CSW/POE-g-MA/PA6三元复合材料的结构和性能

采用马来酸酐接枝乙烯一辛烯共聚物(POE-g-MA)对CaS04晶须/尼龙6(CSW/PA6)共混物增韧改性,研究了csw/PA6和CSW/POE-g-MA/PA6复合材料的力学性能、热性能、形貌和加工性能.适量添加CSW可同时提高PA6的刚性和韧性.与纯PA6性能比较,10％CSW/PA6的拉伸强度、弯曲强度、弯曲模量和冲击强度分别增大7.5％、9.1％、21.1％和11.6％;当CSW含量增至30％,CSW/PA6的韧性明显降低.POE-g_MA可促进PA6基体中csw的均匀分散,增强CSW与PA6的界面粘附,提高CSW/PA6 (30/70)的冲击韧性.源于CSW和POE-g-MA的协同作用,CSW/POE-g-MA/PA6 (30/5/65)的冲击强度和弯曲模量与纯PA6相比较,分别提高了36.8％和22.1％,拉伸和弯曲强度接近纯PA6.     

Preparation of the HIPS/MA graft copolymer and its compatibilization in PA6/HIPS blends

The graft copolymer of high impact polystyrene (HIPS) grafted with malice anhydride (MA) (HIPS-g-MA) was prepared with melt mixing in the presence of a free-radical initiator. The grafting reaction was confirmed by IR analyses and the amount of MA grafted on HIPS was evaluated by a titration method. 1–5 wt% of MA can be grafted on HIPS. HIPS-g-MA is miscible with HIPS. Its anhydride group can react with the PA6 during melt mixing the two components. The compatibility of HIPS-g-MA in the HIPS/PA6 blends was evident. Evidence of reactions in the blends was confirmed in the morphology and mechanical properties of the blends. A significant reduction in domain size was observed because of the compatibilization of HIPS-g-MA in the blends of HIPS and PA6. The tensile mechanical properties of the prepared blends were investigated and the fracture surfaces of the blends were examined by means of the scanning electron microscope (SEM). The improved adhesion in a 16%HIPS/75%PA6 blend with 9%HIPS-g-MA copolymer was detected. The morphology of fibrillar ligaments formed by PA6 connecting HIPS particles was observed.     

Effect of pimelic acid on the crystallization, morphology and mechanical properties of polypropylene/wollastonite composites

The pimelic acid (PA) was used as a new surface modifier for wollastonite. The effects of PA treatment on the crystallization, morphology and mechanical properties of polypropylene/wollastonite composites were investigated. The Fourier transform infrared spectroscopy analysis revealed that the PA bonded to the wollastonite's surface and formed the calcium pimelate after reacting with the wollastonite. The results of wide angle X-ray diffraction, differential scanning calorimetry and polarized light microscopy proved that the PA treated wollastonite induced more β-crystalline form and decreased the spherulites sizes of polypropylene. The results of scanning electron microscopy showed that the PA treatment enhanced the interfacial adhesion between the filler and the matrix, indicating the improvement of the compatibility between polypropylene and wollastonite. The toughness of the composites was improved by the more ductile β-form spherulites. When 2.5 wt% of PA treated wollastonite was added, the Izod notched impact strength reached its maximum, a value of 17.33 kJ/m², which was 3.19 times greater than that of the blank polypropylene.     

Carbon fibre-reinforced silicon nitride composite

The processing of silicon nitride reinforced with carbon fibre was studied. The problems of physical and chemical incompatibility between carbon fibre and the silicon nitride matrix were solved by addition of a small amount of zirconia to the matrix and by low-temperature hot-pressing. The composite material possesses a much higher toughness than hot-pressed silicon nitride. Its work of fracture increased from 19.3 J m^–2 for unreinforced Si₃N₄, to 4770 J m^–2; its fracture toughness,K _lc , increased from 3.7 MN m^–3/2 for unreinforced material, to 15.6 MN m^–3/2. The strength remains about the same as unreinforced Si₃N₄ and the thermal expansion coefficient is only 2.51×10^–6 ° C^–1 (RT to 1000° C). It is anticipated that this composite may be promising because of its mechanical and good thermal shock-resistance properties.     

Kinking and compressive failure in uniaxially aligned carbon fibre composite tested under superposed hydrostatic pressure

Initiation and propagation of failure in uniaxially aligned 60% volume-fraction Type III carbon fibre-epoxide compressive specimens, strained parallel to the fibre axis, was studied at atmospheric and superposed hydrostatic pressures, H, extending to 300 MN m^–2. The atmospheric axial compressive strength was approximately 1.5 GN m^–2 and equal to the tensile strength, but mechanisms involving shear-operated failure of the fibres must be discounted since the failure process was very pressure sensitive above H 150 MN m^–2. The results also could not be satisfactorily interpreted by theories involving micro-buckling of individual fibres or laminae when the matrix shear modulus controls the compressive strength. For atmospheric tests and for H<150 MN m^–2 the initiation of failure was associated with transverse cracking (longitudinal splitting) which was followed by kinking. Ahead of the propagating kink band, groups of fractured fibres were observed, which is consistent with failure of these groups by buckling; this process causes composite catastrophic failure. At higher pressures splitting was suppressed, as was interlaminar cracking in doubly-notched (in-plane shear) specimens, but kinking, which became increasingly more difficult to initiate, was the precursor of the failure process. An attempt was made to analyse failure using the fracture mechanics model of Chaplin with some success for the notched specimens.     

Longitudinal shear properties of human compact bone and its constituents,and the associated failure mechanisms

Human compact bone specimens were tested in longitudinal shear at two different strain rates. The maximum stress and energy absorption capacities were 50.40±14.08 MN m^–2 and 20720±9310J m^–2 respectively for 14 embalmed specimens tested at a cross head speed of 2.1×10^–6 m sec^–1. The maximum stress was found to be 75% of the transverse shearing strength. Bone specimens were also tested after selectively dissolving the organic and mineral components. The results showed that the composite strength of bone was much higher than the summation of strengths of its organic and mineral phases. Fractographic examination of the fracture surfaces showed that debonding of the interfaces between the osteons and the surrounding bone matrix and between the osteonal lamellae were the main mechanisms of longitudinal shear failure.     

PA6/K-MAH共混物的制备与性能

研究了K树脂的马来酸酐接枝物(K-M AH)对PA 6的干态力学性能、低温冲击性能和吸水率的影响,结果表明,K-M AH使PA 6在低温及干态条件下的冲击强度大幅度提高,而拉伸、弯曲强度变化较小。通过扫描电镜(SEM)考察了共混物的微观相态,结果显示,K-M AH在PA 6中粒径很小且分散均匀,两相界面模糊,K-M AH与PA 6相容性很好。     

Deformation and fracture behavior of notched and unnotched unidirectional C/C-Mg composite with Young's modulus 520 GPa and tensile strength 1 GPa

Experimental study on tensile fracture behavior of the newly developed C/C-Mg composite, prepared by infiltration of Mg into the pores in the C/C composite heat-treated at 3000°C, was carried out. The volume fraction of the filled Mg was 9–10%. The composite had a specific density 2.1, Young's modulus 520 GPa and Poisson's ratio 0.26. The average tensile strength measured for the specimen with a nominal width 8 mm, gage length 40 mm and thickness 1 mm was 1 GPa. The Young's modulus was improved from 450 to 520 GPa and the strength from 0.9 to 1.0 GPa by Mg-infiltration. The specific Young's modulus and specific strength based on the average measured values were 2.5 × 10⁷ m and 5 × 10⁴ m, respectively, showing high potential as light-weight, stiff and strong structural material. The strength distribution of the composite was described by the two-parameter Weibull distribution function with a shape parameter 7.6 and scale parameter 1060 MPa. Prior to the overall fracture of the composite, the longitudinal cracking arose at the notch tip, due to which the notch tip was blunted and the ligament portion behaved like an unnotched specimen. As a result, the notched strength could be described by the net stress criterion. The apparent critical energy release rate at formation of the longitudinal crack was around 70–90 J/m².     

动态硫化法制备尼龙6/马来酸酐接枝三元乙丙橡胶高韧合金

采用酚醛树脂(PF)、硫磺(S)与过氧化二异丙苯(DCP)作交联剂,研究了马来酸酐接枝三元乙丙橡胶(EPDM-gMAH)的动态硫化对增韧尼龙6(PA6)性能的影响。结果表明,采用PF硫化体系且硫化剂用量为EPDM-g-MAH的1.5%,PA6与EPDM-g-MAH质量比为80/20的合金的综合性能较好,其拉伸强度与缺口冲击强度较未硫化PA6/EPDMg-MAH(80/20)合金分别提高69.5%与128.8%,主要是由于动态硫化提高了PA6与EPDM-g-MAH的相容性。动态硫化还提高了PA6/EPDM-g-MAH合金的热稳定性、PA6的结晶温度和结晶速率。     

短玻纤和SiO2 颗粒增强PA66/ UHMWPE复合材料的力学性能

制备了PA66/ U HMWPE/ HDPE-g-MA H 共混合金, 并对其力学性能和微观结构进行了研究。结果表明: 随着U HMWPE 含量的增加, 共混合金缺口冲击强度显著提高, 拉伸强度、拉伸模量、弯曲强度和弯曲模量下降。为了弥补强度和刚性的损失, 使材料同时具有良好的韧性、强度和刚性, 采用了短玻璃纤维和无机粒子混杂增强PA66/ U HMWPE/ HDPE-g-MAH (80/ 20/ 20) 。经短玻纤和无机粒子混杂增强后, 材料的拉伸强度、弯曲强度、模量和刚性都明显提高, 同时材料缺口冲击强度保持较高水平, 比尼龙66 提高72.9 %。      

POE-g-MA增韧PPO/尼龙6合金的制备和性能

考虑了采用马来酸酐接枝乙烯－1－1辛烯共聚物（POE－g-MA)反应挤出增韧聚苯醚（PPO）／尼龙6合金体系的力学性参能和亚微相态,结果表明,POE与PPO／尼龙6合金的相容性差,增韧效果不佳,POE接枝MA后,通过其分子链上的MA官能团与PPO／尼龙6合金分子链上的氨基反应,获得良好的界面粘结性和相容性,使合金的缺口冲击强度获得大幅度提高,POE－g-MA增韧PPO／尼龙6合金的韧性随MA接枝率的增加而提高,通过与MA的接枝,可显著提高POE与PPO／尼龙6合金的界面粘结性和合金基体中的分散性,并明显减小POE粒子的直径,流变性能研究表明,由于在反应挤出过程中POE－g-MA分子链上的酸酐官能团与尼龙6上的氨基发生化学反应,使POE－g-MA增韧PPO／尼龙6合金的熔体粘度随POE－g-MA的接枝率的增加而显著提高。     

聚碳酸酯/尼龙6共混体系力学性能的研究

探讨了不同增容剂对PC／PA共混体系的影响，研究结果表明：苯乙烯－马来酸酐共聚物（SMA）对PC／PA共混体系有一定增容作用，加入少量SMA后，共混物的力学性能有所提高；自制增容剂B与SMA协同使用对PC／PA共混体系有较好增容作用，协同增容后共混物的冲击强度大幅度提高，同时共混物仍保持较高的拉伸强度和弯曲强度。     

Jute-reinforced polyester composites

Raw jute fibre has been incorporated in a polyester resin matrix to form uniaxially reinforced composites containing up to 60 vol% fibre. The tensile strength and Young's modulus, work of fracture determined by Charpy impact and inter-laminar shear strength have been measured as a function of fibre volume fraction. These properties all follow a Rule of Mixtures relationship with the volume fraction of jute. Derived fibre strength and Young's modulus were calculated as 442 MN m^–2 and 55.5 GN m^–2 respectively. Polyester resin forms an intimate bond with jute fibres up to a volume fraction of 0.6, above which the quantity of resin is insufficient to wet fibres completely. At this volume fraction the Young's modulus of the composite is approximately 35 GN m^–2, the tensile strength is 250 MN m^–2, the work of fracture is 22 kJ m^–2 and the inter-laminar shear strength is 24 MN m^–2. The properties of jute and glass fibres are compared, and on a weight and cost basis jute fibres are seen in many respects to be superior to glass fibres as a composite reinforcement.     

尼龙11/POE共混物的形态与力学性能

采用动态力学分析(DMTA)和扫描电镜(SEM)等方法研究了相容剂乙烯辛烯共聚物接枝马来酸酐聚合物(POE-g-MAH)对尼龙11(PA11)共混体系力学性能及共混物形态的影响。结果表明,混合弹性体中m(POE-g-MAH)/m(POE)=2∶1时,PA11共混物的缺口冲击强度达到81.2 kJ/m2;共混物缺口冲击强度对MAH接枝率敏感;加入混合弹性体,共混体系分子间的作用力增大,损耗峰向高温方向移动,Tg升高;PA11与POE各个共混体系的β松弛峰高显著低于纯PA11的,加入POE和POE-g-MAH可有效降低PA11的吸水性;POE-g-MAH可显著改善PA11/POE共混材料的相容性,使分散相尺寸减小,分布均匀,且材料缺口冲击强度显著增大。     

A novel approach of in situ grafting polyamide 6 to the surface of multi-walled carbon nanotubes

In this report, a novel approach was developed to graft polyamide 6 (PA6) onto the surface of multi-walled carbon nanotubes (MWNTs). MWNTs were covalently functionalized with copoly(styrene-maleic anhydride) (SMA) via free radical polymerization. SMA functionalized MWNTs (MWNTs-g-SMA) were then used as a macromolecular activator of anionic ring-opening polymerization of ε-caprolactam thus to graft PA6 onto the surface of MWNTs. Raman, FTIR spectroscopy and FETEM were used to identify the covalently grafting SMA and PA6 onto the surface of MWNTs. Additionally, the dispersibility of PA6 functionalized MWNTs (MWNTs-g-PA6) in formic acid and melted ε-caprolactam was also demonstrated.     

Tensile properties of directionally solidified Al-Al3Ni composites with off-eutectic compositions

Ingots (1/8 in. diameter) of Al-Al₃Ni with off-eutectic compositions were directionally solidified at two growth rates. At 1 cm h^–1 fibres exhibited a blade-like morphology, and at 11 cm h^–1, a rod-like morphology. Speciments were mechanically evaluated in tension. The composite modulus at stresses above the yield strength of the aluminium matrix obeyed the rule of mixtures, assuming ideal plastic behaviour of the matrix. An extrapolation of these data for composites with rod fibres gave a value of 146 GN m^–2 for the modulus of Al₃Ni. Tensile strength of composites with rod-like fibres followed the rule of mixtures, whereas those with non-uniform blade fibres showed a lower strength. In composites with blade-like fibres the extrapolated aluminium matrix strength was 86.3 MN m^–2, a high value attributed to dispersion hardening, and that of the fibres was 2.69 GN m^–2. Composites with blade-like fibres failed at lower strains than did those with more uniform rod-like fibres.     

Solid–liquid interfacial energy of camphene

The Gibbs–Thomson coefficient and the solid–liquid interfacial energy for camphene have been measured to be (8.58±0.96)×10⁻⁸ K m and (4.43±0.49)×10⁻³ J m⁻², respectively, by a direct method. The grain boundary energy of camphene has also been calculated to be (8.36±0.92)×10⁻³ J m⁻² from the observed grain boundary groove shapes.     

The effect of hydrostatic pressure on the tensile properties of pultruded CFRP

The failure process in waisted tensile specimens of pultruded 60% volume fraction carbon fibre-epoxide was investigated at atmospheric and superposed hydrostatic pressures up to 300 MN m^–2. The maximum principal stress at fracture decreased from ~ 2.0 GN m^–2 at atmospheric pressure to ~ 1.5 GN m^–2 by 200 MN m^–2 superposed pressure and then remained approximately constant. These latter failures were fairly flat and no damage preceding the catastrophic fracture was detected, which indicates that composite strength is solely controlled by fibre strength. Fracture of fibres at lower pressures appeared to commence also in the range 1.5 to 1.6 GN m^–2, but, as it did not result in catastrophic failure, account has to be taken of the resin and the fibre bundles. Debonding was initiated at ~ 1.2 GN m^–2 at atmospheric pressure and this stress increased to ~ 1.5 GN m^–2 when 150 MN m^–2 superposed pressure was applied; the pressure dependence was related to that of the resin tensile strength. This process is described as the first stage, straightening and debond initiation of curved surface bundles, on our model of tensile failure. The second stage, delamination, i.e. the growth of transverse cracks leading to the detachment of these bundles, was impeded by the transverse pressure, being suppressed beyond 150 MN m^–2. Only below this pressure was load redistribution between bundles possible, but, as the pressure was increased from atmospheric, it become more difficult, resulting in a decrease in the composite tensile strength and reduced fibre pull-out.     

The low temperature magnetic properties of austenitic Fe---Cr---Ni alloys. 3. The effect of chromium concentration in Fe---Cr-17wt% Ni alloys

The magnetic properties of ternary Fe---Cr---Ni alloys containing 17 wt% Ni and 18–24% Cr have been studied over a range of temperature from 4.2–35 K by both ac and dc techniques in fields from 5 Am⁻¹ − 6 MA m⁻¹. At room temperature, the matrix of all the alloys was the paramagnetic fcc austenite phase (with an unavoidable 0.1 – 0.5 wt% δ ferrite) and on cooling all the alloys showed distinct peaks in ac susceptibility, though equivalent peaks in dc susceptibility were only observed at low fields in the alloy containing 18 wt% Cr. An analysis of the magnetization/field/temperature results showed that all the alloys were superparamagnetic at low temperature, due to the formation of ferromagnetic clusters in the disordered antiferromagnetic matrix, and that the chromium atoms make no measureable contribution to the magnetization of these clusters. Appropriate susceptibility values are tabulated for use as design data.     

Morphology and structure of tantalum oxide deposit prepared by KrF excimer laser CVD

Tantalum oxide films have been deposited on substrates by decomposing Ta(OCH₃)₅ photolytically in the beam of a KrF excimer laser under various conditions of laser fluence (200–450 J m^–2), repetition rate (20–120 Hz), supply rate of Ta(OCH₃)₅ (50–400 mg h^–1) and substrate temperature (403–723 K). The deposits were highly oriented when produced at laser fluences of 350 and 450 J m^–2. Their XRD patterns suggested the formation of -Ta₂O₅. The (1 1 1 0) planes were preferentially oriented parallel to the substrate surface when produced at lower repetition rates, higher supply rates of Ta(OCH₃)₅, and lower substrate temperatures; whereas (1 1 1 1) planes were similarly oriented when the conditions were reversed. The preferred orientation may be explained in terms of supersaturation. The deposits produced at a fluence of 200 J m^–2 were, however, rather amorphous.