Influence of silicon carbide filler on mechanical and dielectric properties of glass fabric reinforced epoxy composites

Fiber‐reinforced polymeric composites (FRPCs) have emerged as an important material for automotive, aerospace, and other engineering applications because of their light weight, design flexibility, ease of manufacturing, and improved mechanical performance. In this study, glass‐epoxy (G‐E) and silicon carbide filled glass‐epoxy (SiC‐G‐E) composite systems have been fabricated using hand lay‐up technique. The mechanical properties such as tensile strength, tensile modulus, elongation at break, flexural strength, and hardness have been investigated in accordance with ASTM standards. From the experimental investigations, it has been found that the tensile strength, flexural strength, and hardness of the glass reinforced epoxy composite increased with the inclusion of SiC filler. The results of the SiC (5 wt %)‐G‐E composite showed higher mechanical properties compared to G‐E system. The dielectric properties such as dielectric constant (permittivity), tan delta, dielectric loss, and AC conductivity of these composites have been evaluated. A drastic reduction in dielectric constant after incorporation of conducting SiC filler into epoxy composite has been observed. Scanning electron microscopy (SEM) photomicrographs of the fractured samples revealed various aspects of the fractured surfaces. The failure modes of the tensile fractured surfaces have also been reported. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

环氧树脂/纳米纤维素复合材料的制备与性能研究

以木粉为原料制备纳米纤维素（CNF）,经甲基丙烯酸缩水甘油酯（GMA）改性后采用溶液共混法与环氧树脂（EP）复合,制得EP/CNF⁃GMA复合材料;通过对EP/CNF、EP/CNF⁃GMA复合材料力学性能、透光性能、亲水性、热稳定性和微观结构的表征,研究了CNF和GMA含量对复合材料性能的影响及其机理。结果表明,EP/CNF复合材料的拉伸强度、断裂伸长率、透光率随CNF含量的增大呈先增后减的变化趋势,亲水性随CNF含量的增大而增大;CNF含量为0.6 %（质量分数,下同）时,EP/CNF复合材料性能最优,拉伸强度为32.166 MPa,断裂伸长率为20.995 %,600 nm处透光率为79.8 %,接触角为77.34°。经GMA改性后,CNF与EP的相容性得到了改善,提升了EP/CNF复合材料的力学性能和热稳定性;随GMA含量的增加,EP/CNF⁃GMA复合材料的拉伸强度、断裂伸长率、透光率和亲水性均发生变化;GMA含量为4.8 %时EP/CNF⁃GMA复合材料性能最佳,拉伸强度为57.933 MPa,断裂伸长率为18.762 %,600 nm处透光率为86.3 %,接触角为81.42 °。     

Mechanical properties of biodegradable composites from poly lactic acid (PLA) and microcrystalline cellulose (MCC)

Biodegradable composites were prepared using microcrystalline cellulose (MCC) as the reinforcement and polylactic acid (PLA) as a matrix. PLA is polyester of lactic acid and MCC is cellulose derived from high quality wood pulp by acid hydrolysis to remove the amorphous regions. The composites were prepared with different MCC contents, up to 25 wt %, and wood flour (WF) and wood pulp (WP) were used as reference materials. Generally, the MCC/PLA composites showed lower mechanical properties compared to the reference materials. The dynamic mechanical thermal analysis (DMTA) showed that the storage modulus was increased with the addition of MCC. The X‐ray diffraction (XRD) studies on the materials showed that the composites were less crystalline than the pure components. However, the scanning electron microscopy (SEM) study of materials showed that the MCC was remaining as aggregates of crystalline cellulose fibrils, which explains the poor mechanical properties. Furthermore, the fracture surfaces of MCC composites were indicative of poor adhesion between MCC and the PLA matrix. Biodegradation studies in compost soil at 58°C showed that WF composites have better biodegradability compared to WP and MCC composites. The composite performances are expected to improve by separation of the cellulose aggregates to microfibrils and with improved adhesion. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2014–2025, 2005     

Investigation into the morphological and mechanical properties of date palm fiber-reinforced epoxy structural composites

This study aims to examine the morphology and mechanical properties (tensile, flexural, and compressive) of epoxy composites reinforced with epoxy date palm leaves (EDPL), epoxy date palm branch (EDPB), and epoxy/hardener date palm core shell (EDPC) fibers (particle size <1 μm depend on the date palm fibers). A three-step technique was used to obtain the composites. The EDPL composites showed a maximum tensile strength of 3.45 MPa, while the EDPB composites showed maximum compressive and flexural rigidity of 9.46 and 5.55 MPa, respectively, owing to the good compatibility of fiber-matrix bonding. In this work, epoxy composites reinforced with date palm fibers (DPF) leaves, branches, and core shell were recycled using a cost-effective and easily reproducible three-step technique. EDPC fibers fabricated with 64.65% weight carbon fibers content demonstrated improved tensile strengths and stiffness properties. The three samples of palm date composites revealed mechanical properties that could be used to trial these fibers for manufacturing purposes, and to exploit their extraordinary mechanical properties shown in current results.     

Surface modification of nanocrystalline cellulose and its application in natural rubber composites

As a biopolymer with high mechanical strength, nanocellulose was generally considered as a green filler for reinforcing polymer. In this study, nanocrystalline cellulose (NCC) isolated from softwood pulp was successfully modified by cetyltrimethyl ammonium bromide (CTMAB), a cationic surfactant, and the modified nanocrystalline cellulose (m-NCC) was used to reinforce natural rubber (NR). In this composite architecture, it was found that when the filler content was 5 or 10 phr, the surface modification of NCC improved the dispersion state of NCC in NR matrix and the interfacial interaction between NR and NCC. Therefore, the NR/m-NCC composites exhibited outstanding mechanical properties, and its tensile strength, elongation at break and tear strength was increased by 132.8, 20, and 66.1%, respectively, compared to pristine NR composites. Besides, the modified NCC could accelerate the vulcanization and improve wet-skid resistance and aging resistance of NR composites. It is envisioned that the modified NCC has the potential to be generalized to manufacturing other polymer matrix composites strengthened with nanocellulose.     

Characterization and mechanical properties of ultraviolet stimuli‐responsive functionalized cellulose nanocrystal alginate composites

The poor mechanical properties of alginate when exposed to aqueous solution have been a problem plaguing researchers within the biomedical field. In order to be able to improve the mechanical properties in a systematic manner functionalized cellulose nanocrystals (CNCs) were added to alginate and UV‐induced crosslinked following an azo‐initiated free radical polymerization. CNCs were functionalized with 4‐pentenoic acid (PA‐g‐CNCs) using a simple, environmentally friendly solvent‐free esterification. The dimensional and crystallinity properties of PA‐g‐CNCs remained unchanged following esterification. Thermogravimetric analysis, Fourier transform infrared spectroscopy, and ¹³C nuclear magnetic resonance indicated that 4‐pentenoic acid was present on the surface of CNCs through bulk analysis. These PA‐g‐CNCs were then used in the creation of composites with an azo‐initiator to induce UV‐dependent crosslinking for the improvement of the mechanical properties of alginate. It was shown that the properties of alginate can be enhanced with the addition of functionalized CNCs to nanocomposites in mechanical testing in wet and dry conditions. These results suggest that the addition of PA‐g‐CNCs and crosslinking by UV‐dependent free radical polymerization improves the performance of alginate when tested in dry conditions, but without any apparent dependence to azo‐initiated crosslinking when exposed to water in regards to mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45857.     

Thermal and mechanical properties of polypropylene nanocomposite materials reinforced with cellulose nano whiskers

We use polypropylene (PP, an apolar polymer) and cellulose nano whiskers (CNW, a polar material) to produce nano polymer composites with enhanced mechanical and thermal properties. To improve compatibility, maleic anhydride grafted PP has also been used as a coupling agent. To enhance the uniform distribution of CNW in the composite, the matrix polymer is dissolved in toluene, and sonification and magnetic stirring are applied. Good film transparency indicates uniform CNW dispersion, but CNW domains in the composite film observed under an scanning electron microscope may indicate slight agglomeration of CNW in the composite film. The tensile strength of the composite compared with neat PP improves by 70–80% with the addition of CNW. The crystallinity has also been improved by about 50% in the CNW reinforced samples. As the content of CNW increases, the composite exhibits higher thermal degradation temperature, higher hydrophilicity, and higher thermal conductivity. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

环氧树脂/碳化硅复合材料的热性能及韧性

采用碳化硅作为增强剂制备了环氧树脂/碳化硅复合材料,考察了复合材料的热学及力学性能。实验结果表明,碳化硅的添加使环氧树脂的玻璃化温度提高。当碳化硅添加质量分数为3%时,复合材料的韧性与纯环氧树脂相比提高了35%。     

Impact of water absorption on the creep performance of epoxy/microcrystalline cellulose composites

Recently, considerable effort has been made to study cellulose/epoxy composites. However, there is a gap when it comes to understanding the post-conditioning anomalous effect of moisture uptake on their mechanical and dynamic-mechanical properties, and on their creep behavior. In this work, up to 10.0 wt% microcrystalline cellulose (MCC) was incorporated into epoxy resin by simple mixing and sonication. Epoxy/MCC composites were fabricated by casting in rubber silicone molds, and rectangular and dog-bone test specimens were produced. The moisture uptake, dynamic mechanical, chemical, tensile, and creep behavior were evaluated. The incorporation of MCC increased the water diffusion coefficient. The changes in storage modulus and glass transition temperature, combined with Fourier-transform infrared spectroscopy analysis, evidenced that water sorption in epoxies causes both plasticization and additional resin crosslinking, although the latter is prevented by the addition of MCC. The creep strain of the composites increased by 60% after conditioning, indicating that plasticization induced by water sorption plays an important role in the long-term properties of the composites.     

Effects of plasma treatment on mechanical properties of rubber/cellulose fibre composites

Natural rubber materials reinforced with cellulose fibres have been studied with respect to crosslink density, tensile strength and stress relaxation. The fibres have been grafted with butadiene or divinylbenzene by plasma treatment. Chemiluminescence analysis was used to indicate the grafting on the surface of the cellulose fibres and also to estimate the effect of the plasma on the cellulose fibres. The results indicate the possibility of obtaining a surface layer on the fibres, which is a conceivable way of improving the mechanical properties of rubber composites.     

Influence of alkali fiber treatment and fiber processing on the mechanical properties of hemp/epoxy composites

Industrial hemp fibers were treated with a 5 wt % NaOH, 2 wt % Na₂SO₃ solution at 120°C for 60 min to remove noncellulosic fiber components. Analysis of fibers by lignin analysis, scanning electron microscopy (SEM), zeta potential, Fourier transform infrared (FTIR) spectroscopy, wide angle X‐ray diffraction (WAXRD) and differential thermal/thermogravimetric analysis (DTA/TGA), supported that alkali treatment had (i) removed lignin, (ii) separated fibers from their fiber bundles, (iii) exposed cellulose hydroxyl groups, (iv) made the fiber surface cleaner, and (v) enhanced thermal stability of the fibers by increasing cellulose crystallinity through better packing of cellulose chains. Untreated and alkali treated short (random and aligned) and long (aligned) hemp fiber/epoxy composites were produced with fiber contents between 40 and 65 wt %. Although alkali treatment generally improved composite strength, better strength at high fiber contents for long fiber composites was achieved with untreated fiber, which appeared to be due to less fiber/fiber contact between alkali treated fibers. Composites with 65 wt % untreated, long aligned fiber were the strongest with a tensile strength (TS) of 165 MPa, Young's modulus (YM) of 17 GPa, flexural strength of 180 MPa, flexural modulus of 9 GPa, impact energy (IE) of 14.5 kJ/m², and fracture toughness (K_Ic) of 5 MPa m^1/2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhanced oil resistance and mechanical properties of nitrile butadiene rubber/lignin composites modified by epoxy resin

This is probably the first report on developing nitrile butadiene rubber (NBR) composites with enhanced performance s via lignin bridged epoxy resin in the rubber matrix. NBR/lignin masterbatch has been prepared through latex‐compounding method, and then epoxy resin (F51) was added in the NBR/lignin compounds by the melt compounding method. Lignin‐epoxy resin networks were synthesized in situ during the curing process of rubber compounds through epoxide?hydroxyl reactions. Compared with lignin filler, lignin‐F51 networks showed an improved oil resistance ability and led to increased mechanical properties, crosslinking density, and thermal stability of the rubber composites. This method provides a new insight into the fabrication of novel interpenetrating polymer networks in rubber composites and enlarges the potential applications of lignin in high performance rubber composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42922.     

Green esterification: A new approach to improve thermal and mechanical properties of poly(lactic acid) composites reinforced by cellulose nanocrystals

Cellulose nanocrystal (CNCs)‐reinforced poly(lactic acid) (PLA) nanocomposites were prepared using twin screw extrusion followed by injection molding. Masterbatch approach was used to achieve more efficient dispersion of CNCs in PLA matrix. Modified CNCs (b‐CNCs) were prepared using benzoic acid as a nontoxic material through a green esterification method in a solvent‐free technique. Transmission electron microscopy images did not exhibit significant differences in the structure of b‐CNCs as compared with unmodified CNCs. However, a reduction of 6.6–15.5% in the aspect ratio of b‐CNCs was observed. The fracture surface of PLA‐b‐CNCs nanocomposites exhibited rough and irregular pattern which confirmed the need of more energy for fracture. Pristine CNCs showed a decrease in the thermal stability of nanocomposites, however, b‐CNCs nanocomposites exhibited higher thermal stability than pure PLA. The average storage modulus was improved by 38 and 48% by addition of CNCs and b‐CNCs in PLA, respectively. The incorporation of b‐CNCs increased Young's modulus, ultimate tensile stress, elongation at break, and impact strength by 27.02, 10.90, 4.20, and 32.77%, respectively, however, CNCs nanocomposites exhibited a slight decrease in ultimate strength and elongation at break. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46468.     

Effects of a liquid metal co-filler on the properties of epoxy/binary filler composites

Liquid metals (LMs) with high fluidity and high thermal conductivity (TC) are receiving considerable attention in the research on thermal management polymer composites as alternatives to conventional rigid solid fillers or as co-fillers to overcome the trade-off between TC and composite processability at high filler loads. While most previous studies have investigated the effects of LM fillers in soft elastomeric matrices, their effects on the composite properties with rigid matrices, such as epoxy-based polymers, have not been discussed extensively. Herein, we investigated the effects of LM eutectic Ga-In (EGaIn) as a co-filler on the properties of rigid epoxy-based composites with a binary filler (Al₂O₃/EGaIn) system. The increase in the volume fraction of LM fillers significantly improves the processability of uncured precursor composites but markedly decreases the mechanical strength of the cured composites at their high loads—the latter effects have rarely been examined in previous studies. However, with adequate LM loads, the composites exhibited superior mechanical properties compared with the all-solid-filler system, withstanding a surprisingly high compressive load (~100 kN) under which the all-solid-filler system fractured. Furthermore, the epoxy/binary filler composites exhibited reasonably high TC values (~1 W/mK) comparable to that of commercial epoxy molding compounds, suggesting their potential applicability for electronic packaging.     

Aerocellulose based on all‐cellulose composites

Novel aerogels (or aerocellulose) based on all‐cellulose composites were prepared by partially dissolving microcrystalline cellulose (MCC) in an 8 wt % LiCl/DMAc solution. During this process, large MCC crystals and fiber fragments were progressively split into thinner crystals and cellulose fibrils. The extent of the transformation was controlled by using cellulose concentrations ranging from 5 to 20 wt % in the LiCl/DMAc solution. Cellulose gels were precipitated and then processed by freeze‐drying to maintain the openness of the structure. The density of aerocellulose increased with the initial cellulose concentration and ranged from 116 up to 350 kg m^?3. Aerocellulose with relatively high mechanical properties were successfully produced. The flexural strength of the materials reached 8.1 MPa and their stiffness was as high as 280 MPa. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of water sorption on the structure and mechanical properties of an epoxy resin system

The characteristics of sorption and diffusion of water in an amine‐cured epoxy system based on tetraglycidyl diaminodiphenylmethane and a novolac glycidyl ether resin were studied as a function both of the polymer microstructure, known from previous works, and the temperature. Water‐sorption experiments and dynamic mechanical analysis (DMA) were performed. Tensile stress–strain and Rockwell hardness tests were conducted to investigate the effects of absorbed water on the mechanical properties of the material. Competing effects of the sorption of water in the free volume and of strong interactions between water molecules and polar groups of the network were used to explain the diffusional behavior observed, which followed Fick's second law. DMA analysis seemed to be sensitive to the water effects and the viscoelastic behavior was related both to the water‐sorption processes and to the microstructure of the system. An important impact of water uptake on the tensile properties at break was also appreciated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 71–80, 2001     

Mechanical properties of natural rubber/grafted cellulose fibre composites

Mechanical properties of natural rubber/allyl acrylate and allyl methacrylate grafted cellulose fibre composites are presented. Stress/strain measurements and dynamic mechanical measurements indicate that the adhesion between grafted fibres and matrix is better than that in samples containing untreated cellulose fibres. This makes it possible to vary the composite properties by varying the fibre type and/or fibre amount.     

改性微晶纤维素的制备及其对填充丁苯橡胶性能的影响II 改性棉纤维素对填充丁苯橡胶性能的影响

研究了微晶纤维素(MCC)和改性微晶纤维素(MMCC)的用量对丁苯橡胶(SBR)硫化胶物理机械性能的影响,以及分别填充20phrMCC和MMCC的SBR复合材料的耐磨性和动态力学性能分析。结果表明,当MCC和MMCC的用量都为20phr时,硫化胶有最大的拉伸强度,分别为15.3MPa和19.0MPa;填充MMCC的SBR复合材料的磨耗体积比填充MCC的降低了41%;填充20phr的MCC和MMCC的SBR具有相似的玻璃化温度。     

Construction of thermoplastic cellulose esters matrix composites with enhanced flame retardancy and mechanical properties by embedding hydrophobic magnesium hydroxide

Biomass-based composites with renewability and biodegradability have attracted extensive researches, but their applications are hindered by poor mechanical properties and flame retardancy. Cellulose ester matrix composites (CEMC), a kind of biomass-based composites, were prepared with inorganic crystals as flame retardant and reinforcement. Cellulose acetate oleate (CAO) prepared by mechanical activation-assisted solid-phase reaction was used as thermoplastic matrix. Hydrophobic oleate-magnesium hydroxide (O-MH), which was surface-modified with oleic acid, was embedded into CAO to prepare O-MH/CAO composites by hot pressing. The introduction of oleoyl contributed to favorable thermoplasticity of cellulose ester, resulting in enhanced thermal stability and mechanical properties of CEMC. The uniform dispersion of O-MH in the CAO matrix via metal–organic coordination increased the mechanical properties and flame retardancy of O-MH/CAO composites, ascribing to the toughening effect and combustion inhibition effect induced by O-MH. This study provides a feasible technology for fabricating the CEMC with outstanding thermal stability and mechanical properties.