共查询到18条相似文献,搜索用时 62 毫秒
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有机过氧化物交联间规聚丙烯研究 总被引:5,自引:0,他引:5
用DSC对三羟甲基丙烷三甲基丙烯酸酯(TMPTMA)存在下的间规聚丙烯过氧化物交联进行了研究。根据交联过程中反应热焓的变化结合交联前后凝胶含量的结果确定了工艺条件。单独使用过氧化物或多官能团单体均难以使sPP交联,在sPP/TMPTMA/DCP交联体系中,多官能团单体聚合后在sPP基体中形成的中间产物通过捕捉sPP大分子自由基形成了交联结构。随DCP和TMPTMA用量的增加,交联程度增大,但高温下长长时间反应会导致sPP的降解反应加剧,凝胶含量下降。 相似文献
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SEBS增容等规聚丙烯/间规聚苯乙烯共混体系的结构与性能 总被引:1,自引:0,他引:1
用3种组成相近而分子量不同的苯乙烯-乙烯/丁烯-苯乙烯共聚物(SEBS)作为增容剂,对等规聚丙烯/间规聚苯乙烯(iPP/sPS)共混物进行增容。研究了共聚物的分子量对iPP/sPS共混物的形态结构及力学性能的影响。结果表明,中、低分子量的SEBS具有较好的增容作用,能有效提高共混物的拉伸强度;而高分子量的SEBS则能显著改善共混物的韧性。用SEM观察了增容剂在共混物中的分布情况,揭示了共混物的力学性能不仅取决于增容剂的界面活性,而且还与增容剂在共混物中的分布密切相关。 相似文献
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间规聚丙烯的非等温结晶过程与动力学研究 总被引:3,自引:0,他引:3
用DSC法研究了间规丙烯(s-PP)的非等温结晶动力学,并以Борохоьский方程进行非等温结晶数据处理,确定了动力学结晶(Gc)。结果表明,冷却速度(a)在1.25-20(-K/min)范围内,s-PP非等温结晶过程中t0.5和tmax均随a增加成指数下降,二者关系为t0.5=1.102a^0.012tmax。非等温结晶过程中有二次结晶发生,结晶前,后期成核与生长机理有明显差别。结晶初期成核结晶受a影响较大,结晶后期则基本上的二维条带和圆形生长,后期结晶速度大于前期。s-PP非等温结晶活化能为137.3J/mol。 相似文献
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等规聚丙烯DSC熔融双峰的成因 总被引:1,自引:0,他引:1
论述了多种产生熔融双峰的情况及原因,对最近研究等规聚丙烯DSC熔融双峰的进展进行了评述,最后,介绍了笔者在这一领域的最新研究成果。 相似文献
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用差示扫描量热仪考察了熔融结晶过程中晶核的残留对尼龙6多晶形成的影响。在熔融成型过程中尼龙6易形成较稳定的α和γ晶型。实验结果表明,在此过程中,尼龙6的α和γ晶核都对尼龙6的结晶有诱导性能,当尼龙6的熔体中存在其中一种晶型的晶核时,在结晶过程中则优先形成这种晶型。γ晶型在γ晶核不被熔融消失的情况下会向更稳定的α晶型转变,而这种转变不具有可逆性。 相似文献
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利用 DSC法研究了低等规度聚丙烯 ( LIPP)的等温结晶动力学。根据 Avrami方程求出了各个结晶温度下的结晶动力学参数 k( T)、n和 t1/ 2 ,研究了 L IPP的结晶度及结晶速率与结晶温度的关系。利用Hoffman等温结晶理论 ,求出 LIPP的 σe 为 3.0 7× 10 -2 J/ m2 。 相似文献
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不同氯含量氯化聚丙烯的热降解 总被引:6,自引:0,他引:6
用TG-DTG-DSC法研究了低氯化聚丙烯(Cl-PP)在空气、N2气流中线性升温时的热降解,发现随Cl%增加,主链脱HCL的失重率增大,而主链的降解失重率减小;N2气中平衡热降解温度TP1、T0.1随CL%的提高而下降,而TP2、TP3与其无关;空气中TP1、TP2随CL%的提高而下降,T0.1、TP3与其无关。 相似文献
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用广角X射线衍射(WAXD),SEM,DSC和TGA方法研究了聚苯胺的晶性问题,结果表明,不同条件下所得聚苯胺其本征型的结晶行为差别较大。当聚合溶液的酸浓度在0.001~7N范围内时,随着酸浓度增加,其本征态聚合物的结晶性降低。所得产物的掺杂态较本征态更容易结晶,结晶度随掺杂剂浓度的升高而增加。适当的热处理可提高聚苯胺的结晶能力。 相似文献
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T. Chinnadurai S. Arungalai Vendan C. C. Rusu 《Materials and Manufacturing Processes》2018,33(7):718-726
The polypropylene material meets the needs and requirements in automotive industry due to its features such as wide range of physical properties, ease of processing, and low cost. This research has focused on the investigation of the behavior of polypropylene during ultrasonic welding process. The lap welded samples were examined by modern methods such as Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR). Also, the morphology of the non-welded and welded regions of the polypropylene samples was analyzed by Scanning Electronic Microscopy (SEM) method. TGA and DSC results showed a negligible difference between the mass loss of the molded and the welded propylene materials. Furthermore, the SEM images revealed the formation of voids in close correlation with vibration amplitude. The weld strength and bond integrity appears to be higher for higher vibrations, emphasizing that the lap joint interface strength is higher when the tendency of voids formation is decreasing. The stress-strain curve of the material, plotted for three ultrasonic welding variants, illustrated that increasing the main process parameters (pressure, time, and vibration amplitude) makes the weld strength higher, but a decrease in plasticity was noticed in the welded polypropylene samples. 相似文献
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Differential scanning calorimetry (DSC) combined with a curve-fitting program was utilized to quantitatively determine the polymorphic composition of famotidine in the compacts prepared by different compression treatments. Two types of famotidine compacts (compact I or II) were prepared by compressing a conical shape or a flattened shape of powder bed of famotidine form B. The compact I was constructed by a transparent region in the center with an opaque region surrounded outside, but the compact II was formed by a whole opaque region only. A drilled disc sample was prepared and then directly determined by DSC analysis. The Raman spectral results clearly indicate that all the compacts whether in any region before DSC determination were only of famotidine form B and independent of compression pressure applied. Under DSC determination, however, the curve-fitted relative compositions of form B in the drilled disc I sample were gradually reduced to 23–24% with the increase of compression pressure, whereas the curve-fitted relative composition of form A was slowly increased up to 76–77%. A transitional phase of famotidine form B (form B*) in the transparent region of the compact I after applying >150 kg/cm2 of compression pressure was easily detected, and then transformed to famotidine form A under DSC heating process. But this transitional phase and polymorphic transformation of famotidine could not be detected by other spectroscopic methods. This suggests that the DSC heating system was a preferred method not only to quantitatively analyze the polymorphic transformation of famotidine but also to find a newly transitional phase of famotidine in the compressed compact. 相似文献
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纤维长径比对混凝土力学性能影响显著,而长径比变化的实质是纤维直径和形态均发生变化,因此现有研究多是通过改变聚丙烯(PP)纤维(包含粗、细PP纤维)直径或截面形态设置长径比梯度,从而导致变量不唯一。本文对粗PP纤维(d=700 μm)和细PP纤维(d=80 μm)长径比对混凝土力学性能的影响进行了试验研究,分析了粗、细PP纤维增强混凝土的力学特性。结果表明:粗、细PP纤维增强混凝土坍落度随所掺纤维长径比增大而先降低后趋于稳定,抗压、抗弯、劈拉强度随所掺纤维长径比增大而呈现出先增大后减小的趋势,700 μm粗PP纤维最优长径比为42,80 μm细PP纤维最优长径比为200。此外,提出了宏观力学拟合计算理论用于分析粗PP纤维长径比对PP纤维增强混凝土抗弯强度的影响,以此来增强试验结果的预测性和可控性;对粗、细PP纤维在混凝土中的摩擦粘结机制进行了力学分析,掌握了影响摩擦粘结力的具体因素。 相似文献
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Creep behavior and manufacturing parameters of wood flour filled polypropylene composites 总被引:2,自引:0,他引:2
Sun-Young Lee Han-Seung Yang Hyun-Joong Kim Chan-Seo Jeong Byeong-Soo Lim Jong-Nam Lee 《Composite Structures》2004,65(3-4):459-469
The influence of wood flour content, coupling agent and stress loading level on the creep behavior of wood flour–polypropylene composites was investigated. Maleated polypropylene (MAPP; Epolene G-3003™) was used as the coupling agent to treat the wood flour used as reinforcing filler for polypropylene composite. The tensile strength and modulus of various wood flour–polypropylene composites (WPCs), manufactured using the melt blending, extrusion, and palletizing methods, were measured before performing the creep test. The residual tensile strength, creep strain, and fractional deflection of the resultant wood flour–polypropylene composites were measured by means of the creep test. It was shown that the tensile strength decreased with increasing wood flour level in the composites. The creep strain also decreased as the wood flour level increased. The presence of the coupling agent increased the tensile strength of the wood flour–polypropylene composites, compared with the specimens made of pure polypropylene. For those composites containing the coupling agent, the creep deflection was significantly lower than those made without any coupling agent. The creep strains of the WPC specimens observed during the creep test fitted perfectly with the four-element burger creep model. Further investigation is required of the effects of combined mechanical and environmental loading in varying proportions. 相似文献
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