共查询到20条相似文献,搜索用时 78 毫秒
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以废旧高密度聚乙烯(PE-HD)和蒙脱土(MMT)为原料,采用熔融插层法制备纳米复合材料,考查制备工艺对该材料热氧老化性能和燃烧性能的影响。结果表明,PE-HD复合MMT或有机蒙脱土(OMMT)后,抗热氧老化性能显著降低,阻燃性能增强;十六烷基三甲基溴化铵(CTAB)、OMMT、马来酸酐(MAH)和过氧化二异丙苯(DCP)加入量分别增加时,PE-HD/OMMT纳米复合材料的抗热氧老化性能无显著变化,阻燃性能呈现先增强后降低或稳定的趋势;当CTAB加入量为1 %、OMMT加入量为3 %、MAH和DCP加入量为1.5 %时,PE-HD/OMMT纳米复合材料的极限氧指数达到19.4 %,阻燃性能最好。 相似文献
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研究了制备剥离型(苯乙烯/马来酸酐)共聚物(SMAH)蒙/脱土(MMT)纳米复合材料的方法。研究表明,通过原位插层及熔融插层只能制备出插层型的SMAH/MMT纳米复合材料。为了制备剥离型的SMAH/MMT纳米复合材料,先将尼龙6(PA6)与MMT熔融插层制备出PA6/MMT纳米复合材料,再用抽提的方法将PA6/MMT复合材料中的部分PA6除去,得到含有少量PA6的剥离型MMT,然后将剥离型MMT与SMAH共混,从而制备出剥离型的SMAH/MMT纳米复合材料。该复合材料的粘度低于SMAH,且具有较好的加工性能。 相似文献
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用Haake流变仪,对三元乙丙橡胶(EPDM)进行熔融接枝马来酸酐(MAH),考察了单体、引发剂(DCP)用量对接枝率的影响。结果表明,在EPDM接枝MAH的反应中,随着DCP用量的增加,接枝率增大;随着MAH用量的增加,接枝率趋于一个平衡值。PEN EPDM g MAH共混物韧性的测定可以在很宽的温度(21℃~118℃)和组分〔(0~14wt%)EPDM g MAH〕范围中进行。发现了增加温度和增加EPDM g MAH含量对EPDM g MAH增韧PEN的脆韧转变有相同的影响。 相似文献
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傅李丹;陈思;王勇杰;孟季凤;王旭 《中国塑料》2010,24(6):19-23
通过熔融法分别制备了三元乙丙橡胶(EPDM)/纳米碳酸钙(nano-CaCO3)交联母料及其与聚酰胺6(PA6)共混的三元复合材料。利用场发射扫描电子显微镜研究了EPDM交联对PA6/EPDM/nano-CaCO3三元复合材料形态的影响。结果表明,随着过氧化二异丙苯含量从0.30%(质量分数,下同)降低到0时,PA6/EPDM/nano-CaCO3三元复合材料中"沙袋结构"粒子粒径变小;冲击强度从22 kJ/m2提高到47 kJ/m2;拉伸强度和弯曲强度变化不明显。在受到外力作用时,含有均匀分散的"沙袋结构"粒子的三元复合材料通过"沙袋结构"粒子诱发微纤化和"扩张带"耗散外界作用能。 相似文献
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以苯乙烯接枝马来酸酐共聚物(SMA)为增容剂对聚对苯二甲酸乙二醇酯(PET)/丙烯腈-丁二烯-苯乙烯(ABS)共混物进行研究;采用熔体质量流动速率试验机和毛细管流变仪研究了PET/ABS/SMA共混物的流变行为,并对其lgγw~lgτw、lgηa~lgγw、lgηa~1/T曲线进行了分析。结果表明:在260~266℃及剪切应力为24.5~73.5 MPa时,PET/ABS/SMA共混物均为假塑性流体;增容剂SMA的加入明显地降低了共混物的非牛顿指数(n),并且使PET的黏流活化能(ΔE)较大幅度的升高,但过量的SMA会使ΔE下降。随着SMA的增加,共混物的黏度先增加后减小,SMA用量达到5%时,达到最大值。 相似文献
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A new ampholytic homopolypeptide, , which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO4 and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu2+ and Ca2+, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu2+ complex near 240 nm. Dependence of the peak intensity on pH at various q values () indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu2+ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu2+ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu2+-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation. 相似文献
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Silvia Schicker Daniel E. García Igor Gorlov Rolf Janssen Nils Claussen 《Journal of the American Ceramic Society》1999,82(10):2607-2612
Wet milling of Al2 O3 -aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al2 O3 and Fe2 O3 /Al/Al2 O3 powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe2 O3 /Al/Al2 O3 powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al2 O3 powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8. 相似文献
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Sintering kinetics of the system Si3 N4-Y2O3 -Al2 O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si3 N4 were studied with additions of 4 to 17 wt% Y2 O3 and 4 wt% A12 O3 . Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si3 N4 and glass or β '-Si3 N4 , α '-Si3 N4 , and glass. The compositions and amounts of the residual glassy phases are estimated. 相似文献
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Akira Akimoto 《Polymer》1974,15(4):216-218
The polymerization of vinyl chloride has been investigated using an catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed. 相似文献
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Mats Carlsson Mats Johnsson Mats Nygren 《Journal of the American Ceramic Society》1999,82(8):1969-1976
Ta0.33 Ti0.33 Nb0.33 C and Ta0.33 Ti0.33 Nb0.33 C x N1− x whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N2 . The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO2 , Ta2 O5 , Nb2 O5 , C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl2 ( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature. 相似文献