改性微晶纤维素/线性低密度聚乙烯复合材料的流变性能

采用硅烷偶联剂3-氨基丙基三乙氧基硅烷(KH-550)对微晶纤维素(MCC)进行改性,通过熔融共混法制备了改性MCC/LLDPE复合材料,并对复合材料的流变行为和动态力学性能进行了研究。动态流变测试结果表明,所有复合材料的储能模量、损耗模量和复数黏度随着MCC含量的增加而增加,而受温度的影响变化不大。稳态流变结果表明,MCC/LLDPE复合材料熔体均为假塑性流体,在高剪切速率下复合材料较纯LLDPE有着更低的剪切黏度。动态力学分析结果表明,MCC的加入大大提高了复合材料的刚性。     

蒙脱土含量对尼龙1010复合材料流变行为的影响

通过熔融共混挤出法制备了不同蒙脱土(OMMT)含量的尼龙1010(PA1010)的复合材料,研究了OMMT的含量对PA1010/OMMT复合材料流变性能的影响。流变行为研究结果表明,增加OMMT的用量,复合材料储能模量、损耗模量、黏流活化能增大,零剪切黏度明显提高,当OMMT的用量大于5 phr时,PA1010/OMMT体系的黏度发生突变,储存模量-角频率曲线在低频区出现第二平台,对应于应变扫描曲线上出现的2段线性黏弹区域,而稳态流变测试表明,在210℃共混体系黏度随剪切速率的增大而减小,属于非牛顿流体,呈现出剪切变稀的现象,而透射电镜、X射线衍射结果表明,当OMMT的用量为7 phr时,OMMT主要以剥离的形式分散在基体中。     

MC尼龙6/Kevlar纤维复合材料的动态流变性能

利用应力熔体流变仪研究了MC尼龙6及MC尼龙6/Kevlar纤维(KF)复合材料的动态流变性能。结果表明,随着剪切频率ω的增加,MC尼龙6及其复合材料熔体的动态黏度η′均减小,储能模量G′和损耗模量G″均增大;随着纤维用量的增加,MC尼龙6的熔体黏度呈增加的趋势;低频率时,纯MC尼龙6熔体以粘性流动为主,高频率时,熔体以弹性流动为主;加入纤维后,复合材料的熔体以粘性流动为主,且不同纤维含量的复合材料有着相似的G′~ω和G″~ω。这些结论也可由lgG′~lgG″关系图得到。     

乙烯-乙烯醇共聚物/尼龙6复合材料的加工流变性能

采用熔融共混法制备了乙烯-乙烯醇共聚物/尼龙6(EVOH/PA6)复合材料,用高级毛细管流变仪和旋转流变仪研究了复合材料的加工流变特性.通过幂律模型对EVOH/PA6复合材料的黏度与剪切速率(?γ)的关系进行了拟合,并用Arrhenius方程描述了复合材料黏度与温度的关系.结果表明,EVOH/PA6复合材料为假塑性流体,复合材料的表观黏度(ηa)和非牛顿常数(n)随着EVOH添加量的增加而增大.在角频率(ω)扫描范围内,EVOH的加入提高了EVOH/PA6复合材料的储能模量(G')、损耗模量(G″)和复数黏度|η*|.用Han曲线、Cole-Cole曲线和扫描电子显微镜(SEM)等方法研究发现,EVOH和PA6之间具有较好的相容性.另外,EVOH/PA6复合材料在EVOH的添加量达到15％(质量分数)时形成了微观相分离结构.     

异氰酸酯功能化碳纳米管/热塑性聚氨酯弹性体复合材料的制备及流变性能

采用甲苯-2,4-二异氰酸酯(TDI)对碳纳米管(CNT)进行表面修饰,制得TDI功能化CNT(CNT-TDI),将其分散于4,4′-二苯基甲烷二异氰酸酯中,通过原位聚合法制备CNT-TDI/热塑性聚氨酯弹性体(TPU)复合材料。利用FTIR、XPS和TG等测试手段,表征和分析了CNT-TDI的表面结构;利用旋转流变仪研究了CNT-TDI含量对CNT-TDI/TPU复合材料动态流变性能的影响。结果表明,TDI成功接枝改性CNT,接枝率约17%。动态流变研究结果表明,随CNT-TDI含量增加,复合材料的储能模量(G′)、损耗模量(G″)和复数黏度(η*)均明显提高,G′和G″交点对应的频率向低频移动,损耗峰频率也向低频偏移,说明复合材料的结构性增强,大分子链松弛时间延长;Han曲线上移且逐渐靠近对角线,van Gurp-Palmen曲线下移,说明复合材料的弹性响应逐渐增强;Cole-Cole曲线拖尾现象消失,说明填料的加入降低了TPU基体的微相分离程度。     

溶剂型丙烯酸酯压敏胶的流变性能研究

针对分子量不同的溶剂型丙烯酸酯共聚物压敏胶的流变性能进行研究,通过频率扫描、振幅扫描两种不同模式进行流变性能测试,并对其蠕变性能进行了测试,通过测试,分析了分子量对流变性能的影响。结果表明,分子量增大,区分频率值(f*)变小,零剪切黏度(η0)变大,样品的弹性变好;在振幅扫描模式下,随着分子量变大,样品的线性黏弹区域变大,弹性模量(G′)与黏性模量(G″)均变大,但弹性模量增大的幅度大于黏性模量,因此,随着分子量变大,样品逐渐从G′G″,样品由黏弹性液体流变行为逐渐向黏弹性固体流变行为转变;蠕变测试说明分子量增大,有利于改善样品的抗剪切变形能力与蠕变回复能力,蠕变回复时间也随之变大。     

UFPR含量对PP/UFPR复合材料动态和瞬态流变行为的影响

研究了超细全硫化粉末橡胶(UFPR)的含量在0%～70%(质量分数,下同)变化时,PP/UFPR复合材料的动态及瞬态流变行为的变化规律。结果表明,当UFPR含量低于15%时,复合材料的流变性质与PP基体类似,但材料非均相性随UFPR含量逐渐增加而增加;当UFPR的含量超过25%时,复合材料的储能模量(G′)出现"第二平台",表明材料内部类网络结构形成;当UFPR含量增至50%和70%时,复合材料的G′失去频率(ω)依赖性,呈现出典型的橡胶特征。     

环氧呋喃树脂反应性增容PLA/PBS共混体系的动态流变学表征

用熔融共混法制备不同环氧呋喃树脂(FER)含量的聚乳酸/环氧呋喃树脂/聚丁二酸丁二醇酯(PLA/FER/PBS)共混物,使用旋转流变仪、扫描电镜(SEM)和万能试验机等手段研究了FER含量对PLA/PBS共混体系的动态流变行为和相容性的影响。结果表明:当应变(γ)小于30%时动态模量不随γ的变化而变化,共混体系表现出线性黏弹行为;当γ大于30%后动态模量明显降低,出现了"Payne"效应。FER能改善PLA/PBS共混体系的加工性能;PLA/PBS共混体系有两个不同的驰豫过程,使曲线出现两个明显的半圆弧,加入FER后PLA和PBS两相的形态发生了改变;当FER含量为0.3 phr时共混体系的Han曲线与v GP曲线重叠,表明PLA和PBS的相容性较好;当FER含量为0.3 phr时PLA与PBS的界面黏附性最佳,表明PLA与PBS具有最为理想的界面相容性;FER添加量为0.3 phr时共混物的拉伸强度和冲击强度分别达到最大值56.9 MPa和4.33 k J/m2,比PLA/PBS共混物提高了11.2%和37.0%。     

纳米ZnO填充乙烯-醋酸乙烯酯共聚物的动态流变行为

为提供纳米ZnO/乙烯-醋酸乙烯酯共聚物(EVA)复合材料加工及性能优化的理论依据,通过熔融共混法制备了纳米ZnO/EVA复合材料,采用DSC研究了复合材料的熔融结晶行为,采用旋转流变仪分析了纳米ZnO质量分数以及偶联剂表面处理对复合材料体系动态流变行为的影响。结果表明:随着纳米ZnO质量分数的提高,纳米ZnO/EVA复合材料的结晶温度和熔融温度均先上升后下降;但改性纳米ZnO质量分数对改性纳米ZnO/EVA复合材料的熔融温度和结晶温度影响不大。当纳米ZnO的质量分数大于20%时,纳米ZnO/EVA体系的复数黏度发生突变,储存模量-角频率曲线在低频区出现第二平台,对应于应变扫描曲线上出现的两段线性黏弹区域,表明因纳米ZnO粒子间相互关联、团聚及粒子与基体间的相互作用形成了局部有序的逾渗网络结构;而纳米ZnO经偶联剂表面处理后,体系的复数黏度下降,储存模量-角频率曲线没有出现平台,说明改性纳米ZnO在复合材料体系中分散得更加均匀。研究表明偶联剂对纳米ZnO的表面处理改善了纳米ZnO在EVA中的分散性。     

端羧基分散剂对PS/纳米CaCO_3复合材料性能的影响

以巯基乙酸为链转移剂制备了不同分子量的含端羧基聚丙烯酸丁酯(PBACOOH)低聚物分散剂,并将其用于聚苯乙烯(PS)/纳米CaCO3复合材料的分散改性。通过动态流变仪、电子拉力机及差示扫描量热仪对复合材料性能进行表征。结果表明,PBACOOH可提高PS/纳米CaCO3复合材料的拉伸强度及缺口冲击强度,缺口冲击强度的增幅最高可达54%。含量为纳米粒子用量1%(质量分数)的PBACOOH分散剂使复合材料熔体储能模量、损耗模量及黏度下降,G′与G″的交点频率向高频方向移动。随分子量降低及端羧基含量增加,物理老化试样在Tg转变区的解缠结热焓增大。     

Dynamic and steady state viscoelastic behavior and morphology of MAPP treated PP/sisal composites

The present paper summarizes an experimental study on the molten viscoelastic behavior of PP/sisal composites under steady and dynamic state. Variations in melt viscosity and die swell of the composites with an increase in shear rate, fibre loading and coupling agent concentration have been investigated using capillary rheometer. It was observed that with the addition of sisal fibers and MAPP, the melt viscosity of the composites increased due to improved fiber–matrix interfacial adhesion. Further the dynamic viscoelastic behavior measured, employing parallel plate rheometer revealed an increase in the storage modulus (G′) indicating higher stiffness in case of fibre filled composites as compared with the virgin matrix. Time temperature superposition was applied to generate various viscoelastic master curves. The fiber–matrix morphology of the extrudates was also examined using scanning electron microscopy, which corroborated the findings of the rheological properties. The extrudate cross sections of the composites displayed uniform distribution of fibers within the PP matrix with lesser surface irregularities at high shear rates.     

Effects of extrusion temperature on the rheological,dynamic mechanical and tensile properties of kenaf fiber/HDPE composites

The effects of extrusion processing temperature on the rheological, dynamic mechanical analysis and tensile properties of kenaf fiber/high-density polyethylene (HDPE) composites were investigated for low and high processing temperatures. The rheological data showed that the complex viscosity, storage and loss modulus were higher with high processing temperature. Complex viscosities of pure HDPE and 3.4 wt% composite with zero shear viscosity of ⩽2340 Pa s were shown to exhibit Newtonian behavior while composites of 8.5 and 17.5 wt% with zero shear viscosity ⩾30,970 Pa s displayed non-Newtonian behavior. The Han plots revealed the sensitivity of rheological properties with changes in processing temperature. An increase in storage and loss modulus and a decrease in mechanical loss factor were observed for 17.5 wt% composites at high processing temperature and not observed at low processing temperature. Processing at high temperature was found to improve the tensile modulus of composites but displayed diminished properties when processed at low processing temperature especially at high fiber content. At both low and high processing temperatures, the tensile strength and strain of the composite decreased with increased content of the fiber.     

MWNTs/HDPE的导电性和流变学性质

利用熔融共混的方法制备了多壁碳纳米管(MWNTs)/高密度聚乙烯(HDPE)导电复合体系,并研究了该体系的流变学性质和导电性质。流变测量结果表明,碳纳米管的加入使体系的黏度和模量有很大的提高,并且高填充含量时复合体系的黏度表现出强剪切变稀行为,而储能模量则在低频区出现所谓的"第二平台";从黏度、损耗模量随填充含量的变化图上可以看出,碳纳米管的质量分数达到8%时,黏度和损耗模量随含量增加的幅度明显增大,表明在该点形成了粘弹逾渗结构,该值和电阻测量得到的逾渗阈值相近。     

分子结构对LLDPE动态流变行为的影响

通过动态流变行为测试,研究了一系列丁烯共聚和己烯共聚LLDPE的储能模量、损耗模量、零切黏度和动态黏度的变化规律,并讨论了它们与分子结构的关系。研究表明:(1)两个系列的LLDPE样品所得到的动态交点G_x随着重均相对分子质量的增大,其对应的频率越低;(2)两个系列的复数黏度和重均相对分子质量的关系式不符合Raju的经验方程;(3)一定含量的长支链可以加剧剪切变稀的程度,而动态黏度在聚合物重均相对分子质量相差不大的情况下,随着分子量分布的增大而增大。     

云母/聚丙烯共混物熔体的拉伸流变性能

采用双料筒毛细管流变仪和Haul-off牵伸设备, 研究了云母(Mica)/聚丙烯(PP)共混物在拉伸流场中的流变性能。结果表明: Mica/PP共混物熔体拉伸流动属于拉伸变稀型, 随着云母含量的增加, 熔体的表观拉伸黏度逐渐增大。熔体的拉伸应力和表观拉伸黏度均随温度的升高而下降。随着拉伸应变速率的提高, 熔体的拉伸应力增大, 表观拉伸黏度减小, 熔体拉伸流动活化能呈下降趋势。云母微粒的加入使聚丙烯熔体的拉伸模量明显增大, 但随着拉伸速度的提高, 共混熔体的拉伸模量下降显著。为了提高Mica/PP共混物的纺丝稳定性, 应严格控制好拉伸速度和加工温度。     

聚丁二酸丁二醇酯/聚羟基烷酸酯熔融共混物的结晶及流变力学行为

用熔融共混法制备聚丁二酸丁二醇酯(PBS)/聚(3-羟基丁酸酯-co-4-羟基丁酸酯)[Poly(3HB-co-4HB)]复合降解材料,利用差示扫描量热(DSC)、旋转流变仪及万能拉力机对其结晶、流变行为及力学性能进行研究。结果表明,在PBS中加入Poly(3HB-co-4HB)后,发现结晶起始温度(To,c)、结晶峰温度(Tp,c)以及结晶结束温度(Te,c)有所提高,结晶度随着Poly(3HB-co-4HB)的增加呈先增大后下降的趋势;PBS/Poly(3HB-co-4HB)复合降解材料随着Poly(3HB-co-4HB)添加量的增大,断裂伸长率和拉伸强度却呈下降趋势;同时剪切储能模量(G′)、剪切损耗模量(G″)呈现出单增趋势。因此,在复合降解材料中添加适量的Poly(3HB-co-4HB)能改善PBS的结晶、流变及力学行为。     

Anisotropic rheology of continuous fibre thermoplastic composites

The anisotropic rheology of continuous fibre thermoplastic composites has been resolved into along fibre and transverse components using a balanced pair of off-axis specimens in a commercial rotational rheometer with a parallel disc geometry. Existing theory has been used to demonstrate a small but consistent difference between the components of shear modulus and viscosity obtained from dynamic viscoelastic measurements. Transverse viscosity and yield stress are higher. The use of maximum shear rate (product of maximum shear strain and angular frequency), used here with apparent Maxwell viscosity, eliminates the strain dependence of the rates and correlates with steady shear viscosity and shear rate data. Differences in yield stress and viscosity are associated with the fibre-polymer system and the fibre volume fractions.     

Rheological behavior of anionic collagen injectable gels in the presence of rhamsan for plastic surgery applications

The present paper describes the rheological properties of anionic collagen gels and anionic collagen:rhamsan composites gels in the concentration of 0.7, 4 and 6%, estimated to be used as injectable biomaterials for plastic reconstruction. Rheological studies of these gels showed that independently of pH, composition and concentration the viscoelastic behavior was dependent on the frequency, with the storage modulus always greater than the loss modulus (G′ > G″ and δ < 45°). Creep experiments showed that anionic collagen:rhamsan composites equilibrated at pH 7.4 were less elastic and more susceptible to deformation in comparison to gels equilibrated at pH 3.5. Flow experiments indicated that the force needed for the extrusion of anionic collagen:rhamsan composites, in comparison to anionic collagen, was significantly smaller and with a smoother flow, suggesting the association with rhamsan may be a good alternative in the replacement of glutaraldehyde to stabilize the microfibril assembly of commercial collagen gel preparations. Finally, on the basis of dynamic viscosity profiles found for different preparations, some of these composites are potential candidates to be utilized in laryngology.