纤维素纳米纤维对聚乳酸结晶、流变和拉伸性能的影响

采用熔融共混⁃注射成型制备了聚乳酸（PLA）/纤维素纳米纤维（CNFs）可生物降解纳米复合材料,利用差示扫描量热仪、流变测试、拉伸性能测试等手段,考察了CNFs含量对PLA/CNFs复合材料结晶行为、流变特性和力学性能的影响规律。结果表明,少量的CNFs能均匀分散在PLA基体中,CNFs可作为PLA的异相成核剂,提高结晶速率常数,缩短半结晶时间,CNFs的含量为5 %（质量分数,下同）时,半结晶时间由纯PLA的10.4 min缩短至2.9 min;CNFs体现出润滑作用,使PLA/CNFs复合材料的储能模量和损耗模量均低于纯PLA;CNFs的含量为3 %时,复合材料的断裂伸长率较纯PLA提高了41.2 %。     

埃洛石纳米管对聚酰胺66/热致液晶原位复合材料性能及微观形态的影响

采用熔融共混方法制备了埃洛石纳米管（HNTs）／聚酰胺66（PA66）／热致液晶聚合物（TLCP）原位混杂复合材料,研究了其结晶性能、动态力学性能及微观形态,并提出了相对结晶度的概念。差示扫描量热法分析（DSC）表明：HNTs能促进PA66的结晶并提高晶体的完善程度;随着HNTs含量的增加,体系的相对结晶度逐渐提高;动态力学性能分析（DMA）表明：复合材料的储能模量及损耗模量均随着HNTs含量的增加而显著升高当HNTs含量为40 ％（质量分数,下同）时,复合材料的储能模量及损耗模量分别提高了188％、190 ％;扫描电子显微镜（SEM）显示,TLCP及HNTs均能在基体中均匀分散,且TCLP能较好地沿纤维轴方向取向、成纤。     

纤维素纳米纤丝/聚乙烯醇复合材料热性能与力学性能研究

通过溶液浇铸法制备了纤维素纳米纤丝(CNFs)/聚乙烯醇(PVA)复合材料,利用TG、DSC、DMA等方法考察了CNFs对PVA热性能与力学性能的影响。结果表明:CNFs的加入提高了PVA的结晶度与熔点,但随着CNFs含量的增加,由于CNFs与PVA之间存在较强的氢键作用,限制了PVA分子链的运动,使得PVA的熔点与结晶度略有下降;CNFs的加入使得PVA的玻璃化转变温度、拉伸强度与弹性模量提高,添加2%CNFs的PVA复合材料的拉伸强度与弹性模量均达到最大值,分别较纯PVA提升了28.9%与14.1%。     

PP/Nano-SiO_2复合材料的制备及性能研究

通过熔融共混法制备了聚丙烯/纳米二氧化硅(PP/nano-SiO2)复合材料,并研究了该复合材料的力学性能、热性能和动态流变性能。结果表明:当nano-SiO2用量不大于2%时,随着其用量的增加,复合材料的拉伸强度和冲击强度均呈先升后降趋势,但都高于纯PP的拉伸强度和冲击强度;复合材料的分解温度高于纯PP;复合材料熔体呈现剪切变稀现象,具有假塑性流体的特征,且随着nano-SiO2用量的增加,复合材料的复数黏度、储能模量、损耗模量均逐渐提高,但在低频区和高频区的变化幅度不同。     

硅灰石填充尼龙1010复合材料的制备与力学性能*

利用硅烷偶联剂KH550改性硅灰石,然后通过熔融共混法制备了尼龙(PA)1010/硅灰石复合材料,采用扫描电子显微镜(SEM)、熔体流动速率(MFR)和力学性能测试及动态力学分析(DMA)等对复合材料进行了分析与表征。结果表明,硅灰石均匀分散在PA1010基体中;复合材料的MFR随硅灰石含量的增加而降低,但挤出和注射成型实验表明,当硅灰石质量分数≤70%时,复合材料仍具有良好的加工性能;硅灰石的加入显著提高了PA1010的拉伸性能和弯曲性能,当硅灰石质量分数为70%时,复合材料的拉伸弹性模量与拉伸强度比纯PA1010分别提高了256%与29%,弯曲弹性模量与弯曲强度则分别提高了367%与93%;复合材料的动态储能模量随硅灰石含量的增加而大幅提高,当硅灰石质量分数为70%时,在玻璃化转变温度下的动态储能模量提高了约376%。     

热处理对PEEK/MWCNTs复合材料性能影响

对聚醚醚酮(PEEK)/多壁碳纳米管(MWCNTs)复合材料进行热处理,研究热处理温度对PEEK/MWCNTs复合材料力学性能和热性能的影响。结果表明:热处理可明显提升复合材料力学性能,与未热处理相比,拉伸强度和弯曲强度分别提升了9.2%和18.6%。热处理可明显提高复合材料熔点和结晶度,250℃下热处理的复合材料熔点升到348.13℃,结晶度升到31.5%。同时热处理可明显提高PEEK/MWCNTs复合材料储能模量。最佳热处理温度为250℃,最佳热处理时间为2h。     

应用于3D打印技术的ABS/纳米二氧化钛复合材料制备及力学性能研究

以丙烯腈-丁二烯-苯乙烯共聚物(ABS)为基体及自制的纳米二氧化钛(nano-TiO2)为改性剂,利用加热混制法制备ABS/nano-TiO2复合材料,混炼时以不同质量分数的nano-TiO2进行混炼。针对复合材料的动态力学性能(储能模量和损耗模量)和静态力学性能(拉伸强度、杨氏模量和硬度),对混制挤压成型的线材及3D打印的试样进行对比分析。通过扫描电子显微镜(SEM)分析可知,二氧化钛粉末为纳米级,能量色散X射线光谱(EDS)分析表明,元素含量和种类与设计一致。结果显示,通过添加nano-TiO2,可以提高ABS的拉伸强度、硬度、储能模量及损耗模量;且随着温度增加,ABS/nano-TiO2复合材料的储能模量降低,而损耗模量增加。研究结果可知,添加nano-TiO2可以提升ABS/nano-TiO2复合材料的力学性能,且经3D打印成型试样的各项性能保持稳定。     

环氧树脂改性聚乳酸/低熔点尼龙6/蒙脱土纳米复合材料结构与性能

通过熔融共混法制备了环氧树脂改性聚乳酸 (ePLA)/低熔点尼龙6 (LMPA6)/蒙脱土纳米复合材料。XRD和DSC结果表明,结晶度随着有机蒙脱土（OMMT）加入量的增加呈先增加后减小的趋势。流变行为结果表明,ePLA/LMPA6/OMMT纳米复合材料的黏性响应占主导地位,另外,随着OMMT加入量的增加,储能模量和损耗模量也增加。阻隔性能测试结果表明,OMMT的加入能够有效地改善纳米复合材料的阻隔性能。热重结果表明,OMMT的加入能够显著提高纳米复合材料的热稳定性能。TEM测试结果表明,OMMT加入量较少时,OMMT容易在基体中形成均一的纳米结构。力学性能分析表明,随着OMMT质量分数的增加,纳米复合材料的拉伸强度、断裂伸长率和冲击强度均出现先上升后下降的趋势,且当OMMT质量分数为3%时,纳米复合材料的力学性能均达到最大值,与未加OMMT时相比,分别提高了9.7%、37.8%和35.9%。     

PTW增强POM/TPU复合材料的制备及性能研究

以钛酸钾晶须(PTW)为增强体,采用熔融共混和注射成型法,制备了聚甲醛(POM)/热塑性聚氨酯弹性体(TPU)/PTW复合材料。研究了PTW含量对POM/TPU复合材料力学性能的影响,并借助扫描电子显微镜(SEM)分析了冲击断面形貌。结果表明,TPU的加入有效改善了纯POM的韧性,当TPU含量为10%(质量分数,下同)时,缺口冲击强度是纯POM的2.5倍,但拉伸强度和弯曲强度有所下降;PTW的加入对POM/TPU有较好的增强效果,当PTW含量为15%时,复合材料的拉伸强度、拉伸模量、断裂伸长率、弯曲强度、弯曲模量、缺口冲击强度分别为35.91 MPa、24.17%、144.94MPa、12.26GPa、112.1kJ/m2,拉伸模量、弯曲模量、缺口冲击强度与POM/TPU相比分别提高了14.7%、54.2%和9.2%,综合力学性能达到最佳。     

白炭黑对PP/埃洛石纳米管复合材料结构与性能的影响

将具有天然纳米管结构的埃洛石应用于聚丙烯(PP)改性,通过与白炭黑配合使用制备了性能优良的埃洛石/白炭黑并用填料增强的'PP复合材料,研究了复合材料结构和性能.结果表明,在适宜的填料配比下,并用填料可以使复合材料的弯曲模量、弯曲强度显著增加,拉伸强度和冲击强度基本保持.FHR证明埃洛石和二氧化硅之间存在氢键作用,动态流变(RDA)表明:并用填料使复合材料的储能模量和损耗模量提高.结果表明,并用填料体系的力学性能的提高可能是由于两种填料通过氢键作用形成了无机填料网络.白炭黑的加人提高了体系的结晶温度.扫描电镜(SEM)分析显示,埃洛石与白炭黑能相互促进分散.     

Properties of Chitosan-Filled Polypropylene (PP) Composites: The Effect of Acetic Acid

The main objective of this research was to investigate the effect of chitosan content and chemical modification with acetic acid on mechanical and thermal properties of PP/Chitosan. It was found that the tensile strength, elongation at break and crystallinity of untreated PP/Chitosan composites decreased with increasing filler content; however, Young's modulus and thermal stability increased. The treated chitosan with acetic acid have improved the tensile strength and Young's modulus of PP/Chitosan composites. The thermal analysis results show that chemical modified chitosan had increase thermal stability and crystallinity of treated PP/Chitosan composites. The scanning electron microscopy (SEM) study of the tensile fracture surface of treated PP/Chitosan composites indicated that the presence of acetic acid increased the interfacial interaction between chitosan and polypropylene matrix.     

Oxidized carbon nanofiber/polymer composites prepared by chaotic mixing

Composites of oxidized carbon nanofibers (ox-CNFs) and polymethyl methacrylate and thermoplastic polyurethane (TPU) were prepared in a chaotic mixer and their electrical and mechanical properties were compared with those prepared using untreated carbon nanofibers (CNFs). X-ray photoelectron spectroscopy data of ox-CNFs showed higher oxygen to carbon ratio than CNFs indicating the presence of polar functional groups on the surfaces of ox-CNFs. Consequently, dispersion of ox-CNFs improved in both polymers and the resultant composites showed improved thermal-oxidative stability, higher storage modulus, and higher glass transition temperature. The electrical conductivity, however, decreased with improved nanofiber dispersion. In the case of TPU/ox-CNF composites, maximum values of tensile strength and Young’s modulus were obtained with 1 wt.% fiber content; higher amounts of ox-CNFs promoted phase mixing of soft and hard segment domains and consequently caused a reduction in tensile properties.     

Preparation and characterization of carbon nanofiber reinforced thermoplastic polyurethane nanocomposites

The effect of CNFs on hard and soft segments of TPU matrix was evaluated using Fourier transform infrared (FTIR) spectroscope. The dispersion and distribution of the CNFs in the TPU matrix were investigated through wide angle X‐ray diffraction (WAXD), field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), polarizing optical microscope (POM), and atomic force microscope (AFM). The thermogravimetric analysis (TGA) showed that the inclusion of CNF improved the thermal stability of virgin TPU. The glass transition temperature (T_g), crystallization, and melting behaviors of the TPU matrix in the presence of dispersed CNF were observed by differential scanning calorimetry (DSC). The dynamic viscoelastic behavior of the nanocomposites was studied by dynamical mechanical thermal analysis (DMTA) and substantial improvement in storage modulus (E') was achieved with the addition of CNF to TPU matrix. The rheological behavior of TPU nanocomposites were tested by rubber processing analyzer (RPA) in dynamic frequency sweep and the storage modulus (G') of the nanocomposites was enhanced with increase in CNF loading. The dielectric properties of the nanocomposites exhibited significant improvement with incorporation of CNF. The TPU matrix exhibits remarkable improvement of mechanical properties with addition of CNF. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The Effect of Waste Office White Paper Content and Size on the Mechanical and Thermal Properties of Low-Density Polyethylene (LDPE) Composites

The effect of waste office white paper (WOWP) loading and size on mechanical properties, morphology and thermal properties of LDPE/WOWP composites were investigated. The results showed that increasing of WOWP loading has increased tensile strength and Young's modulus but decreased elongation at break of composites. LDPE/WOWP composites with smaller particle size (31 μm) have higher mechanical properties. Thermal analysis results of composites with particle size (31 μm) show higher thermal stability and crystallinity than composites with particle size (77 μm). Scanning electron microscope (SEM) micrograph indicates that the smaller particle size of filler has better interaction with LDPE matrix.     

Thermal,morphological, and mechanical characterization of novel carbon nanofiber‐filled bismaleimide composites

Novel carbon nanofiber (CNF) ‐filled bismalemide composites were fabricated by a thermokinetic mixing method. The thermal and mechanical properties of composites containing 1 wt % and 2 wt % CNFs were investigated. Thermogravimetric analysis demonstrated that minimal improvement in thermal stability of the nanocomposites was obtained by the addition of CNFs. Dynamic mechanical analysis showed an increase in storage modulus (E′) and glass transition temperature (T_g) upon incorporation of nanofibers. Limiting oxygen index (LOI) has also been found to increase with incorporation of CNFs. Morphological studies of fractured surfaces of the composites has been carried out by scanning electron microscopy to determine the effect of fiber content and dispersion on the failure mechanism. In general, good dispersion was observed, along with agglomeration at some points and some fiber matrix interfacial debonding. A decrease in mechanical strength has been observed and debonding was found as the main failure mechanism. Further research outlook is also presented. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical,thermal, and dynamic mechanical properties of long glass fiber‐reinforced thermoplastic polyurethane/polyoxymethylene composites

Long glass fiber (LGF)‐reinforced thermoplastic polyurethane (TPU) elastomers and polyoxymethylene (POM) (LGF/TPU/POM) composites were prepared by using self‐designed impregnation device. Dynamic mechanical properties of the LGF/TPU/POM composites have been investigated by using dynamic mechanical thermal analysis. The results indicated that the storage modulus and glass transition temperature of the composites increase with increasing the glass fibers content and scanning frequencies. In addition, the Arrhenius relationship has been used to calculate the activation energy of α‐transition of the LGF/TPU/POM composites. The thermal stability of the LGF/TPU/POM composites was investigated by thermogravimetric analysis. The consequence demonstrated that the thermal stability increase with augmenting the content of glass fibers. The mechanical properties of the composites are investigated by a universal testing machine and a ZBC‐4 Impact Pendulum. The results demonstrated the mechanical properties of the composites aggrandize with augmenting the glass fibers content. The good dispersion of the LGFs in the matrix resins is obtained from scanning electron micrographs. POLYM. COMPOS., 35:2067–2073, 2014. © 2014 Society of Plastics Engineers     

Pultruded fiber-reinforced poly(methyl methacrylate) composites. II. Static and dynamic mechanical properties,environmental effect,and postformability

This paper presents a novel process developed to manufacture poly(methyl methacrylate) (PMMA) pultruded composite. The mechanical, thermal, and dynamic mechanical properties, environmental effect, postformability of various fiber (glass, carbon, and Kevlar 49 aramid fiber) reinforced pultruded PMMA composites have been studied. Results show mechanical properties (i.e., tensile strength, specific tensile strength, tensile modulus, and specific flexural strength) and thermal properties (HDT) increase with fiber content. Kevlar fiber/PMMA composites possess the highest specific tensile strength and HDT, carbon fiber/PMMA composites show the highest tensile strength and tensile modulus, and glass fiber/PMMA composites show the highest specific flexural strength. Pultruded glass-fiber-reinforced PMMA composites exhibit good weather resistance. These composite materials can be postformed by thermoforming under pressure, and mechanical properties of postformed products can be improved. The dynamic shear storage and loss modulus (G′, G″) of pultruded glass-fiber-reinforced PMMA composites increased with decreasing pulling rate, and their shear storage moduli are higher than those of pultruded Nylon 6 and polyester composites.     

混炼方式对螺旋纳米碳纤维增强天然橡胶复合材料力学性能的影响

采用干法和湿法两种混炼工艺制备了螺旋纳米碳纤维(HCNFs)/炭黑(CB)/天然橡胶(NR)复合材料,通过扫描电镜、拉伸试验机和应变扫描仪分别对所制备复合材料的界面形貌、力学性能和Payne效应进行了测试分析,考察了混炼方式对复合材料宏观力学性能及Payne效应的影响。结果表明,与纯CB填料相比,在干湿两种混炼方式下,添加适量的HCNFs(1～6份)能提高HCNFs/CB/NR复合材料的300%定伸应力、扯断伸长率、拉伸强度和硬度。与干法混炼相比,湿法混炼能明显增强HCNFs/CB/NR复合材料的Payne效应,并提升在HCNFs高添加量(2～6份)条件下的拉伸强度和扯断伸长率,这主要源于湿法混炼能够有效改善HCNFs在橡胶基质中的分散性。