Effect of moisture on the thermoelectric properties in expanded graphite/carbon fiber cement composites

A kind of dry mixing and pressing process was introduced to prepare expanded graphite/carbon fiber cement composites (EG-CFRC). Significant effect of moisture on the thermoelectric properties of EG-CFRC was observed. The higher the moisture content is, the greater the absolute Seebeck coefficient. The maximum of absolute Seebeck coefficient 11.59 μV/°C was obtained with moisture of 14.98% at 33 °C. Simultaneously, the maximum of electrical conductivity 0.78 S cm⁻¹ was got with moisture of 11.44%. Furthermore, the largest power factor 7.85×10⁻⁴ µW m⁻¹ K⁻² was calculated at 33 °C with moisture of 11.44%. The carrier scattering, polarization effects and high density defects interface of EG-CFRC are attributed to the enhancement of thermoelectric properties in the case of higher moisture content.     

Synthesis and characterization of new oligomeric/polymeric antistatic additives for sheet molding composites

For various applications it is necessary to lower the specific surface resistivity of polymers in an electrostatically conductive area. To improve the antistatic properties of sheet molding composites (SMC) usually conductive inorganic additives, like carbon black, inorganic salts, metal powder, or CNTs, are mixed physically into the matrix. A newly developed concept for antistatic treatment is using oligomeric/polymeric additives, which are synthesized on the base of ingredients of the used polymeric matrix itself. The received additives are compatible with the matrix. Furthermore, the migration of the additives to the surface is prevented and in the case they exhibit double bonds they are able to be linked in the polymeric network permanently by covalent bonds. So unsaturated, polymer‐based antistatic additives with ionic units were developed for unsaturated polyester resin based SMC. The synthesis was realized by polymer analogous reactions and polycondensation reactions from monomer building blocks with ionic units. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44741.     

环氧树脂/ABS复合材料的制备及性能表征

以环氧树脂为基体,苯乙烯-丙烯腈-丁二烯（ABS）树脂为增韧剂,制备了环氧树脂/ABS复合材料,讨论了增韧剂对复合材料的热性能和机械性能的影响。结果表明,ABS的添加可提高复合材料的断裂韧性。扫描电镜结果显示,基体的剪切屈服和橡胶颗粒的微孔洞是ABS增韧环氧树脂的主要增韧机理。     

Synthesis and characterization of fumarate-based polyesters for use in bioresorbable bone cement composites

Fumarate-based polyesters were prepared by the transesterification polycondensation of diethyl fumarate and diols: (±)-1,2-propanediol, (S)-(+)-1,2-propanediol, 2-methyl-1,3-propanediol, and 2,2-dimethyl-1,3-propanediol. Different polyester microstructures were observed by ¹H-NMR and ¹³C-NMR spectroscopy when the reaction was conducted in the presence of p-toluenesulfonic acid monohydrate or metal containing catalysts—aluminum trichloride, titanium tetrachloride, titanium tetrabutoxide, and zinc chloride. The extent of formation of branched structures associated with hydroxyl end groups' addition to the unsaturated polyester double bonds depends on the acidity of the catalyst. The bone cement composites were prepared by mixing the fumarate polyesters with an inorganic filler, CaSO₄ · 2H₂O, and N-vinyl pyrrolidone, which crosslinks on the addition of a radical initiator, benzoyl peroxide, at ambient temperatures. The compressive strength and hydrolytic stability of the cement compositions was correlated with structure of the polyesters. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1123–1137, 1997     

三维石墨烯/聚氨酯复合材料的制备与特性

以氧化石墨烯(GO)为网络骨架的前驱体,通过水热还原、冷冻干燥制备了石墨烯气凝胶(GA);再以聚氨酯(PU)为复合材料的填充体,调节PU软硬度与流动性并真空浸渍气凝胶GA,两步法制备出互咬型三维石墨烯/聚氨酯(3DGP)复合材料。利用SEM、Raman、FTIR对GO、GA、3DGP的结构与形貌进行了表征,并采用TGA-DSC和自制压阻测试平台分析热稳定性和压阻特性。结果表明:6 g/L GO水溶液在还原剂乙二胺(EDA)作用下,GO片层间相互连接形成规整蜂窝状三维网络结构,其孔径约0.8mm,3DGP中PU与GA能很好地咬合;三维网络骨架的连续性为热运输载体声子提供了良好通道,使得3DGP热稳定性能显著提升,失重率5%时温度较PU提升了45℃;具有低迟滞性(8.7%)并且在压阻测量区间表现出两种压阻效应。     

4,4′-(双3,4-二氰基苯氧基)联苯树脂复合材料研究

以二苯砜二胺为固化剂,钼酸铵为催化剂合成了4,4′-(双3,4-二氰基苯氧基)联苯(BPH)的预聚物树脂,采用溶液浸渍法制备了玻璃纤维布预浸料,热压方式制备了玻纤增强4,4′-(双3,4-二氰基苯氧基)联苯树脂复合材料。通过示差扫描量热仪(DSC)、旋转流变仪(Rheometer)、傅里叶变换红外光谱(FTIR)、热重分析仪(TGA)和扫描电子显微镜(SEM)对树脂的固化反应,化学结构,复合材料的热稳定性和断面形貌进行了研究与表征。结果表明,钼酸铵可以显著的促进单体的预聚反应,聚合物玻璃化转变温度为380℃,复合材料具有优良的热稳定性,在氮气和空气中的5%分解温度分别为542℃和482℃,375℃处理20 h后弯曲强度保持率为97%,沸水中处理24 h后吸水率为1.4%。     

Structure and properties of polypropylene composites filled with magnesium hydroxide

Silane and silicone oil modified superfine magnesium hydroxide (MH) was filled into polypropylene (PP) as a flame retardant. The PP and flame‐retarded PP composites were studied for their mechanical properties and rheological behaviors by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), limiting oxygen index (LOI), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that the addition of MH improved flame retardancy of PP/MH composites, but seriously deteriorated mechanical properties of the composites. Surface treatment of MH could significantly improve tensile and impact strength of PP/MH composite because of its enhanced interfacial adhesion between MH and PP matrix. DSC results showed that MH had heterogeneous nucleation effect on PP. Surface treatment of MH weakened its heterogeneous nucleation effect. POM results showed that the dispersion of MH particles played an important role in the crystalline morphology and spherulite size of PP crystals. TGA indicated that MH greatly enhanced the thermal stability of PP. The introduction of treatment agent further improved the thermal oxidative stability of the composite. According to LOI, silane‐treated MH greatly enhanced flame retardancy of PP/MH composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4943–4951, 2006     

耐高温高导热环氧树脂／玻纤／BN复合材料的制备

以4,4-二氨基二苯砜（DDS）和内亚甲基四氢邻苯二甲酸酐（NA）为复配固化剂,采用高温模压成型法制备耐高温高导热环氧树脂／玻纤／氮化硼（BN）复合材料。探讨了BN用量和偶联剂处理对复合材料冲击强度、导热性能和电阻率的影响。结果表明：当nDDS：nNA=3：1时,复合材料的耐热性能最佳。当BN质量分数为8％时,复合材料的冲击强度最高;导热性能随BN用量的增加而增加,当BN用量为15％时,热导率为0．7560W／（mk）,此时复合材料仍保持较高的体积、表面电阻率;当BN填充量为一定值时,偶联剂处理使冲击强度和导热性能得到进一步提高。     

环氧树脂/玻纤/BN导热绝缘复合材料制备研究

采用高温模压成型法制备环氧树脂/玻纤/BN导热复合材料,探讨了BN用量对复合材料力学性能、导热性能和电性能的影响,结果表明.当BN用量为10%时,复合材料的冲击强度和弯曲强度较佳;导热性能随BN用量的增加而提高,当BN用量为20%耐.热导率为0.7438 W/mk,此时复合材料仍保持较好的绝缘性能.     

PBT/TPU/DOPO-MA阻燃复合材料的制备及性能

通过使用9,10-二氢-9-氧杂-10-磷朵菲-10-氧化物（DOPO）和马来酸酐反应合成制备DOPO衍生物阻燃剂DOPO-MA,并且其结构使用傅里叶红外光谱分析（FTIR）和核磁共振氢谱分析（¹H NMR）技术进行表征。将阻燃剂与聚对苯二甲酸丁二醇酯（PBT）和热塑性聚氨酯（TPU）熔融共混以制备PBT/TPU/DOPO-MA阻燃复合材料。通过运用锥形量热、UL-94、极限氧指数（LOI）、热重分析（TGA）、差热分析（DSC）和力学测试,研究了阻燃剂对复合材料的性能影响。测试结果表明,PBT/TPU/DOPO-MA复合材料具有良好的阻燃性能,加入10％DOPO-MA后,LOI从23.2增加到31.6,可达到UL-94 V-1等级,热释放率峰值（PHRR）和最大成热辐射速率（MAHRE）值降低;热重分析测试结果表明,添加DOPO-MA可以使得阻燃复合材料的热稳定性有显著的提高,当加入10％DOPO-MA后,残炭量可从6.87增加到14.36。此外,随着DOPO-MA含量的增加,阻燃复合材料的结晶度可得到一定的提高。     

Synthesis,characterization and dielectric properties of nickel-based polyoxometalate/polyurethane composites

The aim of this study was to synthesis, characterization and investigation of the influence of the polyoxometalate concentrations (1, 3, 5 and 10 wt%) on chemical, thermal, physical and morphological properties of nickel-based polyoxometalate/polyurethane composite (Ni-POM/PU) materials. Firstly, nickel-based polyoxometalate (Ni-POM) compound has been synthesized and characterized through various spectroscopic techniques. Synthesized Ni-POM compounds have been used for preparation of polyurethane composites as a reinforcement. Three different Ni-POM/PU composites containing Ni-POM were prepared by solution mixing and casting techniques. The chemical structure and morphology of prepared Ni-POM/PU composite samples were confirmed by Fourier transform infrared spectroscopy (FTIR), elemental analysis and SEM techniques. Effects of Ni-POM on thermal stability, glass transition temperature, optical transparency, hydrophilicity and physical properties of polyurethane composites were examined. Thermal stabilities and glass temperatures of the materials have been checked by differential thermal analysis (DTA), thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). The SEM results confirmed the highly porous structure and the formation of Ni-POM structures in the polymer matrix. Synthesized composites showed high chemical stability, good processability, and low Tg values. The dielectric properties of the prepared Ni-POM/polyurethane composites were also investigated at room temperature. These results displayed that the dielectric constant of the POM/polyurethane composites decreased with the increase of the Ni-POM content in polymeric matrix.     

Preparation and characterization of poly(vinyl chloride)/virgin and treated sisal fiber composites

Mechanical property changes, thermal stability, and water absorption capacity of poly(vinyl chloride) (PVC)/sisal fiber composites were assessed with respect to the effect of maleic anhydride chemical treatments of the sisal fiber, for five different sisal fiber contents, varying from 0 to 30% by weight in the composite. The composites prepared with the untreated sisal exhibited higher tensile modulus and hardness than the unloaded resin, while elongation and tensile strength were reduced. The deterioration in the mechanical properties of PVC blended with sisal fiber is attributed to the presence of moisture, interfacial defects at the fiber and polymer interface, and fiber dispersion in the PVC matrix. The amount of absorbed water is a function of the amount of fiber in the composite (F0 = 0 phr, F5 = 0.77 phr, and F20 = 4.83 phr). The comparison of the results of characterization of F5, F20, and F30 formulations prepared with the untreated fibers and the treated ones showed a reduction in absorbed water after the chemical treatment of fiber with maleic anhydride (F0 = 0 phr, F5 = 0.28 phr, and F20 = 2.99 phr), thus improving the mechanical properties of composites prepared with the treated sisal. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3630–3636, 2007     

Preparation of polymer/inorganic nanoparticles composites through ultrasonic irradiation

In this paper, ultrasonic induced encapsulating emulsion polymerization was first used to prepare the novel polymer/inorganic nanoparticles composites. The behaviors of several inorganic nanoparticles (SiO₂, Al₂O₃, TiO₂) under ultrasonic irradiation, such as dispersion, crushing, and activation, were studied. The dispersion stability, morphology, and structure of the ultrasonic irradiated nanoparticles were characterized by means of transmission electron microscopy (TEM), Fourier transform infrared (FTIR), and spectrophotometry, respectively. The results show that the inorganic nanoparticles in the aqueous solution can redisperse more effectively by ultrasonic irradiation than by conventional stirring. This is the basis for preparation of polymer/inorganic nanoparticles composites. By this technique, the long‐term stable latex, which mainly consists of polymer/inorganic nanoparticles composite latex particles, were successfully prepared. TEM, FTIR, thermogravimetric analysis, X‐ray photoelectron spectroscopy, spectrophotometry, and element analysis confirmed that well‐dispersed nanoparticles were encapsulated by the formed polymer, and the thickness of encapsulating polymer layer was in the range of 5–65 nm. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1478–1488, 2001     

Preparation and characterizations of polycaprolactone/green coconut fiber composites

The mechanical, thermal, and morphological properties of polycaprolactone (PCL) and green coconut fiber (GCF) composites were evaluated. Blends containing acrylic acid‐grafted PCL (PCL‐g‐AA/GCF) exhibited noticeably better mechanical properties due to better compatibility between the two components. The dispersion of GCF in the PCL‐g‐AA matrix was significantly more homogeneous due to the creation of branched and cross‐linked macromolecules via reactions between carboxyl groups in PCL‐g‐AA and hydroxyl groups in GCF. The tensile strength of the PCL‐g‐AA/GCF composites at break was considerably greater than that of PCL/GCF composites. In addition, the PCL‐g‐AA/GCF blend was more easily processed due to lower melt viscosity. Biodegradation tests were performed with each composite in an Acinetobacter baumannii BCRC 15556 environment. The mass of both composites was reduced by the GCF content within 4 weeks. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Low dielectric loss BST/PTFE composites for microwave applications

Ba_0.3Sr_0.475Ce_0.03La_0.12Ti_0.997Mn_0.003O₃/Polytetrafluoroethylene (PTFE) composites were prepared using powder processing technique. The effects of the ceramic filler volume fraction and the coupling agent on the phase composition, microstructure, dielectric and thermal properties of the composites were investigated in this paper. The ceramic filler dispersion in the PTFE matrix, thus the dielectric loss, permittivity, and dimensional thermal stability of the composite was considerably improved by the modification of BST filler surface using phenyl trimethoxy silane (PTMS) coupling agent. Variation of the dielectric permittivity of the composite with composition was well fitted by the effective medium theory (EMT) model in the experimental compositional range. The obtained silane-treated composite with 0.5 V_f BST exhibits extremely low dielectric loss: ε_r = 16, tan δ = 5.4 × 10⁻⁴ @1 MHz and 5.16 ± 0.6 × 10⁻³ @ 10 GHz. The CTE of the composites was reduced to 43 ppm/°C.     

Preparation and characterization of EVA–sisal fiber composites

In this work, composites of an EVA polymer matrix and short sisal fiber were characterized. The physical‐morphological as well as chemical interactions between EVA and sisal were investigated. When the samples were prepared in the presence of dicumyl peroxide, the results suggest that crosslinking of EVA as well as grafting between EVA and the sisal fibers took place. Morphological changes were studied by scanning electron microscopy (SEM). Results from Hg‐porosimetry, SEM, Fourier transform infrared spectroscopy, surface free energy, and gel content strongly indicate grafting of EVA onto sisal under the composite preparation conditions, even in the absence of peroxide. The grafting mechanism could not be confirmed from solid‐state ¹³C NMR analysis. The grafting had an impact on the thermal and mechanical properties of the composites, as determined by differential scanning calorimetry and tensile testing. Thermogravimetric analysis results show that the composites are more stable than both EVA and sisal fiber alone. The composite stability, however, decreases with increasing fiber content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1607–1617, 2006     

Preparation and characterization of polypropylene/serpentine composites

Composites of serpentine and polypropylene (PP) were prepared by twin‐screw extrusion. Serpentine was collected as rocks from the Ankara–Beynam region and ground into powder with an average particle size of about 3 μm for composite production. Both as‐received (rock) and powdered serpentine were characterized. A silane coupling agent (SCA), γ‐aminopropyl triethoxy silane, was used for the surface treatment of serpentine. Mechanical properties of the composites were measured in terms of impact strength, elastic modulus, stress at yield, stress at break, and percentage strain at break. The addition of serpentine was found to have a profound effect on the reinforcement of the PP matrix. Because of the stronger interactions at the interphase induced by SCA treatment, mechanical properties were improved further in comparison with the untreated composites. Similar thermal and morphological behaviors were recorded for the composites with and without surface treatment. Thermal studies showed an increase in both melting temperature and percentage crystallinity of the composites. Scanning electron microscopy analysis revealed that homogeneous distribution of filler was observed at low filler contents, but a certain extent of agglomeration was also seen at high filler loadings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

新型液晶聚氨酯/环氧树脂复合材料的制备及性能

以联苯二酚,2,4-甲苯二异氰酸酯(2,4-TDI),乙二醇,N,N'-二(ω-羟乙基)均苯四甲酰二亚胺(BHDI)为单体,加成反应合成了1种同时含有联苯基和亚胺基的新型液晶聚氨酯(LCPBI),通过IR,DSC、偏光显微镜及X射线衍射仪对其结构和性能进行表征和分析。将该液晶聚氨酯与环氧树脂(E-51)共混制备了液晶聚氨酯/环氧树脂复合材料,通过力学性能测试,热重分析和电镜分析对其性能进行了研究并探讨了其增韧机理。结果表明,加入质量分数为3%的LCPBI,可使复合材料的冲击强度提高2.5倍,拉伸强度和弯曲强度也有不同程度的提高,热分解温度提高15～20℃。     

PAM-g-PVA/MWCNTs导电复合材料的制备及表征

以硝酸铈胺-PVA为氧化还原引发体系,制备了丙烯酰胺接枝聚乙烯醇（PAM-g-PVA）聚合物,采用共混法,在接枝聚合物中掺杂多壁碳纳米管制备了PAM-g-PVA/MWCNTs气敏传感导电薄膜材料,研究了在不同饱和蒸气中的气敏响应性。结果表明,导电薄膜在乙酸乙酯、正丙醇饱和有机溶剂蒸气中显示负蒸气系数效应（NVC）,在丙酮和盐酸饱和蒸气中为正气系数效应（PVC）,但随着电阻的增加,导电薄膜在盐酸饱和蒸气中呈现负蒸气系数效应。     

剑麻纤维增强热塑性淀粉复合材料的制备及性能研究

为研究剑麻纤维增强的热塑性淀粉复合材料的制备工艺及热稳定性,以玉米淀粉为原料,先制得热塑性淀粉,再以剑麻纤维为骨架增强体制备剑麻纤维增强热塑性淀粉复合材料,通过正交试验优化制备工艺,DSC、TG/DTG、SEM分析其热稳定性及结构。正交试验表明,各因素对材料抗拉强度影响的主次顺序为纤维长度 >纤维用量 >模压成型温度 >填料用量;最佳工艺条件为纤维长度15mm、纤维用量35g、模压成型温度200℃、填料用量5g,此时材料的抗拉强度可达到4.45MPa。利用差示扫描量热分析和热重分析分别对热塑性淀粉及剑麻纤维复合材料的热稳定性进行了分析,结果表明,热塑处理提高了淀粉的熔融温度,有利于淀粉与纤维素羟基间的氢键结合,且热塑过程在一定程度上降低了淀粉的热稳定性;剑麻纤维复合材料的热降解过程主要发生在200~400℃温度区间。SEM分析显示最佳工艺条件下得到的复合材料具有较好的泡孔结构。