Preparation of Silane-Grafted and Moisture Crosslinked Low Density Polyethylene. Part II: Electrical,Thermal and Mechanical Properties

Among different polyethylene cross-linking methods, such as peroxide, irradiation, and silane cross-linking, silane-based methods are the most suitable methods for producing cable insulation and hot water pipe materials due to process simplicity and superior properties of its product. Some electrical, thermal and mechanical properties of silane-grafted water-cross-linked polyethylene were investigated. The effects of silane grafting and gel content on volume resistivity, tensile properties and melting behavior of low density polyethylene (LDPE) were studied. Results indicated that volume resistivity increased with increasing gel content. Stress at break increased with increasing grafting level and gel content. Elongation at break increased with grafting and decreased with gel content. High temperature tensile properties showed that cross-linked polyethylene (XLPE) is more stable than LDPE at high temperature. In differential scanning calorimetry (DSC) analysis a broad endothermic peak appeared for XLPE due to phase separation. Melting point and crystalline percentage decreased with increased grafting level and gel content. Incorporation of carbon black into XLPE reduced the volume resistivity and degree of crystallization.     

Preparation and Characterization of Potato Starch Based Low Density Polyethylene/Low Density Polyethylene Grafted Maleic Anhydride Biodegradable Polymer Composite

Polysaccharide-filled plastics have attracted immense interest from research scientists as a means to develop a biodisintegrable polymer. The objective of the present study is to develop a biodisintegrable polymer composite using potato starch, which may be a step toward an alternative user friendly polymer composite. Keeping in mind the compatibility issue between potato starch and polyethylene, we used a base material with a polar group in its low density polyethylene (LDPE) backbone. Polymer composite sheets with a combination of potato starch, LDPE, and LDPE grafted maleic anhydride (LDPE-g-mA) were prepared. The LDPE and LDPE-g-mA were used in equal amounts and as a base material. The starch contents varied between 0 and 30%. The composites so prepared were tested for their thermal and mechanical properties. The results show that the thermal stability and melting temperature of these composites did not change significantly with various combinations of potato starch. The mechanical testing results show that tensile strength of material could be maintained at up to 15% mixing of potato starch in composites, and at up to 5% mixing of potato starch the percentage elongation was intact.     

线型低密度聚乙烯溶液接枝聚甲基丙烯酸甲酯

用溶液接枝聚合的方法在线型低密度聚乙烯(LLDPE)上接枝聚合极性单体甲基丙烯酸甲酯(MMA)制备LLDPE-g-PMMA,研究了反应时间、单体用量和引发剂用量对接枝反应的影响。结果表明,随着引发剂和单体量的增加,聚合物的接枝率增加,当引发剂质量分数为0.48%,单体比率为150%时,接枝率将达到26.1%。利用红外光谱(FTIR)、核磁共振碳波谱仪(13C-NMR)对其进行结构表征,证明PMMA分子链被接枝聚合到LLDPE上。使用X射线衍射仪(XRD)、差示扫描量热仪(DSC)对接枝聚合物的结晶性能进行了分析,发现接枝聚合没有改变晶型,但结晶焓由61.39 J/g降低到47.18 J/g。     

含产水剂硅烷交联聚乙烯的制备及其性能研究

将硬脂酸(HSt)和氧化锌(ZnO)作为产水剂,通过单螺杆挤出机制备出硅烷交联聚乙烯(SXPE)。通过测量体系凝胶含量、拉伸强度、断裂伸长率,研究了体系的交联度和力学性能,并采用SEM观察挤出物的表面质量,考查其加工性能。结果表明:无需水煮交联工序,添加2.0～3.0phr产水(剂HSt:ZnO=1:1)则能够使SXPE的凝胶含量在一周时间内可达到80%;当产水剂含量为3.0phr时,体系的拉伸强度提高了18.8%,断裂伸长率增加了25.3%。产水剂的加入对熔体加工有润滑作用适,量的产水剂可使挤出物的表面光滑。     

Preparation and Properties of a Reactive Type Nonionic Surfactant Grafted Linear Low Density Polyethylene

Summary A reactive type nonionic surfactant, monostearic acid monomaleic acid glycerol diester (MMGD) was synthesized in our laboratory. Grafting-copolymerization of linear low density polyethylene (LLDPE) with MMGD was carried out by using β ray irradiation in air in a twin-screw extruder. Evidence of the grafting of MMGD as well as its extent was determined by Fourier-transformed infrared (FT-IR) spectroscopy. The effects of monomer concentration, reaction temperature and screw run speed on degree of grafting were studied systematically. The thermal behavior of LLDPE-g-MMGD was investigated by using differential scanning calorimety (DSC). Compared with neat LLDPE, the crystallization temperature (T_c) of LLDPE-g-MMGD increased about 3 °C, and the melting enthalpy (ΔH_m) decreased with increase of MMGD content. It showed that the grafted MMGD monomer onto LLDPE acted as a nucleating agent. The tensile properties and light transmission of blown films were determined. Comparing with neat LLDPE film, no obvious changes could be found for the tensile strength, elongation at break and right angle tearing strength of LLDPE-g-MMGD film. The wettability is expressed by the water contact angle. With an increasing percentage of MMGD, the contact angles of water on film surface of LLDPE-g-MMGD decrease monotonically. Accelerated dripping property of film samples was investigated. The dripping duration of LLDPE-g-MMGD film and commercial antifog dripping film at 60 °C were 52 days and 17 days, respectively.     

CPP-g-MAH的制备及其接枝效率的影响因素

考察了反应温度、加料方式、反应时间、引发剂用量对马来酸酐接枝氯化聚丙烯接枝率和接枝效率的影响。通过改进接枝工艺,优化反应条件,提高了马来酸酐的接枝效率。在较低马来酸酐用量下制备出接枝率约2%、接枝效率达到80%左右的接枝产品,显著降低了原料消耗。     

改性LDPE高发泡弹性材料的研究

以低密度聚乙烯（LDPE）为基体原料,乙烯-辛烯共聚物（POE）为增韧材料,CaCO3为填充料,硼酸酯为改性剂,添加AC发泡剂、DCP交联剂等助剂;采用界面改性、密炼塑化、模压发泡方法制备改性LDPE高发泡弹性材料,并对其性能进行分析研究。结果表明：含LDPE70质量份、POE30质量份、改性CaCO310质量份、AC2质量份、DCP1.4质量份的发泡材料,其拉伸强度2.40MPa、撕裂强度5.82KN/m、断裂伸长率163.2%、密度0.236g/cm3、收缩率1.1%,物理力学性能优良。     

导热PE-LD复合材料的制备与性能研究

采用低密度聚乙烯(PE-LD)为基体材料,石墨、Al N为导热填充材料,通过双辊混炼、模压制备了导热复合材料,并对该复合材料的导热性能、力学性能、热行为进行了分析。结果表明,随着石墨或Al N含量的增加,PE-LD/石墨复合材料和PE-LD/Al N复合材料的热导率逐渐增大;PE-LD/石墨复合材料的热导率高于PE-LD/Al N复合材料的热导率。当石墨与Al N的总质量分数为50%、石墨与Al N的质量比为4∶1时,PE-LD/石墨/Al N复合材料的拉伸强度、弯曲强度均达到最大值,分别为12.8,17.15 MPa;此时PE-LD/石墨/Al N复合材料的热导率达到最大值,为0.618 W/(m·K),略低于添加质量分数50%的石墨时的PE-LD/石墨复合材料的热导率[0.634 W/(m·K)];当石墨与Al N质量比为1∶4时,PE-LD/石墨/Al N复合材料的热导率为0.488 W/(m·K),高于只添加质量分数50%Al N的PE-LD/Al N复合材料的热导率[0.410 W/(m·K)]。当石墨和Al N总质量分数为50%时,随着Al N含量的增加,PE-LD的结晶度增大。     

A Study on Grafting of Natural Rubber and Nitrile Rubber on Thermoplastic Low Density Polyethylene Using Maleic Anhydride and Acrylic Acid

ABSTRACT

LDPE/NR and LDPE/NBR blends were prepared by conventional mixing on two-roll mill. Modified blends were prepared by grafting (reactive blending). Grafting was carried out using acrylic acid and maleic anhydride. Compression-molded sheets were prepared out of the compounds and properties were evaluated. Mechanical properties like tensile strength, ultimate modulus, elongation at break, and hardness were determined. Effect of heat aging and effect of chemicals were estimated. The blends were characterized using FTIR spectrum. The electrical properties, abrasion resistance, solubility tests, and flammability tests for the compounds were also conducted. In all experiments results are found to be much higher for grafted compounds compared to ungrafted blends.     

Preparation and Performance of High-Barrier Low Density Polyethylene/Organic Montmorillonite Nanocomposite

Montmorillonite (MMT) was first modified with dodecyl dimethylbenzyl ammonium (DDA) salt and octadecyl trimethyl ammonium (OTA) salt. Then low density polyethylene (LDPE)/organic montmorillonite (OMMT) nanocomposites were prepared by twin-screw extruder and hot-press. Transmission electron microscopy (TEM) results showed that OMMT layers were homogeneously intercalated into the LDPE matrix. In terms of MMT, the modification effect of OTA is superior to that of DDA. CO₂ and O₂ barrier properties of nanocomposites were increased by 7 times and 4 times with 0.5 wt.% OTA-MMT loading, respectively. At 2 wt% OTA-MMT loading, water vapor permeability of LDPE has also decreased about 2.5 times. Compared with pure PE film, 49.5% and 178% improvement of tensile strength of nanocomposites films were obtained by addition of only 4 wt.% DDA-MMT and OTA-MMT, respectively. In addition, with only 0.5 wt.% OMMT loading, the onset degradation temperature of nanocomposites increases by 23°C and 26°C for LDPE/DDA-MMT and LDPE/OTA-MMT, respectively.     

Influence of Phase Dispersant on the Cocross-Linking of Polyvinyl Chloride with Low Density Polyethylene

The cocross-linking of polyvinyl chloride (PVC) and low density polyethylene (LDPE) was studied by THF extraction, FTIR, and Dynamic rheological analysis. It is found that dicumyl peroxide (DCP) could neither induce the cross-linking of PVC itself nor cause PVC chains to cocross-link with LDPE. Butadiene rubber (BR), as a solid phase dispersant (SPD) can not give a hand to the cocross-linking. However, NBR, both as a compatibilizer and SPD, can induce PVC to be crosslinked or cocross-linked with LDPE initiated by DCP. The composite cross-linking agent that consists of DCP, triallyl isocyanurate (TAIC), and magnesium oxide (MgO) is easy to induce PVC to cross-link itself or cocross-link with LDPE.     

溶液法制备POE-g-MAH及其影响因素

采用溶液接枝法,以过氧化二异丙苯(DCP)为引发剂,马来酸酐(MAH)为单体,制备了POE-g-MAH。通过红外光谱确定了接枝物的结构,采用酸碱滴定法测定了产物的接枝率,详细研究了POE、MAH、DCP用量及反应温度等对接枝率的影响规律。结果表明,当POE∶MAH∶DCP为13∶6∶1、反应温度为150℃、反应时间5h时接枝率达到最大值9.5%。     

Synthesis and Characterization of Linear Low Density Polyethylene Grafted Glycerol Monolauric Acid Monoitaconic Acid Diester

A reactive type dripping agent, glycerol monolauric acid monoitaconic acid diester (GLID) was synthesized in our laboratory. Grafting-copolymerization of linear low density polyethylene (LLDPE) with GLID was carried out by using β-ray irradiation in air in a twin-screw extruder. FT-IR was used to characterize the formation of grafting copolymer and evaluate their degree of grafting. The effects of monomer concentration, reaction temperature and screw run speed on degree of grafting were studied systematically. Crystallization rates of grafted LLDPE were faster than that of plain LLDPE at a given crystallization temperature. The tensile properties and light transmission of blown films were determined. Comparing with neat LLDPE film, no obvious changes could be found for the tensile strength, elongation at break and right angle tearing strength of LLDPE-g-GLID film. Acceleration dripping property of film samples was investigated. The dripping duration of LLDPE-g-GLID film and commercial antifog dripping film at 60° C were 69 days and 17 days, respectively.     

模压法制备物理发泡聚乙烯塑料的研究

研究了以空心玻璃微珠为气体载体,采用模压物理发泡法制备发泡低密度聚乙烯(LDPE)工艺。结果表明用该发泡工艺制备的发泡LDPE泡孔分布均匀,孔径较小,而导热系数下降较大。     

Preparation,Characterization, and Evaluation of Poly(p-azidoaniline) as Thermal Stabilizer for Low Density Polyethylene Films

A series of electrically conducting low density polyethylene/poly(p-azidoaniline) blends containing different loadings of poly(p-azidoaniline) was prepared. The resistance of these blends to accelerated thermal oxidation at 90°C for different time intervals was investigated. The thermal degradation mechanism was determined by attenuated total reflection-Fourier transform infrared technique. The values of melting temperature (T_m), enthalpy of fusion (ΔH_m), and degree of crystallinity showed significant increase upon poly(p-azidoaniline) addition. X-ray diffraction patterns also confirmed increase in degree of crystallinity upon blend formation. Furthermore, scanning electron microscopy observations showed efficient thermal stabilization of low density polyethylene/poly(p-azidoaniline) blends. The mechanical properties showed significant role of poly(p-azidoaniline) as thermal stabilizer for low density polyethylene.     

LDPE HDPE LLDPE的硅烷接枝反应

研究了DCP (过氧化异丙苯)为引发剂,A1 71 (乙烯基三甲氧基硅烷)与A1 51 (乙烯基三乙氧基硅烷)在LDPE (低密度聚乙烯) ,HDPE (高密度聚乙烯) ,LLDPE (线性低密度聚乙烯)上的接枝反应。A1 71接枝反应过程中,当过氧化物的加入量为0 .2 %时,活化能为正值。而当加入量为0 . 0 5%、0 . 1 %、0 . 1 5%、0 2 5%时,活化能为负值。尽管过氧化物在PE (聚乙烯)中交联反应程度的顺序为:LDPE >LLDPE >HDPE ,但A1 71接枝反应程度的顺序为LLDPE >LDPE >HDPE。与A1 71相比,A1 51在LDPE上具有较高的接枝反应速率,但它在水交联反应过程中,呈现出相对较低的反应速率。通过研究加入过氧化物量的变化对A1 71接枝反应热的影响,可知在过氧化物未达到一定量前(这个数值取决于所加入的硅烷的量) ,当过氧化物增加时,反应热是随之增加的。     

Thermal Stability of Gamma Irradiated Low Density Polyethylene Films Containing Hindered Amine Stabilizers

Summary: The thermal stability of gamma irradiated low density polyethylene (LDPE) films in presence of various structures of hindered amine stabilizers (HAS) was investigated by the oxygen uptake method under constant temperature of 180 °C and normal pressure conditions. The thermo‐oxidation was run using air environment. The sigmoidal dependency of oxygen uptake allows the calculation of the main kinetic parameters: oxidation induction time and oxidation rate on the propagation step. The various steps involved in the thermal degradation process were detected by the derivative procedure applied to the dependencies of oxygen uptake on time. It was found that the kinetic parameters of the thermal degradation process, determined by oxygen uptake, revealed the antioxidant role of HAS in γ‐irradiated LDPE films by providing better stability, when compared with the unstabilized samples. Moreover, the results indicated that the dependencies of oxygen uptake on thermal degradation time involved two degradation stages: the former occurring in the ungrafted moiety and the latter taking place after the antioxidant depletion is achieved. The stabilization efficiency of these oxidation inhibitors provides satisfactory thermal resistance to LDPE films, especially those based on an alkoxyamine structure.

Dependencies of oxygen uptake on time at the thermal degradation of LDPE irradiated at 812 kGy. (‐□‐) free of additive; (‐○‐) Tinuvin 123; (‐?‐) Sanduvor PR 31; (‐?‐) Uvasil 299.     

Physicochemical Studies on Interaction Behavior of Potato Starch Filled Low Density Polyethylene Grafted Maleic Anhydride and Low Density Polyethylene Biodegradable Composite Sheets

Study presents compatibility behavior of polar group potato starch and non-polar LDPE using 50%, 0.5% maleated LDPE. The aim was to improve intermolecular interaction between two different types of moieties (LDPE and Potato Starch). Samples were prepared by mixing potato starch (upto 30% by weight) with LDPE and LDPE-grafted maleic anhydride in a single step twin screw extruder having vent zone. XRD and DSC results suggested that maleic-anhydride group of LDPE helped the interaction with starch and brought two chemical moieties closer to each other. FTIR results also strongly supported new bond formation between two chemical moieties.     

高密度聚乙烯催化剂的制备和催化性能

概述了高密度聚乙烯在国民经济中的广泛用途,以及聚乙烯工业的催化剂研究领域的最新进展。     

二烯基双酚A醚接枝低密度聚乙烯的制备

介绍了二烯基双酚Ａ醚（ＤＢＡＥ）与低密度聚乙烯（ＬＤＰＥ）在Ｈａａｋｅ转矩流变仪的混炼器中进行熔融接枝反应,采用红外光谱（ＦＴ－ＩＲ）分析证实了接枝共聚物（ＬＤＰＥ－ｇ－ＤＢＡＥ）并通过对ＬＤＰＥ－ｇ－ＤＢＡＥ的接枝率（ＧＲ）和熔体流动速率（ＭＦＲ）测试,考察了制备条件（反应温度,引发剂用量和ＤＢＡＥ用量）对接枝反应及产物的影响,ＬＤＰＥ－ｇ－ＤＢＡＥ的最终目的是作为高密度聚乙烯／聚碳酸酯共混体系