橡胶改性对硼纤维/环氧单向复合材料力学性能的影响

对环氧树脂进行液体丁腈橡胶改性, 并采用缠绕无纬布层压成型工艺制备了硼纤维/环氧单向复合材料。测试了环氧树脂液体丁腈橡胶改性前后硼纤维/环氧单向复合材料的力学性能, 研究了硼纤维/环氧单向复合材料的纵向拉伸破坏模式。结果表明, 基体中的10%液体丁腈橡胶使硼纤维/环氧单向复合材料的拉伸强度、 弯曲强度、 层间剪切强度和断裂延伸率分别提高了18.42%、 13.39%、 28.45%和43.40%, 但其拉伸和弯曲模量稍有下降。基体中含10%液体丁腈橡胶的硼纤维/环氧单向复合材料的纵向拉伸破坏模式为界面层的内聚破坏和脱黏破坏共存的混合破坏。      

聚乙烯/废天然橡胶的老化和力学性能研究

通过汞灯辐射试验对制备的聚乙烯/废天然橡胶共混物进行了紫外老化试验,研究了防老剂4010对聚乙烯/废天然橡胶的紫外老化性能的影响。结果表明:老化初期聚乙烯/废天然橡胶(60/40)的拉伸强度提高,老化中后期聚乙烯/废天然橡胶拉伸强度下降。防老剂4010的加入提高了聚乙烯/废天然橡胶的紫外老化性能。     

The impact of esterification on the properties of starch/natural rubber composite

The starch was modified by esterification, and the starch/natural rubber composite was prepared by blending the modified starch with natural rubber latex. The morphology, thermal stability and mechanical properties of the composite were investigated. The results show that the crystal structure of starch in the composite disappears after modification with esterification, and the starch particles with an average size around 200 nm homogenously disperse throughout the natural rubber (NR) matrix. The thermal stability of composite is improved significantly after the modification with starch. The mechanical properties of composite are enhanced with the increase of starch loading. The composite possesses the best properties at the starch xanthate content of 20 parts per hundred rubber (phr). The enhanced thermal stability and mechanical properties of modified starch/NR composite are mainly due to the improved phase interface interactions between rubber and starch.     

Natural rubber/epoxidised natural rubber-25 blends: morphology, transport phenomena and mechanical properties

Blends of natural rubber (NR)/epoxidised natural rubber (ENR) were prepared and their morphology, transport behaviour and mechanical properties have been studied. Ebonite method was used to study the blend morphology. Transport behaviour of pentane, hexane, heptane and octane was studied in the temperature range 27–60 °C. Different transport parameters such as rate constant, diffusion and permeation coefficients, and sorption coefficient have been calculated. Temperature dependence of diffusion has been used to estimate the activation parameters. The improved performance of NR/ENR blends has been established from the mechanical studies of unswollen, swollen and deswollen samples.     

过氧化物预硫化天然橡胶/丝素蛋白抗菌复合材料的制备与性能研究

采用三元混合体系溶解丝素蛋白,纯化后与过氧化物预硫化天然橡胶复合,得到了具有抗菌性能的天然橡胶/丝素蛋白(PVNR/SF)复合材料,并对胶乳和胶膜的相关性能分别进行测试分析。结果表明,SF的加入保持了天然胶乳的稳定性。在干燥制成胶膜后,与基体材料有很好的相容性,并且可以在一定程度上起到补强的作用,SF使天然橡胶获得良好的抗菌性能的同时,对基体的热稳定、粘弹等性能没有很大的影响。另外,通过红外光谱我们可以推测SF在胶膜中的抗菌性能与酰胺I结构有关。     

Free-volume properties and toughening behavior of cyanate ester resin/carboxyl-randomized liquid butadiene-acrylonitrile rubber composites

The toughness of cyanate ester resin (CE) matrix was improved significantly with addition of carboxyl-randomized liquid butadiene-acrylonitrile rubber (CRBN). The curing behavior of the system was studied by differential scanning calorimetric (DSC) and Fourier transform infrared spectrum (FTIR). The results showed that carboxyl groups on the CRBN chain had slight activation effect to CE curing reaction at the beginning of the cure process. Phase separation was the main toughening mechanism for CE/CRBN composites. The existence of micro-size pores induced by small amount of the low weight molecular part of CRBN might be another toughening mechanism. The toughening mechanism was proved powerfully from the aspect of free-volume using positron annihilation lifetime spectroscopy (PALS). PALS is qualitatively sensitive to the existence of pores induced by low molecular weight part of CRBN during curing process.     

Ceramic/natural rubber composites: influence types of rubber and ceramic materials on curing,mechanical, morphological,and dielectric properties

Influence of different types of rubber and ceramic material on cure characteristics, mechanical, morphological, and dielectric properties of natural rubber (NR) vulcanizate was studied. Two types of ferroelectric ceramic materials: barium titanate (BaTiO₃) and lead titanate (PbTiO₃) were prepared by solid-state reaction with calcinations at 1100 °C for 2 h. The ceramic powders were then characterized by X-ray diffraction (XRD), particle size analyzer, and SEM techniques. Ceramic/rubber composites were then prepared by melt mixing of rubber and ceramic powders. Two different types of NR (i.e., epoxidized NR [ENR] and unmodified NR) and two types of ceramic powders (i.e., BaTiO₃ and PbTiO₃) were exploited. It was found that incorporation of ceramic powders in rubber matrix and the presence of epoxirane rings in ENR molecules caused faster curing reaction, and higher delta torque but lower elongation at break. This is attributed to lower mobility of molecular chains and higher interaction between ENR molecules. Furthermore, SEM results revealed that the BaTiO₃ composites showed finer and better distribution of the particles in the rubber matrix than that of the PbTiO₃ composite. This caused superior mechanical properties of the BaTiO₃ composites. Furthermore, higher dielectric constant and loss tangent was observed in the ENR/BaTiO₃ composites.     

纳米二氧化硅粒径对橡胶复合材料力学性能的影响

以不同粒径的纳米二氧化硅为填料加到天然橡胶中制备纳米二氧化硅/天然橡胶(NR)复合材料。研究了不同粒径纳米二氧化硅(15,30和80nm)对复合材料的力学性能、应力软化效应、Payne效应、动态热机械性能、压缩生热和损耗因子等基本特性的影响。结果表明,随着纳米二氧化硅粒径的增大,复合材料的抗拉强度变大,应力软化效应增大;同时,复合材料的Payne效应和损耗因子越低,其动态压缩温升越低。Payne效应分析及扫描电镜观察还表明,大粒径纳米二氧化硅在橡胶基体中易于分散均匀,粒子间聚集程度更小,而小粒径的则表现出较明显的团聚现象,粒子在橡胶基体中的分散性对复合材料力学性能有直接影响。     

Dynamic mechanical properties of hydrogenated nitrile rubber: effect of cross-link density,curing system,filler and resin

The effect of cross-link density, curing system, filler and resin on dynamic mechanical properties of hydrogenated nitrile rubber (HNBR) is reported. The storage modulus,G, increases and the loss angle, tan , decreases in the plateau zone with cross-link density. At equal cross-link density, the tan peak value at the transition zone of sulphur cured system, is less than that of peroxide cured system. Tan decreases from 90 to 180 °C and increases beyond 180 °C due to post vulcanization reaction and sulphidic linkage cleavage, respectively. The ZSC 2295 resin increasesG and decreases tan , and is found to be compatible with HNBR. The plateau modulus,G, increases with carbon black loading. The tan is lower for high structure carbon black in the transition zone and higher in the plateau zone when the surface area is high.     

环氧化天然橡胶改性石墨烯-炭黑/天然橡胶复合材料的制备及性能

以环氧化天然橡胶(ENR)为界面改性剂,制备了石墨烯-炭黑/天然橡胶-ENR(GR-CB/NR-ENR)复合材料,研究了ENR用量对GR-CB/NR-ENR复合材料的加工性能、力学性能和动态力学性能的影响。结果表明,ENR的加入可以改善GR-CB/NR-ENR复合材料的加工性能及CB粒子在天然橡胶基体中的分散性,增加GR与NR的相容性,增强填料与NR基体间的界面相容性,同时改善GR-CB/NR-ENR硫化胶的动态力学性能、物理性能和耐老化性能。当ENR添加量为6 wt%时,GR-CB/NR-ENR复合材料撕裂强度和拉伸强度最高,硫化胶耐老化性最好。随着ENR含量的增加,GR-CB/NR-ENR复合材料的压缩疲劳温度先升高后降低;随着应变的不断增大,GR-CB/NR-ENR复合材料的储能模量G'不断减小,损耗因子tanδ先增大后减小;动态模量随着应变的增加急剧下降。      

Thermal and mechanical properties of the açaí fiber/natural rubber composites

The açaí fruit industrial processing produces a large amount of waste, mainly seeds and fibers, which is a serious environmental and public health problem. The objective of this work was to use these fibers to obtain composites with natural rubber from different clones. The effect of the addition of açaí fibers and the type of clone were investigated using thermogravimetric analysis (TGA) under inert and oxidative atmospheres, differential scanning calorimetry (DSC), water sorption, and mechanical properties. The açaí fibers exhibited a thermal behavior comparable to other natural fibers industrially used in polymeric composites. The addition of the fibers did not influence the thermal stability of the composites. There was no significant effect of the type of clone and the addition of the fiber on the glass transition temperature, which was approximately ?59 °C for all samples. Water sorption behavior of the compounds and of the composites was similar to that of the other materials with natural rubber that are reported in the literature. The promising performance of the composites with açaí fibers opens a new area of use for such fibers.     

Effect of montmorillonite modification on mechanical properties of vulcanized natural rubber composites

Natural rubber-clay composites were prepared by direct polymer melt intercalation. Ca-montmorillonite Jelšovy Potok (JP; Slovakia) and Na-montmorillonite Kunipia-F (KU; Japan) were ion exchanged with octadecyltrimethylammonium (ODTMA) bromide and were used as aluminosilicate fillers. Silica Ultrasil VN3 was used in amount of 15 phr as conventional filler. The effect of clay or organoclay loading from 1 up to 10 phr on the mechanical properties was evaluated from the tensile tests (stress at break, strain at break and modulus M100). Organic modification resulted in an increase of toluene uptake degree for both fillers. While an addition of unmodified KU had no effect on tensile strength and deformation at break, a reinforcing effect was observed for the mixture containing 10 phr of unmodified JP. Both ODTMA modified fillers (KU and JP) exhibited substantial increase in tensile strength and deformation at break; JP proved to be more effective compared to KU also if modified with ODTMA. The highest stress at break and strain at break values for natural rubber composites were obtained with 15 phr of SiO₂ and 10 phr of montmorillonite; however, the effect of exchangeable cation was minor.     

Effect of multi-wall carbon nanotubes on the mechanical properties of natural rubber

Multi-walled carbon nanotubes (MWNTs) were used to prepare natural rubber (NR) nanocomposites. Our first effort to achieve nanostructures in MWNTs/NR nanocomposites were formed by incorporating carbonnanotubes in a polymer solution and subsequently evaporating the solvent. Using this technique, nanotubess can be dispersed homogeneously in the NR matrix in an attempt to increase the mechanical properties of these nanocomposites. The properties of the nanocomposites such as tensile strength, tensile modulus, tear strength, elongation at break and hardness were studied. Mechanical test results show an increase in the initial modulus for up to 12 times in relation to pure NR. In addition to mechanical testing, the dispersion state of the MWNTs into NR was studied by transmission electron microscopy (TEM) in order to understand the morphology of the resulting system. According to the present study, application of the physical and mechanical properties of carbon nanotubes to NR can result in rubber products which have improved mechanical, physical and chemical properties, compared with existing rubber products reinforced with carbon black or silicone.     

Densification and mechanical properties of liquid phase sintered tantalum

This paper has as main objective to investigate the influence of nickel (Ni), iron (Fe) and copper (Cu) addition on the tantalum (Ta) powder processing, by promoting a liquid phase sintering (LPS). The role of these metals is to lower the Ta sintering temperature, maintaining good densification and mechanical properties. Ni, Fe and Cu 1wt% additions to Ta powder were performed. Samples were cold pressed at 350 MPa. Sintering was carried out at 1300 to 2000 °C, for 1 hour, under a vacuum of 10^‐6 Pa. Density, linear shrinkage and activation energy were measured and calculated. Hardness and compression tests were also conducted. Ni was the most promissing Ta LPS activator, once it enabled the best results of densification and mechanical properties.     

膨胀型阻燃剂对硫化天然胶乳胶膜力学性能和阻燃性能的影响

以聚磷酸铵(APP)、季戊四醇(PER)和三聚氰铵(MEL)组成膨胀型阻燃体系(IFR),考察阻燃剂配比及用量对硫化天然胶乳力学性能和阻燃性能的影响,并通过热重分析仪分析其热稳定性、扫描电镜(SEM)分析阻燃剂在胶乳中的分散效果。结果表明,添加PER和MEL的硫化胶膜力学性能很好,但阻燃性能较差;添加APP和IFR的硫化胶膜力学性能较差,但是阻燃性能很好;SEM观察发现APP与橡胶相容性差;热失重分析可知,改性的硫化胶膜比未改性的硫化胶膜的阻燃性好,且IFR改性硫化胶膜的阻燃效果是最好。     

Compatibility studies of natural rubber/poly(methyl methacrylate) blends by viscometry and phase separation techniques

The compatibility of binary blends of natural rubber (NR) and poly(methyl methacrylate) (PMMA) has been analysed from the viscosity behaviour. For this, the equations developed by both Krighbaum and Wall, and their modified forms by Williamson and Wright, were used. The interaction between polymers in solution has been interpreted qualitatively based on the heat of mixing (ΔH) and interaction parameter (X1). Viscometry and spectroscopy studies and calculation of the heat of mixing and the interaction parameter indicated the heterogeneous nature of NR/PMMA blends. The effects of graft copolymer of natural rubber and poly(methyl methacrylate) (NR-g-PMMA) as an emulsifying agent on the interfacial properties of NR/PMMA blends were studied based on the phase separation behaviour. The demixing behaviour is found to be a function of graft copolymer concentration, mode of mixing, nature of solvent and molecular weight of homopolymers and graft copolymers. The demixing behaviour has been studied by noting the phase separation time and volume of the phase separated region. The addition of graft copolymer decreases the demixing behaviour of the blends. This revised version was published online in November 2006 with corrections to the Cover Date.     

Free-volume correlation with mechanical and dielectric properties of natural rubber/multi walled carbon nanotubes composites

The microstructure, mechanical strength, dielectric properties, Doppler broadening measurements and positron life time studies of the composites containing multi walled carbon nanotubes (MWCNTs) and natural rubber (NR) are investigated. The uniform distribution of MWCNTs in the elastomer medium is studied by Raman spectroscopy and the electron microscopy images show the composite’s internal microstructure. Free volume sizes and interstitial mesopore sizes of the nanocomposites are determined by positron annihilation lifetime spectroscopy (PALS). PALS investigates the influence of the nanotubes in regulating the interphase nanoscale character. Strong interfacial interaction causes an apparent reduction of the free-volume fraction of NR probably by depressing the formation of free-volume holes in the interfacial region. The mechanical percolation and percolation observed from the dielectric measurements are correlated with the life time values. It is established that the sub-nano level free volumes and nano level structure of the composites have significant roles in regulating the mechanical properties.     

Structure and properties of polylactide/natural rubber blends

Polylactide, PLA, is a biodegradable thermoplastic polyester derived from biomass that has restricted packaging applications due to its high brittleness and poor crystallisation behaviour. Here, new formulations based on natural rubber–PLA blends have been developed. The processing windows, temperature, time, and rotor rate, and the rubber content have been optimised in order to obtain a blend with useful properties. The rubber phase was uniformly dispersed in the continuous PLA matrix with a droplet size range from 1.1 to 2.0 μm. The ductility of PLA has been significantly improved by blending with natural rubber, NR. The elongation at break improved from 5% for neat PLA to 200% by adding 10 wt% NR. In addition, the incorporation of NR not only increased the crystallisation rate but also enhanced the crystallisation ability of PLA. These materials are, therefore, very promising for industrial applications.     

Crosslinked natural rubber nanocomposites reinforced with cellulose whiskers isolated from bamboo waste: Processing and mechanical/thermal properties

Crosslinked natural rubber (NR) nanocomposites were prepared using cellulose nanowhiskers (CNWs) that were extracted from bamboo pulp residue of newspaper production, as the reinforcing phase. The coagulated NR latex containing bamboo nanowhiskers (master batch) was compounded with solid NR and vulcanizing agents using a two-roll mill and subsequently cured to introduce crosslinks in the NR phase. No evidence of micro-scaled aggregates of cellulose nanowhiskers in NR matrix was observed in Scanning Electron Microscopy (SEM) images. The addition of CNWs had a positive impact on the tensile strength, E-modulus, storage modulus, tan delta peak position and thermal stability of the crosslinked NR. Theoretical modeling of the mechanical properties showed a lower performance than predicated and therefore further process optimization and/or compatibilization are required to reach the maximum potential of these nanocomposites.     

Thermal,mechanical and rheological properties of polylactide toughened by expoxidized natural rubber

This paper concerns on the use of epoxidized natural rubber (ENR) as toughening agent for polylactide (PLA). ENR with epoxidation content of 20 mol% (ENR20) and 50 mol% (ENR50) were separately melt blended with PLA using an internal mixer. DSC results suggested that PLA/ENR blends were amorphous after melt blending while they were crystalline and revealed two melting peaks in the thermograms after being annealed at 100 °C. Mechanical tests showed that the introduction of ENR reduced the tensile modulus and strength but enhanced the elongation and the impact strength of PLA. The impact strength of the 20 wt% ENR20/PLA and ENR50/PLA blends increased to 6-fold and 3-fold, respectively, compared to that of pure PLA. This enhancement was due to a good interfacial adhesion between ENR and PLA. Both ENR20/PLA and ENR50/PLA blends performed very strong shear thinning behavior, and the complex viscosity, storage and loss modulus of the blends also increased after blending with ENR.