聚丙烯基纳米复合材料的制备方法与力学性能

综述了聚丙烯(PP)基纳米复合材料的制备方法和力学性能的研究进展，介绍了目前国内外研究的以PP为基体与粘土层状物、无机、金属纳米粒子复合制备的复合材料的表面处理、制备方法与材料力学性能的关系。用传统的表面处理方法可改善纳米粒子的分散性与力学性能，少量纳米粒子可使PP同时获得增强增韧。     

Effect of needle density on the mechanical properties of fiber-reinforced polypropylene composites

The partial impregnation textile preform consisting of chopped-strand, long glass fiber and nonwoven polypropylene (PP) has been prepared by needle-punching to improve fiber–matrix distribution before processing. These unconsolidated textile preforms were then preheated and hot-pressed for consolidation and formation. A multichannel recorder was used to determine the completion of impregnation on multilayer glass fiber-reinforced PP, which could significantly reduce the required consolidation time. The effect of needle density on their impregnation has studied by scanning electron microscopy and optical microscopy, along with mechanical analysis. The increasing needle density up to 400 st/cm² has increased the flexural modulus, but the impact strength decreased. The optimal needle density contained proper flexural and impact properties is 50–100 st/cm², consistent with the observations from scanning electron microscopy and optical microscopy. A similar phenomenon is also observed by using nonwoven maleic-anhydride-modified polypropylene (mPP) instead of unmodified PP. However, the effect of needle punching on flexural and impact properties is not significant in mPP, which is probably due to better adhesion between glass fiber and mPP matrix. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2169–2176, 1999     

原位成纤复合法改善聚丙烯的力学性能

采用原位成纤复合法制备了均聚聚丙烯(PP-H)/聚对苯二甲酸乙二酯(PET)原位成纤复合材料,研究了PET原位微纤化对PP-H力学性能的影响.实验采用的设计工艺可实现PET在PP-H基体中原位微纤化;原位生成的PET纤维对PP-H力学性能的影响呈各向异性,表现为拉伸及弯曲强度提高,冲击强度下降,改善效果受PET微观形态...     

Microstructure control and mechanical properties of porous silicon nitride ceramics

Porous silicon nitride ceramics with a fibrous interlocking microstructure were synthesized by carbothermal nitridation of silicon dioxide. The influences of different starting powders on microstructure and mechanical properties of the samples were studied. The results showed that the microstructure and mechanical properties of porous silicon nitride ceramics depended mostly on the size of starting powders. The formation of single-phase β-Si₃N₄ and the microstructure of the samples were demonstrated by XRD and SEM, respectively. The resultant porous Si₃N₄ ceramics with a porosity of 71% showed a relative higher flexural strength of 24 MPa.     

成核剂对聚丙烯力学性能与结晶行为的影响

研究了两种类型的成核剂对国产共聚聚丙烯的结晶形态以及拉伸强度、冲击强度的影响。结果表明:加入TMB-5型成核剂,聚丙烯的冲击强度有一定程度改善,w(TMB-5)为0.1%时,改性聚丙烯的缺口冲击强度达到最大;TMX-2型成核剂可改善聚丙烯的拉伸性能,但抗冲击性能降低较大;TMB-5型成核剂可显著地改变聚丙烯的结晶行为,诱导聚丙烯在结晶过程中主要形成β晶;TMX-2型成核剂可诱导聚丙烯在结晶过程中主要生成α晶,与纯PP相比,α晶的形成能力增强。     

Nanoparticle effects on the morphology and mechanical properties of polypropylene spunbond webs

We report morphology and mechanical properties of natural nanoclay incorporated spunbond polypropylene composite webs. Nanocomposite spunbond webs were produced with up to 5 wt % natural nanoclay additives on Reicofil®‐2 spunbond line. Influence of nanoclay on the resin rheological properties, processibility, and mechanical properties of webs were studied. Wide angle X‐ray diffraction and transmission electron microscopy analysis were used to investigate the nanocomposite morphology. Intercalated and flocculated morphology was observed for all the concentrates and for all the spunbond fiber webs. The microstructure and polymer morphology in the presence of additives was characterized using a polarized optical microscope. At higher percentage, excess clay platelets were excluded out of the spherulite boundaries. About 20–30% increase in tear strength was observed for webs with up to 2 wt % nanoclay additives. Compared with the control polypropylene spunbond web, nanoclay reinforced samples showed better dimensional stability. Different failure mode was observed for spunbond webs with additives. Spunbond webs with even as low as 1 wt % clay retain their morphology and integrity in bond point after thermal bonding. Nanoclay incorporated spunbond webs showed significant improvements in the stiffness. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

β成核剂对聚丙烯力学性能的影响

通过在抗冲聚丙烯基础树脂中添加自主研制的酰胺型高效β成核剂,在升高聚丙烯耐热温度的同时有效提高聚丙烯树脂EPS30R的冲击强度,研究酰胺型β成核剂PA-01、TMB-5和FB-1添加量对聚丙烯树脂EPS30R力学性能的影响,通过微观形态分析增韧的内在原因,并考察成核剂对聚丙烯树脂EPS30R的成核效果。结果表明,添加β成核剂后,聚丙烯的力学性能明显改善,且β成核剂诱导聚丙烯的成核效果较好。     

Enhancing thermal insulation and mechanical strength of porous ceramic through size-graded MA Hollow Spheres

In this study, a series of porous ceramics were prepared using different ratios of small and large size MA hollow ceramic spheres as pore-forming agents, and their thermal insulation properties were investigated. The results showed that increasing the proportion of small size hollow ceramic spheres could effectively decrease the thermal conductivity and improve the compressive strength of the porous ceramics. The optimal porous ceramic was prepared with a ratio of 10∼50 of small and large size hollow ceramic spheres, which had a thermal conductivity of 0.368 W/(m·K) at 800 °C and a compressive strength of 22.43 MPa. Microscopic analysis indicated that the enhanced thermal insulation and mechanical properties were due to the improved pore structure and the enhanced bonding strength between the ceramic spheres and the matrix. The findings provide valuable insights for the development of high-performance thermal insulation materials.     

Computational study of thermal and mechanical properties of nylons and bio-based furan polyamides

We have investigated thermal and mechanical properties of bio-based furan polyamides and petroleum-based nylons with atomistic simulations. Glass transition temperatures estimated from a series of simulations at different temperatures were in good agreement with experimental measurements. Stress–strain relationships under uniaxial deformation conditions were also obtained and analyzed. Overall, polymers with smaller repeat units exhibited slightly higher glass transition temperatures and elastic moduli, which were attributed to higher cohesive energy densities. Furan polyamides displayed higher van der Waals cohesive energy densities and maintained more rigid planar structures near furan rings compared to nylons. As a result, bio-based furan polyamides showed higher glass transition temperatures and comparable mechanical properties despite having overall weaker hydrogen bonding than nylons.     

聚烯烃弹性体/聚丙烯热塑性弹性体的制备及力学性能

以过氧化物为硫化剂,用动态硫化法制备了聚烯烃弹性体(POE)/聚丙烯(PP)热塑性弹性体,研究了硫化剂用量、填料种类和加工次数对体系力学性能的影响。结果表明,增加硫化剂用量可以提高体系的拉伸强度,降低拉伸永久变形和压缩永久变形。碳酸钙和滑石粉对POE/PP体系无明显增强作用,炭黑的增强作用较此二者明显一些,这三种填料加入后都会使体系的扯断伸长率降低而硬度增大。加入石蜡油会使体系的扯断伸长率和压缩永久变形增大、硬度和拉伸强度降低。加工次数对POE/PP体系的力学性能无明显影响,说明体系具有较好的重复加工性能。     

Morphology and mechanical properties of polypropylene/organoclay nanocomposites

Polypropylene (PP) nanocomposites were prepared by melt intercalation in an intermeshing corotating twin‐screw extruder. The effect of molecular weight of PP‐MA (maleic anhydride‐ modified polypropylene) on clay dispersion and mechanical properties of nanocomposites was investigated. After injection molding, the tensile properties and impact strength were measured. The best overall mechanical properties were found for composites containing PP‐MA having the highest molecular weight. The basal spacing of clay in the composites was measured by X‐ray diffraction (XRD). Nanoscale morphology of the samples was observed by transmission electron microscopy (TEM). The crystallization kinetics was measured by differential scanning calorimetry (DSC) and optical microscopy at a fixed crystallization temperature. Increasing the clay content in PP‐ MA330k/clay, a well‐dispersed two‐component system, caused the impact strength to decrease while the crystallization kinetics and the spherulite size remained almost the same. On the other hand, PP/PP‐MA330k/clay, an intercalated three‐component system containing some dispersed clay as well as the clay tactoids, showed a much smaller size of spherulites and a slight increase in impact strength with increasing the clay content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1562–1570, 2002     

PP/木粉复合材料的热性能

以聚丙烯(PP)/木粉(WF)复合材料(WPC)为对象,研究了WF及马来酸酐接枝聚丙烯(PP-g-MAH)含量对WPC热性能的影响。PP和WF的熔融热焓分别为75.84 J/g和189.50 J/g,而w(WF)为10%,20%,30%,40%,50%的WPC的熔融热焓分别为54.99,40.37,38.66,27.34,22.09 J/g,加入PP-g-MAH后,WPC熔融热焓值有所提高。所有WPC在200～750℃的热分解都是分两步完成的,WF含量越高,两步分解现象越明显,第一步失重率越大;WPC每步分解的起始分解温度及峰值温度均有所提高,WPC对热更稳定。     

废电路板中回收玻璃纤维对聚丙烯基复合材料力学性能的影响

以废电路板中的回收玻璃纤维粉体（RFGP）作为聚丙烯基复合材料的填充料,采用熔融共混方法制备了玻璃纤维粉体/聚丙烯复合材料（PPMC）,并通过其力学性能测试和缺口冲击断面形貌观察,分别研究了RFGP的表面改性、粒级及填充量对PPMC力学性能的影响。结果表明：经过γ-氨基丙基三乙氧基硅烷（KH-550）表面改性处理的RFGP可明显提高PPMC力学性能,其中粗粒级的RFGP对PPMC力学性能的提高幅度比细粒级的更显著,并随填充量的增加先升高后降低;当改性RFGP的粒级为180～450 μm及填充量为30%时,PPMC的弯曲模量、弯曲强度、拉升强度和冲击强度最大增幅分别为68.4%、31.2%、25.9%和41.4%。     

Structural and mechanical properties of advanced polymer gels with rigid side-chains using coarse-grained molecular dynamics

Computational modeling was utilized to design complex polymer networks and gels which display enhanced and tunable mechanical properties. Our approach focuses on overcoming traditional design limitations often encountered in the formulation of simple, single polymer networks. Here, we use a coarse-grained model to study an end-linked flexible polymer network diluted with branched polymer solvent chains, where the latter chains are composed of rigid side-chains or “spikes” attached to a flexible backbone. In order to reduce the entropy penalty of the flexible polymer chains these rigid “spikes” will aggregate into clusters, but the extent of aggregation was shown to depend on the size and distribution of the rigid side-chains. When the “spikes” are short, we observe a lower degree of aggregation, while long “spikes” will aggregate to form an additional secondary network. As a result, the tensile relaxation modulus of the latter system is considerably greater than the modulus of conventional gels and is approximately constant, forming an equilibrium zone for a broad range of time. In this system, the attached long “spikes” create a continuous phase that contributes to a simultaneous increase in tensile stress, relaxation modulus and fracture resistance. Elastic properties and deformation mechanisms of these branched polymers were also studied under tensile deformation at various strain rates. Through this study we show that the architecture of this branched polymer can be optimized and thus the elastic properties of these advanced polymer networks can be tuned for specific applications.     

Fabrication and properties of C/SiC porous ceramics by grinding-mould pressing-sintering process

High temperature resistant porous ceramics are considered to be prime candidates for applications in the transpiration cooling system of a hypersonic vehicle. This paper describes a new preparation process including grinding-mould pressing-sintering process, which is successfully used to fabricate C/SiC porous ceramics with high compressive strength and excellent permeability. The effects of carbon fiber content on the microstructure, mechanical property, pore size distribution and permeability of this porous ceramic are investigated in detail. The results indicate that this porous ceramic prepared in this study exhibits high compressive strength (～270.82 MPa) and excellent permeability (～3.937 × 10^?8 mm²). The C/SiC porous ceramics fabricated in this study will have potential application in active thermal protection systems.     

Structural design and mechanical properties of porous structured diamond abrasive tool by selective laser melting

Additive manufacturing is an important and promising way to realize the structural-functional integration of diamond abrasive tools. In the presented study, the porous diamond grinding heads with different pore structure and porosity were designed and fabricated by selective laser melting (SLM). By analyzing the stress distribution of overall structures and pore units, the 50 %-porosity square-pore structure with lowest stress concentration degree was optimized. The porous composite samples had good SLM formability, including good integrity and connectivity of pore units, and the diamond abrasives were evenly distributed and exhibited good retention and protrusion height. The high retention was attributed to the multiple interfacial system composed of carbide layer and solid solution strengthening layer. Compared with other porous samples, the 50 %-porosity square-pore structured sample with frame supporting unit and uniform stress distribution showed high deformation resistance of 430 MPa in yield strength and energy absorption capacity of 56.4 MJ/m³, which well verified the simulation results. The wear and grinding tests showed that the sharpness and self-sharpening ability of porous samples were significantly superior to the full-dense sample, and the grinding ratio increased with the increasing of the porosity.     

Additive manufacturing of complex-shaped and porous silicon nitride-based components for bionic bones

Si₃N₄ is a novel implant material with promising applications in the replacement of human hard tissues. The biomimetic human bone structure used in this study was created using digital light-processing technology. The effect of pore-forming agent content on the curing and mechanical properties of Si₃N₄ ceramics was studied. The obtained results indicated that with an increase in the pore-forming agent content, the cure depth of the ceramic suspension first increased and then decreased, while the excess cure width decreased. Furthermore, as the pore-forming agent content increased, the porosity of the sample increased, whereas the compressive strength and Young's modulus decreased. The maximum porosity of the sample at the optimal mass ratio (pore-forming agent: Si₃N₄ = 5:10) is 58.48 ± 0.49%, and the compressive strength and Young's modulus are 79.01 ± 6.78 MPa and 18.18 ± 0.26 GPa, respectively.     

Effect of chain composition on the mechanical response of structural gel: A molecular dynamics simulation

Polymer gels, defined either from the structural point of view (structural gel) or by their mechanical properties (mechanical gel), are ubiquitous in our daily life. In our previous work (J. Phys. Chem. B, 2011, 115, 11345), we reported that, the mechanical gel formed by strong solvophobic ABA block copolymers with fixed chain compositions shows a strong mechanical response, which meant the formed gel had a high modulus. In this work, we focus on the effect of chain composition on the relationship between structural gel and mechanical gel, where the chain length of block copolymer is lower than its entanglement chain length for simplicity. Our results show that the chain composition has a great effect on the mechanical response of the ABA copolymer solutions with a strong solvophobicity. On the other hand, for the structural gel formed by weak solvophobic block polymers, we do not find any strong mechanical responses even we change the chain composition in a wide range. Moreover, we find three typical gelation processes, companied with three kinds of different mechanical responses. These results may provide us an effective method to control the mechanical property of a polymer gel as expected.     

Effect of maleimide curing on mechanical properties of ground tyre rubber/waste polypropylene blends

Abstract

Blends of ground tyre rubber and waste polypropylene with a maleimide curing system (50∶50 blends of ground tyre rubber/waste polypropylene) were prepared in a Haake Rheocord Polylab System, at 180°C and 90 rev min^–1 for 5 min. The curing agent and the activator used were N,N′-meta-phenylene dimaleimide (HVA-2) and di(tert-butylperoxyisopropyl) benzene (DTBPIB) respectively. The HVA-2 level varied from 0 to 5 parts per hundred parts (pphp), while the DTBPIB level varied from 0 to 1 pphp. Melt viscosity, tensile strength and elongation at break showed an increase with HVA-2 content, while the impact energy showed an optimum at 3 pphp level. The addition of the DTBPIB increased melt viscosity further and produced a homogeneous phase morphology of the blends. Impact energy improved with the DTBPIB level, while elongation at break and tensile strength showed an optimum at 0·6 pphp. Swelling behaviour and gel/sol from the boiled xylene extractions were studied, and the results obtained were correlated with the impact and tensile properties.     

Influence of structural organization on tensile properties in mesomorphic isotactic polypropylene

The effects of annealing on the structure and mechanical properties of mesomorphic isotactic polypropylene have been investigated using wide-angle and small-angle X-ray scattering and rheo-optics in addition to tensile tests. Young's modulus of mesomorphic phase was estimated to be 5 GPa using Takayanagi model. The α-crystallitic iPP prepared by annealing the quenched mesomorphic iPP was transparent because of the absence of spherulitic structure. It was found that the mechanical yielding of α-crystallitic iPP is dominated by the plastic flow of crystalline structural units whereas the yield process of α-spherulitic iPP quenched at 80 °C is caused by the fracture or fragmentation of crystalline structural units.