原子转移自由基聚合接枝改性纳米SiO2的研究进展

纳米SiO2粒子极易团聚,在有机介质中难以均匀分散,从而大大地限制了其优异性能的发挥,有必要对其进行化学改性处理。原子转移自由基聚合(atom transfer radical polymerization,ATRP)是对纳米SiO2粒子进行接枝改性的一种有效途径,通过ATRP对纳米SiO2粒子进行表面改性,可以制备集无机纳米粒子和聚合物的优点于一身的SiO2-聚合物复合材料,且接枝链的长度及分子量分布可控,拓展了纳米SiO2的应用领域。本文主要综述了ATRP、RATRP(reverse ATRP)、AGET ATRP(activators generated by electron transferATRP)和ARGET ATRP(activators regenerated by electron transfer ATRP)方法对纳米SiO2接枝改性的研究现状。     

原子转移自由基聚合接枝改性纳米Si02的研究进展

纳米SiO2粒子极易团聚,在有机介质中难以均匀分散,从而大大地限制了其优异性能的发挥,有必要对其进行化学改性处理。原子转移自由基聚合（atom transfer radical polymerization,ATRP）是对纳米Si02粒子进行接枝改性的一种有效途径,通过ATRP对纳米SiOz粒子进行表面改性,可以制备集无机纳米粒子和聚合物的优点于一身的SiO2-聚合物复合材料,且接枝链的长度及分子量分布可控,拓展了纳米SiO。的应用领域。本文主要综述了ATRP、RATRP（reverse ATRP）、AGETATRP（activators generated by electron transfer ATRP）和ARGETATRP（activators regenerated by electron transferATRP）方法对纳米Si02接枝改性的研究现状。     

核/壳纳米复合粒子填充聚苯乙烯的流变行为

采用细乳液聚合制备了以偶联剂改性纳米二氧化硅粒子(SiO2)为核、交联聚苯乙烯(PS)为壳的SiO2@PS复合纳米粒子(SCCSN).采用透射电子显微镜(TEM)、动态光散射(DIS)法考察了SCCSN的粒子形貌特征,发现SCCSN呈球形,粒径约90 nm,均匀分散;采用热失重(TG)、调制式差示扫描量热(MDSC)与动态力学分析(DMA)研究了SCCSN的结构特征,发现PS包覆率随交联剂含量增加而升高,且玻璃化转变温度(Tg)显著升高.交联壳层不仅能够将聚合物锚固在SiO2表面,屏蔽SiO2粒子与基体PS间相互作用,而且阻止PS壳层与基体PS分子链间的缠结.MDSC结果显示,SiO2与SCCSN填充可降低复合物Tg.动态流变结果表明,填充PS熔体非线性流变行为与PS分子链解缠结有关,SiO2与SCCSN均不影响填充熔体非线性流变机理.SCCSN的SiO2核对PS的增强效应略优于SiO2,且增强效应与壳层交联度有关.     

纳米SiO_2对PDMS/PIB不相容共混物在低剪切速率下凝聚行为的影响

借助在线剪切-显微装置研究了简单剪切流场下疏水纳米二氧化硅(SiO2)粒子对聚二甲基硅氧烷/聚异丁烯(PDMS/PIB=90 wt%∶10 wt%)不相容共混物实时结构演变过程的影响.研究表明,分散相尺寸的大小及其分布由粒子含量和剪切速率共同决定.少量纳米SiO2的加入能够抑制PIB分散相的凝聚,分散相的尺寸随着纳米SiO2含量的增大而减小,并且呈现出双峰分布.但随着SiO2粒子含量的进一步增加,分散相尺寸的双峰分布现象逐渐消失.SiO2的加入还导致PIB分散相对剪切速率的依赖性降低.当SiO2粒子含量低于2.5wt%时,较高的剪切速率凝聚得到的分散相的尺寸较大;当SiO2粒子含量超过2.5 wt%后,低速和高速剪切速率下凝聚得到的分散相尺寸基本相同.粒子的包覆、分散相的破碎和凝聚是出现以上现象的根本原因.     

PBD/PDMS共混物分散相的聚并捕获行为

借助显微-剪切装置在线研究了低速剪切场下SiO2纳米粒子含量、分散相聚丁二烯(PBD)浓度和剪切速率对PBD/聚二甲基硅氧烷(PDMS)不相容体系中聚并捕获行为的影响.结果表明,聚并捕获所形成的液滴尺寸与形状规整度由粒子含量、分散相浓度和剪切速率等因素共同决定.在较低的SiO2纳米粒子含量或较高的分散相浓度下,PBD液滴在低剪切场下发生聚并捕获,形成尺寸较大、形状不规则的液滴.增加SiO2纳米粒子含量或减小分散相浓度,能够减小分散相的尺寸并提高分散相的规整度.增加剪切速率能有效地减小分散相的尺寸并提高分散相的规整度.     

单分散空心SiO2纳米微球的合成与表征

聚乙烯吡咯烷酮(PVP)功能化的聚苯乙烯(PS)粒子在SiO2包覆的同时被乙醇/氨水介质溶解, 得到了单分散空心SiO2纳米微球. 该空心SiO2纳米微球的尺寸和形态可以通过PVP, NH4OH和正硅酸乙酯(TEOS)的用量来调节. PVP用量增加导致PS粒子变小, 从而得到较小的空心SiO2纳米微球; NH4OH用量增加, 空心SiO2纳米微球表面变得粗糙; TEOS用量增加, 空心SiO2纳米微球的壳层厚度增加. 包覆(溶解)温度是控制空心SiO2纳米微球形成的最有效手段. 在70 ℃的包覆(溶解)温度下可以获得全部空心的SiO2纳米微球.     

超支化聚乙烯亚胺接枝二氧化硅的制备及在聚丙烯改性中的应用

首先利用3-缩水甘油氧基丙基三甲氧基硅烷(简称GPS)作为偶联剂,对纳米SiO2进行表面改性,获得表面含有环氧基的SiO2纳米粒子(SiO2-GPS).利用这些环氧基与超支化聚乙烯亚胺(HPEI)分子中的氨基进行反应,得到SiO2接枝超支化聚乙烯亚胺的纳米粒子(SiO2-GPS-g-HPEI).然后利用SiO2-GPS-g-HPEI与聚丙烯(PP)和PP接枝的马来酸酐(PP-g-MAH)共混、模压,制备PP/SiO2-GPS-g-HPEI/PP-g-MAH复合材料.红外光谱测试和热失重分析(TGA)测试结果表明,SiO2纳米粒子表面依次接枝了GPS和HPEI;扫描电子显微镜(SEM)的测试结果显示,SiO2-GPS-g-HPEI在聚丙烯基体中分散良好,其材料的冲击断裂为韧性断裂;复合材料共混时,扭矩的增加证明了共混物中分散相(SiO2-GPS-g-HPEI)与基体(PP/PP-g-MAH)界面之间存在一定的相互作用.少量SiO2-GPS-g-HPEI加入PP/PP-g-MAH中,冲击强度可增加96.3%,拉伸强度也有较大的提高.     

聚丙烯酸丁酯接枝的纳米SiO2对聚甲醛的改性

采用原子转移自由基聚合法(ATRP)在纳米SiO2粒子表面接枝聚丙烯酸丁酯(PBA)制备了纳米复合粒子SiO2-g-PBA,并以此对聚甲醛(POM)进行改性. 通过红外光谱、热失重分析、透射电子显微镜及扫描电子显微镜等分析技术进行了表征. 结果,SiO2-g-PBA在POM中分散均匀,使POM/SiO2-g-PBA复合材料的缺口冲击强度明显高于POM及POM/ SiO2复合材料. 当SiO2-g-PBA纳米复合粒子的质量分数为2%时,POM/SiO2-g-PBA复合材料的冲击强度达71.2 kJ/m2,较纯POM提高了7倍多,同时拉伸强度也有一定的提高,达到68.1 MPa.     

纳米SiO_2粒子锚固偶氮引发剂及接枝聚甲基丙烯酸甲酯

对纳米SiO2 粒子锚固偶氮引发剂 ,进而引发甲基丙烯酸甲酯聚合而制备聚甲基丙烯酸甲酯(PMMA) 纳米SiO2 复合粒子进行了研究 .纳米SiO2 先用环氧型硅烷偶联剂处理 ,再与偶氮二氰基戊酸发生缩合反应而锚固上偶氮引发剂 ,通过差示扫描量热和元素分析证明了引发剂在纳米SiO2 表面的锚固 .通过改性纳米SiO2 存在下MMA的乳液聚合 ,制备得到了接枝率为 2 3 2 %、接枝效率为 36 1%的PMMA 纳米SiO2 复合粒子 .经乳液聚合后 ,纳米SiO2 粒子团聚程度减小 ,在水相中分散稳定 .     

ZnO纳米棒改性超高分子量聚乙烯纤维及其性能研究

采用低温水热法在超高分子量聚乙烯(UHMWPE)纤维表面成功制备了致密均匀的ZnO纳米棒阵列,利用纳米棒阵列与树脂形成啮合结构,有效增强了纤维和树脂之间的界面结合强度.采用扫描电镜(SEM)、示差扫描量热法(DSC)、热重分析(TGA)、X射线衍射(XRD)等手段对纤维改性前后结构与性能变化进行了分析,并通过单丝拔出实验表征了其与环氧树脂间的界面剪切强度(IFSS);探索了反应时间、前驱液浓度对界面性能的影响.研究结果表明这种改性方法对纤维的本征性能几乎无影响,改性后纤维增重仅5%,而与树脂复合后界面剪切强度提升58%,单丝拨出时破坏发生在纳米棒阵列与纤维之间.进一步,利用该方法对UHMWPE织物进行改性,发现使用单宁酸可提高纳米棒阵列与纤维之间的结合力,使得到的UHMWPE@ZnO和UHMWPE@TA-ZnO织物的防穿刺能力分别提升20%和42%.     

The influence of chitin nanocrystals on structural evolution of ultra-high molecular weight polyethylene/chitin nanocrystal fibers in hot-drawing process

Ultra-high molecular weight polyethylene (UHMWPE)/chitin nanocrystal (CNC) fibers were prepared. Compared with the pure UHMWPE fibers, the ultimate tensile strength and Young’s modulus of UHMWPE/CNC fibers are improved by 15.7% and 49.6%, respectively, with the addition of chitin nanocrystals (CNCs) of 1 wt%. The melting temperature (T _m) of UHMWPE/CNC fibers was higher than that of pure UHMWPE fibers. Pure UHMWPE fibers and UHMWPE/CNC fibers were characterized with respect to crystallinity, orientation and kebab structure by wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM). It is found that the CNCs act as the shish structure in UHMWPE/CNC fibers and the kebab crystals are grown around the CNCs. There was almost no difference between pure UHMWPE fibers and UHMWPE/CNC fibers in orientation. But the degree of crystallinity of various stages of UHMWPE/CNC fibers was respectively higher than the corresponding stage of pure UHMWPE fibers. Moreover, the addition of 1 wt% CNCs improved the thickness of kebab crystals and accelerated the transformation of kebab to shish.     

Structure and properties of regenerated cellulose fibers from aqueous NaOH/thiourea/urea solution

Regenerated cellulose fibers were successfully prepared through dissolving cotton linters in NaOH/thiourea/urea aqueous solution at ?2 °C by a twin-screw extruder and wet-spinning process at varying precipitation and drawing conditions. The dissolution process of an optimized 7 wt% cellulose was controlled by polarizing microscopy and resulted in a transparent and stable cellulose spinning dope. Rheological investigations showed a classical shear thinning behavior of the cellulose/NaOH/thiourea/urea solution and a good stability towards gelation. Moreover, the mechanical properties, microstructures and morphology of the regenerated cellulose fibers were studied extensively by single fiber tensile testing, X-ray diffraction, synchrotron X-ray investigations, birefringence measurements and field-emission scanning electron microscopy. Resulting fibers demonstrated a smooth surface and circular cross-section with homogeneous morphological structure as compared with commercial viscose rayon. At optimized jet stretch ratio, acidic coagulation composition and temperature, the structural features and tensile properties depend first of all on the drawing ratio. In particular the crystallinity and orientation of the novel fibers rise with increasing draw ratio up to a maximum followed by a reduction due to over-drawing and oriented crystallites disruption. The microvoids in the fiber as analysed with SAXS were smaller and more elongated with increasing drawing ratio. Moreover, a higher tensile strength (2.22 cN/dtex) was obtained in the regenerated fiber than that of the viscose rayon (2.13 cN/dtex), indicating higher crystallinity and orientation, as well as more elongated and orientated microvoid in the regenerated fiber. All in all, the novel extruder-based method is beneficial with regard to the dissolution temperature and a simplified production process. Taking into account the reasonable fiber properties from the lab-trials, the suggested dissolution and spinning route may offer some prospects as an alternative cellulose processing route.     

Properties of partially hydrolyzed PAN fibers

The properties of base PAN (polyacrylonitrile) fibers and their partially hydrolyzed PAN-COOH fibers were characterized by means of a Fourier transform infrared spectrophotometer, elemental analyzer, specific surface area analyzer etc. The main factors that can affect the strength of the base PAN fibers and how the hydrolysis reaction happens in alkaline conditions are discussed. Acidic hydrolyzed PAN-COOH fibers, having a strength of 9.6 cN/dtex, capacity of 0.26 mmol/g, BET area of 0.58 m²/g (calculated on dry basis) were prepared. The conversion rate from -CN to -COOH, the ways that groups of -COOH array on the surface of the fibers and the possible maximum amounts of -COOH are discussed in detail. __________ Translated from Transactions of Beijing Institute of Technology, 2008, 28(2) (in Chinese)     

LLDPE/纳米SiO_2复合材料的力学性能和光学性能研究

采用熔融共混方法制备了LLDPE 纳米SiO2 复合材料 ,并对该体系的力学性能和光学性能进行了系统研究 .结果表明 ,随着纳米SiO2 的加入 ,复合材料的弹性模量显著提高 ,冲击强度与拉伸强度呈峰形变化 ,且均在SiO2 含量为 3phr左右达到最大值 .加入少量的纳米SiO2 后 ,复合材料薄膜对长波红外线 (7～ 1 1 μm)的吸收能力较LLDPE膜有了显著提高 ,透光率略有下降但雾度提高 ,透光质量得到改善 .同时表明 ,纳米SiO2 的表面处理方法对膜的光学性能有显著影响     

Surface modification of ultrahigh‐molecular‐weight polyethylene fibers

To prevent the loss of fiber strength, ultrahigh‐molecular‐weight polyethylene (UHMWPE) fibers were treated with an ultraviolet radiation technique combined with a corona‐discharge treatment. The physical and chemical changes in the fiber surface were examined with scanning electron microscopy and Fourier transform infrared/attenuated total reflectance. The gel contents of the fibers were measured by a standard device. The mechanical properties of the treated fibers and the interfacial adhesion properties of UHMWPE‐fiber‐reinforced vinyl ester resin composites were investigated with tensile testing. After 20 min or so of ultraviolet radiation based on 6‐kW corona treatment, the T‐peel strength of the treated UHMWPE‐fiber composite was one to two times greater than that of the as‐received UHMWPE‐fiber composite, whereas the tensile strength of the treated UHMWPE fibers was still up to 3.5 GPa. The integrated mechanical properties of the treated UHMWPE fibers were also optimum. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 463–472, 2004     

Electrical and dielectric properties in carbon fiber‐filled LMWPE/UHMWPE composites with different blend ratios

Carbon fiber (CF) filled low‐molecular‐weight polyethylene (LMWPE) and ultra‐high molecular weight polyethylene (UHMWPE) composites were prepared by the gelation from solution and the kneading in the melting state. The content of carbon fibers was fixed to be 23.5 vol %. The resistivity, positive temperature coefficient (PTC), and dielectric behaviors of the composites became more pronounced with increasing content of LMWPE with much higher thermal expansion than that of UHMWPE. The PTC effect became most significant, when the blend ratio of LMWPE to UHMWPE was 9/1. Beyond 9/1, the PTC effect was less pronounced. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) revealed that the UHMWPE and LMWPE chains within the composite crystallized independently by gelation from solution and were virtually unaffected by the presence of carbon fibers. Consequently, it was confirmed that carbon fibers selectively were localized in the mixed region of LMWPE and UHMWPE for the composite (3/1 and 6/1) and mainly in the region of LMWPE for the 9/1, 12/1, and 15/1 composites. This indicated that the content of carbon fibers within LMWPE region was the highest for the 9/1 composite and the 9/1 composite provides the most significant PTC effect. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 359–369, 2008     

静电纺丝制备SiO2短纤维对聚丙烯冲击性能的影响

采用静电纺丝技术, 结合正硅酸乙酯(TEOS)的溶胶-凝胶反应制备出了直径为500 nm的SiO2短纤维(n-SF). 纤维经过硅烷偶联剂KH570表面处理后, 与聚丙烯(PP)通过螺杆混合制得复合材料. 通过SEM观察, KH570处理过的SiO2短纤维(n-MSF)在PP基体中分散均匀, 界面结合良好. DSC和XRD测试结果表明, n-SF和n-MSF的加入均可提高PP的结晶速率, 同时改变PP中β晶含量, 进而影响冲击强度; 冲击实验结果表明, n-MSF添加量为3%(质量分数)时, 复合材料冲击性能比纯PP提高了40.3%.     

Mechanical properties of interlayer hybrid textile composite materials based on modified aramid and UHMWPE fabrics

Aramid fibers and ultra-high molecular weight polyethylene (UHMWPE) fibers lack active surface functional groups, and the surface is smooth, limiting their practical application in textile composite materials. In this study, zinc oxide nanorods were used to grow on aramid fibers surfaces, and oxygen plasma followed by treatment with a silane coupling agent was used to modify UHMWPE fibers. The effects of surface modification on the surface morphology and composition, and mechanical properties of fibers and composites were investigated. The mechanical response of interlayer hybrid textile composite materials based on modified aramid and UHMWPE fabrics was examined. The results reveal that surface roughness, active surface functional groups, and wettability that can be controlled by treatment conditions and parameters are important for improving interface adhesion. In addition, the interlayer hybridization pattern as a result of using dissimilar layer materials and altering stacking sequence has a great impact on the mechanical behavior of hybrid textile composite materials.     

Influence of finishing oil on structure and properties of multi-filament fibers from cellulose dope in NaOH/urea aqueous solution

Cellulose multi-filament fibers have been spun successfully on a pilot plant scale, from a cellulose dope in 7 wt% NaOH/12 wt% urea aqueous solution pre-cooled to −12 °C. Coagulation was accomplished in a bath with 10 wt% H₂SO₄/12 wt% Na₂SO₄ and then 5 wt% H₂SO₄ aqueous solution. By using different finishing oil, including H₂O, 4% glycerol aqueous solution, 2% polyvinyl alcohol (PVA) aqueous solution, 2% polyethylene glycol octyl phenylether (OP) aqueous solution, mobol and 2%glycerol/1%PVA/1%OP aqueous solution (PGO), we prepared six kinds of the cellulose multi-filaments, with tensile strength of 1.7–2.1 cN/dtex. Their structure and properties were investigated with scanning electron microscope (SEM), ¹³C NMR solid state, wide-angle X-ray diffraction (WAXD) and tensile testing. The cellulose fibers treated with PGO possessed higher mechanical properties and better surface structure than others. Interestingly, although the orientation of the cellulose multi-filaments is relatively low, the tensile strength of the single-fiber was similar to that of Lyocell. It was worth noting that the dyeability of the multi-filament fibers was superior to viscose rayon.     

Effects of different ultrahigh molecular weight polyethylene contents on the formation and evolution of hierarchical crystal structure of high-density polyethylene/ultrahigh molecular weight polyethylene blend fibers

In this paper, the blend fibers of ultrahigh molecular weight polyethylene (UHMWPE) and high-density polyethylene (HDPE) were prepared by solution blending and gel spinning process. The uniformity of the blend fibers has been confirmed by rheological data and thermodynamic unimodal curve. They were further characterized by single fiber strength test, scanning electron microscopy, wide-angle X-ray diffraction, small-angle X-ray scattering, and so forth, to explore the structural evolution mechanism with the change of UHMWPE content. The results showed that when the molar content of UHMWPE was only 2.9 mol%, entanglement appeared in the structure of shish-kebab, and when the proportion reached 20 mol%, an interlocking structure could be observed. With the increase of UHMWPE content, kebab began to be networked, and when the content reached 33 mol%, kebab's orientation reached its peak. After that, the interlocking network structure gradually improved. When the content reached 50 mol%, the shish's orientation reached saturation, and the shish-kebab network became perfect. In addition, with the increase of UHMWPE content, stress-induced recrystallization occurred on the wafer, some kebab would be converted into shish crystals, and when the content exceeded 50 mol%, the microfibers began to merge, and the wafer became denser, but still had entanglements. Our work has proposed a quantitative explanation for the evolution of hierarchical crystal structure of HDPE/UHMWPE blend fibers.