红外光谱法鉴别掺假天然胶乳

在天然胶乳中按不同比例掺入木薯粉或面粉,制备掺假天然胶乳,采用傅里叶转换红外光谱进行表征和分析。结果表明:在天然胶乳中掺入木薯粉或面粉,红外光谱在3 500~4 000 cm~(-1)波段出现指纹区,掺入量越高,指纹区的波动幅度越大;在木薯粉或面粉的特征谱带,随着掺入量的增大,吸收强度增强。     

木薯淀粉/天然橡胶复合材料制备工艺研究

以木薯淀粉和天然胶乳为主要原料,将木薯淀粉和天然胶乳共混共沉制备木薯淀粉/NR复合材料。研究了制备工艺对复合材料力学性能的影响。结果表明:当木薯淀粉浓度为20%,搅拌速度为450r·min~(-1),搅拌时间为30min和木薯淀粉用量为20份时,木薯淀粉/NR复合材料具有较好的力学性能。     

天然胶乳胶膜干燥过程及交联结构研究

采用失重法、溶胀法及红外光谱,研究了天然胶乳厚胶膜的干燥动力学过程及干燥过程与橡胶分子链交联密度的关系。结果表明,天然胶乳胶膜的干燥温度和厚度显著影响其干燥过程,通过动力学拟合结果,建立了干燥动力学方程;胶膜干燥开始后,橡胶分子交联密度迅速上升,达到最大交联密度后,交联密度随干燥时间的增加而降低,红外光谱的研究结果也证明了这一规律。干燥过程对天然胶膜的交联结构有明显影响。     

蜂蜜中掺入蔗糖或葡萄糖后的红外光谱分析

对掺入不同含量蔗糖或葡萄糖后的蜂蜜进行红外光谱测定和分析,结果表明:掺有不同含量蔗糖或葡萄糖的掺假蜂蜜,其红外光谱在1200~900 cm-1间的峰形和峰强变化与掺入的蔗糖或葡萄糖的含量相关,具有一定的变化规律,据此可快速判断蜂蜜中掺入的蔗糖或葡萄糖的大致含量。     

胶乳和乳液

胶乳 (latex)和乳液 (emulsion)都是聚合物在水介质中形成的相对稳定的多分散体系 ,其区别在于胶乳是橡胶微粒的水分散体系 ,而乳液则是树脂微粒的水分散体系。胶乳旧称乳胶 ,可分为天然胶乳、合成胶乳和改性胶乳3类。天然胶乳是从橡胶植物中用采割或浸出等方法获得的 ,按性质和用途分为通用天然胶乳、特种天然胶乳及改性天然胶乳。通用胶乳即是 3种浓缩胶乳 ;特种天然胶乳有高浓度天然胶乳 (干胶质量分数 6 4 %以上 )、阳离子胶乳、耐寒胶乳、接枝胶乳等。浓缩胶乳按保存系统用氨量多少分为高氨浓缩胶乳和低氨浓缩胶乳 ,离心浓缩胶乳即分高…     

偶联剂对木薯淀粉补强天然胶乳硫化胶膜性能的影响

采用偶联剂改性木薯淀粉补强天然胶乳,研究偶联剂种类和用量对木薯淀粉/天然胶乳硫化胶膜物理性能和动态力学性能的影响,并对其微观结构进行观察.结果表明,加入偶联剂Si69的硫化胶膜的物理性能较好,当偶联剂Si69用量为0.6份时,硫化胶膜的综合物理性能达到最佳.动态力学性能分析表明,淀粉经偶联剂改性后,硫化胶膜的损耗因子减小,玻璃化温度向低温方向移动,低温使用性能提高.扫描电子显微镜分析显示,偶联剂的加入可以改善淀粉在天然胶乳中的分散效果,提高淀粉与橡胶的界面结合作用.     

东南亚天然橡胶胶乳的研究进展

东南亚地区是世界上相对最好的天然橡胶胶乳(简称天然胶乳或胶乳)原材料的生产圣地,产胶量约占世界总产量的90%。着重介绍了东南亚天然胶乳产业的发展现状,综述了天然胶乳的化学组成、提取工艺以及改性方法,并详述了东南亚天然胶乳制品的应用(如胶乳枕、床垫和手套等)。最后对东南亚天然胶乳的发展方向进行了展望。     

掺杂天然胶乳的鉴别及分析方法研究

研究影响天然胶乳干胶含量测量值的白糖、食盐、淀粉、尿素、氯化铵、硫酸铵、碳酸氢钠、碳酸钙、滑石粉、高岭土和石灰粉11种可能的天然胶乳掺杂物检测,重点讨论掺入高岭土、碳酸钙、滑石粉和淀粉的天然胶乳的定性及定量分析方法,旨在建立一套简单、快速、准确、可行的掺杂天然胶乳检测方法,以利于收胶站及橡胶加工企业评价天然胶乳质量。     

天然胶乳手套与合成胶乳手套的发展

介绍天然胶乳手套的起源和发展以及天然胶乳检查手套、外科手套、织物浸渍防护手套、家用手套、工业手套的用途、规格、特点和表面形式,指出因天然胶乳手套存在安全性能和使用性能的不足,促进了合成胶乳手套和人造胶乳手套的发展。丁腈胶乳检查手套因技术进步和成本降低成为天然胶乳检查手套的主要竞争者;低蛋白无粉天然胶乳外科手套、氯丁胶乳外科手套和聚异戊二烯胶乳外科手套成为对天然胶乳过敏症医护人员的选择;在非医疗领域,合成胶乳手套和人造胶乳手套适用于特殊领域的防护需求。     

增稠剂对天然胶乳热稳定性的影响

介绍了增稠剂在天然胶乳工艺中的应用，试验表明在胶乳中加入0．5－2．0份阿拉伯树胶粉，不仅对胶乳的粘度有影响，而且对胶乳的热稳定性也有明显的作用。     

微波辐射对木薯淀粉结构的影响

考察了不同含水量的木薯淀粉经不同形式（敞口和封口形式）微波辐射的温度变化曲线及其多层次结构.结果表明：无论以那种形式辐射,木薯淀粉样品含水量越低,样品温度升高幅度越大,且都会出现等温转换,含水量越高等温转换时间越长,敞口辐射较封口辐射的等温转换更显著; FTIR结果显示,微波辐射不破坏木薯淀粉分子的化学键,没有新的化合物产生,红外结晶指数略有降低;偏光显微镜和光学显微镜的结果显示,木薯淀粉的结晶结构有所变化,而其形态结构没有变化.这些结果表明,经微波加工的木薯淀粉食品对人或其他生物是安全的.     

Preparation of low‐protein natural rubber latex: Effect of polyethylene glycol

Low‐protein content natural rubber latex was produced by using a nonionic surfactant‐polyethylene glycol (PEG). Extractable protein content of natural rubber latex was found to decrease with PEG treatment and reduction increased with increase in the molecular weight of PEG. The low‐protein latex samples were characterized by tensile testing, Fourier transform infrared and thermogravimetric analysis. The results have shown 35% reduction in the extractable protein content, without any compromise on the mechanical properties of the latex; however, thermal stability of low‐protein latex was found to be reduced marginally with PEG treatment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

P(MMA-co-AM)两亲性共聚物改性天然乳胶的研究

以甲基丙烯酸甲酯(MMA)和丙烯酰胺(AM)为共聚单体,合成了不同配比的两亲性共聚物P(MMA-co-AM) 乳液,并将制得的P(MMA-co-AM) 共聚物乳液按设定比例与天然乳胶(NRL)共混。通过红外光谱、透射电镜、扫描电镜、力学及耐溶剂性测试,研究了不同共聚单体配比的P(MMA-co-AM)及其添加量对NRL性能的影响。结果表明,两亲性的P(MMA-co-AM)共聚物乳液可有效填补乳胶薄膜表面的孔洞,增强其拉伸强度。利用单体质量比为90:10的P(MMA-co-AM)共聚物乳液,当NRL与共聚物乳液质量比为8:2时,形成的乳胶膜拉伸强度提高了54.19%,而断裂伸长率无显著降低,力学性能最优。同时乳胶膜的耐溶剂性也得到了较大提高。     

Effect of natural rubber on wood‐reinforced tannin composites

Natural rubber latex was added to composite materials formulated from a quebracho tannin adhesive crosslinked with hexamethylenetetramine and wood flour as a reinforcing filler. The final microstructure of the thermoset modified by the addition of different concentrations of latex was observed by scanning electron microscopy. The flexural and impact behavior of the modified materials was analyzed and related to the final microstructure of the composites. The effect of exposing the materials to humid environments was also evaluated. The measurements indicated that the addition of latex did not significantly reduce water absorption. However, it facilitated the preparation process of samples with low filler contents because of the increased viscosity of the mixture, which inhibited particle settling. On the other hand, the flexural properties increased with the addition of latex‐containing proteins through a reaction similar to tanning in leathers. The impact properties presented a similar trend, with the largest change occurring between 0 and 5% natural rubber in the matrix formulation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

高红外发射率辐射型外墙节能涂料的研制

基于红外辐射产生机理,采用过渡区金属氧化物掺杂、高温固相烧结法制备陶瓷红外辐射材料,通过正交试验优化工艺条件,并确定配方,制得的红外辐射粉经XRD表征,生成了高红外活性的四氧二铁酸钴反尖晶石相,在26℃,8～13.5μm波段"大气窗口"的发射率大于94%。以此红外材料为功能填料,氟碳乳液为基料,辅以其他颜填料及助剂,制得了在"大气窗口"波段内发射率大于78%的外墙节能涂料,SEM测试表明漆膜表面平整紧密,其他基本性能良好。     

Volatile Compounds in Tomato-Based Dried Products

The effect of drying of tomato juice and products on their volatiles retention was evaluated. Fresh tomato juice and its two blends—one with 5% maltodextrin and another with 5% tapioca flour—were dried in a forced-air circulation dryer. The volatiles retention was the highest in tomato powder prepared with 5% maltodextrin, followed by the one prepared with the addition of 5% tapioca flour, which retained most of the sulfur compounds. The concentrations of dimethyl sulfide, 2-ethyl furan, hydroxymethyl furfural, acetaldehyde, and α-terpineol increased in dried powder and that of low-boiling-point compounds decreased over the drying period.     

Multi-walled carbon nanotube reinforced self-crosslinking hydrogenated carboxylated nitrile butadiene rubber latex film with improved properties

A dielectric self-crosslinking hydrogenated carboxylated nitrile butadiene rubber (HXNBR) latex film was prepared by diimide reduction hydrogenation of XNBR latex and the doping of multi-walled carbon nanotube (MWCNT). The structures of the HXNBR and XNBR were characterised by Fourier transform infrared spectroscopy (FTIR) and ¹HNMR, confirming the successful hydrogenation of XNBR. The mechanical, thermal, and electrical properties of the prepared HXNBR latex films were studied, and the HXNBR latex film reinforced by only 3?phr MWCNTs exhibited improved mechanical, thermal, and dielectric properties.     

天然胶乳厚胶膜热风干燥与红外干燥对比研究

采用失重法研究了天然胶乳厚胶膜在热风与红外线两种干燥方式下的干燥过程。研究结果表明,在相同条件下,红外干燥的干燥速率常数远大于热风干燥,采用红外干燥可大大缩短干燥时间,干燥温度和厚度均显著影响干燥过程,红外干燥对温度更敏感。通过动力学拟合结果,得到了干燥动力学方程,可以预测干燥时间。     

Effect of olive residue benzylation on the thermal and mechanical properties of poly(vinyl chloride)/olive residue composites

The changes in mechanical properties, the thermal stability, and the water absorption capacity of poly (vinyl chloride)/olive residue flour composites were studied as a function of various residue olive flour ratios, i.e., 0, 5, 15, and 25% by weight taking into account the effect of benzylation chemical treatment of the filler. The study showed that composite samples prepared with the untreated filler exhibited higher tensile modulus and hardness compared with the neat resin, whereas elongation and tensile strength were observed to decline. On the other hand, the PVC hardness was found to increase with addition of the untreated olive residue flour (ORF), however the composite samples prepared with the benzylated flour exhibited lower hardness than those prepared with untreated olive residue. Moreover, the amount of absorbed water depends on the amount of filler in the composite. The comparison of the results obtained from the samples of F5, F20, and F30 formulations between the untreated and treated ORF indicated a reduction in absorbed water for the composite samples containing treated ORF with benzyl chloride. As a result, the mechanical properties of the treated composites were improved. Furthermore, the thermal characterization of the different samples carried out by color change test and thermogravimetric analysis revealed an increase in the onset temperatures of decomposition for the treated composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Self-assembled natural rubber/multi-walled carbon nanotube composites using latex compounding techniques

Functionalization of multi-walled carbon nanotubes (MWCNTs) plays an important role in eliminating nanotube aggregation for reinforcing polymeric materials. We prepared a new class of natural rubber (NR)/MWCNT composites by using latex compounding and self-assembly technique. The MWCNTs were functionalized with mixed acids (H2SO₄/HNO₃ = 3:1, volume ratio) and then assembled with poly (diallyldimethylammonium chloride) and latex particles. The Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy were used to investigate the assembling mechanism between latex particles and MWCNTs. It is found that MWCNTs are homogenously dispersed in the natural rubber (NR) latex as individual nanotubes since strong self-aggregation of MWCNTs has been greatly depressed with their surface functionalization. The well-dispersed MWCNTs produce a remarkable increase in the tensile strength of NR even when the amount of MWCNTs is only 1 wt.%. Dynamic mechanical analysis shows that the glass transition temperature of composites is higher and the inner-thermogenesis and thermal stability of NR/MWCNT composites are better, when compared to those of the pure NR. The marked improvement in these properties is largely due to the strong interfacial adhesion between the NR phase and MWCNTs. Functionalization of MWCNTs represents a potentially powerful technology for significant reinforcement of natural rubber materials.