共查询到19条相似文献,搜索用时 156 毫秒
1.
LDPE/1,2—PBD共混体系的辐射交联 总被引:3,自引:0,他引:3
聚合物共混物经辐射交联后,具有多种优良性能,这些性能都与交联度有关。溶胶分数与辐照剂量间的关系常常被用来表征聚合物的辐射交联程度和交联行为。本文试图将共混物的组成、组份的分子链结构与其溶胶分数与辐照剂量间的关系式联系起来,从而预期共混体系的辐射交联行为。 相似文献
2.
3.
4.
制备了含原位聚合物核壳粒子的聚丙烯/乙丙橡胶/高密度聚乙烯(PP/EPR/HDPE)共混物,并通过动态流变方法对其熔体结构稳定性进行了研究.动态时间扫描结果表明,PP/EPR/HDPE共混物具有较好的热稳定性.动态频率扫描结果表明,当EPR含量较低时,共混物中聚合物核壳粒子分散相的存在导致体系的长时松弛行为更加显著.当熔体结构在大应变下遭到破坏后,含核壳粒子分散相的共混物具有比普通PP/EPR共混物更快的结构回复速率,且结构回复速率随着核壳粒子的尺寸增大而加快.通过增大普通PP/EPR体系的EPR含量使其橡胶粒子尺寸与三元共混物中原位聚合物核壳粒子尺寸接近时,两者呈现类似的流变行为,这表明PP/EPR/HDPE体系的熔体结构稳定性源于核壳粒子结构导致的分散相尺寸增大的作用. 相似文献
5.
环境温度对紫外辐照HDPE结构与性能的影响研究 总被引:1,自引:0,他引:1
采用元素、XPS、GPC分析,凝胶和力学性能测定,研究了空气中不同环境温度下紫外辐照官能化HDPE的结构、粘着性以及紫外辐照官能化HDPE对HDPE/聚乙烯醇(PVA)体系的增容作用。实验结果表明,提高环境温度可显著提高引入C-O、C(=O)O和C=O等含氧基团的速度。在相同辐照时间下,随环境温度提高,辐照HDPE的分子量下降、分子量分布变宽以及剥离强度提高的幅度增大,并在70℃时产生凝胶。较高环境温度下辐照的HDPE对HDPE/PVA共混体系有较好增容作用,在HDPE/PVA(83/17)体系中加入10%(质量分数)的70℃环境温度下辐照24h的HDPE,共混物的拉伸屈服强度和缺口冲击强度分别从30.8MPa和110J/m提高到34.9MPa和142J/m。 相似文献
6.
研究了富氧气氛中高密度聚乙烯(HDPE)的γ-射线辐照氧化及其与尼龙-6(PA6)的共混增容和共混材料的阻隔性能.FT-IR测试结果表明, 经γ-射线辐照的HDPE与PA6发生了化学反应或产生了弱相互作用.SEM照片显示4γHDPE (4h辐照,66Gy/min)与PA6具有良好的相容性,PA6在共混体系中呈层状分布.共混材料的阻隔性能测试结果表明4γHDPE/PA6共混物对二甲苯的阻隔性较HDPE/PA6共混物有明显提高.力学性能测试显示4γHDPE/PA6共混物力学性能优良. 相似文献
7.
《高分子学报》2017,(12)
为了控制发泡体内部泡孔结构,以制备聚丙烯(PP)泡沫为例,提出在CO2作为发泡剂进行物理发泡过程中,以水为助发泡剂,利用其发泡过程中汽化吸热,原位冷却发泡体内部.将PP与聚乙二醇(PEG)熔融共混制备共混物(PP/PEG),PEG的存在赋予了共混物吸水的能力.采用红外线成像仪测试发泡体表层和芯部温度,利用扫描电子显微镜表征了泡孔结构.结果表明,与纯PP发泡体相比,在同样发泡条件下,PP/PEG共混物发泡体内部温度明显降低,内部与表层泡孔结构相近,且发泡倍率提高.进一步分析讨论了PP/PEG共混物发泡体内部温度明显降低的机理.这种方法适用于不同聚合物体系和不同发泡工艺,如:模压、挤出、釜式发泡工艺. 相似文献
8.
马来酸酐接枝热塑性弹性体在PP/PA6共混物中的作用 总被引:10,自引:0,他引:10
研究了马来酸酐接枝热塑性弹性体 (TPEg )作为增容剂对聚丙烯 (PP) 尼龙 6 (PA6 )共混体系的相容性、相态以及物理力学性能的影响 .研究结果表明TPEg的加入大大改善了PP PA6共混体系的相容性 ,且随TPEg含量的增大分散相粒径明显降低 ,共混物的韧性以及延展性大大提高 ,同时拉伸强度及模量仍保持较好的水平 .TPEg增容的PP PA6共混物的非等温结晶行为的研究表明 ,共混物中PP和PA6的结晶行为不同于各自纯的聚合物 ,PA6作为成核剂使PP的结晶温度提高 ;而PA6由于TPEg的加入 ,出现分级结晶现象 ,一级结晶温度略低于纯PA6的结晶温度 ,且随TPEg含量增大结晶受阻 ,二级结晶温度与PP的接近 .由于PP、PA 6以及TPEg之间存在较强的相互作用 ,三元共混物中PP及PA6的玻璃化转变温度分别较其纯聚合物升高 .基于上述结果 ,提出了本共混体系的结构模型 相似文献
9.
研究了富氧气氛中高密度聚乙烯(HDPE)的γ-射线辐照氧化及其与尼龙-6(PA6)原共混增容和共混材料的阻隔性能。FT-IR测试结果表明,经γ-射线辐照的HDPE与PA6发生了化学反应或产生了弱相互作用。SEM照片显示4γHDPE(4h辐照,66Gy/min)与PA6具有良好的相容性,PA6在共混体系中呈层状分布。共混材料的阻隔性能测试结果表明4γHDPE/PA6共混物对二甲苯的阻隔性能HDPE/PA6共混物有明显提高。力学性能测试显示4γHDPE/PA6共混物力学性能优良。 相似文献
10.
高强超韧高密度聚乙烯/聚丙烯共混物性能与微相分离结构的研究 总被引:4,自引:0,他引:4
在常规注射过程中 ,难以获得超高性能的共混体系注射制件 ,已有的研究表明 ,采用高剪切注射 ,可以抬高共混体系的最低临界相容温度曲线 (LCST)的位置 ,增加相容性 .当熔体进入模具后 ,冷却的同时相容性下降 ,开始相分离 ,相分离程度发展到某一程度即可获得高性能的制件 .对于高密度聚乙烯 (HDPE)、聚丙烯 (PP)两组分均为结晶型聚合物的共混体系 ,由于其相形态与结晶形态相互制约、竞争 ,微相分离程度难以控制 ,因此对其液 液相形态与结晶过程的控制是获得共混物最终形态与性能的关键 .采用振动保压注射成型技术不仅对HDPE、PP各自力学性能有明显的自增强作用 ,而且对HDPE/PP共混体系的力学性能也有十分明显的改善 .DSC、WAXD、SEM结果表明共混体系拉伸强度的提高主要取决于试样中串晶数量和大分子链的定向程度 ,而冲击强度则主要取决于两组分微观的相分离程度 .研究结果表明 ,HDPE/PP含量为 92 / 8的试样拉伸强度为 97 1MPa,80 / 2 0试样的缺口冲击强度为 4 5 5kJ/m2 ,较静态试样分别提高 4 3倍和 9 5倍 .采用振动填充注射技术针对某一组分可以获得高强度、高韧性的共混制件 . 相似文献
11.
The radiation crosslinking of EPR/SBR blend has been studied. A relationship between sol fraction and radiation dose for the different weight ratio polymer blends and the method to calculate βb value of EPR/SBR blend system have been established. 相似文献
12.
13.
间规聚苯乙烯 (sPS)由于熔点高达 2 70℃ ,并具有优良的耐热、耐水、耐溶剂及良好的电绝缘性[1] ,已成为一种新型高性能的半结晶热塑性工程塑料 .但是sPS分子链刚性比较大 ,比较脆 ,结晶速度快 ,加工流动性差 ,特别是在熔体加工过程中很容易开裂 ,因此限制了其广泛应用 .为了提高它的韧性和改善其加工性能 ,通常采用物理共混和化学共聚的方法 .如sPS aPS共混物 ,苯乙烯和丙烯的嵌段共聚物等 .间规聚苯乙烯与聚丙烯之间不相容 ,使用物理共混方法得到的共混物的性能得不到明显改善 .最近我们试图采用一种新型3 茚基乙酰丙酮为给电… 相似文献
14.
In this paper, calculating the molecular internal rotating steric factor of polymers by the radiation crosslinking method is studied and a relationship between the molecular internal rotating steric factor (σ) and crosslinking parameter βis established~([1]) by taking account of the effect of polymer chain flexibility on βvalue, σvalue of polymer obtained by this method is in agreement with that given with other method. 相似文献
15.
The structure effects of polymers on the relationship between sol fraction and radiation dose arediscussed in detail. In consideration of the deviation of experimental results from Charlesby-Pin-ner's and Chen-Liu-Tang's expressions relating sol fraction to radiation dose, we introduced an ex-ponent βconcerned with the structure and property parameters of a polymer (glass transition tem-perature T_g and molecular internal rotating steric factor δ) and assumed that the fracture density isproportional to R~β(R is radiation dose). Thus, a general expression, formula (9), relating solfraction to radiation dose is derived. When β=1 andβ=0.5, this expression is reduced to the above-said two expressions. Us-ing this general expression, the experimental data of a number of polymers are treated. It is shownthat the expression is in good agreement with the experimental results, βvalue is in the range of 0. 5 to1.0. 相似文献
16.
The capillary extrusion of polypropylene (PP) and high-density polyethylene (HDPE) immiscible blends was studied in this work by rheo-particle image velocimetry (Rheo-PIV). The PP/HDPE blends were prepared by single screw extrusion and extruded through a transparent capillary die at a temperature of 200 °C and concentrations of 80/20, 60/40, 40/60 and 20/80 wt%, respectively. PIV measurements described accurately the flow behavior of PP/HDPE blends and revealed continuous velocity profiles in the die, without macroscopic phase separation, for all the blends in the resolution range of the PIV technique. The flow behavior of all the blends was shear-thinning (power-law) type and their viscosities laid in between the values corresponding to the neat polymers and increased in an exponential way along with the concentration of the highest viscosity component in the blend (HDPE). Also, it was found that the extruded blends acquired a stratified morphology and that HDPE mitigates extrudate distortions in PP, meanwhile PP eliminates slip and flow instabilities in HDPE by migrating to the region of highest shear stresses in the die. Migration of PP to the capillary wall was corroborated by Raman spectroscopy measurements on the periphery of solid extrudates. Finally, via calculations of the density of the molten blends under flow using the velocity profiles in the die, we show that the homopolymers are compatible in the molten state and follow a simple inverse relation for their density, and an exponential one for their viscosity. 相似文献
17.
Xiaoxi Li Haiyan Wu Jian Dai Ting Huang Yong Wang 《Journal of Polymer Science.Polymer Physics》2011,49(12):898-906
Previous work showed that there was a synergistic effect of nucleating agent (NA) and elastomer in improving the fracture resistance of isotactic polypropylene (PP), relating to the formation of large amounts of β‐PP (β‐NA nucleated system) or the decrease of the spherulites diameters of α‐PP (α‐NA nucleated system). To find the direct relation between the synergistic efficiency of NA/elastomer and the microstructures of the materials, in this work, the ethylene‐propylene‐diene terpolymer (EPDM) modified PP blends with compounded NAs (β/α) were adopted and the changes of the microstructure and mechanical properties were investigated comparatively. The results showed that, with the adjustment of the mass fraction of compounded NAs, the microstructures of PP matrix including supermolecular structure and the relative fraction of β‐PP (Kβ) change accordingly. Specifically, the Kβ of β‐PP was successfully adjusted in the wide range of 0–78.9%. Consequently, the stiffness and the fracture resistance of the PP/EPDM blends were easily controlled in different degrees. It is believed that this work could provide a guide map for the design and preparation of certain polymer blends satisfying certain requirement. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献
18.
In blends of immiscible polymers, amphiphilic species are needed for both morphological stabilization and improvement of the mechanical properties throughout successive processing steps. In order to obtain the required concentration of amphiphilic copolymer at the interface, it seemed of interest to test the possibility of creating these species by in situ reactivity at the interface, for instance by condensation reactions occurring between functionalized polymers. There is another possibility based on the fact that most of the polymers are hydrocarbon compounds, so they are subjected to free-radical reactivity by hydrogen abstraction on the different hydrocarbon sites. The created free-radical polymeric species may react together leading to the well known reactions of crosslinking, grafting and/or chain degradation. Therefore, this work deals with reciprocal free-radical reactivity of two kinds of semi-crystalline polymers, namely one polyolefin (LDPE, HDPE, PP or EPR) associated with a polyamide (PA-11 or PA-6). The reaction has to occur mainly at the interface, where the resulting grafted copolymers have to be anchored for final stabilization of the biphasic system. The level of interfacial grafting and the resulting properties of the reacted blends were characterized carefully, confirming the efficiency of the interpolymeric grafting. 相似文献
19.
The compatibility between isotactic polypropylene(i PP) and ethylene-propylene-diene terpolymer(EPDM) in the blends was studied. SAXS analysis indicates that i PP and EPDM phases in the binary blend are incompatible. Isothermal crystallization behaviors of i PP in phase-separated i PP/EPDM were studied by in situ POM equipped with a Linkam shear hot stage. It was found that typical spherulites of i PP were formed both in neat i PP and in i PP/EPDM blends. The radial growth rate(d R/dt) of spherulites of i PP in the blend was not influenced by EPDM phases. Further investigations on isothermal crystallization of i PP in i PP/EPDM after shear with a fixed shear time showed that the crystallization rate of i PP in the blends increased with increasing shear rates, whereas, the crystallization rate was much lower than that of neat i PP. WAXD results showed that ?-crystal i PP was formed in neat i PP as well as in i PP/EPDM blends after shearing and the percentage of ?-crystal bore a relationship to the applied shear rate. The presence of EPDM resulted in lower percentage of ?-crystal in the blends than that in neat i PP under the same constant shear conditions. SAXS experiments revealed that shear flow could induce formation of oriented lamellae in i PP and i PP in the blends, and the presence of EPDM led to a reduced fraction of oriented lamellae. 相似文献