尼龙6/氯化钾复合材料的结晶与性能

通过熔融共混法制备了不同KCl含量下的尼龙6(PA6)/KCl复合材料,采用示差扫描量热仪(DSC)、流变仪、红外光谱(IR)、电子拉伸机等研究了KCl含量对PA6/KCl复合材料结晶行为、流变性能及力学性能的影响,并研究了其受限机制.力学性能研究结果表明,随着KCl含量的增加,PA6/KCl复合材料拉伸强度和冲击强度呈现出先增大后减小的趋势,在KCl含量为3 phr时,复合材料拉伸强度和冲击强度分别达到最大值82.67 MPa和7.34 k J/m~2,较纯PA6分别增加了10.8%和34.68%,动态力学性能测量结果表明,在测量温度范围内,复合材料的储能模量均高于纯PA6,在25℃体系储能模量(G')随KCl含量的增加而增大,复合体系抵抗弯曲变形能力增加,而结晶行为研究结果表明,增加KCl的含量,PA6/KCl复合材料的成核温度、晶体生长温度、熔融温度及玻璃化转变温度均向低温方向移动,成核密度和成核速率也逐渐减小,结晶能力下降,结晶度减小,结晶度由原来25.30%变为19.34%,而结晶诱导时间逐渐增加.流变性能研究结果表明,随着KCl含量的增加,复合体系的零剪切黏度逐渐增加,且所有的体系均呈现出假塑性流体行为,剪切变稀现象越来越明显,特征松弛时间τ_1、τ_2和τ_3逐渐增加,复合体系的松弛机制发生变化.     

改性木纤维/聚乳酸复合材料的制备与性能研究

通过双螺杆挤出机共混制备了不同方法改性的木纤维/聚乳酸可生物降解复合材料,利用DSC、SEM、DMA、冲击和拉伸力学性能测试等手段,对比分析了木纤维的不同改性处理方式对复合材料热性能、界面形态和力学性能的影响.结果表明:复合材料的聚乳酸结晶动力学明显得到改善,木纤维促进了聚乳酸的异相成核过程.改性后的木纤维聚乳酸复合材料界面结合和力学性能均得到明显改善,以性能最优的硅烷偶联剂处理的木纤维和聚乳酸复合材料为例,其拉伸应力(62.1MPa)、杨氏模量(4525.0 MPa)和冲击强度(11.5k J/m~2)比纯聚乳酸分别提高2.9%,36.0%和14.0%.     

成核剂对PHBV等温结晶行为的影响

用DSC方法测定了氮化硼及滑石粉成核剂对 (β 羟基丁酸酯 与 β 羟基戊酸酯 )共聚物 (简称PHBV)等温结晶行为的影响 .结果表明 ,Avrami方程指数n、成核机理、晶体生长方式基本上不受成核剂的影响 .少量的成核剂可使结晶成核自由能降低 ,结晶速率加大 ,其中氮化硼的效果最为显著     

PHB与PHBV的β晶结构及其与力学和降解性能关系的研究进展

聚(3-羟基丁酸酯)(poly(3-hydroxybutyrate),PHB)和聚(3-羟基丁酸酯-co-3-羟基戊酸酯)(poly(3-hydroxybutyrate-co-3-hydroxyvalerate),PHBV)的结晶速率慢,二次结晶现象严重导致其在室温存放过程中性能劣化。通过拉伸诱导形成β晶可以有效抑制二次结晶现象,使机械性能提高并在室温下稳定。本文综述了PHB与PHBV的β晶结构及形成与转化机制的研究现状。重点概述了β晶结构对力学性能的影响及其增韧机制的研究进展,简要概述了β晶结构与降解性能之间的关系,最后对β晶结构研究现状中存在的空白进行了分析。     

成核剂对PHBV等温结晶行为的影响

用DSC方法测定了氮化硼及滑石粉成核剂对(β-羟基丁酸酯-与-β-羟基戊酸酯) 共聚物(简称PHBV)等温结晶行为的影响. 结果表明,Avrami方程指数n、成核机理、晶体生长方式基本上不受成核剂的影响.少量的成核剂可使结晶成核自由能降低,结晶速率加大,其中氮化硼的效果最为显著.     

月桂酸碱金属离子盐/芳基杂环磷酸铝盐复配体诱导等规聚丙烯结晶成核作用

以芳基杂环磷酸铝盐(AHP-Al OH)作为成核主体,分别含有Li+、Na+、K+3种碱金属离子的月桂酸盐(alkali metal salt of lauric acid,AMSLA)为配体,研究了该类复配体系协效诱导等规聚丙烯(i PP)成核作用规律.通过偏光显微观察、示差扫描量热分析、力学性能测试、光学性能测试以及耐热性能表征等手段,研究不同碱金属离子对复合材料结晶结构、结晶行为以及力学性能、光学性能、耐热性的影响.结果表明,Li L、Na L和KL对i PP的成核作用较差,对球晶尺寸的细化不明显,平均尺寸为161μm,与纯i PP在球晶尺度在同一数量级,结晶温度提高小于6.5℃,成核有效性低于20%,对复合材料力学性能、光学性能及耐热性的改善非常有限;APH-Al OH对i PP的成核作用达到中等水平,晶体尺寸比纯i PP减小了1个数量级,达到16μm,结晶温度提高13.7℃,成核有效性提高到45.4%,力学性能,光学性能及耐热性同样达到中等水平;Li L、Na L和KL与APH-Al OH复配后对i PP的球晶尺度迅速减小至5μm以下,比纯i PP球晶尺寸小2个数量级,结晶峰值温度可提高20℃以上,成核有效性高达60%以上,拉伸强度、弯曲强度、弯曲模量平均分别提高15.0%、44.2%、64.0%.雾度值平均下降72.8%,透光率平均增加13.9%,热变形温度平均升高53.8%.AMSLA和APH-Al OH之间表现出极强的协效成核作用,AMSLA中碱金属阳离子对复配体之间的协效成核作用影响对不同性能之间有不同表现,其对结晶峰值温度,力学性能、耐热性能方面的影响表现为Na+K~+Li~+,而对光学性能方面表现为Li~+Na~+K~+.     

具有环状结构的二氧化硅微聚集体的制备、表征及应用

通过溶胶-凝胶法制备二氧化硅溶胶,并采用喷雾干燥法对其进行形态调控.扫描电镜(SEM)结果表明,喷雾干燥使二氧化硅颗粒发生了形态重组,形成均匀的具有环状结构的二氧化硅微聚集体(PC16MS).通过熔融共混制备了二氧化硅/聚丙烯(PP)纳米复合材料,研究了PC16MS的加入对其微观结构、晶体结构、结晶行为、球晶形态、结晶成核密度和球晶生长速率等方面的影响.采用差示扫描量热(DSC)、偏光相差显微镜(POM)和广角X射线衍射(WAXRD)分析表明,在PP结晶初始阶段,PC16MS的加入大幅度提高了基体材料的成核密度,且使晶粒细化,缩短了结晶时间;当添加2%(质量分数)的PC16MS时,复合材料的结晶温度相对于纯PP提高了10.4℃,成核效率达到39.1%,优于大部分无机成核剂的成核效率.在相同条件下,添加2%未经过喷雾干燥处理的纳米二氧化硅(NC16MS),复合材料的结晶温度相对于纯PP提高3.26℃,成核效率达到12.3%.结果表明,喷雾干燥使二氧化硅颗粒发生了形态重组,形成的均匀介稳态微聚集体在熔融挤出过程中重新分散成纳米粒子,从而有效提高了二氧化硅作为成核剂的成核效率.     

拉伸力场主导作用下硫酸钙晶须(CSW)/PBS复合材料的制备与性能研究

利用基于拉伸力场主导作用下的叶片塑化挤出机分别制备硫酸钙晶须(CSW)含量为0、5%(wt)、10%(wt)、15%(wt)、20%(wt)的硫酸钙晶须(CSW)/PBS复合材料,并讨论了CSW的含量对复合材料力学性能、热稳定性、结晶性能的影响。测试结果表明:当CSW的添加量为PBS的15%(wt)时,复合材料的综合力学性能最优,拉伸模量,弯曲模量和弯曲强度分别提高;随着CSW含量的增加,球晶尺寸减小,成核密度增加,结晶温度也有显著提高;引入CSW对PBS的熔融行为没有影响;热失重分析表明CSW有助于提高复合材料的热稳定性。     

聚丙烯/累托石纳米复合材料的非等温结晶动力学研究

在双螺杆挤出机上熔融共混制备了聚丙烯 (PP) 有机累托石 (OREC)纳米复合材料 ,采用广角X 射线衍射 (WAXD)定性地分析了PP OREC纳米复合材料及纯PP的结晶形态 ,由半峰宽定性地判断了对应晶面法向的晶粒的大小 .结果表明有机累托石没有改变聚丙烯的结晶晶型 (纳米复合材料主要还是α晶型 ) ,但是细化了晶粒的尺寸 .采用差示扫描量热法 (DSC)定量地研究了复合材料的非等温熔融结晶动力学 ,对所得数据分别用Jeziorny法的Mo法进行了处理 ,表明非等温结晶动力学参数Zc 及Avrami指数n随冷却速率的增加而增加 ,复合材料的Avrami指数n大于纯PP的n ;对相同配比的纳米复合材料 ,随着结晶度的增加 ,单位结晶时间里达到一定结晶度所需要的降温速率F(T)增大 ,对同一个设定的结晶度 ,纳米复合材料的F(T)比纯PP的小 ,说明需要的降温速率减小 .所有这些均说明有机累托石可作为聚丙烯的结晶成核剂 .     

多壁碳纳米管/聚丙烯复合材料的晶型及非等温结晶动力学

采用熔融共混法制备了多壁碳纳米管/聚丙烯(MWNT/PP)复合材料,利用X射线衍射法(XRD)、差示扫描量热法(DSC)分别研究了纯聚丙烯(PP)及MWNT/PP复合材料的晶型和非等温结晶动力学行为,并运用Mo法研究了纯PP及MWNT/PP复合材料的非等温结晶动力学行为。结果表明,多壁碳纳米管(MWNT)的加入使PP发生了由β晶型向α晶型的转变。MWNT在结晶过程中具有异相成核效应,提高了PP的结晶温度和结晶速率。MWNT/PP复合材料的结晶活化能均明显高于纯PP。MWNT的加入使PP在单位时间内达到一定结晶度所需的降温速率减小。     

纳米Al_2O_3改性双酚A型环氧丙烯酸酯的制备与性能研究

选用硅烷偶联剂KH570对纳米Al_2O_3进行表面改性处理,并用改性后的Al_2O_3对双酚A环氧丙烯酸酯进行复合改性,研究了纳米Al_2O_3含量(1%(wt)~5%(wt))对树脂性能的影响。结果表明:改性纳米Al_2O_3质量分数为5%时的复合材料的体积收缩率最小,为6.48%;粒子质量分数为2%时,树脂的凝胶率最大,为88.3%;热失重测试结果表明,改性纳米Al_2O_3提高了树脂的热稳定性;拉伸性能显示,随着改性纳米Al_2O_3质量分数的增加,复合材料的拉伸强度先升高后下降,当改性纳米Al_2O_3质量分数为3%时,复合树脂拉伸强度最大,为34.74MPa,与未改性树脂相比,拉伸强度提高了108.27%。本文所制备的改性光敏树脂可适用于3D打印环境。     

碳纳米管改性聚苯硫醚熔纺纤维的结构与性能研究

将多壁碳纳米管(MWCNTs)和聚苯硫醚(PPS)经过熔融挤出后制备成复合材料切片,并采用熔融纺丝法制得碳纳米管改性聚苯硫醚复合纤维.采用扫描电镜(SEM)、拉曼光谱、示差扫描量热分析(DSC)、动态机械分析(DMA)以及力学性能测试等表征手段研究了复合纤维中碳管的分散状态,与基体的界面作用,复合纤维的结晶性能以及力学性能,从而探讨了聚苯硫醚/碳纳米管复合纤维体系的微观结构与宏观性能之间的关系.研究表明,聚苯硫醚分子结构与碳纳米管之间具有的π-π共轭作用使碳管较为均匀的分散在基体中,界面结合较为紧密.同时熔融纺丝过程中的拉伸作用使碳管进一步解缠并使碳管沿纤维拉伸方向取向.另一方面,拉曼光谱显示拉伸作用有效地增强了界面作用,有利于外界应力的传递.碳管的良好分散以及强的界面作用使复合纤维力学性能得到大幅度的提高,当碳管含量达到5 wt%时,复合纤维的模量有了明显的提高,拉伸强度较纯PPS纤维提高了近220%.     

Crystallization behavior, thermal and mechanical properties of PHBV/graphene nanosheet composites

Biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/graphene nanosheet (GNS) composites were prepared via a solution-casting method at low GNS loadings in this work. Transmission electron microscopy revealed that a fine dispersion of GNSs was achieved in the PHBV matrix. The thermal properties of the nanocomposites were investigated by thermogravimetric analysis, and the results showed that the thermal stability of PHBV was significantly improved with a very low loading of GNSs. Nonisothermal melts crystallization behavior, spherulitic morphology and crystal structure of neat PHBV and the PHBV/GNSs nanocomposites were investigated, and the experimental results indicated that crystallization behavior of PHBV was enhanced by the presence of GNSs due to the heterogeneous nucleation effect; however, the two-dimensional (2D) GNSs might restrict the mobility of the PHBV chains in the process of crystal growing. Dynamic mechanical analysis studies showed that the storage modulus of the PHBV/GNSs nanocomposites was greatly improved.     

磺化石墨烯/天然橡胶复合材料的性能研究

以磺化石墨烯为填料,将其填充到天然胶乳中,混合均匀后共沉淀,采用传统橡胶加工方法制备了天然橡胶复合材料。对磺化石墨烯的结构和形貌进行了表征,测定了硫化胶的力学性能、耐磨性能、透气性能和导热性能。研究结果表明:磺化石墨烯表面含有丰富的活性官能团,为少层片状结构,硫化胶的力学性能、耐磨性得到了提高,而透气性和导热性有所下降。当石墨烯添加量为2.0%(wt)时,复合材料的拉伸强度最大为27.06MPa;磨耗体积仅为0.08cm~3;导热系数最小为0.42W/(m·K);透气量最低,为1.98×10~(-4)cm~3/(m~2·d·Pa)。     

Mechanical properties and enzymatic degradation of poly[(R)-3-hydroxybutyrate] fibers stretched after isothermal crystallization near Tg

Poly[(R)-3-hydroxybutyrate] (P(3HB)) fibers with high tensile strength were prepared by stretching the fibers after isothermal crystallization near the glass transition temperature. Two samples with different molecular weights (M_w = 0.7 × 10⁶ and 4.3 × 10⁶) were used to investigate the effect on tensile strength. Increasing the time for isothermal crystallization of P(3HB) fibers resulted in a decrease in the maximum draw ratio. But, the tensile strength of P(3HB) fibers increased remarkably when the isothermal crystallization time was prolonged to more than 24 h. The tensile strength of low-molecular-weight drawn fibers was higher than that of high-molecular-weight fibers. Therefore, it can be concluded that this procedure does not increase the tensile strength of the high-molecular-weight drawn fibers. This is because, in this drawing method, small crystal nuclei grow initially during the isothermal crystallization process. Then, the molecular chains between the small crystal nuclei that acted as the entanglement points are oriented by stretching. In the case of the high-molecular-weight fibers, because the molecular length between the entanglement points of the small crystal nuclei is too long, the molecular chains are not sufficiently oriented by the stretching process. However, in the case of the low-molecular-weight fibers, the molecular length is suitable for generating the extended chains. Based on the result of X-ray analysis of P(3HB) fibers stretched after isothermal crystallization, fibers have the oriented α-form crystal with 2₁ helix conformation and β-form with planar zigzag conformation. The enzymatic degradation of the stretched P(3HB) fibers was performed by using an extracellular PHB depolymerase purified from Ralstonia pickettii T1. The enzymatic erosion rate of β-form was faster than that of α-form in the P(3HB) fibers stretched after isothermal crystallization.     

β-羟基丁酸与β-羟基戊酸共聚物 (PHBV)/蒙脱土纳米复合材料的结构与性能

用溶液复合法成功地制备了插层型PHBV／蒙脱土纳米复合材料。采用X射线衍射（XRD）和透射电子显微镜（TEM）研究了复合材料的结构，硅酸盐片层间距从1.8nm升至2.4nm左右。同时研究了复合材料的结晶，熔融，动态力学行为和力学性能，发现有机蒙脱土的加入，可以加快PHBV的结晶,降低熔融温度，使基体的玻璃化转变温度升高，提高了材料的力学性能，有机蒙脱土含量在3％时，其综合性能最佳。     

高强度聚(R-3-羟基丁酸酯-co-R-3-羟基己酸酯)纤维的制备及其力学性能的调节

通过优化聚(R-3-羟基丁酸酯-co-R-3-羟基己酸酯)(PHBHHx)原纤维的制备工艺,采用较低的挤出温度,极大加快了原纤维的结晶速率,缩短了后续加工所需时间.随后通过“等温结晶-拉伸-固定长度退火”的方法制备了力学性能优异的PHBHHx纤维,纤维平均拉伸强度达262 MPa,断裂伸长率大于120％.利用二维X射线衍射和拉曼光谱研究了纤维的晶体结构,结果表明高强度的PHBHHx纤维中晶区和非晶区的分子链都具有很好的取向性,并且纤维中没有形成β晶结构.进一步研究发现通过改变退火工艺,可以很方便地调节纤维的力学性能,使得PHBHHx材料可以广泛应用于不同的领域.     

Preparation of Low-dielectric Permittivity Polyimide Resins with High Surface Activity from Chemically Bonded Hyperbranched Polysiloxane

Thermosetting resin matrix is the key component of advanced wave-transparent composites,where low dielectric constant,excellent processability,high thermal stability,as well as good bonding ability are required for resins.Herein,we prepared a series of phenylethynyl terminated polyimide(PI)resins by grafting amine-functionalized hyperbranched polysiloxane(HBPSi)to PI chains during the in situ polymerization.The effects of HBPSi on the processability of oligomers,molecular packing,thermal stability,dielectric property and bonding ability to reinforce Kevlar fibers of the cured PI/HBPSi composite resins have been examined in detail.The dielectric constants of the cured composite resins were greatly reduced from 3.29 to 2.19 without compromising its processability and thermal stability.Meanwhile,the 10 wt％HBPSi-containing PI resin demonstrated better bonding ability to reinforce fibers with the interfacial shear strength(IFSS)of 37.64 MPa,compared with that of neat PI-6 matrix(27.34 MPa),and better adhesion to metal with the lap shear strength of 10.48 MPa,50％higher than that of neat resin PI-6(6.98 MPa).These resultant PI/HBPSi composite resins exhibit excellent comprehensive properties,indicating their great potential as low-dielectric constant resin matrix in radar radome.     

Synthesis and Characterization of Acrylated Epoxidized Castor Oil Nanocomposites

Renewable resource-based epoxidized castor oil (ECO) was synthesized and used as a prime material to develop acrylated epoxidized castor oil (AECO) networks. AECO nanocomposites were prepared by the sol-gel method from organo-modified montmorillonite (OMMT) clay and silane. It was found that the AECO/1 wt.% OMMT system increased in tensile strength from 28 to 37 MPa and flexural strength from 54 to 63 MPa as compared with the AECO system. The non-isothermal cure kinetics of the bio-based systems was studied using differential scanning calorimetry. The activation energy of the AECO/OMMT system obtained from Kissinger and Flynn-Wall-Ozawa models is lower than that of AECO system.     

Simultaneous Enhancement of Toughness and Strength of Stretched iPP Film via Tiny Amount of β-Nucleating Agent under "Shear-free"Melt-extrusion

Herein,isotactic polypropylene films with small β-nucleating agent content were fabricated via a melt-extrusion-stretched technology with intended "shear-free" in barrel and die.Compared with neat films,the tensile strength,elongation at break and strain energy density at break of iPP film with 0.05 wt％ β-nucleating agent are significantly improved by 13.8％,39.6％ and 90.6％,respectively,indicating the simultaneously enhanced toughness and strength.Additionally,the β-crystal content gradually increases with increasing β-NA content,while the relative total daughter content of α-and β-crystal exhibits opposite tendency.Moreover,nucleation and crystal growth induced by various β-NA contents are different.This work proves an efficient strategy to enhance mechanical properties of isotactic polypropylene film via controlling elongation flow and addition of appropriate β-NA content.