HDPE/CB高分子导电复合体系的单轴形变与压阻行为

根据基体形变及其与渗流网络结构之间的关系,研究了高密度聚乙烯(HDPE)/炭黑(CB)复合材料压阻行为的发生机制及其影响稳定性的力学因素.结果表明,单轴压阻行为的产生源于材料受外力变形而导致的渗流网络微结构变化,且这种变化强烈依赖于填料含量.当填料含量较低时(渗流阈值附近),体系电阻率随压力升高而表现为电阻正压力系数行为;当填料含量较高时,体系电阻率随压力升高显现电阻负压力系数效应.完全卸载的零压力下,电阻基线随压缩循环随循环次数增大而发生漂移,这种漂移与轴向残余压缩应变有关,可以通过增加循环次数来加以稳定.交联可以减小残余压缩应变,并抑制高填充复合体系电阻基线的漂移.     

Mucin from loach skin mucus and its interfacial behavior on gold surface

Loach skin mucin was isolated from loach skin mucus and found to be similar to mammalian mucins in many aspects, i.e., low amino acid residue content, high molecular weight, presence of hydrophobic blocks and gel-forming characteristics in water. However, loach skin mucin can form a weak gel in water at a much lower concentration （3 mg/mL） than mammalian mucins, indicating its good hydrophilicity. Loach skin mucin can also form a stable adsorption layer on gold surface in aqueous environment, owing to the existence of hydrophobic blocks within mucin. The nature of high hydrophilicity and interfacial behavior give loach skin mucin potential as excellent material for use in solid-water interfaces for antifouling and lubrication, and should be crucial to the versatile functions of loach skin mucus.     

Effects of nanosilica on crystallization and thermal ageing behaviors of polyethylene terephthalate

The effects of nanosilica(Si O2) on crystallization and thermal aging behaviors of polyethylene terephthalate(PET) have been studied using differential scanning calorimetry(DSC) and polarized optical microscopy(POM), viscometry, tensile testing and scanning electron microscopy(SEM). For non-isothermal and isothermal crystallizations, the crystallization rate of PET increases considerably with increasing content of Si O2 providing a large number of nucleation sites, but the relative crystallinity of the nanocomposites has little differences with that of neat PET. According to POM observation, the nucleation of PET becomes faster and the nucleation density increases significantly with increasing Si O2 content. For PET and its nanocomposites thermally aged at 190 °C, the results of intrinsic viscosity, carboxyl content and tensile test show that the degradation rate of PET is reduced with the addition of a small content of Si O2, but the degradation rate increases with further addition of Si O2, owing to the dual effect of Si O2 on PET degradation.     

Influence of ZnSt2 on structure of acrylate-based ionomers with different lanthanide (La(III)) ion and acid contents

A series of acrylate processing aid（ACR）-based ionomers with different lanthanide（La（Ⅲ）） ion and acid contents were synthesized,and the interaction between ionomer and zinc stearate（ZnSt₂） was investigated immediately after thermally annealing the ionomer/ZnSt₂（3/1 in weight） mixtures at 180℃.The results revealed that the ion groups in ionomer have a strong interaction with ZnSt₂.The annealed mixtures contained hot alcohol extractable and unextractable ZnSt₂.The melting of ZnSt₂ and the thermal behavior of the ionomer in the annealed mixtures were seriously influenced by the contents of La（Ⅲ） and acid in the ionomers.The ionomer containing 0.25 mmol/g acid and 0.37 mmol/g La（Ⅲ） has a detectable cluster phase.Annealing its ZnSt₂ mixture could break down the cluster phase and lower glass transition temperature of the ionomer matrix.However,washing away the extractable ZnSt₂ led to the reappearance of the cluster transition temperature and return of the glass transition temperature of matrix to the original position.     

多壁碳纳米管填充聚苯乙烯熔体的恒温依时性动态模量逾渗行为

在恒温(170～190℃)热处理过程中,多壁碳纳米管(MWCNTs)填充聚苯乙烯(PS)熔体发生动态模量逾渗(DMP)行为,且该行为服从时-温叠加(TTS)原理.MWCNTs体积分数(φ)低于逾渗阈值(φc)时,填充熔体在恒温热处理过程中保持类液行为,热处理对MWCNTs分散状态无显著影响,动态储能模量(G')与动态损耗模量(G″)活化能(EG'与EG″)分别高于、低于PS黏流活化能(Eω),而与PS熔体恒频动态模量活化能相一致;φ>φc时,热处理促成MWCNTs进一步团聚,填充熔体在热处理过程中发生类液-类固转变,EG'与EG″均低于Eω,而动态逾渗时间活化能(Et'与Et″)显著高于Eω且随φ增高而增大.在逾渗转变区,EG'与EG″发生不连续变化.PS/MWCNTs复合体系的恒温依时DMP行为与MWCNTs聚集所导致的三维弹性网络的形成密切相关,PS大分子终端松弛不是决定DMP的关键因素.     

橡胶材料的结构与黏弹性

橡胶基体与补强剂粒子通过界面相互作用而形成高度"结构化"的三维黏弹性材料.讨论了结合橡胶(BdR)形成机制、分子弛豫特性、补强机理、非线性黏弹性的基础研究进展,分析了已有研究结果所存在的矛盾或争议,结合本课题组在高填充橡胶材料黏弹性方面的研究,探讨了结构-性能关系并提出展望.虽然BdR形成机制(物理吸附、化学吸附)、补强机理(针对"孤立粒子"的Einstein-Smallwood、Guth-Gold方程及其修正形成、针对"粒子团簇"的粒子簇动态团聚模型、针对"粒子网络"的逾渗模型和拥挤网络模型)、非线性行为(粒子-粒子相互作用说、粒子-橡胶(界面)相互作用说、粒子网络说、互穿网络说)等长期存在争议,长达一个多世纪的研究已基本弄清橡胶材料的结构(动力学)非均质性、应变(应变速率)放大效应、界面相互作用(粒子表面高分子存在能动性梯度)等基本事实.在分析BdR对橡胶黏弹行为影响研究结果的基础上,提出今后橡胶科学研究的两个重要方向,即将结构(动力学)非均质性纳入补强与非线性黏弹性理论范畴,以BdR或粒子-橡胶凝胶为纽带建立微观效应(多时间尺度的分子运动、多空间尺度的粒子分散状态)-宏观性能关系.     

部分水解聚甲基丙烯酸甲酯/氢氧化钙复合物对硬质聚氯乙烯热稳定性与透明性及塑化行为的影响

采用溶液沉淀法制备了部分水解的聚甲基丙烯酸甲酯(h-PMMA)/氢氧化钙(Ca(OH)2)复合物.采用X-射线衍射(XRD)、红外光谱(FTIR)、等离子体发射光谱和差示扫描量热表征了h-PMMA/Ca(OH)2复合物的组成与结构;采用刚果红测试、动态热稳定测试和热失重分析(TGA)研究了复合物对聚氯乙烯(PVC)的热稳定效果;通过紫外-可见(UV-Vis)光谱、扫描电镜(SEM)照片和熔融塑化曲线研究了复合物对PVC透明性和塑化行为的影响.结果表明,在Ca(OH)2晶体生长过程中,h-PMMA通过—COO-/Ca2+离子配位作用吸附于Ca(OH)2表面,不仅限制了Ca(OH)2粒子尺寸,且有助于Ca(OH)2在PVC中均匀分散.所得h-PMMA/Ca(OH)2复合物在显著提高PVC热稳定性和塑化能力的同时,还使PVC保持透明性.     

尼龙短纤维/白炭黑填充天然橡胶的流变与动态力学行为

以尼龙短纤维(NSF)增强天然橡胶(NR)混炼胶为研究体系,以马来酸酐接枝天然橡胶(MNR)为增容剂,考察增容剂、NSF含量对NR/NSF母胶动态流变行为的影响;将NR/NSF母胶加入30份白炭黑(Si O2)填充NR混炼胶中,对比研究NR/NSF、NR/NSF/Si O2混炼胶的线性与非线性流变行为及动态力学行为,采用修正的两相模型分析"粒子相"的增强作用,探讨硫化胶储能模量E'和损耗因子tanδ的变化.结果表明,MNR影响NSF在基体中的分散性和NSF/NR混炼胶的动态流变行为;高填充Si O2和少量NSF之间存在协同增强作用,使NR/NSF/Si O2混炼胶的补强因子和应变放大因子均高于NR/NSF混炼胶,显著增加"粒子相"的黏性与弹性贡献,限制"粒子相"的松弛;硫化胶的E'和tanδ峰值随NSF体积分数增加分别升高和降低.     

聚苯硫醚/低熔点玻璃复合体系的熔融制备与力学性能

选取低熔点玻璃(LMTG)为无机组分,聚苯硫醚(PPS)为聚合物基体,在适宜的温度下熔融制备了复合体系(PPS/LMTG).探讨了加工工艺对体系中LMTG无机相形态的影响,研究了加工温度低于LMTG软化温度制备的普通填充体系(PPS/LMTG300)和高于软化温度制备的熔融液-液复合体系(PPS/LMTG400)的力学性能.结果表明,对于所选择的体系,可以在325~450℃内实现有机无机相液-液复合;温度场、剪切场均影响LMTG分散相的形貌,液-液复合过程中LMTG分散相液滴在剪切场中呈现类似变形、破裂、凝聚和松弛回复等特征;与普通填充体系PPS/LMTG300相比,由液-液复合得到的PPS/LMTG400体系中无机相在复合过程中原位生成平均粒径更小的形态,其粒子基体相互作用减弱;且经过液-液复合,粒子分散性得到了较大的改善,PPS/LMTG400体系中即使含量高达66 wt%,无机粒子仍然具有优良的增强效果.