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探讨了在动态保压注射成型中少量高摩尔质量聚乙烯(HMWPE)的诱导作用对高密度聚乙烯(HDPE)结晶行为的影响.通过扫描电子显微镜(SEM)可观测到HDPE在HMWP诱导下生成了一种类似网状的串晶结构.该结构沿流动方向高度取向,垂直流动方向的片晶相互连接.实验结果证明,该结构可以同时大幅度提高试样的强度和韧性,其结构大大优于一般的串晶结构.差示扫描量热法(DSC)测试结果表明,少量HMWPE诱导的HDPE动态成型试样(B4)结晶度明显高于普通成型试样(SO)和未加高分子诱导的动态成型试样(BO).广角X射线衍射(WAXD)结果显示B4内部晶体沿着流动方向的取向度也明显高于SO和BO.本研究可得到如下结论:少量HMWPE确实能有效诱导HDPE的结晶和取向,使HDPE的结晶行为得到明显改善. 相似文献
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将少量相对高分子量的高密度聚乙烯(HDPE)加入到相对低分子量的通用级HDPE中,在复合应力场作用下挤出制成管材。通过力学性能测试、SEM、WAXD及DSC分析对制品的性能及结构进行了表征,结果表明:在剪切或拉伸应力场中,高分子量HDPE的大分子链会成为初级晶核,促进诱导体系生成大量倾斜排列的串晶和串晶互锁结构,明显改善了管材试样周轴两向的力学性能。 相似文献
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采用动态保压注塑成型技术来控制分散相相形态和橡胶粒子在基体中的取向排列.纯尼龙,动态样与静态样具有相同的冲击强度.在加入橡胶后,动态样与静态样的冲击强度变化趋势基本一致,在橡胶含量为20%t时,体系完成脆韧转变冲击强度达到最大,在橡胶含量为30%和40%时冲击强度又下降.但与静态样相比,当橡胶含量为10%t时,动态样与静态样的冲击强度一致,而当橡胶含量超过10%时,动态样的冲击强度较静态样高.结合平行于熔体流动方向的SEM照片,在橡胶含量为10%时,动态样中的橡胶粒子与静态样一样并未被拉长与取向,而在橡胶含量超过10%时,动态样剪切层中的橡胶粒子被拉长且沿熔体流动方向取向.实验表明,在改善共混物界面相容性的基础上,适当的低剪切应力场能进一步提高橡胶分散相对冲击强度的贡献. 相似文献
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用增韧母料(E-TMB)分别与高密度聚乙烯(PE-HD)2200J(HE1)、5000S(HE2)热机械共混制得HE1/E-TMB和HE2/E-TMB共混物,研究了E-TMB中弹性体配比(M/N)、基体树脂和弹性体配比(H/E)对共混物结晶行为的影响,并将其和简单共混对照样对比。结果表明,与纯PE-HD和简单共混物对照样相比,HE1/E-TMB和HE2/E-TMB的结晶起始温度升高,且随M/N比值的减小而增大,随H/E比值的减小而减小;HE1/E-TMB的结晶焓减小而成核速率和结晶速度增大,HE2/E-TMB的结晶焓增大而成核速率和结晶速度减小,HE2/E-TMB的成核速率随M/N比值的减小而减小。 相似文献
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廖永衡 《现代塑料加工应用》2004,16(5):11-13
利用振动注塑装置,在注塑时加入振动力场,高密度聚乙烯(HDPE)拉伸强度明显提高,特别当振动压力幅度提高后,拉伸强度提高更加明显,试验样条拉伸强度最大提高43%,此时注射温度为190℃,振动压力幅度为60MPa。通过扫描电镜(SEM)观察了HDPE的微观形态,发现HDPE的微观形态发生了较大的变化,无振动时结晶晶体为球晶形态,加入振动力场后,沿流动方向取向明显,更有明显的串晶产生。 相似文献
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注塑成型保压参数对塑件翘曲变形的影响 总被引:1,自引:0,他引:1
以阿基米德螺旋线塑件为例,应用Moldflow软件模拟塑件保压过程,研究了保压压力和保压方式对塑件翘曲变形的影响,并利用模腔压力测量仪测定不同保压参数下的模腔压力,得到模腔压力曲线。结果表明:保压压力对塑件的翘曲变形和体积收缩率均有显著影响;与恒压保压方式相比,分段保压使模腔压力均匀,塑件表面质量高,塑件体积收缩均匀。 相似文献
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Zhanchun Chen Lei Gao Rongfei Wang Xueqin Gao Cong Deng 《Polymer-Plastics Technology and Engineering》2013,52(3):221-226
In order to better understand the effect of small amount of both high-molecular-weight polyethylene (HMWPE) and low-molecular-weight polyethylene (LMWPE) on the mechanical properties and crystal morphology under the shear stress field, the dynamic packing injection molding (DPIM) was used to prepare the oriented pure polyethylene samples and its blends ones with different contents of HMWPE and LMWPE. The experiment substantiated that the further improvement of tensile strength and impact stength along the flow direction (MD) of HDPE/HMWPE/LMWPE samples was achieved, while the tensile strength along the transverse direction (TD) still substantially exceeded that of conventional molding. When the contents of HMWPE and LMWPE were respectively 8% in blends, the tensile strength in both flow and transverse directions of the samples were highly enhanced, with improvements from 27.75 MPa to 115.43 MPa (about 316%), in MD and from 23MPa to 32.74 MPa (about 42.34%), in TD; besides the impact strength was improved from 21.55 KJ/m2 to 72.6 KJ/m2 (about 236.89%), in MD but decreased from 17 KJ/m2 to 6.92 KJ/m2 in TD. The obtained samples were characterized via DSC, WAXD and SEM. For HDPE/HMWPE/LMWPE, the shish-kebab structure which is composed of stretched chains (shish) and lamellae (kebab) was seen in the oriented region of DPIM samples and the spherulites existed in the oriented region of SPIM samples. Furthermore, the appropriate amount HMWPE and LMWPE (about 8%, respectively) blended into mixture can improve the thickness and the length of lamellae, and the degree of crystallinity in shear region by DPIM which were approved by DSC and SEM, at the same time, it can also enhance the intensity of orientation of lamellae in shear region confirmed by SEM and WAXD. The reason of improvement of mechanical properties is the existence of these thicker, longer and more orientated lamellae in shear region. 相似文献
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高密度聚乙烯振动注射试样的结构与性能 总被引:4,自引:4,他引:0
为了研究高密度聚乙烯振动注射试样的晶体结构与性能.研制并采用压力振动装置进行振动注射实验一通过振动,高密度聚乙烯由常规注射试样的典型球晶结构转变为明显取向的片晶结构,在不同的振动条件下,片晶的尺寸和取向度都不同。振动试样的拉伸强度随振动频率和振动压力的提高而提高,最大增幅为41.0%。断裂伸长率随振动压力的增高而下降,随振动频率的增高开始时下降,然后开始回升。 相似文献
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Nan Sun Bin Yang Long Wang Wei Yang Kai Zhang 《Polymer-Plastics Technology and Engineering》2013,52(8):804-809
Position dependence for the supermolecular morphology of linear low density polyethylene (LLDPE) prepared by gas-assisted injection molding (GAIM) was examined using scanning electron microscopy (SEM). Combined morphological feature of both spherulites and those with ring-bands was observed, which differs from our previous studies on the HDPE counterparts. Dynamic rheological measurements were also carried out to interpret the formation mechanism of the morphological feature. The difference in hierarchical crystalline structures between LLDPE and HDPE can be due to their different chain branches as well as the resultant different response to the local shear fields during the GAIM process. 相似文献
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采用自行研制的压力振动注塑装置,在不同振动频率、振动压力下得到尼龙6注塑试样。结果表明,振动试样拉伸性能比静态试样有所提高,随振动频率或振动压力的提高,试样的拉伸强度发生变化。运用DSC(差示扫描量热分析)和SEM(扫描电镜)对试样结构进行了表征,测试结果表明,振动作用能使球晶数量增加,完善结晶,提高结晶度。 相似文献
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Steffen Krug Julian R. G. Evans Johan H. H. ter Maat 《Journal of the American Ceramic Society》2001,84(12):2750-2756
Many ceramic injection molding vehicles include semicrystalline polymers which characteristically adopt a spherulitic growth morphology. Usually the spherulites are rendered invisible by the opacity of the ceramic powder but in this study they are clearly visible. Polyoxymethylene (POM), has been used as the vehicle. The growth of the spherulites is shown to be dependent on cooling rate and hence on position in the molding. Furthermore, migration of low molecular weight additives by syneresis is shown to occur and to influence the crack path in the as-molded state. An unusual composite fractograph is shown in which fracture faces made after molding, after binder removal, and after sintering are contiguous. Only after molding does the crack path follow the spherulite boundaries; behavior that is also widely reported for unfilled POM. 相似文献
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Mohammad Reza Jozaghkar Hassan Arabi Farshid Ziaee 《Polymer-Plastics Technology and Engineering》2019,58(5):560-572
In the present work, the rheology, morphology, and interfacial interaction of polyethylene/polyhexane-1 (PE/PH-1) blends with various polyethylene types with different molecular architectures are investigated. The scanning electron microscopy (SEM) images showed a droplet-matrix morphology in all percentage of PH-1 for all blend systems and the size of droplets increased proportionally with PH-1 content. The minimum droplet size is observed for high-density polyethylene (HDPE)/PH-1 blends. The homogeneity of the blends at various compositions is assessed by using viscoelastic parameters determined by dynamic oscillation rheometry in the linear viscoelastic region. A distinct Newtonian plateau at low frequencies is perceived and the variations of complex viscosity (η*) versus angular frequency (ω) for all blend systems are in good agreement with Carreau-Yasuda model. The complex viscosity of samples at various percentages of PH-1 showed the negative deviation from mixing rule in low and high frequencies for all blend systems. The Cole-Cole plots deviated from semi-circular shape at higher percentages of PH-1 than 10wt% in the blends of low-density polyethylene (LDPE)/PH-1 and linear low-density polyethylene (LLDPE)/PH-1. By using emulsion theoretical model, the lowest interfacial tension is found for HDPE/PH-1 blends comparing with its counterparts based on LDPE and LLDPE and the best fitting with experimental data was observed for this blends system. 相似文献
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