Rheological behaviour of borosilicate composites with metallic and non-metallic dispersions

Silicate matrix composites are potential candidates for high-temperature applications. In the present investigation, the effect of metallic (Cu) and non-metallic (SiC particulates, platelets, short fibres and whiskers) additions on the rheological behaviour of borosilicate matrix composites has been evaluated. The hot-pressed composites were tested both in compression and tension in the temperature range of 625–725°C. SiC reinforced composites tested in compression exhibited varying degree of strengthening and strain rate sensitivity depending on the volume fraction and morphology of reinforcements. The degree of strengthening and strain rate sensitivity depends on the volume fraction and morphology of reinforcements. Strengthening effect increased with the volume fraction and aspect ratio of reinforcements. The flow behaviour of composites changed from Newtonian to non-Newtonian with strain rate sensitivity index value changing from unity to 0.48. A similar trend was seen in the rate sensitivity of copper composites. However, copper additions decreased the strength of the composites at lower temperatures because of the softer copper phase. Pre-oxidation of copper particles had certain strengthening effect on the composite. The apparent viscosity of SiC reinforced composites increased with volume fraction and aspect ratio of reinforcements. However, in particulate composites, the viscosity found to increase with particle size. The mechanical/hydrodynamic interactions among the particulates appeared to be responsible for such a behaviour. With increasing strain rate, the viscosity decreased progressively confirming the shear thinning of the composites. The tensile ductility of the composites with 40 vol% reinforcements was evaluated at 700°C. While 400% elongation was observed in SiC particulate, platelet and copper composites, in short fibre/whisker composites, the tensile elongation values were only 150%. Further, the elongation of SiC platelet and copper composites improved by decreasing temperature and volume fraction of reinforcements, and also elongation values >500% were recorded. The tensile ductility of borosilicate composites was limited by onset and growth of cavities nucleated at the reinforcement/matrix interfaces.     

Soy protein isolate/kraft lignin composites compatibilized with methylene diphenyl diisocyanate

Methylene diphenyl diisocyanate (MDI) was used to compatibilize kraft lignin (KL)/soy protein isolate (SPI) blends. The structure and properties of the resultant composite materials were investigated with wide‐angle X‐ray diffraction, differential scanning calorimetry, dynamical mechanical thermal analysis, scanning electron microscopy, and tensile and water absorption tests. The results indicated that graft copolymerization and a moderate degree of crosslinking between KL and SPI occurred in the composites because of the compatibilization of MDI, which favored the strengthening of the materials. Interestingly, the addition of 2 parts of MDI caused a simultaneous enhancement of the modulus, strength, and elongation of KL/SPI blends. The structure with grafting and moderate crosslinks reduced the water absorption of the materials. However, the excess crosslinks hindered the interaction between KL and SPI, resulting in a reduction of the mechanical properties. Scanning electron microscopy showed that the domains of the graft copolymer and crosslinking enrichment existed in the blends. When the MDI content was relatively low, these domains became concentric points of stress, enhancing the mechanical properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 624–629, 2004     

HDPE/木质素复合材料的制备及性能

采用甲酸法制备了木质素,将木质素和羟甲基化木质素分别与高密度聚乙烯(HDPE)熔融共混制备了 HDPE／木质素复合材料,研究了其力学性能和相态结构。结果表明:随术质素或羟甲基化木质素加入量的增加,复合材料的断裂伸长率逐渐提高;弯曲模量和弯曲强度随羟甲基化木质素含量的增加分别提高了17.3％和12．2％;与木质素共混时,弯曲强度在木质素质量分数为2．5％处达到最高值(16．1 MPa),随后叉呈下降趋势;HDPE／木质素和 HDPE／羟甲基化木质素的断裂拉伸强度分别提高了8．0％和16．2％;但材料的抗冲击性能有所降低;总体上,木质素的羟甲基化使复合材料的性能优于木质素复合材料。     

Effect of nanoclay on the mechanical and damping properties of aramid short fibre‐filled styrene butadiene rubber composites

The effect of nanoclay loading on the alteration of tensile and dynamic mechanical properties of aramid short fibre‐filled styrene butadiene rubber composites was investigated. In all the composites, 20 phr of N330 black was used. Dynamic mechanical thermal analysis was used to investigate the viscoelastic damping at lower dynamic strains. Compressive hysteresis was evaluated to characterize higher strain static damping properties. Matrix–fibre interaction and filler distribution were investigated using morphological analyses. Matrix–filler interface, estimated by the half height width of the tan δ peak, plays a major role in energy dissipation. The matrix–fibre interaction parameter shows a similar trend with low strain tensile stress values. Nanoclay addition to the composites leads to improved elongation at break and frequency damping properties. Compressive hysteresis reflects no improvement of hysteresis with nanoclay loading. Dynamic storage moduli, matrix–fibre interaction parameter and energy dissipation properties of the short fibre‐filled composites are negatively affected by nanoclay addition. However, ultimate elongation is improved markedly on nanoclay addition. In respect of tensile strength and elongation at break values, two composite samples (KF5NC10 and KF10NC10) offer optimum properties. Copyright © 2009 Society of Chemical Industry     

Preparation and performances of ethylene–propylene–diene terpolymer/acrylic rubber reinforced with a dough‐modeling compound

A novel composite was prepared by the addition of a dough‐modeling compound (DMC) reinforcement and an ethylene–propylene–diene terpolymer (EPDM)/acrylic rubber (ACM) matrix. We studied the DMC/EPDM/ACM mass ratio and vulcanizing process by testing the tensile strength, Shore A hardness, elongation at break, and wear and thermal properties. The results show that the mechanical properties, thermal properties, and wear resistance of the composites were good when the DMC/EPDM/ACM mass ratio was 70/25/75 and the cure conditions were 180°C under 10 MPa for 25 min. The crosslinking structure of the composites was studied by IR, and this further proved the interaction between DMC, ACM, and EPDM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of a silane coupling agent on the properties of white rice husk ash–polypropylene/natural rubber composites

White rice husk ash (WRHA)–polypropylene (PP)/natural rubber (NR) composites were prepared using a Brabender Plasticorder at 180 °C and a rotor speed of 50 rev min^?1. The mechanical and water‐absorption properties were studied. The incorporation of WRHA into the PP/NR matrix has resulted in the improvement of the tensile modulus; however, the tensile strength, elongation at break and stress at yield decreased with increasing WRHA loading. Poor filler matrix interactions are believed to be responsible for the decrease in the properties. Incorporation of a silane coupling agent, 3‐aminopropyl triethoxysilane (3‐APE), improved tensile modulus, tensile strength and stress at yield of the composites. Water‐absorption studies indicate that the use of the coupling agent reduced the amount of water absorbed by the composites. © 2001 Society of Chemical Industry     

Maleated Natural Rubber as a Coupling Agent for Recycled High Density Polyethylene/Natural Rubber/Kenaf Powder Biocomposites

Kenaf powder (KP) was incorporated into recycled high density polyethylene (rHDPE)/natural rubber (NR) blend using an internal mixer at 165°C and rotor speed of 50 rpm. The tensile strength and elongation at break of the composites decreased, while the tensile modulus increased with increasing filler loading. The water absorption was found to increase as the filler content increased. The maleic anhydride grafted natural rubber was prepared and used to enhance the composites performance. The addition of MANR as a coupling agent improved the tensile properties of rHDPE/NR/KP biocomposites. The water absorption was also reduced with the addition of MANR.     

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。     

Effect of Polyethylene-Grafted Maleic Anhydride (PE-g-MAH) on Properties of Low Density Polyethylene/Eggshell Powder (LDPE/ESP) Composites

The effect of polyethylene-grafted maleic anhydride (PE-g-MAH) on the tensile properties, morphology and thermal properties of low-density polyethylene (LDPE)/eggshell powder (ESP) composites was studied. LDPE/ESP composites with different eggshell powder content and the addition of PE-g-MAH were prepared with Z-blade mixer at 180°C and rotor speed of 50 rpm. The tensile strength, elongation at break and thermal stability of LDPE/ESP composites with PE-g-MAH were greater than LDPE/ESP composites, and their differences became more pronounced at higher filler content. The interfacial adhesion between ESP and LDPE was improved with the addition of PE-g-MAH as evidenced by the morphological study.     

Thermoplastic Elastomer Composites of Palm Ash-Filled Ethylene Vinyl Acetate/Natural Rubber Blends: Effects of Palm Ash Loading and Size

Thermoplastic elastomer composites of ethylene vinyl acetate (EVA)/natural rubber (NR) blends filled with palm ash were prepared by melt-mixing using a Haake Rheomix Polydrive R600/610 at 120°C with rotor speed of 50 rpm for 10 minutes. Increase in palm ash loading in composites resulted in increase the value of stabilization toque, Young's modulus and swelling resistance of the composites, but decreased the tensile strength and elongation at break. Scanning electron microscope micrographs revealed that higher filler loading resulted in agglomeration of palm ash in the composites. When smaller particle size of palm ash was used, further improvement in tensile strength, elongation at break, swelling resistance and stabilization torque value were observed.     

In situ dispersion and compatibilization of lignin/epoxidized natural rubber composites: reactivity,morphology and property

Lignin, a naturally occurring polymer, was viewed as a potential substitute of carbon black for reinforcing rubber materials. However, it shows no reinforcing effect if directly mixed with rubber. In this study, lignin was in situ dispersed at submicrometer size and highly compatible with epoxidized natural rubber (ENR) by using a high‐temperature dynamic heat treatment (HTDHT). Rheology analysis indicated that the ring opening reaction between lignin and ENR occurred at 160°C or above, which was further confirmed by infrared spectroscopy. Due to the consumption of acidic groups of lignin by ENR, the retardant vulcanization effect of lignin was weakened. Morphology observation and dynamic mechanical analysis demonstrated the perfect lignin dispersion and the strong interactions between lignin and ENR. The mechanical properties of the lignin/ENR composites were significantly improved by using HTDHT. Compared to the directly mixed rubber composites, the tensile strength and tear strength of the heat treated rubber composites filled with 40 phr lignin were increased by 114% and 23%, respectively. Especially, the 300% modulus of the heat treated rubber composite was increased by ca. 400%. X‐ray diffraction results indicated that the reinforcement of the composites originated from the presence of lignin rather than the strain‐induced crystallization of ENR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42044.     

Mechanical Properties of Melt-processed Blend of Amorphous Corn Flour Composite Filler and Styrene-Butadiene Rubber

The corn flour composite fillers were prepared by blending corn flour with rubber latex, dried, and cryogenically ground into powders, which were then melt-blended with rubber polymers in an internal mixer to form composites with enhanced mechanical properties. The composites prepared with melt-blending method were compared to those prepared with a freeze-drying method. The composite fillers prepared with styrene-butadiene were compared to those made with carboxylated styrene-butadiene matrix. Dynamic effects showed that the corn flour composite fillers produced composites with good tensile strength, elongation ratio, and toughness at 500 mm/min strain rate. Tear resistance of different composites was also studied.     

Studies on the properties of polypropylene/(waste tire dust)/kenaf (PP/WTD/KNF) composites with addition of phthalic anhydride (PA) as a function of KNF loading

The properties of polypropylene/(waste tire dust)/kenaf (PP/WTD/KNF) composites with the addition of phthalic anhydride (PA) as a function of KNF loading were studied. Composites containing constant PP and WTD compositions of 70 and 30 parts by weight per hundred parts of resin (phr), with various KNF loadings (0, 5, 10, 15, and 20 phr), were prepared by using a Thermo‐Haake Polydrive internal mixer at a temperature of 180°C with a rotor speed of 50 rpm. The results showed that tensile strength and elongation at break decreased, while tensile modulus, stabilization torque, water absorption, and thermal stability increased with increased KNF loading. PP/WTD/KNF composites with PA showed higher tensile strength, tensile modulus, and water uptake but lower stabilization torque and elongation at break when compared with PP/WTD/KNF composites. Scanning electron microscopy morphological study on the tensile fractured surface proves that the interfacial adhesion between PP/WTD and KNF was enhanced with the addition of PA. J. VINYL ADDIT. TECHNOL., 20:193–200, 2014. © 2014 Society of Plastics Engineers     

In situ composites from blends of polycarbonate and a thermotropic liquid‐crystalline polymer: The influence of the processing temperature on the rheology,morphology, and mechanical properties of injection‐molded microcomposites

This work was aimed at understanding how the injection‐molding temperature affected the final mechanical properties of in situ composite materials based on polycarbonate (PC) reinforced with a liquid‐crystalline polymer (LCP). To that end, the LCP was a copolyester, called Vectra A950 (VA), made of 73 mol % 4‐hydroxybenzoic acid and 27 mol % 6‐hydroxy‐2 naphthoic acid. The injection‐molded PC/VA composites were produced with loadings of 5, 10, and 20 wt % VA at three different processing barrel temperatures (280, 290, and 300°C). When the composite was processed at barrel temperatures of 280 and 290°C, VA provided reinforcement to PC. The resulting injection‐molded structure had a distinct skin–core morphology with unoriented VA in the core. At these barrel temperatures, the viscosity of VA was lower than that of PC. However, when they were processed at 300°C, the VA domains were dispersed mainly in spherical droplets in the PC/VA composites and thus were unable to reinforce the material. The rheological measurements showed that now the viscosity of VA was higher than that of PC at 300°C. This structure development during the injection molding of these composites was manifested in the mechanical properties. The tensile modulus and tensile strength of the PC/VA composites were dependent on the processing temperature and on the VA concentrations. The modulus was maximum in the PC/VA blend with 20 wt % VA processed at 290°C. The Izod impact strength of the composites tended to markedly decrease with increasing VA content. The magnitude of the loss modulus decreased with increasing VA content at a given processing temperature. This was attributed to the anisotropic reinforcement of VA. Similarly, as the VA content increased, the modulus and thus the reinforcing effect were improved comparatively with the processing temperature increasing from 280 to 290°C; this, however, dropped in the case of composites processed at 300°C, at which the modulus anisotropy was reduced. Dynamic oscillatory shear measurements revealed that the viscoelastic properties, that is, the shear storage modulus and shear loss modulus, improved with decreasing processing temperatures and increasing VA contents in the composites. Also, the viscoelastic melt behavior (shear storage modulus and shear loss modulus) indicated that the addition of VA changed the distribution of the longer relaxation times of PC in the PC/VA composites. Thus, the injection‐molding processing temperature played a vital role in optimizing the morphology‐dependent mechanical properties of the polymer/LCP composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Novel milling route for controlling structure and properties in SBS elastomer blends containing dispersed PA6 and PP particles

Abstract

A novel technique to optimise the morphology and thus to enhance the mechanical properties of styrene/butadiene/styrene (SBS) triblock copolymer blends containing dispersed polyamide 6 (PA6)/polypropylene (PP) is reported. The SBS-PA6-PP composite was prepared by blending SBS with PA6-PP ultrafine powder, which was obtained by pulverising PA6 and PP in a pan mill at ambient temperature. The mechanical properties of the composite were determined and the variations of the phase structure of the composites prepared at different processing temperatures were studied by TEM. The thermooxidative stabilities of the composites were tested by thermogrivimetry (TG). The results indicate that preparing a PA6-PP ultrafine powder by the solid state mechanochemical process can improve the compatibility of PA6 with PP and SBS and accelerate the dispersion of PP and PA6 as well as their combination with SBS at the phase interface. The tensile strength of the composite can be increased greatly with an ultrafine powder content of 4-8%, while the elongation at break remains approximately constant. The variation of processing temperature causes a change in the phase structure of the plastics, which has a great effect on the properties of the composite. When the processing is carried out at the melting temperature of the PP, the PP particles combine to form a fibrillar structure that can increase the tensile strength of the matrix from 12·7 to 25 0 MPa. The temperature at which a 10% weight loss occurs in the composite increases from 396·0 to 412·7°C and the temperature of maximum weight loss increases from 454·3 to 479·3°C with an ultrafine powder content of 4%. PRC/1747     

Vapour phase synthesis and characterisation of Cf/SiC composites with self-healing Si-B-C monolayer coating

Carbon fibre reinforced CVI-SiC matrix (C_f/SiC) composite is well known for its superior properties such as low density, high specific modulus, high fracture toughness, and high temperature mechanical properties. In the present work, 2.5-Directional C_f/SiC composites with (PyC/SiC) _n=4 multilayer interface having two different thicknesses with a density of ~2.1 g cm^-3 are prepared through isobaric isothermal chemical vapour infiltration technique. High temperature tensile properties of the prepared composites with and without Si-B-C seal coating are studied and the results are presented. Samples prepared without seal coat exhibited a K_ICof ~ 30 MPa m^1/2, and tensile strength of ≥200 MPa at room temperature. Si-B-C seal coated C_f/SiC composites has shown significant increase (28%) in high temperature tensile strength at 1200 °C and 1500 °C respectively compared to uncoated composites. Microstructural observations, XRD, and XPS studies support the observed thermomechanical behaviour of these composites at 1200 °C and 1500 °C.     

Water resistance,mechanical properties,and biodegradability of poly(3‐hydroxybutyrate)/starch composites

Composites of poly(3‐hydroxybutyrate), P(3HB), and starch were prepared by solution casting technique. To improve adhesion of starch to P(3HB), stearic acid was added as a compatibilizer and glycerol as a plasticizer. The water resistance, mechanical, and biodegradable properties of the P(3HB)/starch composites were studied. Diffusion and penetration coefficients of water increased with increasing starch content in the composites. The results showed that the elastic modulus and strain at rupture of the P(3HB)/starch composites were enhanced by increasing starch content upto 10 wt % and the tensile strength increased from 21.2 to 93.9 MPa. The presence of starch content higher than 10 wt % had an adverse effect on the mechanical properties of the investigated composites. The biodegradation rate using Actinomycetes increased proportionally to the starch content in the composite and accelerated in a culture medium of pH ≈ 7.0 at 30°C. Enzymatic degradation experiments showed that lipase produced by Streptomyces albidoflavus didnot degrade P(3HB)/starch composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

碳纳米管/HDPE复合材料的制备及性能研究

将酸化处理以后的碳纳米管（CNTs）与高密度聚乙烯（HDPE）复合，采用机械共混法制备了定向CNTs／HDPE复合材料，并对其力学性能、相态结构、流变性能及热性能进行了研究。结果表明：CNTs的加入，提高了复合材料的屈服强度和拉伸模量，但同时却降低了材料的断裂强度和断裂伸长率；CNTs在HDPE基体中有了较好的分散性和相容性；CNTs的加入对复合材料流变性能产生了较大的影响，加入少量的CNTs可以使复合材料体系的表观粘度降低，有利于HDPE加工性能的改善；CNTs加入后，HDPE的熔融温度和结晶熔融焓均有所下降。     

Electrically conductive kraft lignin-based carbon filler for polymers

Commercial kraft lignin was thermostabilised by heating up to 250 °C at a rate of 0.01 °C min⁻¹ in ambient atmosphere. Subsequent carbonisation at 2000 °C in argon atmosphere yielded carbon microparticles containing ordered graphitic domains. Micromechanical characterisation by nanoindentation yielded average values of 1.39 GPa for hardness and 8.2 GPa for the indentation modulus of carbon particles. Composite films of polycaprolactone with different carbon content were prepared by means of solvent evaporation casting. Tensile testing revealed an increase in composite stiffness while strength and elongation at break decreased with the loaded amount of carbon microparticles. Electrical conductivity of the composites was exemplarily observed for a carbon microparticle loading of 15% (w/w). Using a composite film as strain sensor in three-point bending, high sensitivity of electrical conductivity towards the applied strain was observed.     

Overall properties of fibrillar silicate/styrene–butadiene rubber nanocomposites

The mechanical properties, heat aging resistance, dynamic properties, and abrasion resistance of fibrillar silicate (FS)/styrene butadiene rubber (SBR) nanocomposites are discussed in detail. Compared with white carbon black (WCB)/SBR composites, FS/SBR composites exhibit higher tensile stress at definite strain, higher tear strength, and lower elongation at break but poor abrasion resistance and tensile strength. Surprisingly, FS/SBR compounds have better flow properties. This is because by rubber melt blending modified FS can be separated into numerous nanosized fibrils under mechanical shear. Moreover, the composites show visible anisotropy due to the orientation of nanofibrils. There is potential for FS to be used to some extent as a reinforcing agent for rubber instead of short microfibers or white carbon black. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2725–2731, 2006