溶胶-凝胶法制备PET/SiO2纳米复合材料及其TG、DSC分析

采用溶胶-凝胶（sol-gel）法，将正硅酸乙酯和水加入到制备聚对苯二甲酸乙二酯（PET）的中间产物对苯二甲酸双羟乙酯(BHET)中,在液态下均匀混合，高温下快速发生溶胶-凝胶反应，再按PET缩聚反应制得PET/SiO₂纳米复合材料。通过TEM、TG、DSC对材料进行了表征和研究。结果表明，SiO₂在PET中均匀分散，其尺寸在10～100 nm之间，PET/SiO₂纳米复合材料的热降解活化能较普通PET有明显提高，但初始降解温度和结晶性能均有所降低。     

催化剂对正硅酸乙酯常压合成SiO2气凝胶的研究

以正硅酸乙酯为硅源,分别以 HF 和 HF/氨水为催化剂,通过溶胶-凝胶法常压制备 SiO2 气凝胶.研究表明以 HF 为催化剂能有效地加快反应的速度,当以 HF/氨水为催化剂时对产品的合成和性能产生更大的影响.用热重分析仪(TG-DTA)、比表面(BET)、XRD、傅里叶变换红外光谱仪、激光粒度仪等仪器对两种产品微结构测试结果表明:两种产品都是非晶纳米多孔结构,体积平均粒径小于 20μm,为介孔结构.     

PET/纳米SiO2复合材料的制备(Ⅱ):纳米SiO2在PET中的分散性研究

研究了分散方法、纳米材料的加入体系、分散时间、分散剂的种类及SiO2 的加入量对纳米SiO2 在PET/纳米SiO2 中分散性的影响 ,用TEM对其分散情况进行表征 ,并对其分散机理进行探讨与研究。其结果表明 :采用球磨分散法并以氨基硅烷A1 1 2 0分散剂时分散效果最佳 ;当分散时间达 7 5h时 ,分散液中SiO2 基本以纳米尺寸存在 ;将分散液加入对苯二甲酸二甲酯熔体中并在球磨状态下进行酯交换SiO2 的分散效果最好 ,1 0 0nm以下的SiO2 达 95 0 7% ;体系中随SiO2 量的增加 ,其分散性变差 ,当纳米SiO2 的加入量为 1 %～ 4 %时 ,粒径在 1 0 0nm以下的SiO2 由 88%下降到 61 %。     

原位聚合PET/纳米SiO2复合材料性能研究

采用原位聚合方法合成PET/纳米SiO2复合材料,并对其常规性能及结晶性能进行研究。结果表明,纳米粒子的引入使得聚酯熔体的表观粘度上升,端羧基下降;纳米粒子的引入使得聚酯的结晶性能增加。     

二氧化硅无机薄膜的制备及性能研究

采用溶胶-凝胶法,以正硅酸乙酯为原料,不同浓度氨水溶液做催化剂制备了SiO2薄膜,用可见分光光度计,综合热分析仪、X射线粉末衍射等分析手段对薄膜进行表征。研究发现,随氨水浓度的提高,所制备的SiO2薄膜的透光率提高,薄膜与基底的附着力也相应提高。XRD分析结果表明二氧化硅薄膜具有非晶态的无序结构。     

纳米SiO_2制备方法研究

以溶胶—凝胶法(sol-gel)为基础,乙醇作溶剂,在氨水催化作用下,研究了正硅酸乙酯(TEOS)通过水解聚合反应制备Si O2微球的方法,并探讨n(水)/n(TEOS)(简称H)及反应时间等因素的影响。本实验借助激光散射粒度分布分析仪研究Si O2微球在溶液态的分布情况,同时使用SEM对烘烤干燥后的Si O2微球进行表征,该方法制得的纳米Si O2微球分布集中,平均粒径在90 nm左右。     

纳米二氧化硅制备工艺的研究

以TEOS(正硅酸乙酯)为前驱体、氨水为催化剂和无水乙醇为溶剂,采用溶胶-凝胶法制备了纳米二氧化硅。利用傅里叶变换红外光谱(FT-IR)仪和纳米激光粒度分布仪对纳米二氧化硅的结构、粒径及其分布进行了表征,并着重探讨了反应温度、催化剂浓度和反应时间等对纳米二氧化硅粒径的影响。研究结果表明:当反应温度为60℃、催化剂浓度为0.82 mol/L和反应时间为3~4 h时,制得的纳米二氧化硅平均粒径为300 nm左右。     

SiO2-TiO2纳米复合材料的制备及其应用研究

纳米TiO2粒子是一种良好的无机半导体材料,具有独特的催化、光学等性能,应用广泛,但在反应体系中易团聚,降低了其催化性能.通过与纳米SiO2粒子复合,使其优异性能得到充分发挥,拓展了其应用领域.本文主要综述了SiO2-TiO2纳米复合材料的制备方法,如溶胶-凝胶法、化学沉淀法、微乳液法,并对该复合材料的应用进行了归纳与评价.     

单分散球形SiO2颗粒的制备及表征

以氨水作催化剂,采用溶胶-凝胶法制备出单分散、粒径约300～500 nm的亚微SiO2粒子.研究了氨水浓度、乙醇用量、正硅酸乙酯/水的体积比及硅烷偶联剂浓度对SiO2粒子粒径、分散度及其表面结构的影响,同时还研究了SiO2胶体粒子的稳定性能和成核生长机理.结果表明:SiO2粒子粒径随氨水浓度的增加,先增大后减小,分散度增大;且随着乙醇用量的增加,粒径减小,分散度下降.硅烷偶联剂的加入使得SiO2胶体粒子表面有机成分增多,疏水性增强,其水乳液在常温下不能长久放置,且硅烷偶联剂浓度愈高,粒子间愈容易发生黏连.     

溶胶-凝胶法制备SiO2杂化有机硅树脂及其耐热性能研究

无机基有机复合光功能材料是材料学界和光学界的研究热点。为了解决传统无机凝胶材料的机械加工性能差,光损耗大等问题,将有机基团引入到无机凝胶基质中,不但可以较好地优化基质的结构,还可在很大程度上改善材料的性能。以一甲基三甲氧基硅烷（MTMS）和正硅酸乙酯（TEOS）为原料,甲醇为溶剂,盐酸为催化剂,通过溶胶-凝胶法制备出分子级复合的SiO2杂化有机硅树脂。分析了SiO2杂化有机硅树脂的合成机理,借助傅立叶变换红外光谱表征其结构,TG和马弗炉灼烧实验研究SiO2杂化有基硅树脂的耐热性能,结果表明SiO2杂化有机硅树脂500～600℃的失重只有3％,具有良好的耐热性,并探讨了耐热机理。     

PP/纳米SiO2复合材料的阻燃性能研究

将磷系阻燃剂1,3,5-三（5,5-二甲基-1,3-二氧杂环己内磷酸基）苯（FR）、聚磷酸铵（APP）、纳米SiO2复配,制备聚丙烯(PP)纳米复合阻燃材料。采用氧指数测定仪、水平垂直燃烧测定仪、热重分析仪、锥形量热仪对PP纳米复合阻燃材料的阻燃性能进行了研究。结果表明,FR/APP/SiO2提高了PP的氧指数、水平燃烧等级、热稳定性和残炭率,降低了热释放速率。当阻燃剂FR/APP/SiO2的总体含量为25 %,FR/APP/SiO2配比为15/7/3的情况下,PP纳米复合阻燃材料的氧指数为29.4 %,水平燃烧等级为FH-1。     

复合阻燃剂/PET共混物的流变性研究

将复合阻燃剂/PET共混改性,其质量比为2%～7%。研究表明,复合体系为非牛顿假塑性流体,其表观黏度随剪切速率的增大而减小;随着复合阻燃剂含量增大,共混物非牛顿流动指数下降,剪切速率上升,流变性能改善;共混物的黏流活化能为78.3 kJ/mo1,黏温依赖性与普通PET相似。     

PVAc/SiO2纳米复合乳液的性能研究

采用原位乳液聚合法制备了PVAc／纳米SiO2复合乳液,研究了纳米粒子对PVAc粘接强度和耐水性能的影响,并基于纳米压痕试验,分析了PVAc／纳米SiO2复合乳液的力学性能。研究表明,适量的纳米SiO2能显著改善PVAc胶层的粘接强度和耐水性能,并能明显提高PVAc薄膜的弹性模量、硬度及抗蠕变能力。     

Study on flammability of montmorillonite/styrene‐butadiene rubber (SBR) nanocomposites

The flammability of montmorillonite (MMT)/SBR nanocomposites, prepared by the technique of cocoagulating rubber latex and clay aqueous suspension, was investigated. Flammability studies, performed on the cone calorimeter, showed that the maximum heat release rate (HRR) of SBR decreased from 1987 to 1442 kw/m² with the introduction of nanoclay (20 phr). This nanocomposite had the lowest mass loss rate and the largest amount of char upon combustion compared with conventional SBR composites with the same clay loading and pure SBR. The permeability properties of MMT/SBR composites were also measured. It was deduced that the lowered permeability was responsible for the reduced mass loss rate and hence the lower HRR. Unfortunately, the oxygen index (OI) of the nanocomposites was not as high as expected. Combination of Mg(OH)₂ and clay was effective for the improvement of both mechanical properties and OI. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 844–849, 2005     

纳米二氧化硅在PET中分散新方法的研究

利用超声波、偶联剂KH-570对纳米SiO2进行了分散和表面改性,用溶液共混法制备了PET树脂/纳米SiO2复合材料。通过熔点和特性黏度的测试以及红外光谱、扫描电子显微镜等研究了材料的结构和性能。结果表明:溶液共混法不改变PET的化学结构,制成的复合材料仍满足PET的纺丝要求,并且SiO2呈纳米尺度分布在PET树脂中。     

IFR/SiO2和IFR/MgSiO3协效阻燃TPU材料的性能比较

以三嗪成炭发泡剂（CFA）及聚磷酸铵（APP）复配成膨胀阻燃剂(IFR),以二氧化硅(SiO2)及硅酸镁(MgSiO3)为协效剂制备阻燃TPU材料,对比研究了2种热塑性聚氨酯弹性体（TPU）材料的阻燃性能、力学性能、热降解行为、炭层的表面形貌及表面元素组成。结果表明,当IFR总添加量为30 %（质量分数,下同）,SiO2占IFR的5 %时,1.6 mm样条在燃烧时产生大量熔滴,材料通过UL 94 V-2级,极限氧指数（LOI）为39.5 %,而当阻燃剂总添加量为26 %,MgSiO3占IFR的5 %时,1.6 mm样条在燃烧时无滴落,材料通过UL 94 V-0级,LOI为35.7 %,表明MgSiO3在该阻燃体系中具有很好的抑制熔滴的作用;与添加SiO2相比,MgSiO3的加入对材料拉伸性能的影响更小;MgSiO3的加入使得炭层中磷元素含量明显增加;MgSiO3的加入使得阻燃TPU材料在燃烧时产生了更加连续、致密且具有良好强度的炭层,对内部材料起到了更好的保护作用,从而提高了材料的阻燃性能。     

Study of thermal,flammability and mechanical properties of intumescent flame retardant PP/kenaf nanocomposites

Detrimental physical and mechanical properties are common problems for composites when their flame retardancy is improved through filler additions. An increased interest of the synergistic nanoparticle addition to improve the flame retardancy of natural fiber composites is the aim of this work. The paper investigates the synergistic effect of two different nanoparticles (halloysite nanotubes (HNTs) and montmorillonite (MMT) nanoclay) on the flame and mechanical properties in an intumescent ammonium polyphosphate (APP)-based polypropylene (PP)/kenaf composite system. First, the nature of nanoparticle dispersion in PP through X-ray diffraction (XRD) and transmission electron microscopy (TEM) reveals that under twin screw compounding process, the partial exfoliation and intercalation have taken place within the nanocomposites. An increase in the decomposition temperature was observed under thermogravimetric analysis (TGA), with the presence of HNT. However, MMT tends to lower the maximum decomposition temperature under inert atmosphere. The flammability analysis in an intumescent flame retardant (IFR) system shows that the suitable amount of high aspect ratio nanoparticles with their exfoliation characteristics effectively helps to reduce the sustained combustion. Even though, improved stiffness properties can be observed with the presence of increased filler content, particle agglomeration tends to reduce the mechanical strengths of these composites due to low compatibilization and crack propagation.     

4A分子筛和SiO2对EVA/IFR复合材料性能的影响

以聚磷酸铵(APP)复配季戊四醇(PER)为膨胀型阻燃剂(IFR)制备了无卤阻燃乙烯-醋酸乙烯共聚物(EVA)/IFR复合材料,通过极限氧指数仪、热失重分析仪及扫描电子显微镜研究分析了4A分子筛和SiO2的加入对复合材料阻燃性能、热稳定性能及复合材料残炭表面形貌的影响。结果表明,加入4A分子筛可以明显提高复合材料的极限氧指数,当添加1份4A分子筛时,复合材料的极限氧指数达到31%,比未添加时提高了2%;4A分子筛的加入使复合材料在燃烧过程出现熔融滴落现象;继续加入SiO2可以进一步提高复合材料的极限氧指数,当添加3份SiO2时,复合材料的垂直燃烧测试达到V-0级。     

How Hydrogen Bond Interactions Affect the Flame Retardancy and Anti‐Dripping Performances of PET

To systematically study how the H‐bonding interaction affect the flame retardancy and anti‐dripping behavior of poly(ethylene terephthalate) (PET), two series of PET‐based copolyesters are prepared by introducing two benzimidazole monomers with similar structure. One (2‐(4‐methoxycarbonyl‐phenyl)‐1H‐benzimidazole‐5‐carboxylic acid methyl ester, PBM) contains H‐bonding donor, the other (2‐(4‐methoxycarbonyl‐phenyl)‐1‐methylbenzimidazole‐5‐carboxylic acid methyl ester, PNM) weeds out the H‐bonding donor by replacing ? NH group with ? N? CH₃. The dynamic rheological behavior, fire resistance and fire‐retardant mechanism of the PET‐co‐PBMs and PET‐co‐PNMs are contrastively investigated. PET‐co‐PNMs have flow behaviors similar to neat PET. While, for PET‐co‐PBMs, the movements of the molecular chains are restricted due to the H‐bonding interaction, leading to higher melt viscosity, which is conducive to the anti‐dripping property. It can be proved that benzimidazole groups promote the carbonization of substrates to form more stable charred layers in combustion, showing an obvious barrier action in condensed phase. Unfortunately, the enhancement of carbonization alone is not enough to inhibit the dripping behavior satisfactorily, and PET‐co‐PNMs fail to pass UL‐94 V‐0 rating. While, PET‐co‐PBMs exhibit better self‐extinguishing and anti‐dripping performances benefiting from strong H‐bonding interactions. The revealed effects of H‐bonding interactions on the fire resistance and anti‐dripping behavior of polymers will guide further design of flame retardants.     

Morphology and crystallization behavior of the PP/PET nanocomposites

Nanocomposites containing polypropylene (PP), PET, and montmorillonite were prepared in a twin‐screw extruder. X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, polarized optical microscopy, and differential scanning calorimetry were used to characterize the samples. Intercalated and exfoliated morphology were observed in the nanocomposites. The PET domains usually presented spherical shapes and they were the start point to PP crystallization. The average diameter and number of PET domains was evaluated. The influence of addition of PP‐MA as compatibilizer on PP/PET was investigated. The interconnected morphology was observed in the nanocomposite containing PP‐MA. The clay located predominantly in the interphase and in the PET phase. The crystallization process was monitored and the PET crystallization rate was slower in the nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009