Characterization and properties of in situ emulsion polymerized poly(methyl methacrylate)/graphene nanocomposites

Poly(methyl methacrylate) (PMMA)/graphene nanocomposites were prepared by in situ emulsion polymerization. Raman and Fourier transform infrared spectra showed that PMMA polymer contained partially reduced graphite oxide. Dynamic mechanical analysis and differential scanning calorimetry analysis showed that graphene in the PMMA matrix acted as reinforcing filler; it enhanced the storage moduli and glass transition temperatures of the nanocomposites. Thermogravimetric analysis showed that the thermal stability of the nanocomposites increased by ca. 35 °C. The electrical conductivity of nanocomposite with 3 wt.% graphite oxide was 1.5 S m⁻¹ at room temperature.     

Synthesis and effect of polyphosphazenes on the thermal,mechanical and morphological properties of poly(etherimide)/thermotropic liquid crystalline polymer blend

Effect of functionalized polyphosphazene as compatibilizer in melt-compounded polyetherimide (PEI)/liquid crystalline polymer (LCP) blend has been investigated in details. DMTA study showed the variation in glass transition temperature (T_g) in presence of polyphosphazene having different funtionalization. Superior thermal stability of polyphosphazene aided composites is exhibited from thermo-gravimetric analysis. From dielectric measurements it was clear that polyphosphazene-aided PEI/LCP blend can act as low dielectric material as well as high dielectric material depending on the nature of pendant group used. Scanning electronic microscopic observation revealed that the addition of small amount of polyphosphazene results in a decrease in average disperse domain sizes of LCP phase leading to improved filler-matrix adhesion.     

Mechanical and thermal properties of compatibilized composites of polyethylene and esterified lignin

Lignin have been esterified using phthalic anhydride and then blended with (up to 40 wt.%) low density polyethylene (LDPE). Maleic anhydride grafted LDPE has been added as compatibilizer. The mechanical and thermal properties of the blends were measured according to ASTM standards and compared with those of neat LDPE. The results reveal that addition of compatibilizer improved the mechanical properties significantly approaching values close to those of neat LDPE. The scanning electron micrographs of the blend specimens also support the above observations. Thermogravimetric analysis showed greater thermal stability for the compatibilized blends. The char content has been found to increase with increasing filler (lignin phthalate) content. DSC analysis revealed that the crystallinity values of the blends slightly increase by the addition of filler (lignin phthalate).     

PET in situ composites improved both flame retardancy and mechanical properties by phosphorus-containing thermotropic liquid crystalline copolyester with aromatic ether moiety

A novel phosphorus-containing thermotropic liquid crystalline copolyester with aromatic ether moiety (TLCP-AE) was used to prepare the in situ composites of poly(ethylene terephthalate) (PET)/liquid crystalline polymer. The morphological structure and properties of PET/TLCP-AE in situ composites were investigated using scanning electron microscopy (SEM), capillary rheometer, tensile tests, limiting oxygen index tests (LOI), cone calorimeter and thermogravimetric analysis (TGA). The rheological measurements show that the viscosity ratio of TLCP-AE to PET at 260 °C is less than 1, which meets a precondition for TLCP-AE to form fibrils in PET matrix during processing. The mechanical, LOI and cone tests prove that TLCP-AE can improve the mechanical properties and flame retardancy of PET synchronously. Moreover, TGA results exhibit that the initial decomposition temperatures and the final residues of PET/TLCP-AE composites increase with increasing TLCP-AE content.     

纳米HA/PU复合材料的力学性能和热性能

以4 , 4′-亚甲基二环己基二异氰酸酯( H₁₂MDI) 、聚乙二醇、蓖麻油、1 , 4-丁二醇和具有生物活性的纳米羟基磷灰石(n-HA) 为原料, 采用预聚法制备了纳米羟基磷灰石/ 聚氨酯( HA/PU) 复合材料, 并对其力学性能和热性能进行了研究。结果表明: 复合材料的拉伸强度和断裂伸长率随n-HA 含量的增加而提高。当n-HA 的质量百分数为30 %时, 复合材料的综合力学性能达到最佳, 与纯PU 相比, 拉伸强度和断裂伸长率分别提高了186 %和107 %。动态力学分析得出复合材料的储能模量随n-HA 质量百分含量的增加而显著上升。TGA 试验表明HA/PU 纳米复合材料的热稳定性能随n2 HA 的添加得到改善, 而DSC 分析显示n-HA 的加入在一定程度上降低了PU 软段的结晶度。这些结果均表明该n-HA/PU 是一种有应用前景的组织工程材料。      

板料弯曲回弹影响因素的有限元模拟研究

通过静态力学、动态力学实验方法,研究了热致性液晶聚合物(LCP)的种类对环氧树脂共混物在不同温度下的拉伸强度和应力-应变曲线的影响,通过TEM观察了共混物的相形态结构.结果表明,反应型液晶聚合物(LCPU)比其它种类的液晶聚合物对环氧树脂的改性效果更好;在不同温度下,其拉伸强度和应力～应变行为均比其它材料优越;固化物的动态力学结果表明:反应型的液晶聚合物键入了固化网络,出现新的松弛,TEM结果表明,反应型的液晶聚合物在基体材料中形成大小在nm数量级的液晶聚集微区,没有反应基团的液晶聚合物PHBHT在10%的加入量下,与环氧的共混物结构也有液晶聚集微区产生,但是聚集区大小在微米量级.     

Mechanical, thermal and electrical properties of aluminum nitride/polyetherimide composites

The mechanical, thermal and electrical properties of modified AlN/polyetherimide (PEI) composites were investigated. It revealed that the surface of AlN modified by silane could effectively increase the adhesion with matrix, which was beneficial for AlN to reinforce the polyetherimide matrix. After silane modification, the AlN showed good dispersion and wetibility in the polyetherimide matrix and imparted excellent mechanical, electrical and thermal properties. The tensile strength, modulus, electrical and thermal stability were improved with the increasing of AlN content. The tensile strength of AlN/PEI composites increased by 27% when 12.6 vol.% AlN was added to neat polyetherimide. The thermal conductivity of the 57.4 vol.% AlN/PEI composites increased three times compared with neat polyetherimide. Test results indicate that the silane grafted AlN incorporated into the polyetehetimide matrix effectively enhance the thermal stability, thermal conductivity and mechanical properties of the polyetherimide composites.     

聚醚酰亚胺和热致性液晶高分子原位复合材料的研究进展

综述了近年来聚醚酰亚胺和热致性液晶高分子共混形成原位复合材料的研究进展。液晶高分子在共混物中既起到增强剂的作用。又起到加工助剂的作用。应用Taylor理论可描述液晶分散相在基质高分子中的成纤过程。讨论了各自聚合物以及共混物的流体动力学行为和聚合物间的相容性、混合程序、混合物组成等因素对原位复合材料的形态和力学性能的影响。     

Preparation and thermal properties of soluble poly(phthalazinone ether sulfone ketone) composites reinforced with multi-walled carbon nanotube buckypaper

A nanocomposite with soluble high-performance poly(phthalazinone ether sulfone ketone) (PPESK) as matrix and multi-walled carbon nanotube buckypaper (MWCNT-BP) as reinforcement was fabricated by hot-press processing. The morphologies, dynamic and static mechanical behavior, thermal stability of the MWCNT-BP/PPESK composites were studied using scanning electron microscope (SEM), dynamic mechanical analyzer (DMA) and thermogravimetric analyzer (TGA). SEM microphotographs revealed a high impregnation degree of the MWCNT-BP/PPESK composites. Dynamic and static mechanical analysis revealed that the nanocomposites possessed high storage modulus, and good retention rate of mechanical strength even at 250 °C, which is mainly attributed to satisfied impregnation and strong interactions between MWCNT-BP and PPESK. Thermogravimetric analysis exhibited that the nanocomposites had excellent thermal stability. These investigations confirm that MWCNT-BP can be effectively used to manufacture high-loading CNT/PPESK composites with improved properties.     

Mechanical,thermal expansion,and flammability properties of co-extruded wood polymer composites with basalt fiber reinforced shells

Basalt fiber (BF) filled high density polyethylene (HDPE) and co-extruded wood plastic composites (WPCs) with BF/HDPE composite shell were successfully prepared and their mechanical, morphological and thermal properties characterized. The BFs had an average diameter of 7 μm with an organic surfactant surface coating, which was thermally decomposed at about 210 °C. Incorporating BFs into HDPE matrix substantially enhanced flexural, tensile and dynamic modulus without causing a noticeable decrease in the tensile and impact strength of the composites. Micromechanical modeling of tensile properties for the BF/HDPE composites showed a good fit of the selected models to the experimental data. Compared to neat HDPE, BF/HDPE composites had reduced linear coefficient of thermal expansion (LCTE) values. The use of the pure HDPE and BF/HDPE layers over a WPC core greatly improved impact strength of core–shell structured composites. However, the relatively less-stiff HDPE shell with large LCTE values decreased the overall composite modulus and thermal stability. Both flexural and thermal expansion properties were enhanced with BF reinforced HDPE shells, leading to well-balanced properties of core–shell structured material. Cone calorimetry analysis indicated that flammability performance of core–shell structured composites was improved as the BF content increased in the shell layer.     

PA66短纤维用于提高聚甲基乙撑碳酸酯力学与热学性能的研究

聚甲基乙撑碳酸酯(PPC)分子间作用力较低、力学和热学性能较差,通过双螺杆挤出制备PPC/PA66短纤维复合材料,促进PA66短纤维与PPC形成氢键作用力,有利于提高PPC材料的综合性能。红外光谱分析结果表明PA66短纤维的羰基与PPC分子链中的羟基之间形成了氢键,PA66短纤维的引入提高了PPC的力学性能和热学性能。当短纤维含量为20%(质量分数)时,复合材料的缺口冲击强度提高了315.8%,初始分解温度和玻璃化温度分别提高了32.2和3.8℃。当短纤维含量继续增加至30%(质量分数)时,由于高含量的纤维之间容易发生团聚,导致复合材料的力学性能略有下降。PPC力学和热学性能的显著提高,主要原因是氢键作用力的形成和PA66短纤维受力后发生的拉丝形变所引起。     

Mechanical and thermal performance of distillers grains filled poly(butylene succinate) composites

The mechanical and dynamic mechanical properties, morphology, melting and crystallization behavior, as well as thermal stability of poly(butylene succinate)/distillers grains (PBS/DG) composites with different DG contents were investigated. The tensile modulus, crystallization rate, and crystallinity of PBS in the composites were efficiently enhanced in the presence of DG. The thermogravimetric analysis of the PBS/DG composites showed that their flame retardancy leveled up. The scanning electron microscopy analysis of the PBS/DG composites indicated that the DG was not damaged during the melt processing. These results supported the application of DG as fillers in polymer composites. Consequently, this study opened a new application of DG and has potential to decrease the cost of PBS-based materials with a variety of enhanced properties.     

改性纳米SiO2/硅橡胶复合材料的制备及性能

为提高纳米SiO₂在硅橡胶（SR）基体中的分散性及两相间的界面结合力,设计以羟基硅油（HSO）和γ-甲基丙烯酰氧基丙基三甲氧基硅烷（KH570）为纳米SiO₂的表面封端改性剂,并将改性SiO₂与双组份加成型液体SR复合得到改性纳米SiO₂/SR复合材料。通过一系列表征手段对改性纳米SiO₂的形貌结构及其在乙醇中的分散性等进行分析,研究了改性纳米SiO₂对纳米SiO₂/SR复合材料的断面形貌、力学性能及热稳定性的影响。结果表明:KH570成功接枝到纳米SiO₂表面并与SR基体间形成化学键。当HSO协同KH570改性纳米SiO₂时,可有效改善纳米SiO₂在SR基体中的分散性能及纳米SiO₂与SR两相间的界面结合性能,并显著提高纳米SiO₂/SR复合材料的力学性能和热稳定性。将SiO₂∶HSO∶KH570以质量比为2.0∶0.2∶0.6处理的改性纳米SiO₂粒子,得到的改性纳米SiO₂/SR复合材料起始热分解温度提高了230℃。当SiO₂∶HSO∶KH570质量比为2.0∶0.2∶0.45时,改性纳米SiO₂/SR复合材料的拉伸强度和断裂伸长率分别提高了约1倍。      

Mechanical and thermal properties of chicken feather fiber/PLA green composites

Chicken feather fiber (CFF)/reinforced poly(lactic acid) (PLA) composites were processed using a twin-screw extruder and an injection molder. The tensile moduli of CFF/PLA composites with different CFF content (2, 5, 8 and 10 wt%) were found to be higher than that of pure PLA, and a maximum value of 4.2 GPa (16%↑) was attained with 5 wt% of CFF without causing any substantial weight increment. The morphology, evaluated by scanning electron microscopy (SEM), indicated that an uniform dispersion of CFF in the PLA matrix existed. The mechanical and thermal properties of pure PLA and CFF/PLA composites were compared using dynamic mechanical analysis (DMA), thermomechanical analysis (TMA) and thermogravimetric analysis (TGA). DMA results revealed that the storage modulus of the composites increased with respect to the pure polymer, whereas the mechanical loss factor (tan δ) decreased. The results of TGA experiments indicated that the addition of CFF enhanced the thermal stability of the composites as compared to pure PLA. The outcome obtained from this study is believed to assist the development of environmentally-friendly composites from biodegradable polymers, especially for converting agricultural waste – chicken feather into useful products.     

Study on thermal properties of graphene foam/graphene sheets filled polymer composites

The polymer composites composed of graphene foam (GF), graphene sheets (GSs) and pliable polydimethylsiloxane (PDMS) were fabricated and their thermal properties were investigated. Due to the unique interconnected structure of GF, the thermal conductivity of GF/PDMS composite reaches 0.56 W m⁻¹ K⁻¹, which is about 300% that of pure PDMS, and 20% higher than that of GS/PDMS composite with the same graphene loading of 0.7 wt%. Its coefficient of thermal expansion is (80–137) × 10⁻⁶/K within 25–150 °C, much lower than those of GS/PDMS composite and pure PDMS. In addition, it also shows superior thermal and dimensional stability. All above results demonstrate that the GF/PDMS composite is a good candidate for thermal interface materials, which could be applied in the thermal management of electronic devices, etc.     

纳米填料改性丁基橡胶复合材料的力学性能、芥子气防护性能和燃烧性能

以有机蒙脱土、纳米级SiO₂气凝胶和沉淀法白炭黑等具有不同粒子形状和结构特性的纳米粒子为增强填料,采用熔体共混法制备了丁基橡胶复合材料。采用SEM和XRD对复合材料的微观结构进行了表征,并研究了不同纳米填料对复合材料的力学性能、芥子气防护性能和燃烧性能的影响。结果显示：纳米级SiO₂气凝胶/丁基橡胶复合材料的力学性能最优,填充15 wt% SiO₂气凝胶的复合材料的拉伸强度和撕裂强度分别比丁基橡胶硫化胶提高了9倍和2.2倍。复合材料的芥子气防护性能与纳米填料的粒子形状有密切的关系,填充15 wt%层片状结构有机蒙脱土的复合材料的芥子气防护时间达到了21h以上,明显优于填充近似球形粒子的纳米级SiO₂气凝胶和白炭黑的复合材料的防护性能。然而纳米填料使复合材料的氧指数和氧化分解温度只有少量提高,阻燃性能改善有限。     

Influence of fiber content on mechanical,morphological and thermal properties of kenaf fibers reinforced poly(vinyl chloride)/thermoplastic polyurethane poly-blend composites

Kenaf (Hibiscus Cannabinus) bast fiber reinforced poly(vinyl chloride) (PVC)/thermoplastic polyurethane (TPU) poly-blend was prepared by melt mixing method using Haake Polydrive R600 internal mixer. The composites were prepared with different fiber content: 20%, 30% and 40% (by weight), with the processing parameters: 140 °C, 11 min, and 40 rpm for temperature, time and speed, respectively. After mixing, the composite was compressed using compressing molding machine. Mechanical properties (i.e. tensile properties, flexural properties, impact strength) were studied. Morphological properties of tensile fracture surface were studied using Scanning electron microscope (SEM). Thermal properties of the composites were studied using Thermogravimetric Analyses (TGA). PVC/TPU/KF composites have shown lower tensile strength and strain with increase in fiber content. Tensile modulus showed an increasing trend with increase in fiber content. Impact strength decreased with increase in fiber content; however, high impact strength was observed even with 40% fiber content (20.2 kJ/m²). Mean while; the 20% and 30% fiber contents showed higher impact strength of 34.9, 27.9 kJ/m²; respectively. SEM showed that there is poor fiber/matrix adhesion. Thermal degradation took place in three steps. In the first step, composites as well as the matrix had a similar stability. At the second step, matrix showed a slightly better stability than the composites. At the last step, composites showed a better stability than the matrix.     

聚醚醚酮和烯丙基化合物改性双马来酰亚胺复合材料微观结构及力学性能

采用浓H₂SO₄氧化聚醚醚酮（PEEK）得到磺化聚醚醚酮（SPEEK）,以3,3'-二烯丙基双酚A （BBA）、双酚A双烯丙基醚（BBE）为活性稀释剂、SPEEK为改性剂、双马来酰亚胺（BMI）树脂为基体,浇注成型制备SPEEK/BBA-BBE-BMI复合材料,同时研究了SPEEK的改性效果及复合材料微观形貌与力学性能。结果表明：SPEEK改性效果较好,在FTIR中存在明显的磺酸基团特征峰,SEM和能谱分析表明,SPEEK微观形貌变化明显,硫元素含量较高;SPEEK/BBA-BBE-BMI复合材料的微观形貌显示,SPEEK在基体中呈现直径为2 μm左右的多孔状两相结构,且分散均匀,此多孔结构改善了复合材料的断裂形貌,由脆性断裂转变为韧性断裂,当断裂纹遇到SPEEK组分时受阻而出现不规则发散,此变化会赋予复合材料更加优异的性能。力学性能测试结果显示,当SPEEK含量为5wt%时,SPEEK/BBA-BBE-BMI复合材料的弯曲强度和冲击强度达到最佳,分别为147.93 MPa和15.74 kJ/mm²,分别比基体提高了49.47%和66.21%。     

Enhancement of fracture toughness,mechanical and thermal properties of rubber/epoxy composites by incorporation of graphene nanoplatelets

Carboxyl terminated butadiene acrylonitrile (CTBN) was added to epoxy resins to improve the fracture toughness, and then two different lateral dimensions of graphene nanoplatelets (GnPs), nominally <1 μm (GnP-C750) and 5 μm (GnP-5) in diameter, were individually incorporated into the CTBN/epoxy to fabricate multi-phase composites. The study showed that GnP-5 is more favorable for enhancing the properties of CTBN/epoxy. GnPs/CTBN/epoxy ternary composites with significant toughness and thermal conductivity enhancements combined with comparable stiffness to that of the neat resin were successfully achieved by incorporating 3 wt.% GnP-5 into 10 wt.% CTBN modified epoxy resins. According to the SEM investigations, GnP-5 debonding from the matrix is suppressed due to the presence of CTBN. Nevertheless, apart from rubber cavitation and matrix shear banding, additional active toughening mechanisms induced by GnP-5, such as crack deflection, layer breakage and separation/delamination of GnP-5 layers contributed to the enhanced fracture toughness of the hybrid composites.