Preparation and Properties of Aramid-Silica Hybrids with Inter-Phase Bonding Through (3-glycidoxypropyl)-trimethoxysilane

Nano-composites from aramid-silica system have been prepared via sol-gel process. Poly (phenyleneterephthalamide) copolymer chains were prepared by reacting a mixture of p- and m-phenylenediamines with terephthaloyl chloride in dimethylacetamide used as solvent. The sol-gel process in the polymer matrix was carried out through hydrolysis and condensation of a mixture of tetraethoxysilane and (3-glycidoxypropyl) trimethoxysilane. The latter was used to develop linkage, on one hand with silica network structure using alkoxy groups and on the other hand with aramid chains at its secondary amine groups through glycidal groups of silane. Mutual interaction between the two disparate phases aramid and silica network was thus created. Thin films of the composites containing different proportions of silica ranging from 5.0 to 25.0-wt% were cast by the solvent elution technique. The α-relaxation temperature associated with the glass transition was measured by the dynamic mechanical thermal analysis. The results showed an increase in the glass transition temperature from 328°C for the pure aramid to 352°C for the hybrid materials containing 25-wt% silica, an indicative of the increased interfacial interaction between the two phases. Films having relatively low silica content were flexible and transparent, but those with high silica content were opaque and brittle. These films were tested for their tensile strength, modulus and toughness. The mechanical strength of the composites as compared to the pure aramid increased initially but with further addition of silica the strength decreased. The initial increase can be explained due to increased interfacial interaction between the two phases, however agglomeration of silica particles was responsible for decreasing strength at higher silica contents.     

Design of TiO2@graphene nanosheets with rough surface and its reinforcement to polyarylene ether nitriles

The interfacial interaction is extremely important when dealing with filler‐reinforced polymer materials. Herein, in order to improve the interfacial interaction with the polyarylene ether nitriles (PEN) matrix, a three‐dimensional rough structure was designed. First, needle‐like TiO₂ nanocrystals were grown on each surface of the graphene. Morphology analysis proved that rough TiO₂ nanocrystals were coated on the graphene nanosheets. Then, TiO₂@graphene/PEN composites were fabricated to investigate the filler–matrix interaction. Thereafter, the different polymer chains could be interlocked by the TiO₂ “needles” when the rough TiO₂@graphene was embedded into the polymer resin. The surrounding PEN polymer chains (work as ropes) could tie to the “needles” (work as wood pile). That is to say, the effective polymer chain length was greatly lengthened, resulting in the improvement of interfacial interactions and mechanical properties. Most importantly, the morphology, mechanical and rheological tests of the composites also proved the improvement of interfacial interactions and mechanical properties. Copyright © 2015 John Wiley & Sons, Ltd.     

The interfacial enhancement of LLDPE/whisker composites via interfacial crystallization

Interfacial interaction plays a key role in the preparation of high performance polymer composites. In this work, in order to explore the possibility to enhance the interfacial interaction via interfacial crystallization of polymer matrix onto the filler surface, interfacial crystallization structure and mechanical properties of linear low density polyethylene (LLDPE)/whisker composites were investigated. The composites were firstly prepared by melt compounding, followed by processing in both traditional and dynamic injection molding. DSC, WAXD, SEM were used to characterize the interfacial crystallization structure. And the mechanical properties were measured by tensile testing. An imperfect shish‐calabash structure, with whisker served as shish, and irregular LLDPE spherulite as imperfect calabash, was formed during common injection molding processing. Such a structure was considered as the main reason for the strong interfacial adhesion and the obviously improved tensile strength and modulus. Furthermore, introducing shear could cause the formation of relatively perfect shish‐calabash structure, leading to the stronger interfacial adhesion. Copyright © 2011 John Wiley & Sons, Ltd.     

Poly(dimethylsiloxane)/palygorskite composites: preparation,characterization, and properties

Poly(dimethylsiloxane) (PDMS) composites were prepared by simple blending process using palygorskite (PG) or modified palygorskite (MP). This study has been designed to determine the influences of PG or MP on the thermal stability and the mechanical properties of PDMS composites. The thermal stability of PG and MP were also studied by thermogravimetric analysis (TGA). The results showed that MP had the similar thermal stability to PG, and PG or MP not only increased the thermal stability but also improved the mechanical properties of PDMS composites. Meanwhile, compared with PG/PDMS composites, MP/PDMS composites had better thermal stability and mechanical properties owing to the better dispersion of MP into the matrix, the stronger chemical interfacial interaction between MP and the matrix. Copyright © 2010 John Wiley & Sons, Ltd.     

Thermal and microstructural characterization of compatibilized polystyrene/natural fillers composites

Composites of polystyrene (PS) with cellulose microfibres and oat particles, obtained by melt mixing, were examined. The compatibilization of the composites was carried out by addition of maleic anhydride-functionalized copolymers (SEBS-g-MA, PS-co-MA) and poly(ethylene glycol) to improve the fibre–matrix interfacial interactions. The plain components and their composites were characterised by FT-IR, DSC, TGA, SEM microscopy and mechanical tests. The properties of the various systems were analysed as a function of both fibre and compatibilizer amount. The compatibilized PS composites showed enhanced fibre dispersion and interfacial adhesion as a consequence of chemical interactions between the anhydride groups on the polymer chains and the hydroxyl groups on the fibres, as demonstrated by FT-IR spectroscopy. DSC analysis pointed out a neat increase of T _g of composites on addition of SEBS-g-MA, as compared to PS-co-MA. The thermal stability of composites was also influenced by the type and amount of fibres, as well as by the structure and concentration of compatibilizer. The effect of the reactive copolymers on the composites properties was accounted for on the basis of the polymer–polymer miscibility and chemical interactions at the matrix/filler interface.     

Effect of carbon nanotubes on mechanical and electrical properties of polyimide/carbon nanotubes nanocomposites

Multi-walled carbon nanotubes (MWNTs) reinforced polyimide nanocomposites were synthesized by in situ polymerization using 4,4′-oxydianilline, MWNTs, and pyromellitic dianhydride followed by casting, evaporation and thermal imidization. A homogeneous dispersion of chemically modified MWNTs was achieved in polyimide matrix as evidenced by scanning electron microscopy and atomic force microscopy. The incorporation of the modified MWNTs enhanced the mechanical properties of the polyimide due to the presence of strong interfacial interaction between the polymer matrix and the nanotubes in polymer composites. The resultant polyimide/MWNTs nanocomposites were electrically conductive with significant conductivity enhancement at 3 wt% MWNTs, which is favorable for many practical uses.     

Reactive copolymer functionalized graphene sheet for enhanced mechanical and thermal properties of epoxy composites

Uniform dispersion of graphene nanosheets (GNS) in a polymer matrix with strong filler–matrix interfacial interaction, preserving intrinsic material properties of GNS, is the critical factor for application of GNS in polymer composites. In this work, a novel reactive copolymer VCz–GMA containing carbazole and epoxide group was designed, synthesized and employed to noncovalently functionalize GNS for preparing epoxy nanocomposites with enhanced mechanical properties. The presence of carbazole groups in VCz–GMA enables the tight absorption of copolymer on to graphene surface via π–π stacking interaction, as evidenced by Raman and fluorescence spectroscopy, whereas the epoxide segments chemically reacts with the epoxy matrix, improving the compatibility and interaction of graphene with epoxy matrix. As a result, the VCz–GMA–GNS/epoxy composite showed a remarkable enhancement in both mechanical and thermal property than either the pure epoxy or the graphene/epoxy composites. The incorporation of 0.35 wt % VCz–GMA–GNS yields a tensile strength of 55.72 MPa and elongation at break of 3.45, which are 42 and 191% higher than the value of pure epoxy, respectively. Increased glass transition temperature and thermal stability of the epoxy composites were also observed. In addition, a significant enhancement in thermal conductivity was achieved with only 1 wt % VCz–GMA–GNS loading. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2776–2785     

Synthesis of maleimide substituted polystyrene–silica hybrid utilizing michael addition reaction

The transparent polymer hybrids were prepared from polystyrene bearing pendant maleimide moieties (16%) and tetraethoxysilane (TEOS) using γ-aminopropyltriethoxysilane (γ-APS) as a crosslinking agent by an in situ sol–gel process by utilizing Michael-addition reaction. Maleimide substituted polystyrene was synthesized by a mild Friedel-Crafts reaction of polystyrene and N-chloromethylmaleimide. Fourier Transform Infrared (FTIR) spectral data confirms the occurrence of Michael-addition reaction between the pendant maleimide moieties of the styrene copolymer and γ-aminopropyltriethoxysilane. The percentage of maleimide substitution was calculated from ¹H NMR spectrum. The transparent hybrid shows high solvent resistance at the boiling point of Tetrahydrofuran (THF) since the polystyrene-substituted-maleimide (PS-s-MA) was covalently bonded with siloxane matrix. Thermal properties of the transparent hybrid materials were investigated by Differential scanning calorimeter (DSC) and Thermo gravimetric analysis (TGA) in order to ascertain their glass transition temperature (Tg) and thermal stability behaviour. Morphology and transparency of the organic–inorganic hybrids were confirmed by Scanning electron microscopy (SEM) and optical images. The homogeneity of the polymer hybrids was also examined by nitrogen porosimetry studies.     

Epoxy matrix composites reinforced with purified carbon nanotubes for thermal management applications

The role of carbon nanotube purification treatment as a means to improve the thermal properties of polymer matrix composites was investigated. Particular emphasis was placed on clarifying the processing‐property relationship in polymer composites for thermal management applications. The results indicated that purification treatment is critical to the thermal properties of derived polymer composites. Purification treatment can yield a twofold increase in composite thermal conductivity because of improved effectiveness in interfacial interaction and increased chemical purity of the filler. However, there is a trade‐off between the benefits and disadvantages associated with purification treatment, particularly when thermal and electrical properties are both concerned. Purification treatment gives rise to a sharp decrease in composite electrical conductivity by at least two orders of magnitude because of the lack of an effective percolating network. The effect of purification treatment on composite electrical properties is more significant than on its thermal properties.     

Effect of sepiolite fiber on the structure and properties of the sepiolite/silica aerogel composite

Sepiolite fiber-reinforced silica aerogel composites for thermal insulators were prepared by dispersing sepiolite fiber in silica sol, aging, solvent exchanging, and drying in supercritical fluid. The surface treated sepiolite fiber and sepiolite/silica aerogel composite were characterized by scanning electron microscope; transmission electron microscope and Fourier transform infrared spectroscopy. The influence of surface treated sepiolite fiber on the mechanical and thermal properties of the aerogel composite was studied. The results indicate the hydroxyl groups on silica sol particles surface able to condense with the hydroxyls of sepiolite fibers with forming Si–O–Si between sepiolite fibers and aerogel matrix in the sol–gel process, which achieves excellent interfacial interaction in the sepiolite/silica aerogel composite, so the mechanical properties of the aerogel composite have been improved effectively without sacrificing much thermal insulating performance.     

Preparation and characterization of modified graphite oxide/poly(propylene carbonate) composites by solution intercalation

Modified graphite oxide (MGO)/Poly (propylene carbonate) (PPC) composites with excellent thermal and mechanical properties have been prepared via a facile solution intercalation method. An intercalated structure of MGO/PPC composites was confirmed by X-ray diffraction and scanning electron microscope. The thermal and mechanical properties of MGO/PPC composites were investigated by thermal gravimetric analysis, differential scanning calorimetric, dynamic mechanical analysis, and electronic tensile tester. Due to the nanometer-sized dispersion of layered graphite in PPC matrix and the strong interfacial interaction between MGO and PPC, the prepared MGO/PPC composites exhibit improved thermal and mechanical properties in comparison with pure PPC. Compared with pure PPC, the MGO/PPC composites show the highest thermal stability and the T_g is 13.8 °C higher than that of pure PPC, while the tensile strength (29.51 MPa) shows about 2 times higher than that of pure PPC when only 3.0 wt.% MGO is incorporated. These results indicate that this approach is an efficient method to improve the properties of PPC.     

尼龙6/高岭土界面相互作用对其复合材料力学性能和流变行为的影响

<正> 无机填料填充复合材料的性能,除了依赖于聚合物基体和填料固有的内在性质外,很大程度上依赖于它们之间的界面性质。因此,研究聚合物/填料界面相互作用,对合理地设计具有优良性能的复合材料具有十分重要的意义。 目前,还很难对粉末填料与聚合物基体之间界面相互作用进行定量的研究,而且关于这方面的报道也较少。本文利用接触角法测定了高岭土填料和尼龙6基体的表面自由能、界面张力、粘附功等热力学参数,对高岭土与尼龙6之间界面相互作用与复合材料力学性能、流变行为的关系进行了分析和探讨。     

Role of adsorbed chain rigidity in reinforcement of polymer nanocomposites

The thermomechanical behavior of polymer nanocomposites is mostly governed by interfacial properties which rely on particle–polymer interactions, particle loading, and dispersion state. We recently showed that poly(methyl methacrylate) (PMMA) adsorbed nanoparticles in poly(ethylene oxide) (PEO) matrices displayed an unusual thermal stiffening response. The molecular origin of this unique stiffening behavior resulted from the enhanced PEO mobility within glassy PMMA chains adsorbed on nanoparticles. In addition, dynamic asymmetry and chemical heterogeneities existing in the interfacial layers around particles were shown to improve the reinforcement of composites as a result of good interchain mixing. Here, the role of chain rigidity in this interfacially controlled reinforcement in PEO composites is investigated. We show that particles adsorbed with less rigid polymers improve the mechanical properties of composites. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 9–14     

碳纳米管改性聚苯硫醚熔纺纤维的结构与性能研究

将多壁碳纳米管(MWCNTs)和聚苯硫醚(PPS)经过熔融挤出后制备成复合材料切片,并采用熔融纺丝法制得碳纳米管改性聚苯硫醚复合纤维.采用扫描电镜(SEM)、拉曼光谱、示差扫描量热分析(DSC)、动态机械分析(DMA)以及力学性能测试等表征手段研究了复合纤维中碳管的分散状态,与基体的界面作用,复合纤维的结晶性能以及力学性能,从而探讨了聚苯硫醚/碳纳米管复合纤维体系的微观结构与宏观性能之间的关系.研究表明,聚苯硫醚分子结构与碳纳米管之间具有的π-π共轭作用使碳管较为均匀的分散在基体中,界面结合较为紧密.同时熔融纺丝过程中的拉伸作用使碳管进一步解缠并使碳管沿纤维拉伸方向取向.另一方面,拉曼光谱显示拉伸作用有效地增强了界面作用,有利于外界应力的传递.碳管的良好分散以及强的界面作用使复合纤维力学性能得到大幅度的提高,当碳管含量达到5 wt%时,复合纤维的模量有了明显的提高,拉伸强度较纯PPS纤维提高了近220%.     

A thermal and mechanical study under dynamical conditions of polypropylene/mica composites containing atactic polypropylene with succinil‐fluoresceine grafted groups as interfacial modifier from the matrix side

The dynamic thermal and mechanical behavior of Polypropylene/Mica composites—with improved properties induced by the presence of succinil‐fluoresceine groups onto atactic polypropylene with different grafting levels—is the subject of this article. A further correlation of these with the macroscopic mechanical performance of the composite materials is also discovered. The atactic polypropylenes containing succinil‐fluoresceine grafted groups were previously obtained in our laboratories by chemical modification of a byproduct of industrial polymerization reactors. The interfacial modifications induced by replacing a little amount of polymer matrix in the composite material by the grafted atactic polypropylene is clearly concluded either from a microscopic or a macroscopic point of view. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1564–1574, 2000     

Structural morphology developments in the interfacial phase of heterocoagulated composite particles: dynamic mechanical measurements

The dynamic mechanical properties of polymeric composites composed of poly (methyl methacrylate) continuous-phase and various inclusion types of heterocoagulated composite particles were investigated in order to relate them to the morphology of shell region of composite particles. Using the heterocoagulation process, large particles were encapsulated with various types of small particles: (1) conventional linear-type polymer particles; (2) crosslinked polymer particles; and (3) reactive polymer particles capable of forming crosslinked structure, whereby the interfacial properties of the composite become modified. These composite particles were subsequently annealed to form continuous shell regions and then mixed with matrix particles. It is shown that chain diffusion movement of the small particles having different chain characteristics influences the network formation at the interfacial shell region. The ability of maintaining interfacial domain structure depends on the degree of network formation.     

Facile fabrication of organically modified boron nitride nanosheets and its effect on the thermal stability,flame retardant,and mechanical properties of thermoplastic polyurethane

Although hexagonal boron nitride (h‐BN) has presented a potential prospect in polymer composite fields, undesirable interfacial interaction with polymer matrix that generates serious aggregation of nanomaterials has suppressed its enhancement effect. Moreover, the chemically inert surface of h‐BN also makes the commonly used approach that improves the interfacial interaction between nanofillers and polymeric matrix invalid. Herein, the functionalized modification of chemically inert h‐BN was successfully fabricated by the adsorption of cetyl‐trimethylammonium bromide, with electrostatic interactions. The obtained h‐BN (cetyl‐trimethylammonium bromide‐BN) was well characterized by systematic tests and then added into thermoplastic polyurethane (TPU) matrix. The inclusion of functionalized h‐BN can dramatically improve thermal stability, flame retardant, and mechanical properties of TPU composites. With the incorporation of as low as 4.0 wt% nanofillers, maximal value of heat release rate and total heat release of TPU were reduced by 57.5% and 17.8%, compared with those of pure TPU, respectively. Moreover, tensile strength of TPU composite with a loading of 2.0 wt% was increased by 79.3% in comparison with that of neat TPU. The facile functionalized approach of chemically inert h‐BN paves the way for promising applications of h‐BN in the development of flame retardant polymer materials.     

Smart modification of inorganic fibers and flammability mechanical and radiation shielding properties of their rubber composites

Facile and smart method for the modification of inorganic fibers has been developed. The polyaniline was synthesized on basalt fiber surface presenting an organic polymer shell to the inorganic fibers. The modified basalt fibers were dispersed in rubber-producing well-dispersed rubber composites. Various mass loadings of modified basalt fibers were dispersed and optimized. The effect of radiation on the properties of developed rubber composites was investigated by exposure to different gamma radiation doses. The flammability, thermal and mechanical properties were studied. The flammability of developed composites was improved achieving 62 and 16% reduction in the peak heat release rate compared to blank rubber and unmodified basalt fiber-based rubber composite, respectively. This is in addition to significant reduction in emission of CO and CO₂ gases by 65 and 58%, respectively. Also, the tensile strength property was enhanced by 38 and 53% compared to blank and unmodified basalt composite, respectively. The role of polyaniline layer on inorganic fiber surface and their effect on the properties of the produced composites was studied. The organic polymer shell achieved good compatibility and interfacial adhesion of basalt fibers with rubber matrix and radiation protection effect for the developed composites.     

Effect of compatibilization on thermal degradation kinetics of HDPE-based composites containing cellulose reinforcements

Dynamic thermogravimetric analysis under nitrogen flow was used to investigate the thermal decomposition process of high-density poly(ethylene) (HDPE)-based composites reinforced with cellulose fibers obtained from the recycling of multilayer carton scraps, as a function of the cellulose content and the compatibilization. The Friedman, Flynn–Wall–Ozawa, and Coats–Redfern methods were used to determine the apparent activation energy (E _a) of the thermal degradation of the cellulose component into the composites. E _a has been found dependent on the cellulose amount and on the cellulose/polymer matrix interfacial adhesion. In particular, it has been evidenced an increase of the cellulose thermal stability as a consequence of the improved interfacial adhesion between the components in NFR composites.     

The nanomechanical behavior of a graphite nanoplatelet/polycarbonate nanocomposite

Quasi-static nanoindentation has been used to characterize the mechanical properties of polycarbonate reinforced with graphite nanoplatelets (GNPs). Poor dispersion or low quality interfacial interactions of GNPs in a polymer matrix can significantly decrease the relative improvement in the material's mechanical strength and stiffness. In this study, the surfaces of GNPs were modified to achieve better dispersion and interfacial interaction between fillers and matrix. The GNP/PC nanocomposite has a heterogeneous microstructure, and the original mechanical properties between filler and matrix have large differences. Using a spatially sensitive probe method leads to measured values of modulus and hardness that correlate with the indentation sampled volume. A grid indentation procedure was performed with variable sampling volumes to provide a statistical measurement of modulus and hardness for the nanocomposite materials. The surface treatment leads to a significant increase in both stiffness and hardness for GNP reinforced composites.