聚甲醛/不同表面修饰二氧化硅纳米复合材料的力学性能、热性能及结晶行为

将氨基改性纳米二氧化硅(RNS)和甲基改性纳米二氧化硅(DNS)分别加入到聚甲醛(POM)基体中,采用熔融共混法在双螺杆挤出机上制备出POM/RNS和POM/DNS纳米复合材料,并对其力学性能、热性能及结晶行为进行了研究。结果表明,当RNS和DNS的含量较低时,可以提高纳米复合材料的拉伸强度和缺口冲击强度,随着纳米填料含量的增加呈先增加后降低的趋势;而弹性模量则随着纳米填料含量的增加而不断增加;RNS的加入能够大幅度提高POM的热分解温度,而DNS则对POM的最大热分解温度影响不大;RNS和DNS均具有较强的异相成核能力,它们的加入可以促进POM结晶温度的上升,并导致POM晶粒尺寸减小。     

PC/纳米SiO2复合材料的热降解行为

采用熔融共混法制备了聚碳酸酯(PC)/纳米二氧化硅(SiO2)复合材料。采用X射线衍射和扫描电子显微镜研究了PC和PC/纳米SiO2复合材料的结构,采用热重分析了PC和PC/纳米SiO2复合材料的热降解行为,用Kissinger-Akahira-Sunose法研究了PC和PC/纳米SiO2复合材料的热降解动力学。结果表明:PC的内部结构没有发生变化,且纳米SiO2在基体中分散均匀;加入纳米SiO2能显著改善PC的热稳定性,且PC和PC/纳米SiO2复合材料的热降解温度均随升温速率提高呈线性增加;PC和PC/纳米SiO2复合材料的热降解活化能均随转化率升高而增加,且PC/纳米SiO2复合材料的活化能明显高于PC。     

纳米二氧化硅对PBS结晶性能及力学性能的影响

采用热重分析法研究了硅烷偶联剂用量对纳米二氧化硅（SiO2）的表面改性效果;通过差示扫描量热（DSC）、热台偏光显微镜（POM）及力学性能等测试手段研究了改性纳米SiO2对聚丁二酸丁二醇酯(PBS)结晶性能和力学性能的影响。结果表明,在偶联剂用量为5份、渗透剂用量为2份的条件下,纳米SiO2的表面改性效果最好。纳米SiO2有异相成核作用,可以使PBS的结晶速率增大,相对结晶度降低,但对结晶温度的影响不大,仅在高填充量时（10 %）有4 ℃的增幅。随着纳米SiO2含量的增加,PBS的拉伸强度和断裂伸长率先升高后降低,但拉伸强度的变化幅度很小,断裂伸长率则在纳米SiO2含量为1.5 %时达到最大值10.79 %,较纯PBS的7.53 %提高了43.3 %。     

原位聚合法制备共聚POM/SiO_2纳米复合材料结构与性能表征

以三聚甲醛和1,3-二氧戊环为单体,以氟化硼乙醚络合物为引发剂,用原位聚合方法制备共聚POM/SiO2纳米复合材料.使用FESEM和FT-IR研究纳米复合材料的微观形貌和组成,并且使用DSC及XRD等研究纳米复合材料的结晶行为.结果表明:纳米SiO2粒子在POM基体中分散均匀,且达到了纳米级的分散;纳米SiO2粒子的存在未影响共聚POM的分子链结构,POM高分子链与纳米SiO2表面的高能活性点发生了作用(例如氢键、配位键等),但并未发现化学作用的证据;共聚POM/SiO2纳米复合材料的熔点升高;部分纳米粒子充当了成核剂使结晶加快、球晶尺寸减小,还有部分纳米粒子的存在阻碍了片晶的生长,破坏了球晶的对称性.     

可反应性纳米SiO2/尼龙1010复合材料的热性能和结晶行为

采用熔融共混法制备可反应性纳米SiO2(RNS)/尼龙1010复合材料.通过X射线衍射(XRD)、热重分析(TGA)和差示扫描量热法(DSC)研究RNS对尼龙1010的热力学性能和结晶行为的影响.结果表明:RNS的加入没有改变复合材料的结晶形态.但其晶格尺寸发生了一定程度的改变;同时提高了复合材料的热稳定性,使其熔融温度升高.结晶温度降低,结晶程度更加完善.     

PP/纳米SiO2复合材料的非等温结晶动力学

采用差示扫描量热法研究了聚丙烯（PP）/纳米SiO2复合材料的非等温结晶动力学,研究了纳米粒子的成核活性及复合材料的结晶有效能垒。研究结果表明,纳米SiO2起到异相成核的作用,使PP的结晶峰温升高,结晶总速率增大;增容剂马来酸酐接枝聚丙烯(PP-g-MAH)提高了纳米SiO2的成核活性;添加纳米SiO2使复合材料的结晶有效能垒降低,PP-g-MAH使复合材料的结晶有效能垒增大,但低于纯PP的结晶有效能垒。     

ATRP法制备纳米SiO2-g-PBA及其对POM改性

采用原子转移自由基聚合(ATRP)法在纳米二氧化硅(Si02)粒子表面接枝聚丙烯酸丁酯(PBA),产物为纳米siO2-g-PBA,采用透射电镜(TEM)、偏光电子显微镜(PLM)等手段研究了纳米SiO2及纳米SiO2-g-PBA复合粒子的添加对聚甲醛(POM)结晶性能及热稳定性的影响.结果表明.采用ATRP法有少量的PBA接枝了:纳米SiO2表面,且该粒子在POM中分散均匀;纳米SiO2及纳米SiO2-g-PBA复合粒子的添加不改变POM的晶型,但POM的晶粒尺寸变小.a纳米SiO2-g-PBA复合粒于的异相成核作用较纳米SiO2明显;纳米SiO02及纳米Si2-g-PBA复合粒子使POM的结晶温度升高,熔点升高,结晶度升高.纳米SiO2及纳米SiO2-g-PBA复合粒子的添加使得POM的热稳定性得到了提高.且纳米SiO2-g-PBA复合粒子的作用更明显.     

聚甲醛/可反应性纳米SiO2复合材料的等温结晶及热分解行为

采用熔融共混法制备了聚甲醛(POM)/可反应性纳米二氧化硅(RNS)复合材料。通过差示扫描量热仪研究了RNS对POM等温结晶行为的影响,利用热重分析仪研究了该材料的热分解变化,用Avrami方程和Hoffman-Laurititzen理论进行了分析。结果表明,RNS在POM结晶过程中起到了异相成核作用,结晶速率常数K增大,半结晶时间t1/2降低,表面自由能下降,Avrami指数n有所降低,说明RNS改变了POM的结晶和生长过程,RNS提高了POM复合材料的热稳定性,其中,添加5%RNS的POM复合材料起始分解温度提高了32℃,用FOW法和Fried-man法计算其分解过程的表观活化能均高于POM,这说明RNS与POM之间存在着较强的相互作用,RNS既是POM的成核剂又是热稳定剂。     

制样方法对SiO2/PA6复合材料基体PA6结晶熔融行为的影响

采用差示扫描量热法(DSC)研究了原位聚合法和熔融共混法制样方法对纳米SiO2/PA6纳米复合材料结晶熔融行为的影响,结果表明:通过阴离子原位聚合法制备的纳米复合材料,由于采用超声波分散技术,纳米粒子在基体的分散性好。随着纳米粒子含量的升高,纳米粒子的诱导成核能力增强;熔融共混法制得复合材料中,SiO2在机械力的剪切作用下,很难均匀地分散,多以团聚体的形式存在,在PA6基体结晶时,结晶成核的条件相匹配,有较强的成核效应,纳米粒子的含量影响不大。     

可生物降解聚(3-羟基丁酸酯-co-4-羟基丁酸酯）/层状?-磷酸锆纳米复合材料的制备及性能

以可生物降解聚（3-羟基丁酸酯-co-4-羟基丁酸酯）[P(3,4)HB]为基体,有机改性层状化合物?-磷酸锆（OZrP）为增强相,采用溶液插层法制备了P(3,4)HB/OZrP纳米复合材料。分别用X射线衍射仪（XRD）、扫描电镜（SEM）、偏光显微镜（POM）、热重分析仪（TGA）和差式扫描量热仪（DSC）等对其微观结构、热稳定性、结晶行为及降解性能进行了表征与分析。研究表明,具有纳米片层结构的OZrP能均匀分散在P(3,4)HB基体中形成纳米复合结构,OZrP能通过异相成核作用促进P(3,4)HB的结晶,并能促进P(3,4)HB的降解,但降低P(3,4)HB 的热稳定性。     

Effect of functionalized nanosilica on properties of polyoxymethylene‐matrix nanocomposites

Amino group and methyl group functionalized nano‐silica (coded as RNS and DNS) particulates were separately used as nanofillers to prepare polyxymethylene‐matrix (denoted as POM‐matrix) nanocomposites by melt blending. The tensile strength, Young's modulus, and impact toughness of as‐prepared POM‐matrix nanocomposites were measured, and their thermal decomposition behavior and crystallization behavior were analyzed by means of thermogravimetric measurement and differential scanning calorimetry and polarized light microscope. Moreover, the morphology of as‐prepared POM‐matrix nanocomposites was observed with a transmission electron microscope. Results show that incorporating a proper content of RNS and DNS contributes to improve the tensile strength, Young's modulus and impact toughness of POM, and POM‐DNS nanocomposites with a high content of inorganic filler have better mechanical properties than POM‐RNS counterparts. Besides, POM‐matrix nanocomposites have a higher crystallization onset temperature and a smaller grain size than neat POM, which is due to the heterogeneous nucleation effect of DNS and RNS. Moreover, incorporating RNS containing surface amino group helps to increase the thermal stability of POM‐RNS nanocomposites and leads to an increase of initial decomposition temperature by about 27°C; but the introduction of DNS has little effect on the thermal decomposition behavior of POM. The reason lies in that RNS containing surface amino group can strongly chemically interact with thermal decomposed products of POM (it can absorb formaldehyde and formic acid generated via thermal decomposition of POM) but DNS with surface methyl group cannot absorb formaldehyde and formic acid. POLYM. COMPOS., 35:127–136, 2014. © 2013 Society of Plastics Engineers     

Effect of in situ surface‐modified nano‐SiO2 on the thermal and mechanical properties and crystallization behavior of nylon 1010

Nylon 1010 composites filled with two types of surface‐modified SiO₂ nanoparticles (RNS and DNS) were prepared by melt blending. The mechanical properties of the composites were evaluated. The influences of the surface‐modified nano‐SiO₂ on the thermal stability, crystallization behavior, and microstructure of nylon 1010 were investigated by thermogravimetric analysis, differential scanning calorimetry (DSC), X‐ray diffraction, and transmission electron microscopy. And the interfacial interactions between the fillers and polymer matrix were examined using a Fourier transformation infrared spectrometer. It was found that the addition of the surface‐modified nano‐SiO₂ had distinct influences on the thermal stability, mechanical properties, and crystallization behavior of nylon 1010. RNS and DNS as the fillers had different effects on the mechanical properties of nylon 1010. The composites filled with RNS at a mass fraction of 1–5% showed increased break elongation, Young's modulus, and impact strength but almost unchanged or even slightly lowered tensile strength than the unfilled matrix. The DNS‐filled nylon 1010 composites had obviously decreased tensile strength, whereas the incorporation of DNS also contributed to the increase in the Young's modulus of nylon 1010, but less effective than RNS. Moreover, the nylon 1010 composites had better thermal stability than the neat polymer matrix, and the composites filled with RNS were more thermally stable than those filled with DNS. The difference in the crystallinity of neat nylon 1010 and its composites filled with RNS and DNS was subtle, although the surface‐modified nano‐SiO₂ could induce or/and stabilize the γ‐crystalline formation of nylon 1010. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of particle size on thermomechanical properties of particulate polymer composite

Particulate composite materials (PCM) consisting of a matrix reinforced by micro to nano-sized dispersed phase are receiving the attention of designers as a promising futuristic materials. This study unearths the thermal and mechanical behavior of maleic anhydride grafted polypropylene/silica (MA-g-PP/silica) composites for reinforcement ranging from micro- to nano-size. The monodisperse silica spherical particles were used in all the formulations of composites. Further the volume fraction was kept the same in all the compounded thermoplastic composites ranging from 100 nm to 130 μm in a co-rotating conical twin-screw micro-compounder. The micrographs were obtained from transmission electron microscopy (TEM) and the scanning electron microscopy (SEM). The SEM and TEM results revealed a good dispersion of the silica spheres within the MA-g-PP matrix. The compounded composite materials were injection molded to fabricate tensile test specimens (ASTM D638 type V) and tested for tensile properties. In order to investigate the effect of particle size on crystallite structure of the matrix, the composites were tested on differential scanning calorimeter and X-ray diffraction (WAXD). The thermal stability and degradation kinetics were studied via thermogravimetric analysis. The results show increase in crystallization rate, crystallinity percentage, Young’s modulus, strength and thermal stability of MA-g-PP by addition of the silica particles. Further it was observed that the small-sized dispersed phase had better overall thermal and mechanical behavior than its larger sized counterpart.     

Microinjection molding of polyoxymethylene/multiwalled carbon nanotubes composites with different matrix viscosities

This study features the effect of matrix viscosity on the properties of carbon nanotubes reinforced polyoxymethylene (POM/CNT) microparts, which were obtained via melt blending and subsequent microinjection molding (μIM) processes, under a defined set of processing conditions. Results of compression molding and μIM were compared to assess the influence of processing methods (i.e., thermomechanical history) on the electrical and thermal conductivities, melting and crystallization behavior as well as the thermal degradation resistance of POM/CNT composites. Filler orientation in POM/CNT microparts was evaluated using Raman spectral analysis. The electrical conductivity measurements revealed that matrix viscosity plays a significant role in determining the distribution of CNT. Also, the extreme shearing conditions that prevail in μIM are unfavorable for the construction of random conductive pathways within the micromoldings, as corroborated by transmission electron microscopy. Although the thermal degradation resistance of both POM/CNT composites and corresponding microparts deteriorated with increasing filler concentration, samples prepared with higher matrix viscosity showed higher thermal stability when compared with lower matrix viscosity counterparts. This study provides valuable insights into fabricating multifunctional microparts for potential industrial applications in replacement of metallic components for precision electronic instruments.     

Study on Mechanical and Tribological Property of Nanometer ZrO2-filled Polyoxymethylene Composites

The polyoxymethylene (POM) matrix composites with different contents of nano-ZrO₂ particles were prepared. The effect of ZrO₂ on the crystallization and thermal property of POM were investigated through polarizing microscopy (PLM) and differential scanning calorimetry (DSC). The surface hardness and the tribological performance were measured by Rockwell sclerometer and ring-on-block tribometer, respectively. The surface morphology of the wear scar were observed by scanning electron microscope (SEM). The results show that the nano-ZrO₂ acted as the nucleation agent in POM and decreased the crystallite size of POM, increased the crystal growth rate. The wear resistance was enhanced and the friction coefficient was changed a little.     

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。     

POM/GF-MWCNTs复合材料的制备及其性能研究

将经γ氨丙基三乙氧基硅烷（KH550）处理后的多壁碳纳米管（MWCNTs）接枝到玻璃纤维（GF）表面,制成GF-MWCNTs复合填料,通过双螺杆挤出机熔融共混制备出聚甲醛（POM）/GF-MWCNTs复合材料,并对其力学性能、热性能及电性能进行了测试。结果表明,GF-MWCNTs添加量较低时,复合材料的拉伸强度和缺口冲击强度都有所提高,且分别在3 %（质量分数,下同）和1 %时达到最大值,之后则随着填料含量的增加而不断降低;当GF-MWCNTs的添加量达到10 %时,复合材料的拉伸强度和缺口冲击强度已然低于纯POM;加入GF-MWCNTs提高了复合材料的热稳定性,使POM的结晶温度和结晶度提高;GF-MWCNTs能降低复合材料的体积电阻率,但由于未在POM基体中形成逾渗网络,复合材料导电性提高并不明显。     

Effect of organosilane coupling agents on microstructure and properties of nanosilica/epoxy composites

Three types of silane coupling agents, γ‐aminopropyltriethoxysilane, γ‐glycidoxypropyltrimethoxysilane, and γ‐methacryloxypropyltrimethoxysilane, were used as modifiers to modify the surface of the nanosilica, respectively, and the nanocomposites of the epoxy resin filled with nano‐sized silica modified by three silane coupling agents were prepared by physical blending. The properties of the modified silica nanoparticles were characterized by Fourier transform infrared spectrum and particle‐size analyzer. The microstructure, mechanical behavior, and heat resistant properties of the nanocomposites were investigated by transmission electron microscopy, scanning electron microscopy, thermo gravimetric analyses, differential thermal gravity, differential scanning calorimetry, and flexural tests. The results showed that these modifiers are combined to the surfaces of nanosilica by the covalent bonds, and they change the surface properties of nanosilica. The different structures of coupling agents have different effects on the dispersibility and stability of modified particles in the epoxy matrix. In comparison, the silica nanoparticles modified by γ‐glycidoxypropyltrimethoxysilane exhibit a good dispersivity. The nanocomposites with 4 wt% weight fraction nanosilica modified by γ‐glycidoxypropyltrimethoxysilane have higher thermal decomposing temperature and glass transition temperature than those of the other two composites with the same nanosilica contents, and they are raised by 43.8 and 8°C relative to the unmodified composites, respectively. The modified silica nanoparticles have good reinforcing and toughening effect on the epoxy matrix. The ultimate flexural strengths of the composites with 4 wt% nanoparticles modified by γ‐aminopropyltriethoxysilane, γ‐glycidoxypropyltrimethoxysilane, and γ‐methacryloxypropyltrimethoxysilane are increased by 10, 30, and 8% relative to the unmodified composites, respectively. The flexural fracture surfaces of modified composites present ductile fracture features. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers     

聚酰胺酰亚胺/二氧化硅复合材料的制备及性能

将二氧化硅(SiO_2)纳米颗粒用阳离子表面活性剂——十六烷基三甲基溴化铵(CTAB)修饰后,加入到含有L–丙氨酸的新型光学活性聚酰胺酰亚胺(PAI)中,采用新型超声波空化技术,制备出一种功能性的PAI/SiO_2复合材料。研究了SiO_2纳米颗粒含量对复合材料的复合情况和耐热性能的影响。利用傅立叶变换红外光谱仪、X射线衍射仪、扫描电子显微镜、透射电子显微镜、热重分析仪等对复合材料的结构、表面形貌和热稳定性进行表征。结果表明,SiO_2纳米颗粒与PAI成功复合;当SiO_2纳米颗粒含量为10%时,复合材料的表面形貌最佳,SiO_2纳米颗粒均匀分散在PAI基体中;复合材料失重10%时,热分解温度可达410℃,800℃下的残炭率为45.0%,极限氧指数为35.5%,热稳定性有了一定的提升。