA)研究了氯化钙凝固天然橡胶(NR-c)在空气气氛中的热降解行为。研究结果表明,NR-c热氧降解属于多步反应,与传统酸凝固天然橡胶(NR-a)相比,NR-c降解特征温度均明显降低,NR-c的DTA放热峰明显向低温漂移,抗氧化性能明显下降。     

射流凝固天然橡胶的热降解特性研究

本文用热氧分析研究了射流凝固天然橡胶的热降解行为,结果表明:在N2气氛下,射流凝固天然橡胶的热降解为一步反应;在空气气氛下,射流凝固天然橡胶的热降解行为为三步反应。     

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...     

微生物凝固天然橡胶热降解研究

用热重分析（TG）研究微生物凝固天然橡胶在30℃～600℃的热降解行为,探讨微生物凝固工艺对天然橡胶热稳定性的影响。结果表明,微生物凝固天然橡胶的热降解是一步反应,主要发生在300℃～450℃之间,为放热反应。起始降解温度To=332.3℃,最大降解速率温度Tp=377．3℃,终止降解温度Tf=445．2℃。酸凝固天然橡胶的To、Tp都比微生物凝固天然橡胶的低,证明微生物凝固天然橡胶的热稳定性比酸凝固天然橡胶的好。     

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。     

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。     

134BAPB／PMDA聚酰亚胺薄膜的热降解动力学研究

采用热重分析法（TG）对1,3-双（4-氨基苯氧基）苯（134BAPB）／均苯四甲酸二酐（PMDA）聚酰亚胺（PI）薄膜在氮气和空气气氛下的热失重过程进行了研究,并利用NETZSCH Thermokinetics动力学软件对其热降解过程进行了动力学分析,求得了热降解动力学参数和方程。结果显示其在氮气气氛中的热降解动力学方程为：lndx/dt=18．7774-169063.5/8.314×T＋ln（1-x）;在空气气氛中的热降解动力学方程为：ln dx/dt=20．1886-186315.3/8.314×T＋ln（1-x）。     

酚醛树脂复合材料热降解过程的研究

利用热重分析法对碳纤维增强S-157酚醛树脂在氮气和空气气氛下的热降解过程进行分析,研究了热降解气氛、升温速率与材料热降解温度、残炭率之间的关系,以及对其烧蚀性能的影响,并求得该复合材料的热降解活化能,分析其热降解机理,为烧蚀防热复合材料的热性能评价提供一种研究方法。     

气氛对低氮天然橡胶热降解的影响

采用热重分析(TG),研究了恒定升温速率下,低蛋白橡胶在氮气和空气气氛中的热降解行为,考察了反应气氛对降解速率、降解率和动力学参数的影响,分析了两者降解机理的可能差别。发现降解温度和降解率,氮气中均高于空气中;表观反应级数氮气中为2.0级,空气中为1.9级。     

SIS-g-BMA热降解动力学研究

采用热重分析法和差示热重分析法研究苯乙烯-异戊二烯-苯乙烯三元嵌段共聚物(SIS)与甲基丙烯酸丁酯(BMA)的接枝共聚物(SIS-g-BMA)在氮气和氧气气氛中的热降解性能.结果表明,SIS-g-BMA在氮气气氛中第1步热降解温度范围为398～739 K,质量损失率为93.7%,最大热降解速率温度为658.2 K,第2步热降解温度范围为739～945 K,质量损失率为6.3%,平均活化能为176.1 kJ·mol-1;在氧气气氛中第1步热降解温度范围为459～719K,质量损失率为76.8%,第2步热降解温度范围为719～776 K,质量损失率为23.2%,最大热降解速率温度为735.0K,平均活化能为51.75 kJ·kJ·mol-1.     

Py-GC/MS研究防焦剂CTP的热裂解行为

采用裂解气相色谱/质谱联用法对防焦剂CTP的热裂解行为进行研究,并对部分热裂解产物的质谱碎裂机理进行探讨。结果表明：防焦剂CTP热裂解适宜条件为：温度　300 ℃,时间　0.2 min,方式　单纯瞬间裂解,固体样品直接进样;不同产地产品的裂解产物具有一致性,热稳定性好;裂解产物共10余个,主峰为原分子,次强峰为邻苯二甲酰亚胺。解析了NIST谱库中不包含的主要裂解产物可能的质谱裂解途径;可根据其中环己硫醇、邻苯二甲酰亚胺、二环己基二硫化物3个裂解产物共同判断防焦剂CTP的存在。     

纯化胶清橡胶的热氧降解研究

采用离心分离的方法制备了胶清橡胶,并测定了该胶清橡胶的蛋白质含量、水溶物含量、丙酮溶物含量、P0和PRI。为探讨水溶物和丙酮溶物对胶清橡胶的热稳定性的影响,采用热重分析法研究了胶清橡胶在空气气氛中的热氧降解行为。研究结果表明,胶清橡胶的蛋白质含量、水溶物含量和丙酮溶物含量较高,Po和PRI数值较低;胶清橡胶在空气中有3个降解过程,经过水和丙酮提纯后的胶清橡胶的热稳定性显著提高。     

Studies in the thermal degradation of poly(vinyl chloride)

Thermal degradation of poly(vinyl chloride) (PVC) was studied in nitrogen atmosphere in the presence of rubber seed oil and epoxidized rubber seed oil, barium and lead soaps of rubber seed oil, and epoxidized seed oil at various temperatures. The rate of dehydrochlorination at 1% degradation and the time required to attain 1% degradation were used to assess the effect of the thermal susceptibility of PVC to dehydrochlorination. It was found that epoxidized rubber seed oil, the metal soaps of rubber seed oil, and epoxidized rubber seed oil markedly enhance the thermal stability of PVC. The order of increasing stabilizing influence was metal soaps of epoxidized rubber seed oil > metal soaps of rubber seed oil > epoxidized rubber seed oil > rubber seed oil. © 1993 John Wiley & Sons, Inc.     

Kinetics of the thermal degradation and thermal stability of conductive silicone rubber filled with conductive carbon black

The kinetics of the thermal degradation and thermal stability of conductive silicone rubber filled with conductive carbon black was investigated by thermogravimetric analysis in a flowing nitrogen atmosphere at a heating rate of 5°C/min. The rate parameters were evaluated by the method of Freeman–Carroll. The results show that the thermal degradation of conductive silicone rubber begins at about 350°C and ends at about 600°C. The thermal degradation is multistage, in which zero‐order reactions are principal. The kinetics of the thermal degradation of conductive silicone rubber has relevance to its loading of conductive carbon black. The activation energies are temperature‐sensitive and their sensitivity to temperature becomes weak as temperature increases. In addition, the conductive silicone rubber filled with conductive carbon black has better thermal stability than that of silicone rubber without any fillers. Also, conductive silicone rubber filled with conductive carbon black has better thermal stability than that of silicone rubber filled with the same amount of silica. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1548–1554, 2003     

Role of lignin filler in stabilization of natural rubber–based composites

The stabilizing effect of a natural filler, sulfur‐free lignin, on the thermal degradation of natural rubber (NR) was examined. Lignin was incorporated into NR in amounts of 10–30 phr (parts per hundred parts of rubber). It was shown that the lignin preparation used improved the physicomechanical properties of the rubber vulcanizates. Thermogravimetric analysis and differential scanning calorimetry were used to study the thermal degradation of unfilled and lignin‐filled vulcanized natural rubber. Measurements were carried out under atmospheric conditions. It was revealed that lignin used as filler increased the resistance of NR vulcanizates to thermooxidative degradation in air. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1226–1231, 2007     

Kinetics of nonisothermal thermal degradation of styrene-butadiene rubber

The kinetics of thermal degradation of styrene-butadiene rubber (SBR) was studied by conventional thermo-gravimetric technique with various heating rates under nitrogen. A kinetic model which accounts for the effects of scission of polymeric chain at any time was proposed to describe the thermal degradation of SBR. Results showed that the contribution of the thermal degradation of zero-order reaction is greater than that of first-order and second-order reactions. The activation energy of the thermal degradation of SBR was calculated to be 172 kJ/mol using the Arrhenius equation.     

无氨保存胶清及胶清胶性能的研究

采用水溶性、不挥发性的广谱抗菌剂——三嗪衍生物(HY)作为鲜胶乳的新型无氨保存剂,研究了HY对胶清凝固总用酸量、胶清胶及胶清胶硫化胶片性能的影响。结果表明,HY保存胶清凝固总用酸量大大减少,除氮含量略微超标外,胶清胶的各项指标均达到1级胶清胶的标准,胶清胶的塑性保持率(PRI)明显提高。HY胶清胶硫化胶片的拉伸强度和耐热氧老化能力均优于氨胶清胶硫化胶片。热解重量分析(TGA)结果表明,HY和氨胶清胶硫化胶片热氧降解均为2步反应,耐热氧降解能力基本相同。     

Effect of resin components on the degradation of guayule rubber

All natural rubbers are likely to contain some long chain fatty acids or their esters. The individual effect of the four C₁₈ fatty acids (stearic, oleic, linoleic, and linolenic acid) present in the guayule resin on the degradation of guayule rubber has been investigated concurrently by stress–relaxation of radiation cured rubber networks and by gel permeation chromatography studies on the raw rubber in the temperature zone 70–125°C. C₁₈ unsaturated fatty acids enhance the degradation of rubber several fold. The rate of degradation follows the order: rubber ≤ rubber + stearic acid < rubber + oleic acid < rubber + linoleic acid < rubber + linolenic acid. The thermal degradation is slower than the thermooxidative. The rate of degradation monotonically increased with the number of conjugated double bonds and is first order with respect to acid concentration. The activation energy for the chain scission for both thermal and thermooxidative degradation has been found to be 95 ± 10 kJ/mol. The mechanism of degradation of guayule rubber in the presence of fatty acids is discussed.     

Development of a new procedure for lipid extraction from Hevea brasiliensis natural rubber

Non‐isoprene components and especially lipids have been reported to be involved in some key properties of natural rubber. Unfortunately, these results are hardly comparable due to different extraction methods. This work aimed to optimize lipid extraction from natural rubber either in the liquid state (latex) or in the dry state (unsmoked sheets). Extraction of unsmoked sheets from the RRIM 600 clone was carried out with different combinations of organic solvents (chloroform/methanol and hexane/isopropanol mixes). Chloroform/methanol (2 : 1 vol/vol) was found to be the most suitable for lipid extraction from unsmoked sheet rubber. The lipid extraction yield was improved by increasing the exchange surfaces by grinding rubber under liquid nitrogen and extracting the ground rubber for 6 h at room temperature, leading to 1.82% lipid extraction yield (versus dry rubber). Concerning latex extraction, the problem of lipid entrapment in the coagulum from immediate coagulation of latex in the solvent was solved by preliminary two times dilution of latex, giving a 3.24% extract (versus dry rubber) containing a minimum quantity of contaminating polyisoprene. Concerning the nature of lipids, dilution increased mainly neutral lipid extraction, which may suggest that neutral lipids were those entrapped by coagulation.