改性纳米CaCO3/PE-g-MAH/HDPE复合塑料拉伸性能研究

采用硬脂酸(SA)对纳米进行表面活化,考察了改性纳米CaCO3、马来酸酐接枝聚乙烯(PE-g-MAH)分别或共同添加到高密度聚乙烯(HDPE)中形成的复合塑料的拉伸性能.结果表明:用质量分数为7%硬脂酸改性的纳米CaCO3,能较好地促使无机粒子的分散和与HDPE的结合,提高复合塑料的拉伸性能.PE-g-MAH的进一步嫁接作用,可延长硬脂酸分子链,加强硬脂酸和基体树脂之间的缠结作用,从而显著提高了复合塑料的拉伸强度.     

Study on the evaluation of mechanical and thermal properties of natural sisal fiber/general polymer composites reinforced with nanoclay

Composite materials, made by replacing traditional materials, are used because of their capability to produce tailor-made, desirable properties such as high tensile strength, low thermal expansion, and high strength to weight ratio. The need for the development of new materials is essential and growing day by day. The natural sisal/general polymer (GP) reinforced with nanoclay composites has become more attractive due to its high specific strength, light weight, and biodegradability. In this study, sisal–nanoclay composite is developed and its mechanical properties such as tensile strength, flexural strength, and impact strength are evaluated. The interfacial properties, internal cracks, and internal structure of the fractured surface are evaluated using scanning electron microscope. The thermal disintegration of composites are evaluated by thermogravimetric analysis. The results indicate that the incorporation of nanoclay in sisal fiber/GP can improve its properties and can be used as a substitute material for glass fiber-reinforced polymer composites.     

Cellulose man-made fibre reinforced polypropylene—correlations between fibre and composite properties

A series of viscose fibres from the tyre cord type varying in mechanical parameters and titre were compounded with polypropylene to produce fibre reinforced composites. Single fibre strength is analysed in detail and conclusions are drawn with respect to effective strength values in composite applications. Composites were analysed in terms of tensile and impact properties. Correlations between single fibre and composite properties are studied. High fibre elongation leads to favourable composite impact properties via high composite elongations at break. Using water as a plastisizing agent increasing fibre elongation, notched Charpy impact strength can be improved by more than 50%. Using a modified rule of mixtures and a shear lag model for the composite modulus it was shown how a titre reduction improves the composite stiffness by an increased interfacial area. A direct fibre-composite strength correlation was not found.     

Impact of surface adaptation and Acacia nilotica biofiller on static and dynamic properties of sisal fiber composite

Nowadays, the awareness of the public along with strict legitimate forces over the use of polymers, the manufacturing and automotive industries started using the renewable materials. Since, natural fiber reinforced composites play vital role in developing lightweight structural materials, this study focuses on utilizing sisal fiber as reinforcement in polyester matrix along with natural filler. The influence of fiber length and fiber volume fraction on the mechanical properties of sisal fiber was studied initially. Test results revealed that the composite with 20?mm fiber length and 20-volume fraction composite has better mechanical properties. Furthermore, the effect of fiber surface modification has been analyzed using various chemical solutions such as NaOH, KMnO₄, stearic acid, and maleic acid. Of these, NaOH treatment enhances the mechanical properties of composite compared to all other cases. Finally, the influence of Acacia nilotica, a natural filler addition into the alkali-treated sisal fiber composite has been evaluated by mechanical and dynamic mechanical properties. It is found that the addition of natural filler and surface treatment has enhanced the properties of composites due to their synergetic effect. This effect improves the adhesion and uniform stress transfer among the reinforcements. The fiber surface morphology was evaluated using micrographs obtained from scanning electron microscope.     

Thermal and mechanical properties of irradiated poly(vinyl chloride)/calcium carbonate composite

A composite consisting of PVC and CaCO₃ particles was irradiated with different doses of Gamma rays or electron beam in order to compensate the tensile strength decreases by filler addition. The deployment of irradiation process on the composite improved significantly the tensile strength by about 10–20 % using E-beam and Gamma irradiation at a dose of 250 kGy, respectively. Moreover, the irradiated composite exhibited higher thermal stability. Two thermal dehydrochlorination processes after irradiation have been observed instead of three thermal process before. The calculation of the activation energy of each step showed that initiation step consumed about 60 % of the used energy.     

Biomimetic mineralisation of polymeric scaffolds using a combined soaking approach: adaptation with various mineral salts

Biomimetic strategies which utilise hydrogels have been targeted due to favourable hydrogel characteristics such as the presentation of a large surface area for crystal nucleation within a structured yet responsive scaffold. Chitosan hydrogels were prepared and mineralised using a combined method which involves alternate soaking of the films with precursor solutions, followed by treatment with saturated mineral solution. This method has been shown to be effective for the synthesis of calcium carbonate-chitosan composite materials with tensile strength comparable to nacre. The ratio of organic to inorganic is readily controlled through the presoaking solution concentrations. The ubiquity of this method is shown here with respect to switching out both the anion (CaHPO(4)) and the cation (BaSO(4)). Cation doping is also readily achieved allowing formation of Mg-rich CaCO(3). Poly(acrylic acid) added to (Mg,Ca)CO(3)-chitosan systems induces the formation of two polymorphs (vaterite and calcite) which coexist within the composite material. The mineralised scaffolds were analysed by SEM and powder XRD. The successful mineralisation of chitosan templates with various inorganic compounds shows that this combined approach is widely applicable as a biomimetic approach.     

Determination of longitudinal compressive strength of long fiber composites by three-point bending of [0m/90n/0p] cross-ply laminated strips

A new test method is proposed for measuring longitudinal compressive strength of composite laminates by three-point bending of cross-ply laminates. Optimal cross-ply configuration has been designed in order to get compressive stresses higher than tensile stresses. Thermal and mechanical stresses have been calculated based on the hypothesis of Classical Beam Theory. Cross-ply carbon/epoxy strips with different thicknesses and spans have been tested by three-point bending. Failures on the compressive side have been observed in all cases and no evidence of transverse cracking has been found. Experimental results agree well with compressive strength reference values. The possibility of determination of compressive and tensile strengths by three-point bending from a unique cross-ply lay-up has been also analyzed.     

The tensile properties of electrospun nylon 6 single nanofibers

In this article, we have aimed to mechanically characterize the nylon 6 single nanofiber and nanofiber mats. We have started by providing a critical review of the developed mechanical characterization testing methods of single nanofiber. It has been found that the tensile test method provides information about the mechanical properties of the nanofiber such as tensile strength, elastic modulus and strain at break. We have carried out a tensile test for nanofiber/composite MWCNTs nanofiber mats to further characterize the effect of the MWCNTs filling fiber architecture. In addition, we have designed and implemented a novel simple laboratory set‐up for performing tensile test of single nanofibers. As a result, we have established the stress–strain curve for single nylon 6 nanofibers allowing us to define the tensile strength, axial tensile modulus and ultimate strain of this nanofiber. The compared values of the tensile strength, axial modulus and ultimate strain for nylon 6 nanofiber with those of conventional nylon 6 microfiber have indicated that some of the nylon 6 nanofiber molecule chains have not been oriented well along the nanofiber axis during electrospinning and through the alignment mechanism. Finally, we have explained how we can improve the mechanical properties of nylon 6 nanofibers and discussed how to overcome the tensile testing challenges of single nanofibers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1719–1731, 2010     

Novel cellulose fibre reinforced thermoplastic materials

Spun cellulose fibres from the viscose, lyocell and carbamate processes have been used to reinforce thermoplastic commodity polymers, such as polypropylene (PP), polyethylene (PE) and (high impact) polystyrene (HIPS) as well as poly(lactic acid) (PLA) and a thermoplastic elastomer (TPE) for injection moulding applications. A specially developed double pultrusion technique has been employed for compounding. Fibres were analysed in single fibre tensile tests. Strength, stiffness, impact strength, and heat distortion temperature (HDT) were determined for injection-moulded standard test specimen and structural features were revealed by scanning electron microscopy. A strong reinforcing effect was observed in all cases. In particular, high tenacity tyre cord rayon gives excellent composite strength and impact strength, often doubling or tripling the pristine matrix values. In the case of PP, Lyocell type fibres provide enhanced stiffness and HDT, and thus the combination of both fibre types leads to a balanced composite property profile. The PE case is very similar to PP. For HIPS mainly strength and stiffness is increased, while for TPE the property profile is changed completely. With PLA, a biogenic and biodegradable composite with excellent mechanical properties is presented.     

石墨烯/聚乙烯复合材料及其拉伸性能的分子动力学模拟

利用分子动力学方法,模拟石墨烯/聚乙烯复合材料的微观结构和性能,并采用单轴拉伸模拟方法研究石墨烯/聚乙烯复合材料的拉伸性能.结果表明,在石墨烯/聚乙烯复合材料平衡构型中,聚乙烯基体分子在石墨烯表面处形成多层吸附层,吸附层处于动态稳定状态,层内分子可以发生扩散迁移.吸附层内聚乙烯分子发生"吸附固化"现象,分子弯曲程度减弱,发生有序排列,且在垂直于石墨烯方向的运动性能受到抑制.拉伸模拟结果表明,石墨烯能够提高聚乙烯材料的拉伸性能.在弹性区和屈服区,石墨烯阻碍了复合材料在垂直于拉伸方向的压缩变形,聚乙烯分子"吸附固化"结构保持稳定,引起体系整体应力的迅速升高.在软化区,由于石墨烯发生剧烈弯曲,"吸附固化"结构发生破坏,最终引起体系应力迅速减小.在弹性区和屈服区,体系应变主要引起了非键相互作用的改变.在软化区之后,应变主要导致了体系内分子成键相互作用的改变.应变速率能够提高复合材料的屈服应力,而不改变复合材料应力应变的整体趋势.     

The effects of crosslink density and crosslink type on the tensile and tear strengths of NR,SBR and EPDM gum vulcanizates

The effects of crosslink density and crosslink type on the tensile and tear strengths of gum NR, SBR and EPDM vulcanizates have been studied. Over a wide range of crosslink densities, sulphur vulcanizates for these rubbers have higher strengths than the peroxide vulcanizates. These results show that crystallizability of the rubbers is not an important factor in producing separate curves in the strength vs crosslink density plots. Tear strengths appear to be more sensitive to crosslink structures than tensile strengths. A composite plot shows that tensile strengths are approximately proportional to tear strengths for all three rubbers.     

短玻璃纤维增韧硬质聚氯乙烯的机理研究

短玻璃纤维增韧硬质聚氯乙烯的机理研究叶林忠，吴其晔（青岛化工学院高分子材料与工程系，青岛，２６６０４２）关键词短玻璃纤维，硬质聚氯乙烯（Ｒ－ＰＶＣ），增韧机理弹性体增韧塑料机理的研究已经向模型化和定量化方向发展ｌ‘］，刚性粒子增韧塑料的机理正在逐渐完...     

热致液晶聚合物微纤与碳纤维对聚醚砜的混杂增强

热致液晶聚合物微纤与碳纤维对聚醚砜的混杂增强张洪志王育立何嘉松（中国科学院化学研究所工程塑料国家重点实验室北京１０００８０）关键词热致液晶聚合物，碳纤维，混杂复合材料由两种或两种以上纤维增强同一种基体所得到的混杂纤维复合材料，不仅保留了单一纤维...     

Deformation behavior and mechanical properties of hard elastic and porous films of polyethylene

Hard elastic samples of linear polyethylene were prepared by melt extrusion at a high velocity of the melt flow and by subsequent annealing of crystallized samples. The deformation behavior of hard elastic samples obtained by annealing of as-spun samples at different temperatures has been analyzed at uniaxial extension resulting in formation of porous structure. Mechanical properties of microporous films in the longitudinal and transverse directions have been investigated. Composite systems consisting of a microporous polyethylene film and a thin layer of an electroconducting polymer have been prepared. Mechanical properties of composite systems, such as elastic modulus, tensile strength, and break elongation, have been compared with the properties of polyethylene substrates.     

Specimen design for mechanical testing of highly-oriented polymers

Tensile and in-plane shear specimens have been designed using finite element analysis to enable satisfactory testing of highly-drawn flat strip polymer. The analyses have shown that the required specimen geometry for tensile testing is very dependent on the degree of anisotropy of the material. A geometry correction factor has been determined for the in-plane shear specimen to relate the applied load to the shear stress at the centre of the gauge area. Simple tube specimens have also been analysed using anisotropic thin shell theory.     

Structure and mechanical performance of in situ synthesized hydroxyapatite/polyetheretherketone nanocomposite materials

Nano-hydroxyapatite (HA) particles were prepared by a sol–gel method and polyetheretherketone (PEEK) composite materials containing a various amount of lab-prepared HA fillers had been successfully synthesized via an in situ synthesis process. The materials structure was characterized by infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy and the mechanical performance was investigated by a tensile strength test. The tensile strength of HA/PEEK composites reaches an optimal 108 MPa at 6.1% HA content. The composites with HA content below 17.4% exhibit a plastic break mode, while a brittle break mode above 17.4%. The results exhibit that the strong bonding between hydroxyapatite fillers and PEEK matrix has been achieved. And it was proved that this strong bonding may be mainly attributed to the physical factors, such as mechanical interlock between PEEK molecules and HA surface. The study clearly demonstrates that in situ synthesized HA/PEEK composite materials have the potential for use as an alternative material for hard tissue replacement.     

Mechanical,Thermal and Morphological Behaviors of Castor Oil Based PU/PS Interpenetrating Polymer Network-Metakaolin Composites

The meta kaolin (MK) clay particulate filler with different weight ratios viz., 0, 5, 10, 20 and 30 wt% were incorporated into castable polyurethane (PU)/polystyrene (PS) (90/10) interpenetrating polymer network (IPN). The effects of MK particulate filler loading on the mechanical and thermal properties of PU/PS (90/10) IPN composites have been studied. From the tensile behavior, it was noticed that a significant improvement in tensile strength and tensile modulus as an increase in MK filler content. Thermogravimetric analysis (TGA) data reveals the marginal improvement in thermal stability after incorporation of MK filler. TGA studies of the IPN composites have been performed in order to establish the thermal stability and their mode of thermal degradation. It was found that degradation of all composites takes place in two steps. Degradation kinetic parameters were obtained for the composites using three mathematical models. Tensile fractured composite specimens were used to analyze the morphology of the composites by scanning electron microscopic (SEM) technique.     

New additives in glass reinforced polyolefins

Poly(butyl acrylate)-g-poly(4-vinylpyridine) graft copolymer and polypropylene modified with maleic anhydride or poly(maleic anhydride) have been prepared and characterised. These products have been tested as coupling agents in glass reinforced polyolefins. The adhesion of glass fiber or glass filler to polyolefin has been evaluated by “Single fiber composite” method or studying the volume variation under tensile strength. The results indicate that all the prepared additives improve the adhesion between olefin matrix and glass filler or fiber.     

CHANGES OF STRUCTURE AND PROPERTIES OF POLY (ETHYLENE TEREPHTHALATE) CAUSED BY IN-SITU POLYMERIZATION OF PYRROLE

Conductive polymer composites based on crystalline polymer matrix have been prepared by using an in-situ polymerization process of pyrrole in amorphous poly (ethylene terephthalate) (PET) film. The DSC and WAXD measurement and SEM observation show that liquid-induced crystallization of PET matrix has occurred during the preparation of composite films. Depending upon the equilibrium degree of swelling and crystallinity, the limited depth of penetration of pyrrole molecules results in a skin-core structure of the composite film. The skin layer containing charge transfer intercalated polypyrrole has a surface resistance of 3.5×10~4 Ω. Rigid and heat-resistant polypyrrole molecules formed in PET film increase the tensile modulus and, especially, the rigidity of PET at elevated temperatures. However, they decrease the tensile strength and elongation at break, and impair the thermal ductility of PET.