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.     

天然橡胶中非胶组分的作用

综述了非胶组分中蛋白质、类脂物、丙酮溶物、水溶物、无机盐、酶类和细菌等组分的主要成分和含量及其对天然胶乳稳定性以及对天然橡胶生胶综合性能的影响,对天然橡胶的生产加工和科学研究具有理论指导意义。     

改性胶清橡胶及其复合材料的性能研究

采用有机改性钠基蒙脱土对胶清橡胶进行复合改性,制备改性胶清橡胶,并与杂胶、喇叭口胶、泡沫胶和废水胶复合,研究改性胶清橡胶及其复合材料的各项性能.结果表明,改性胶清橡胶塑性初值(P0)和塑性保持率(PRI值)与胶清橡胶相比大幅度提高,物理性能和热性能也明显改善;改性胶清橡胶/杂胶等复合材料的物理性能与杂胶等相比显著提高,P0和PRI值也有不同程度的增大.     

低蛋白天然胶乳的性能与应用

天然橡胶(NR)具有优越的工艺操作性能及物理力学性能,从通用性能来讲,目前尚无其它的材料能替代。NR是由天然生物合成,其主要成分为:橡胶烃、水、非胶物质,其中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。一般新鲜胶乳中蛋白质含量占胶乳重的1%～2%,浓缩天然胶乳(NRL)中所含蛋白质占胶乳总重的1.5%～3.5%。由于NRL含有相当数量的蛋白质,蛋白质的吸水性导致了NRL制品的吸湿性、导电性、生热性,不利于制造绝缘制品。蛋白质含量过高,还易使制品发霉。NRL在胶乳行业中占有特殊地位,NRL已广泛应用于医疗及工业领域,…     

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。     

超滤法浓缩胶清橡胶性能的研究

采用中空纤维柱浓缩法制备天然橡胶胶清橡胶,并对其性能进行研究。结果表明:与未处理胶清橡胶相比,处理后胶清橡胶的丙酮溶物质量分数、塑性初值和塑性保持率均有所增大,挥发分质量分数、杂质质量分数、灰分质量分数和氮质量分数减小。与未处理胶清硫化胶相比,处理后胶清硫化胶的物理性能明显提高;随着处理孔径的增大,硫化胶的物理性能呈下降趋势。与未处理胶清橡胶相比,随着温度的升高,处理后胶清橡胶的损耗因子较小,剪切储能模量较大,表现出较好的加工性能。     

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。     

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。     

PPS／PES共混物热降解行为的研究

本文运用热重分析(TG)、差示热重分析(DTG)方法研究了聚苯硫醚/聚醚砜共混物的热降解行为,考察了热裂解气氛、共混物组成对共混物热降解行为的影响。结果表明:在空气或氮气气氛下。共混物具有不同的热降解行为,共混物的热稳定性随着聚醚矾的含量增加而提高。在空气气氛下,不但存在聚苯硫醚和聚醚砜分子内的交联,而且可能存在分子间的交联。     

聚丁二烯生胶基本性能的研究

研究了不同聚丁二烯生胶的基本性能。门尼松弛实验结果表明,3种丁钠橡胶的门尼粘度低。加工性能好。差示扫描量热法（DSC）实验表明,低顺、高顺及低顺／高顺聚丁二烯橡胶的玻璃化转变温度低,采用开炼机混炼时时温度比较敏感。采用热失重法（TG／DTG）研究了不同聚丁二烯橡胶在空气气氛中的热降解行为,研究结果表明,中乙烯基聚丁二烯橡胶有较好的热稳定性,低顺、高顺及低顺／高顺聚丁二烯橡胶热稳定性相似,3种丁钠橡胶的热稳定性稍差。     

Studies on thermal–oxidative degradation behaviours of raw natural rubber: PRI and thermogravimetry analysis

Abstract

Thermal–oxidative degradation behaviours of raw natural rubber (NR) have been investigated by using thermogravimetry analysis in inert and oxidative atmospheres and the plasticity retention index (PRI). The activation energy E_a, was calculated using Horowitz–Metzger and Coats–Redfern methods and compared with PRI. The E_a values obtained by each method were in good agreement with each other. The June samples are the least stable rubbers among the studied ones, whereas February samples exhibited the highest values of activation energy, therefore in agreement with the PRI behaviour, which indicates that the thermo-oxidative stability of the June samples are the poorest during the thermo-oxidative degradation reaction. Natural rubber is a product of biological origin, and thus these variations in the values of thermal behaviour and PRI might be related to the genetic differences and alterations of climatic conditions that act directly on the synthesis of non-rubber constituents, which are generally reflected in latex and rubber properties.     

纳米碳酸钙含量对室温硫化硅橡胶热稳定性的影响

测试了不同纳米碳酸钙含量的室温硫化硅橡胶的热稳定性,并结合对不同纳米碳酸钙含量填充硫化胶的热降解活化能的计算可知,随着纳米碳酸钙含量的增加热降解活化能增加,说明纳米碳酸钙的填充可提高室温硫化硅橡胶耐热性能。其机理是纳米碳酸钙与硅橡胶的相互作用,从而提高了纳米碳酸钙填充室温硫化硅橡胶的耐热性能。     

金属氧化物对硅橡胶和氟硅橡胶耐热性的影响

着重研究了金属氧化物对甲基乙烯基硅橡胶、甲基苯基乙烯基硅橡胶、三氟丙基甲基乙烯基硅橡胶耐热性的影响。结果表明,Ｆｅ２Ｏ３、ＦｅＯ３／ＳｎＯ２、ＳｎＯ２、ＣｅＯ２等可以显著提高硅橡胶的耐热性;光电子能谱分析结果说明,ＳｎＯ２、ＣｅＯ２在热空气老化过程中从高价态被还原到低价态,发生了多个（或单个）电子转移的氧化还原反应,从而阻止了硅橡胶的热氧化自由基链增长,提高了硅橡胶的耐热空气老化性能。     

硅橡胶和丁基橡胶共混体系的阻尼特性研究

采用机械共混法制备了硅橡胶/丁基橡胶复合材料。研究了丁基橡胶用量对复合材料力学性能、热稳定性和阻尼性能的影响。结果表明,随着丁基橡胶用量的增加,复合材料的力学性能和热稳定性出现降低的现象,但阻尼性能有显著提高。当丁基橡胶用量为100份时,与纯硅橡胶相比,复合材料的有效阻尼温域从0 ℃拓宽到近75 ℃,最大损耗因子从0.11提高到0.80,玻璃化转变温度向高温偏移了8 ℃左右。     

Comparative analysis of ultrasonically devulcanized unfilled SBR,NR, and EPDM rubbers

The comparative study of the continuous ultrasonic devulcanization of various unfilled rubbers [natural rubber, styrene–butadiene rubber (SBR), ethylene–propylene–diene rubber (EPDM)] is carried out by means of a ultrasonic reactor. The power consumption, gel fraction, crosslink density, cure behavior, and physical properties of devulcanized rubbers were measured. The glass transition temperatures of virgin, vulcanized, and devulcanized rubbers were determined in order to characterize the difference in the mobility of rubber molecules for each rubber before and after devulcanization. Thermogravimetric analysis was also used to determine thermal stability of the various rubbers. A unique correlation between gel fraction and crosslink density indicated significant differences in the efficiency of devulcanization of various rubbers. Under certain devulcanization conditions, the mechanical properties of revulcanized SBR and EPDM rubbers were found to improve compared to those of the original rubbers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 434–441, 2003     

高掺量橡胶沥青的结构与性能

轮胎胶粉的多重交联网络限制了其在橡胶沥青中的胶粉掺量。用经螺杆反应挤出方法可控再生的再生胶可制备高掺量（质量分数不小于30%）橡胶沥青。通过溶胶含量、门尼黏度和基本性能测试及加工实况观察,并结合红外光谱和光学显微镜微观分析,探讨了胶粉的再生程度及用量对高掺量橡胶沥青结构与性能的影响。结果表明,再生过程中胶粉的化学键发生断裂,部分交联网络被破坏。与传统橡胶沥青相比,高掺量橡胶沥青的分散更均匀,加工流动性和高温储存稳定性均得以改善。提高胶粉的降解再生程度可明显提高其在沥青中的掺量,进一步提高改性沥青的低温柔性和高温抗变形能力,但易出现加工黏度的临界陡增现象。     

淀粉加速凝固天然橡胶的热降解研究

采用热重分析法(TGA)和差热分析法(DTA)研究了自然微生物凝固天然橡胶(N-NR)和淀粉微生物凝固天然橡胶(S-NR)在空气气氛中的热降解行为,为探索新的天然胶乳加工工艺提供科学依据。研究结果表明:(1)实验条件下,两种凝固方式的橡胶在空气气氛中的降解均为多步反应。(2)S-NR的抗氧化性能较N-NR好。     

硫化胶在高温沥青中结构与性能的研究

采用NR、SBR硫化胶代替废胶粉粉末,在高温沥青(163℃)中进行热存储,测试了不同热存储时间下硫化胶的溶胀指数、交联密度、溶胶含量、硬度、拉伸强度等性能,研究了硫化胶在高温沥青中的结构与性能变化。结果表明,硫化胶在高温沥青中经过一个快速增长而后趋于平缓的溶胀过程;在高温和溶胀作用下,橡胶发生降解,交联密度呈快速下降而后缓慢降低的趋势,溶胶含量随着交联密度的降低显著增加;在溶胀和降解双重作用下,硫化胶硬度、力学性能显著下降。     

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