微注射成型高密度聚乙烯-线性低密度聚乙烯共混物的微结构及力学性能

为提高线性低密度聚乙烯（LLDPE）的拉伸强度和模量,扩大其应用领域,将三种不同相对分子质量的高密度聚乙烯（HDPE）分别与LLDPE共混,通过微注射成型技术制备HDPE-LLDPE制品。综合利用DSC、广角X射线衍射（WAXD）、小角X射线散射（SAXS）和拉伸性能测试研究了共混物在微注射成型过程中的结构演化及力学性能。拉伸测试结果表明,与纯LLDPE相比,HDPE-LLDPE的拉伸强度和模量随HDPE分子量的增加而增加。微结构分析结果显示,随HDPE分子量的增加,HDPE-LLDPE制品的分子链和片晶取向度增大、结晶度增加,且制品内形成了较多取向的Shish-Kebab晶体结构。通过分析微结构的表征结果,解释了HDPE-LLDPE的拉伸强度和模量显著提高的原因。     

Comparison of the influence of copper micro- and nano-particles on the mechanical properties of polyethylene/copper composites

This article reports on the influence of copper content and particle size on the tensile properties of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE) mixed with up to 25 vol.% Cu micro-particles and up to 5 vol.% Cu nano-particles, and on the influence of Cu micro-particle content on the dynamic mechanical properties of these polymers. This influence depends upon the extent of branching and crystallinity in the particular polymer. The copper micro-particles seemed to have a negligible influence on the tensile strength of LDPE and HDPE, while there was quite a significant reduction in tensile strength when LLDPE was used as matrix. The elongation at break generally decreased with increasing copper content, but the effect was more significant in the case of LDPE and HDPE. The tensile modulus generally increased with increasing Cu content, but the extent of increase was lower in the case of the more crystalline HDPE. The nano-copper containing samples showed comparable properties at equivalent Cu contents. The storage and loss moduli generally increased with increasing Cu. For all three polyethylenes the β-transition (where present) was not significantly influenced by the presence and amount of copper, but the α-transition was strongly influenced, especially in the case of LDPE and LLDPE.     

新型淀粉填充型塑料地膜的研制

以低密度聚乙烯（LDPE）、高密度聚乙烯（HDPE）及线性低密度聚乙烯（LLDPE）为基体，加入适量的改性淀粉及聚乙烯蜡，在单螺杆挤出机上实现增容共混过程，制备出具有良好实用性能的塑料地膜．探讨了LDPE、HDPE、LLDPE三种树脂的共混配比、改性淀粉加入量、聚乙烯蜡加入量等对塑料地膜材料力学性能的影响，利用扫描电镜表征了塑料膜的亚微观相态，并考察了塑料膜的生物降解性能．结果表明，聚乙烯蜡的加入可明显改善共混树脂与改性淀粉的相容性，并可提高塑料膜的力学性能和生物降解性能．     

LLDPE及VLDPE对LDPE／HDPE共混物拉伸性能的影响

研究了线性低密度聚乙烯（ＬＬＤＰＥ）和极低密度聚乙烯（ＶＬＤＰＥ）对高密度聚乙烯（ＨＤＰＥ）／低密度聚乙烯（ＬＤＰＥ）共混物拉伸性能的影响。由于ＬＬＤＰＥ或ＶＬＤＰＥ的加入，改善了ＨＤＰＥ与ＬＤＰＥ间的相互作用，提高了ＨＤＰＥ／ＬＤＰＥ共混物的拉伸性能。     

低缠结超高分子量聚乙烯的制备及其对线性低密度聚乙烯的增强作用

利用单活性位点前过渡金属FI催化剂(Fenokishi-Imin catalyst)进行乙烯的聚合反应,在较低的温度下,制备出具有低链缠结度的超高分子量聚乙烯。经高温凝胶色谱(PL-GPC)测定,产物分子量达到了(2~5)×106;差示扫描量热仪(DSC)检测表明其结晶度达到了70%;流变学研究表明,相对于商业超高分子量聚乙烯,产物链缠结密度大大降低。进一步的力学性能测试显示添加少量的低缠结超高分子量聚乙烯对线性低密度聚乙烯的增强作用非常明显,可使拉伸强度和断裂伸长率大大提高。     

结晶度对高密度聚乙烯热氧老化特性的影响

研究了结晶度对高密度聚乙烯(HDPE)在110℃人工热氧老化条件下老化特性的影响,分别采用力学实验、衰减全反射红外光谱技术、凝胶渗透色谱、扫描电子显微镜和X射线衍射技术比较了不同结晶度HDPE的热氧老化特性,研究了结晶度对聚乙烯力学性能、化学结构、相对分子质量、表面微观结构和晶体结构的影响规律。结果表明,结晶度越高,HDPE拉伸强度、拉伸模量和弯曲模量下降越快,抗冲击性能提高;不饱和度增长越剧烈,支化作用和断链作用更明显,羟基指数增长更快,且区别主要集中于老化后期;相对分子质量分布下降越快;表面微观形貌老化程度越严重;主要晶面衍射角和晶胞参数变化越显著。结晶度越高,HDPE缺陷也就越多,在热氧环境中越容易发生氧化,老化现象更严重。     

硅烷交联聚乙烯电力电缆绝缘料基础树脂的性能

利用拉伸试验、红外光谱、凝胶渗透色谱、差示扫描量热、热延伸试验等方法,对几种硅烷交联聚乙烯电力电缆绝缘料用LDPE基础树脂的性能以及LDPE和LLDPE与硅烷的接枝交联性能进行了研究。结果表明,乙烯基硅烷对LLDPE的相对接枝率比对LDPE高,LLDPE和LDPE共混物的硅烷接枝能力高于纯LDPE,LLDPE和LDPE的共混物宜用作硅烷交联聚乙烯电力电缆绝缘料的基础树脂。     

交联定形相变储能材料的研制

分别采用高密度聚乙烯( HDPE) 、高密度聚乙烯和低密度聚乙烯(LDPE) 1∶1的共混物作为基体材料,制备了不同凝胶率的交联定形相变材料, 讨论了材料的凝胶率与交联剂用量之间的关系, 并测定了材料的热性能。通过多次冷热循环实验, 研究了材料的稳定性。结果表明, 交联有利于改善定形相变材料的稳定性, 减少石蜡的渗出。高密度聚乙烯与低密度聚乙烯的共混体系更适合作封装材料。交联程度的不同对材料的相变温度和相变热均不产生影响。多孔填料如硅藻土的添加, 可以进一步减少石蜡的渗出, 提高材料的稳定性。      

TiO_2-(线性低密度聚乙烯-g-马来酸酐)/低密度聚乙烯薄膜的制备及其光催化降解性能

以线性低密度聚乙烯(LLDPE)-g-马来酸酐(MA)作为相容剂制备了可光催化降解的TiO_2-(LLDPE-gMA)/LDPE薄膜。采用SEM、XRD、FT-IR对制备的TiO_2-(LLDPE-g-MA)/LDPE薄膜样品进行了表征。由于引入的LLDPE-g-MA改善了纳米TiO_2与LDPE之间的相容性,TiO_2-(LLDPE-g-MA)/LDPE薄膜具有更高的伸长率。SEM结果显示,LLDPE-g-MA显著削弱了纳米TiO_2在LDPE中的团聚,使高分散度的纳米TiO_2具备更高的光催化降解效率,增加了降解过程中的膜质量的损失。     

Preparation of low-density polyethylene/low-temperature expandable graphite composites with high thermal conductivity by an in situ expansion melt blending process

A facile strategy with the advantages of low cost and ease of mass production was presented to prepare low-density polyethylene (LDPE)/low-temperature expandable graphite (LTEG) composites with relatively high thermal conductivity by an in situ expansion melt blending process. LTEGs were expanded and delaminated into graphite multi-layers and graphite nanoplatelets during processing which synergistically created more thermo-conducting paths in the composites and hence led to great improvements in thermal conductivity. Thermal conductivity of the composite with 60 wt% of LTEG loading was increased by 23 times as compared to the pure LDPE, increasing from 0.47 to 11.28 W/mK. The incorporation of LTEG decreased the melting temperature and the degree of crystallinity of LDPE. Percolation threshold of both the electrical conductivity and rheological measurements was observed at about 8 vol% of LTEG loading. Moreover, the LDPE/LTEG composites showed better thermal stability compared to the pure LDPE.     

雷达吸波包装膜的研究初探

采用2种不同的铁氧体(复合铁酸锌锰及复合铁酸镍锰)与线性低密度聚乙烯(LLDPE)共混制备了雷达吸波包装膜,分别对热压工艺、介电性能、透湿性能及力学性能进行了研究,结果发现粉末状的LLDPE与铁氧体的混合效果优于颗粒状的LLDPE,铁氧体的加入能明显提高LLDPE的介电损耗,但会使LLDPE的透湿率变大,力学性能变差.当复合铁酸锌锰/复合铁酸镍锰的重量比为45/55,且总含量为30%(质量分数)时,制备出的LLDPE膜具有最佳的隐身及综合力学性能.     

Polyethylene/synthetic boehmite alumina nanocomposites: structure,mechanical, and perforation impact properties

Synthetic boehmite alumina (BA) has been incorporated up to 8 wt% in high-density polyethylene (HDPE) and low-density polyethylene (LDPE) by melt compounding. The primary nominal particle sizes of the two BA grades used were 40 and 74 nm, respectively. The dispersion of the BA in PE matrices was investigated by scanning and transmission electron microscopy techniques (SEM and TEM). Specimens of the PE/BA nanocomposites were subjected to dynamic-mechanical thermal analysis (DMTA), static tensile and instrumented falling weight impact (IFWI) tests. It was established that BA was nanoscale dispersed in both HDPE and LDPE. According to DMTA, BA worked as reinforcing filler. This was confirmed in static mechanical tests, too. BA grades and contents influenced the static tensile and dynamic IFWI behaviors of the PE/BA nanocomposites differently. Surprisingly, BA incorporation enhanced the ductility (elongations at yield and break) of HDPE in contrast to LDPE. Unlike HDPE/BA nanocomposites, the perforation impact resistance of the LDPE/BA systems was reduced with increasing BA content at both ambient temperature and T = −30 °C. The lesser the reduction the higher the primary particle size of the BA was.     

LDPE/LLDPE/分子筛保鲜包装膜的力学性能和摩擦性能研究

以低密度聚乙烯(LDPE)和线性低密度聚乙烯(LLDPE)(质量比为80∶20)作为基础物质,添加不同比例的分子筛,吹制保鲜膜,研究了保鲜膜的力学性能和摩擦性能。研究表明:随着分子筛含量的增加,薄膜的拉伸强度、伸长率、耐戳穿强度和撕裂强度均出现一定程度的下降;加入分子筛之后,保鲜膜的摩擦系数上升。     

LDPE / LLDPE / EVA 三元共混膜的力学性能和摩擦性能研究

以低密度聚乙烯(LDPE)和线性低密度聚乙烯(LLDPE)作为基础物质,添加乙烯-醋酸乙烯酯共聚物(EVA),吹制保鲜膜,研究了保鲜膜的力学性能和摩擦性能。研究表明,复合膜的拉伸强度、伸长率、耐戳穿强度和撕裂强度随着EVA含量的增加,总体呈下降趋势,摩擦系数则逐渐上升。     

LLDPE/HDPE/MMT纳米复合材料的制备及性能研究

以线性低密度聚乙烯(LLDPE)、高密度聚乙烯(HDPE)、有机改性的蒙脱土(MMT)为主要原料,选用乙烯-醋酸乙烯酯接枝马来酸酐(EVA-g-MAH)作为增容剂,采用熔融插层法制备了线性低密度聚乙烯/高密度聚乙烯/蒙脱土(LLDPE/HDPE/MMT)纳米复合材料。通过X射线衍射(XRD)分析蒙脱土在聚乙烯基体中的分散情况,并研究蒙脱土的含量对其在基体中分散效果的影响。TG实验结果表明,蒙脱土的加入使LLDPE/HDPE/MMT纳米复合材料的热稳定性得到很大的提高。由DSC曲线可以得出,加入蒙脱土的复合材料相比于纯聚合物,其熔点和热分解温度都有很大的提高,提高程度与蒙脱土的含量有关。     

MPE/LLDPE/LDPE共混熔体的流变学

研究了不同比例共混的茂金属聚乙烯（MPE），线性低密度聚乙烯（LLDPE）及高压聚乙烯（20％固定质量配比的LDPE）熔体的流变学行为，讨论了共混物组成，剪切速率和剪切应力以及温度对熔体流变曲线，熔体粘度和膨胀比的影响，为MPE的共混改性加工提供了理论依据，不同共混比的熔体均为假塑性流体，共混熔体的假塑性随LDPE／LLDPE的增多而增强，共混熔体的转变应力和非牛顿指数随LDPE／LLDPE的增加而降低，对加工的敏感性提高，加工性能得到改善。     

Ion bombardment of polyethylene—influence of polymer structure

Polyethylenes of various macromolecular and supermolecular structures were studied from the point of view of their susceptibility to an ion beam treatment. An influence of molecular weight (M_w), molecular weight distribution (M_w/M_n) and the degree of branching were compared within the set of low-density polyethylenes (LDPE) studied. An influence of the length of branches was compared between LDPE, linear low-density (LLDPE) and high-density (HDPE) polyethylenes. An influence of the degree of crystallinity and the morphology of a crystalline phase were compared for HDPE samples solidified under various thermal conditions and ultra-high molecular weight polyethylene (UHMWPE). Plate polymer targets ∼2 mm were bombarded with 100 keV He⁺ or 130 keV Ar⁺ ions (dose of 10¹⁴-10¹⁶ ions/cm²; ion energy stream density <0.1 μA/cm²), micromechanical properties of their surface layer (hardness, mechanical modulus and elastic recovery) determined and compared to the virgin materials.Ar⁺ ion beam bombardment generally lowers micromechanical properties of the polyethylenes, whereas He⁺ ion beam treatment makes them higher. The effect is the stronger the higher the molecular weight of polyethylene. However, a long chain branching adversely affects the modification. The degree of crystallinity facilitates an ion beam bombardment from the point of view of micromechanical properties of the materials, however, also the morphology of a crystalline phase was found to play a role.     

高密度聚乙烯官能化和增容作用的研究

通过红外光谱分析、与水的接触角测定、力学性能测定,研究了空气中不同环境温度下紫外线辐照对高密度聚乙烯(HDPE)结构与性能的影响以及紫外辐照官能化HDPE对HDPE/聚乙烯醇(PVA)纤维体系的增容作用。实验结果表明,紫外辐照后,HDPE分子链上引入了—C(C=O)CH₃,—CH₂C(=O)CH₂—,—C(=O)O—等含氧官能团,实现了HDPE的官能化。提高环境温度可提高HDPE官能化速度。紫外辐照后,HDPE的杨氏模量和拉伸屈服强度提高,但断裂伸长率和缺口冲击强度下降。官能化HDPE对HDPE/PVA纤维共混体系有增容作用,增容后的共混物的拉伸屈服强度提高和缺口冲击强度得到提高。     

线性双峰聚乙烯/高压聚乙烯/线性低密度聚乙烯共混物的流变行为与力学性能

研究了线性双峰聚乙烯(LBPE)、高压聚乙烯(LDPE)与线性低密度聚乙烯(LLDPE)共混物熔体的流变行为和力学性能。讨论了共混物的组成、剪切应力和剪切速率对熔体粘度和膨胀比的影响。结果说明,共混物熔体为假塑性流体,LBPE含量为70％时熔体粘度最大,含量高于60％时挤出胀大变小,含量高于40％时力学强度增大。     

超高分子量组分对熔体拉伸聚乙烯薄膜结构和性能的影响

在熔体拉伸的高密度聚乙烯薄膜中,含有高取向的片晶结构。分子链轴(c 轴)平行于拉伸方向,b 轴在薄膜平面内,片晶生长方向垂直于拉伸方向。加入少量超高分子量(约2×10~6)组分,导致纤维晶生成。纤维晶平行于拉伸方向,穿过几个片晶区,其长度在微米范围。纤维晶由伸展链分子构成,超高分子量组分是其成核中心。超高分子量组分松弛时间长.在熔体拉伸过程中有利于链伸展。