有机蒙脱土/天然橡胶纳米复合材料的阻燃性能研究

采用机械混炼插层法制备有机蒙脱土/天然橡胶(TMT/NR)纳米复合材料.使用X-射线衍射(XRD)和红外表征了有机蒙脱土的结构特性,并用锥形量热仪测试了纳米复合材料的燃烧性能.结果表明,有机蒙脱土/NR纳米复合材料的热释放速率(HRR)、生烟速率(SPR)等较纯天然橡胶、未改性蒙脱土/NR复合材料均所有降低,表现出较好的阻燃性能.通过对纳米复合材料的燃烧性能和燃烧残余物分析,探讨了该体系的阻燃机理.     

双单体原位接枝插层法制备聚丙烯纳米复合材料的研究Ⅰ.制备、表征及力学性能的研究

用有机插层剂处理蒙脱土原土 ,制得有机蒙脱土 (O MMT) .采用双单体 (马来酸酐和苯乙烯 )原位接枝插层法 ,制备了聚丙烯 蒙脱土纳米复合材料母料 .将母料与聚丙烯基体在双螺杆上共混挤出 ,制得聚丙烯 蒙脱土纳米复合材料 (PP Montmorillonetenanocomposites,PMNC) .这是制备聚合物纳米复合材料的一种新方法 .通过X 射线衍射测试 (XRD)表明 ,有机蒙脱土片层 0 0 1面间距从原土的 1 4 9nm扩大到 2 96nm ,复合材料中蒙脱土片层 0 0 1面间距由有机蒙脱土的 2 96nm扩大到 4 0nm .力学性能测试表明 ,复合材料的力学性能明显优于PP基体 ,在提高材料拉伸强度的同时 ,缺口冲击强度也得到很大的提高 .用扫描电镜 (SEM)对材料的冲击断面形貌进行了研究 ,并从理论上分析了断裂机理 .随着蒙脱土含量的增加 ,冲击断裂形式逐渐从脆性断裂变成韧性断裂     

聚N-甲基苯胺/蒙脱土纳米复合材料的合成及其协同电流变效应

用插层聚合法制备了聚N 甲基苯胺 蒙脱土纳米复合材料微粒 ,通过IR、XRD及TEM对其结构进行了表征 .观察发现聚N 甲基苯胺插入蒙脱土层间后 ,蒙脱土片层间距由 0 96nm扩大至 1 34nm .将其分散在甲基硅油中 (2 0wt% )配制成无水电流变液 ,该复合材料表现出显著的协同效应 ,具有较好的电流变行为 .实验表明在电场作用下聚N 甲基苯胺 蒙脱土纳米复合材料的电流变效应比聚苯胺、蒙脱土都有显著提高 ,在 3kV mm(DC ,74 5s- 1 )时 ,剪切强度达 6 0kPa ;同时抗沉降性极好 ,静置 6 0天沉淀率小于 3% .介电性能测试表明聚N 甲基苯胺 蒙脱土纳米颗粒的介电常数和介电损耗较蒙脱土和聚N 甲基苯胺明显提高 ,电导率也达到了最佳范围 .     

聚氨酯弹性体/蒙脱土纳米复合材料的合成与性能

采用聚氨酯本体预聚法 ,利用原位插层聚合合成了聚氨酯 蒙脱土纳米复合材料 .通过X 射线衍射(XRD)和Molau实验研究了蒙脱土在复合材料中的分散情况 .红外分析 (IR)表明随着蒙脱土含量的增加 ,复合材料羰基氢键减少 .动态力学分析 (DMA)以及差热分析 (DSC)结果说明随着蒙脱土含量的增加 ,材料的玻璃化温度降低 .聚氨酯纳米复合材料的拉伸强度和断裂伸长率同时提高 ,表现出较好的力学性能 .     

机械混炼过程对天然橡胶/有机蒙脱土纳米复合材料结构的影响

采用机械混炼插层法制备天然橡胶(NR)/有机蒙脱土(OMMT)纳米复合材料,研究混炼过程对复合材料结构的影响。结果表明,剪切作用越强并不越有利于大分子链的插层,当辊距为3 mm时,适当增加薄通的次数,有益于分子链插入蒙脱土层间。当薄通次数达到40次时,可形成剥离型的纳米复合材料。且在共混过程中加入偶联剂,可使得蒙脱土与橡胶间的化学交联的比例提高,从而改善复合材料的物理机械性能和热氧老化性能。     

辐照法制备PVAc/蒙脱土纳米复合材料及其表征

蒙脱土有机化后 ,片层结构间距离增大 ,对有机物的亲和性有所增强 .采用VAc单体渗入有机化蒙脱土层间 .经γ 射线辐照引发原位插层聚合 ,使蒙脱土片层结构发生剥离 ,形成无机 有机纳米复合材料 .并用X衍射、红外光谱、扫描电镜以及透射电镜等现代测试手段对复合材料进行了表征     

酚醛树脂/蒙脱土纳米复合材料的制备及固化反应动力学研究

利用自制的有机蒙脱土 ,采用浇模固化成型法制备酚醛树脂 /六次甲基四胺 /蒙脱土纳米复合材料 ,并用XRD观察有机蒙脱土分别在热塑性和热固性酚醛树脂中复合行为 .研究发现 ,由于两种树脂的固化反应机理不同 ,热固性酚醛树脂与蒙脱土复合 ,可得插层型纳米复合材料 ;而采用热塑性酚醛树脂进行固化 ,则得到部分剥离的纳米复合材料 .通过DSC进一步研究热塑性酚醛树脂 /蒙脱土复合体系的固化反应动力学 .运用Kissinger ,Flynn Wall Ozawa ,Crane方法求出活化能和反应级数等动力学参数 .结果发现 ,加入蒙脱土使固化反应活化能下降 ,反应级数减小 ,从而有利于固化工艺的实现 ,便于纳米复合材料实际应用 .     

聚丙烯/蒙脱土纳米复合材料Ⅰ.制备、表征及动态力学性能

用原位接枝插层法成功地制备了聚丙烯 /蒙脱土纳米复合材料 (PPMNC) .采用X射线衍射研究复合材料中蒙脱土硅酸盐片层间距 ,发现硅酸盐片层间距从 1 94nm升至 4nm左右 .同时研究了PPMNC的动态力学性能 ,结果表明 :PPMNC的动态储能模量明显高于聚丙烯 (PP) ,尤其在T >Tg 高温段 ,甚至可以达到PP基体的 2倍     

聚氨酯弹性体/蒙脱土纳米复合材料的合成、结构与性能

采用插层聚合法合成了综合力学性能优异的聚氨酯 蒙脱土纳米复合材料 .X 射线衍射结果表明 ,蒙脱土以平均层间距不小于 4 5nm的宽分布分散在聚氨酯基体中 .加入 7 5wt%左右的蒙脱土 ,复合材料的拉伸强度高于纯PU基体的 2倍 ,断裂伸长率则高于纯PU基体的 4倍以上 .TGA分析表明 ,聚氨酯 蒙脱土纳米复合材料的热稳定性略有提高     

光诱导聚合蒙脱土插层纳米复合材料的研究

用两种光聚合法研究了蒙脱土插层复合材料的制备.用小角X光衍射技术对产物内蒙脱土的结构进行表征,结果表明,蒙脱土经改性后能很好地使聚合单体及预聚物插入黏土层内并在光照下"就地”聚合生成光聚合复合材料.对光聚合法制备蒙脱土纳米复合材料的优缺点进行了初步讨论.     

Structure and properties of NR/BR blend/clay nanocomposites prepared by the latex method

Rubber blend/clay nanocomposites based on the 50/50 (wt %) natural rubber/butadiene rubber was prepared by the latex method via mixing the latex of 50/50 NR/BR blend with different amounts of the aqueous sodium montmorillonite (Na-MMT) dispersion and co-coagulating the mixture. XRD and TEM were used to characterize structure of the nanocomposites. It was found that fully exfoliated structure could be obtained by this method only when the low loading of layered silicate (up to 5 phr) is used. With increasing the clay content, both non-exfoliated (stacked layers) and exfoliated structures can be observed simultaneously in the nanocomposites. Nanocomposites showed mechanical properties better than the clay-free volcanizate. Moreover, modulus, tensile strength, elongation at break and tear strength increased significantly by increasing the clay amount up to 5 phr and then remained almost constant by further increasing the clay content. Improvement in the mechanical properties by increasing the clay loading up to 5 phr was attributed to the nano-reinforcement effect of Na-MMT. TGA results indicated an improvement in the main decomposition temperature by increasing the clay amount.     

Nanocomposites of natural rubber and polyaniline-modified cellulose nanofibrils

Cellulose nanofibrils (CNF) were isolated from cotton microfibrils (CM) by acid hydrolysis and coated with polyaniline (PANI) by in situ polymerization of aniline onto CNF in the presence of hydrochloride acid and ammonium peroxydisulfate to produce CNF/PANI. Nanocomposites of natural rubber (NR) reinforced with CNF and CNF/PANI were obtained by casting/evaporation method. TG analyses showed that coating CNF with PANI resulted in a material with better thermal stability since PANI acted as a protective barrier against cellulose degradation. Nanocomposites and natural rubber showed the same thermal profiles to 200 °C, partly due to the relatively lower amount of CNF/PANI added as compared to conventional composites. On the other hand, mechanical properties of natural rubber were significantly improved with nanofibrils incorporation, i.e., Young’s modulus and tensile strength were higher for NR/CNF than NR/CNF/PANI nanocomposites. The electrical conductivity of natural rubber increased five orders of magnitude for NR with the addition of 10 mass% CNF/PANI. A partial PANI dedoping might be responsible for the low electrical conductivity of the nanocomposites.     

Preparation and characterization of natural rubber with soft nanomatrix structure

Preparation of natural rubber (NR) with a soft nanomatrix structure was made by graft-copolymerization of butyl acrylate (BA) onto deproteinized natural rubber with tert-butyl hydroperoxide/tetraetylenepentamine in latex stage. The resulting graft-copolymer of deproteinized natural rubber and poly (butyl acrylate) (DPNR-graft-PBA) was characterized by Fourier-transform infrared spectroscopy. Conversion and grafting efficiency of BA were dependent upon BA concentration, which were more than 90?mol% under a suitable condition of the graft-copolymerization. Morphology of DPNR-graft-PBA was observed by transmission electron microscopy after staining film specimens with I₂ vapor for 5?min. The NR particles of about 0.5?μm in diameter were dispersed in PBA matrix of about 15?nm in thickness. Storage modulus and loss tangent of DPNR-graft-PBA were measured, and they were related with the soft nanomatrix structure. The tensile strength and elongation at break decreased as monomer concentration increased.     

Effects of cellulose nanocrystals on the vulcanization of natural rubber/cellulose nanocrystals nanocomposite and corresponding regulating strategies

Vulcanization is a vital process in rubber processing, it endows rubber with valuable physical and mechanical properties, making rubber a widely used engineering material. In addition to vulcanization agent, reinforcing fillers play a non-ignorable influence on the vulcanization of rubber nanocomposites. Herein, the effects of cellulose nanocrystals (CNCs) on the vulcanization of natural rubber (NR)/CNCs nanocomposite was studied. It was found that even though the addition of CNCs can effectively improve the dispersion of ZnO in NR matrix, the vulcanization of NR was inhibited. This may be attributed to the CNCs' adsorption of vulcanizing agents (DM, ZnO) and the acidic chemical environment on the surface of CNCs. In order to improve the vulcanization properties of NR/CNCs nanocomposite, tetramethyldithiochloram (TMTD) and triethanolamine (TEOA) were used as a combination accelerator and curing activator, respectively, and polyethylene glycol (PEG) was introduced to screen hydroxyl groups on the surface of CNCs to prohibit the CNCs' adsorption of vulcanizing agents. The results indicate that TMTD and TEOA effectively improved the vulcanization rate of NR/CNCs nanocomposite and increased the crosslink density by an order of magnitude. Subsequently, the tensile strength, tear strength, and so forth. of NR/CNCs nanocomposite were significantly improved. However, PEG hardly help to improve the vulcanization properties of NR/CNCs nanocomposite. In addition, the control samples without CNCs were prepared and characterized, the comparation between NR and NR/CNCs nanocomposite shows that the synergistic effect of crosslink density and CNCs' reinforcement more effectively improve mechanical properties of NR. This work not only elucidates the inhibiting mechanisms of CNCs on the vulcanization of NR, but also provides practical strategies for improving the vulcanization and properties of NR/CNCs nanocomposite. It may accelerate the application of CNCs as rubber reinforcing filler.     

聚氯乙烯/聚丙烯酸丁酯/白泥纳米复合材料的研究

通过多步交换反应及扩散－聚合的方法,使聚丙烯酸丁酯被嵌入到改性层状结构的白泥层间,得到白泥－聚丙烯酸丁酯纳米复合物的微米粒子;然后将聚氯乙烯与白泥－聚丙烯酸丁酯进行熔融共混,制得具有一一特性的有机－无机纳米复合材料,并对复合材料的缺口冲击强度及动态力学性能进行了研究,结果表明,白泥－聚丙烯酸酯含量为5．0wt％时,复合材料的力学性能最佳;聚氯乙烯与高含量的白泥－聚丙烯酸丁酯（分别为25．0wt%和50．0wt%）形成的复合材料,在聚氯乙烯的玻璃化转变温度之前,储能模量出现先降低而后增加的过程。     

Preparation and properties of natural rubber composites reinforced with pretreated carbon nanotubes

In order to achieve dramatic improvements in the performance of rubber materials, the development of carbon nanotube (CNT)‐reinforced rubber composites was attempted. The CNT/natural rubber (NR) nanocomposite was prepared through solvent mixing on the basis of pretreatment of CNTs. Thermal properties, vulcanization characteristics, and physical and mechanical properties of the CNT/NR nanocomposites were characterized in contrast to the carbon black (CB)/NR composite. Through the addition of the CNTs treated using acid bath followed by ball milling with HRH (hydrated silica, resorcinol, and hexamethylene tetramine) bonding systems, the crystallization melting peak in differential scanning calorimetry (DSC) curves of NR weakened and the curing rate of NR slightly decreased. Meanwhile, the over‐curing reversion of CNT/NR nanocomposites was alleviated. The dispersion of the treated CNTs in the rubber matrix and interfacial bonding between them were rather good. The mechanical properties of the CNT‐reinforced NR showed a considerable increase compared to the neat NR and traditional CB/NR composite. At the same time, the CNT/NR nanocomposites exhibited better rebound resilience and dynamic compression properties. The storage modulus of the CNT/NR nanocomposites greatly exceeds that of neat NR and CB/NR composites under all temperature regions. The thermal stability of NR was also obviously improved with the addition of the treated CNTs. Copyright © 2008 John Wiley & Sons, Ltd.     

Influence concentration of modifying agent on properties of natural rubber/organoclay nanocomposites

Sodium-montmorillonite (Na-MMT) nanoclay was modified with different concentrations of octadecylamine organic modifying agent at 0.5, 1.0 and 1.5 times the CEC of Na-MMT. Influence of concentration of modifying agent on properties of the organoclays and natural rubber/organoclay nanocomposites was investigated. It was found that the optimum concentration of modifying agent was 1.5 times the CEC of Na-MMT. That is, at this concentration, larger d-spacing of organoclay particles and higher degree of clay dispersion in natural rubber matrix were observed. Larger interlayer d-spacing also caused enhancement of the mechanical properties of the NR/organoclay nanocomposites. Additionally, the NR/organoclay nanocomposites with higher concentration of modifying agent exhibited faster curing reaction with higher crosslink density. Furthermore, the organoclays with larger d-spacing and higher degree of dispersion in the natural rubber matrix exhibited enhancement of the mechanical and dynamic properties and thermal stability of natural rubber/organoclay nanocomposites.     

Highly enhanced electrical and mechanical properties of methyl methacrylate modified natural rubber filled with multiwalled carbon nanotubes

Developing conductive networks in a polymer matrix with a low percolation threshold and excellent mechanical properties is desired for soft electronics applications. In this work, natural rubber (NR) functionalized with poly(methyl methacrylate) (PMMA) was prepared for strong interfacial interactions with multiwalled carbon nanotubes (MWCNT), resulting in excellent performance of the natural rubber nanocomposites. The MWCNT and methyl methacrylate functional groups gave good filler dispersion, conductivity and tensile properties. The filler network in the matrix was studied with microscopy and from its non-linear viscoelasticity. The Maier-Göritze approach revealed that MWCNT network formation was favored in the NR functionalized with PMMA, with reduced electrical and mechanical percolation thresholds. The obvious improvement in physical performance of MWCNT/methyl methacrylate functionalized natural rubber nanocomposites was caused by interfacial interactions and reduced filler agglomeration in the NR matrix. The modification of NR with poly(methyl methacrylate) and MWCNT filler was demonstrated as an effective pathway to enhance the mechanical and electrical properties of natural rubber nanocomposites.     

Prevulcanized natural rubber latex/clay aerogel nanocomposites

Natural rubber latex (NR)/clay aerogel nanocomposites were produced via freeze-drying technique. The pristine clay (sodium montmorillonite) was introduced in 1-3 parts per hundred rubber (phr) in order to study the effect of clay in the NR matrix. The dispersion of the layered clay and the morphology of the nanocomposites were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Cure characteristics, thermal stability, and the crosslink density of thermal and microwave-cured NR and its composites were investigated. XRD patterns indicated that both intercalated and exfoliated structures were observed at loadings of 1-3 phr clay. SEM studies revealed that the clay aerogel structure was formed at 3 phr clay loading. The increment in Shore A hardness of nanocomposites compared with pure NR signified excellent polymer/filler interaction and the reinforcing effect of the clay to rubber matrix. This was supported by an increase in maximum rheometric torque and crosslink density. The crosslink density of clay-filled NR vulcanizate was found to increase with the pristine clay content in both thermal and microwave curing methods. However, microwave-cured 2 and 3 phr-filled NR vulcanizates exhibited higher crosslink density than those which were thermal-cured under the same curing temperature. In addition, thermal stability studies showed that pristine clay accelerated the decomposition of NR by showing a slight decrease in onset and peak decomposition temperatures along with clay content.