聚丙烯基纳米SiO2复合材料性能研究

采用多种方法对纳米SiO2粒子进行表面处理，并深入探讨了纳米SiO2粒子的分散机理。通过熔融共混法制备了PP／纳米SiO2复合材料，对此复合材料进行了力学性能测试。结果表明：经适当处理的纳米SiO2粒子能均匀地分散在聚丙烯中，对PP的力学性能有显著的改善作用，而且对PP的结晶有明显的异相成核作用。纳米SiO2在用量为2％时可以使PP的缺口冲击强度提高1倍，同时拉伸强度也有很大提高。     

纳米SiO2增强增韧HDPE的研究

采用微胶囊包覆的方法对二氧化硅无机纳米粒子进行表面处理,然后通过熔融共混法制备高密度聚乙烯(HDPE)/SiO2纳米复合材料.力学性能测试及材料断面形貌分析等显示,此改性方法制得的纳米SiO2微胶囊采用常规的熔融混合法就能在基体树脂HDPE中达到纳米级的均匀分散,对基体树脂HDPE具有明显的增强增韧效果.     

纳米SiO2增强增韧HDPE的研究

采用微胶囊包覆的方法对二氧化硅无机纳米粒子进行表面处理．然后通过熔融共混法制备高密度聚乙烯(HDPE)／SiO2纳米复合材料．力学性能测试技材料断面形貌分析等显示．此改性方法制得的纳米SiO2微胶囊采用常规的熔融混合法就能在基体树脂HDPF中达到纳米级的均匀分散，对基体树脂HDPE具有明显的增强增韧效果。     

聚丙烯/纳米SiO2 复合材料的制备和表征

使用熔融共混法制备了聚丙烯（PP）／纳米SiO2复合材料。研究发现，硅烷偶联剂对纳米SiO2在PP中的分散起一定的作用，但不是非常有效。添加马来酸酐接枝聚丙烯（PP—g—MAH）相容剂后，可以使纳米SiO2均匀地分散于PP中。当纳米SiO2的质量分数为2％时性能较优，与纯PP相比，V形缺口冲击强度提高了90％，拉伸强度提高了5％，弯曲强度提高了23％。最后，对PP—g—MAH大幅度改善纳米SiO2在PP中分散效果的机理作了初步推断。     

PP／SiO2纳米粒子复合材料中偶联剂用量的确定

目的：探索聚丙烯／二氧化硅（PP／SiO2）纳米粒子复合材料中偶联剂的最佳用量。方法：首先用熔融共混法制备PP／SiO2纳米粒子复合材料,再通过分析复合材料的力学性能和冲击试样断面的SEM照片来探索硅烷KH－560的最佳用量。结果：硅烷KH－560的用量为SiO2纳米粒子的10％时,PP／SiO2纳米粒子复合材料的综合力学性能最佳。结论：传统的计算处理微米级无机填料硅烷用量的经验公式不能适用于无机纳米粒子。     

有机化纳米SiO2填充尼龙66复合物的结构与性能

通过原位表面修饰法制备了有机化纳米SiO2,用熔融共混法制备了尼龙66/SiO2纳米微粒复合材料并研究了复合材料的力学性能.通过示差扫描量热分析(DSC)和动态力学热分析(DMA)研究了复合材料的结晶性能和动态热机械性能.研究表明,纳米SiO2质量分数为4%的复合材料性能提高较为明显,其中简支梁缺口冲击强度提高51.3%,断裂伸长率提高47.3%,弹性模量提高23.8%;纳米SiO2在尼龙66结晶过程中起到异相成核作用,限制了尼龙66的分子链段运动使得复合材料的玻璃化转变温度提高,提高了尼龙66的结晶速率,降低了结晶度;纳米SiO2质量分数为1%复合材料在0℃时的储能模量较纯尼龙66提高21.1%,损耗模量较纯尼龙66提高83.6%,说明纳米SiO2能改善复合材料的低温脆性.     

纳米二氧化硅粒子增韧聚丙烯的研究

研究了纳米二氧化硅(SiO2)粒子对聚丙烯(PP)的冲击强度和拉伸强度的影响，比较了溶液共混法与聚合法的改性效果差异，并从机理上进行了探讨．研究发现：用溶液共混法制备的纳米SiO2／PP复合材料，其冲击强度在纳米SiO2粒子含量为4％左右时达到最大值，约为未经改性的PP材料的8倍；用纳米SiO2粒子改性的PP材料的拉伸强度与未经改性的PP材料基本一致；在相似的工艺条件下，共混法对PP的增韧效果较聚合法显著．     

Effects of nano-SiO2 on reinforcing and toughening polypropylene

SiO2 nano particle, through surface modification by silicane coupling agent KH-570, was successfully applied to make nano SiO2/PP composite material by the melt-out blending process with twin-screw extruder. Effects of nano SiO2on the reinforcing and toughening of PP were studied by analyzing the material impact broken fracture, the crystal structure and the diameter of SiO2 nano particle using SEM, XRD and TEM, respec-tively. Results showed that the impact strength and the tensile strength of nano SiO2/PP composite material were improved apparently; the impact strength of PP was fracture was increased to 67% when the nano SiO2 content was 4% ; while the nano SiO2 particle upon surface treatment will impose obvious heterogeneous nucleation function over PP crystal.     

纳米ZnO/PP复合材料性能研究

以钛酸酯偶联剂对不同粒径的纳米ZnO粒子进行表面处理 ;采用熔融共混工艺制备了纳米ZnO/PP复合材料 ;并对复合材料力学性能及其结晶性能进行研究。结果表明 :偶联剂改善了复合材料的力学性能 ;平均粒径为 80nm的纳米ZnO质量分数为 4 %时 ,其复合材料的综合性能相对较好 ,复合材料的冲击强度、拉伸强度和弯曲强度均得到不同程度的提高 ;纳米ZnO具有异相成核作用 ,能够起到细化PP球晶的作用。     

PP/SiO2 纳米粒子复合材料中偶联剂用量的确定

目的　探索聚丙烯 /二氧化硅 (PP/Si O2 )纳米粒子复合材料中偶联剂的最佳用量 .方法　首先用熔融共混法制备 PP/Si O2 纳米粒子复合材料 ,再通过分析复合材料的力学性能和冲击试样断面的 SEM照片来探索硅烷 KH-560的最佳用量 .结果　硅烷 KH-560的用量为 Si O2 纳米粒子的 1 0 %时 ,PP/Si O2 纳米粒子复合材料的综合力学性能最佳 .结论　传统的计算处理微米级无机填料硅烷用量的经验公式不能适用于无机纳米粒子     

Preparation and Properties of Heat Resistant Polylactic Acid(PLA)/Nano-SiO_2 Composite Filament

In order to improve the thermal properties of polylactic acid(PLA) filament,nano-SiO_2 was applied to mix with PLA,then they were spun as composite filament by melt-spinning.The dispersion of nano SiO_2 and the fracture surfaces of filaments were studied by scanning electron microscopy(SEM).The properties of composite filament,such as orientation degree,mechanical properties,and surface friction properties,were analyzed.The thermal performances of composite filament were analyzed by differential scanning calorimetry(DSC) and thermo gravimetric analysis(TGA).The results showed that the nano-SiO_2 modified by 5% KH-550 could disperse evenly and loosely in nano-scale,and 1 wt% and 3 wt% nano-SiO_2 dispersed throughout PLA evenly.As the quantity of nano-SiO_2 increased,the properties of composite filament,such as orientation degree,friction coefficient,thermal decomposition temperature,and glass transition temperature,increased more or less.The breaking tenacity increased when 1 wt% SiO_2 was added in PLA,but declined when 3 wt% SiO_2 was added.     

纳米SiO2存在下苯乙烯原位乳液聚合

在纳米二氧化硅(SiO2)存在下,进行苯乙烯(St)原位乳液聚合,制备复合纳米级PS/SiO2微胶囊.着重研究了单体浓度、St/SiO2比、固含量、单体和引发剂的加料方式、聚合温度等因素对苯乙烯转化率和PS/SiO2微胶囊粒径的影响.结果表明,在原位乳液聚合过程中,苯乙烯可插入纳米二氧化硅团聚体的缝隙,随着聚合反应的进行使之崩裂和剥离,并使团聚的纳米二氧化硅重新分散到纳米尺度.St/SiO2比是影响复合微胶囊粒径的主要因素;随着聚合反应的进行,剥离程度加深,复合微胶囊的粒径逐渐减小.     

A Comparative Study on the Pozzolanic Activity between Nano-SiO2 and Silica Fume

The pozzolanic activity of nano-SiO2 and silica fume was comparatirely stndied by X-ray diffraction （ XRD ） , differential scanning calorimetry （DSC）, scanning electron micrascopy （SEM） and the compressive , bond and bending streugths of hardened paste and concrete were also measured. Results indicate that the compressive strength development of the paste made from Ca（OH）2 and nano-SiO2, the reaction rate of Ca（ OH）2 with nano- SiO2 and the velocity of C-S-H gel formation from Ca （ OH）2 with nano-SiO2 showed marked increases over those of Ca（ OH）2 with silica fume. Furthermore, the bond strength at the interface between aggregate and hardened cement paste, and the bending strength of concrete incorporated with 3% .NS increased more than those with SF, especially at early ages. To sum up, the pozzolanic activity of nano-SiO2 was much greater than that of silica fume. The results suggest that with a small amount of nano-SiO2, the Ca（ OH）2 crystal at the interface between hardened cement paste and aggregate at early ages may be effectively absorbed in high performance concrete.     

PET/纳米SiO2复合物的流变性及纺丝性能

聚合物纳米复合材料是现代材料学的重点研究内容之一,对于开发高性能、多功能性材料具有重要意义.本研究采用在合成聚对苯二甲酸乙二醇酯(PET)时直接添加纳米SiO2,制备了可用于纺丝的PET/纳米SiO2复合物.对复合物的流变性、可纺性及纤维力学性能的研究表明:PET/纳米SiO2复合物的熔体流变性属切力变稀流体,随剪切速率的增加,SiO2的增稠作用缓解,熔体粘度下降较大;升高温度也可使熔体粘度有较大下降.因此,可通过提高剪切速率或提高温度改善熔体的流动性能;在SiO2添加量小于2%时,可制得分子量较低、熔体粘度适宜于纺丝的聚酯复合物,该复合物可纺性良好,可用于制备抗起球聚酯纤维.     

Effect of SiO_2 Aerogel-cement Mortar Coating on Strength of Self-Compacting Concrete after Simulated Tunnel Fire

In order to facilitate self-compacting concrete to be better used in tunnel linings that can resist fires,a SiO_2 aerogel-cement mortar coating was prepared.Based on the HC curve,a self compacting concrete cube specimens coated and uncoated with SiO_2 aerogel-cement mortar (SiO_2-ACM) were heated to simulate tunnel fire for 0.5,1,1.5,2,2.5,3 and 4 h,respectively.The residual compressive strength was tested after the specimens were cooled to room temperature by natural cooling and water cooling.The results show that,the damages of specimens become more serious as fire time goes on,but the residual strength of specimens coated with SiO_2-ACM is always higher than that of uncoated with SiO_2-ACM.In addition,the residual strength of specimens cooled by water cooling is lower than that of natural cooling.However,for the specimens coated with SiO_2-ACM,the adverse effects of water cooling are lessened.With the increase of fire time,the protective effect of SiO_2-ACM is still gradually improved.Finally,a formula was established to predict the residual 150 mm cube compressive strength of specimens protected by SiO_2-ACM after a simulated tunnel fire.     

Hydration Mechanism of Cement-based Materials with Different Si-rich Mineral Admixtures

Early hydration mechanism of cement-based materials with silica fume, nano-SiO_2 and silica sol of different contents was investigated, and the detailed effect of these Si-rich mineral admixtures in three stages of early hydration(NG, I, D) using kinetics model was focused. The results showed that silica fume, nano-SiO_2, and silica sol have significant effect on kinetic parameters n, k_1, k_2 and k_3, the fineness and existing form of SiO_2 particles in these Si-rich mineral admixtures are two important factors to affect the hydration process and on the parameters. Through integrated use of methods of hydration heat-Krstulovic-Dabic Modelsynthetical thermal analysis, data of hydration heat were collected, hydration degree was characterized, as well as the resulting crystallization behavior of early hydration, to build a numerical relationship between parameter n and CH contents that n decreases with increasing CH, and thus, a direct connection between hydration heat release behavior and crystallization behavior has been established.     

Coal and gas outburst prevention using new high water content cement slurry for injection into the coal seam

As coal and gas outburst is one of the most serious mine disasters, it is very important to at least control it if not prevent it from occurring. Injecting cement slurry or grouting into the coal seam can strengthen the seam, increase its rigidity coefficient(f), and reduce the volumetric expansion due to gas energy release.This paper reports the results of laboratory experiments on cement-based high water content slurry having different water-cement ratios(W/C) to be used for coal injection. The results show that as the W/C increases, the mobility of the slurry and its setting time increase. The compressive strength and rupture strength, however, are reduced. Furthermore, high W/C grout shows early strength after 7 days, which can be 80% of its 14-day compressive strength. To achieve rapid setting and early strength, the addition of Na_2SiO_3has proven to give the best result, when the concentration of the additive is 3%. The initial and final setting times are 13 and 21 min shorter than samples without Na_2SiO_3, while the compressive strength is more than double. As a retarder, the initial setting time can be extended to 83 min when tartaric acid of 0.4% concentration is added. Through the orthogonal experiment, the optimum recipe of the new high water content slurry has been determined to be: W/C = 2, tartaric acid = 0.2%, Na_2SiO_3= 3%, and12% bentonite. Reinforcement by injection simulation experiments show that the grouting radius of the new slurry mix is 250 mm when the applied grouting pressure is 60 k Pa, 7-day rupture strength and compressive strength are 5.2 and 6.4 MPa, respectively, and are 37% and 88% higher than ordinary cement grout. It can be concluded that the newly developed slurry mix is more effective than the ordinary mix for reinforcing coal and controlling gas outburst.