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线性低密度聚乙烯(LLDPE)是乙烯与少量α-烯烃共聚形成在线性乙烯的主链上,带有非常短小的共聚单体支链的分子结构。

线性低密度聚乙烯为无毒、无味、无臭的乳白色颗粒,密度为0.918~0.935g/cm3。
它与LDPE相比,具有较高的软化温度和熔融温度,有强度大、韧性好、刚性大、耐热、耐寒性好等优点,还具有良好的耐环境应力开裂性,耐冲击强度、耐撕裂强度等性能,并可耐酸、碱、有机溶剂等而广泛用于工业、农业、医药、卫生和日常生活用品等领域。

包装与储运
产品装于聚乙烯重包薄膜袋内,外包装为聚丙烯编织袋,每袋净重25kg。贮存仓库应保持清洁、干燥、阴凉和通风良好。可用火车、汽车、轮船、飞机等运输。可按非危险品运输。运输工具应保持清洁、干燥,不得有铁钉等尖锐物。贮运过程中应注意防火、防水、防晒、防尘和防污染等。装卸时不得使用铁钩。

应用
LLDPE已渗透到聚乙烯的大多数传统市场,包括薄膜、模塑、管材和电线电缆。防渗漏地膜是新开发LLDPE市场。地膜,一种大型挤出片材,用作废渣填埋和废物池衬垫,防止渗漏或污染周围地区。
LLDPE的一些薄膜市场,例如生产袋子、垃圾袋、弹性包装物、工业用衬套、巾式衬套和购物袋,这些都是利用改进强度和韧性后这种树脂的优点。
透明薄膜。抗穿透性和LDPE薄膜的刚度,而不显著影响薄膜的透明度。
注塑和滚塑是LLDPE最大的两个模塑应用。这种树脂优越的韧性和低温、冲击强度理论上适于废物箱、玩具和冷藏器具。另外,LLDPE的高抗环境应力开裂性使其适用于注塑与油类食品接触的模塑盖子,滚塑废料容器、燃料箱和化学品槽罐。
在管材和电线电缆涂敷层中应用的市场较小,在这里LLDPE提供的高破裂强度和抗环境应力开裂性可满足要求。LLDPE的65%~ 70%用于制作薄膜。
共聚过程生成的LLDPE聚合物具有比一般LDPE更窄的分子量分布,同时具有线性结构使其有着不同的流变特性。
LLDPE的熔融流动特性适应新工艺的要求,特别是用薄膜挤出工艺,可产出高质的LLDPE产品。
LLDPE应用于聚乙烯所有的传统市场,增强了抗伸、抗穿透、抗冲击和抗撕裂的性能。它的优异的抗环境应力开裂性,抗低温冲击性和抗翘曲性使 LLDPE对管材、板材挤塑和所有模塑应用都有吸引力。LLDPE最新的应用是作为地膜用于废渣填埋和废液池的衬层。


Linear low-density polyethylene (LLDPE) is a substantially linear polymer (polyethylene), with significant numbers of short branches, commonly made by copolymerization of ethylene with longer-chain olefins. Linear low-density polyethylene differs structurally from conventional low-density polyethylene (LDPE) because of the absence of long chain branching and impurity. The linearity of LLDPE results is almost same as LDPE because LDPE is recycled to make LLDPE . In general, LLDPE is produced at lower temperatures and pressures by copolymerization of ethylene and such higher alpha-olefins as butene, hexene, or octene. The copolymerization process produces an LLDPE polymer that has a narrower molecular weight distribution than conventional LDPE and in combination with the linear structure, significantly different rheological properties.

Production and properties
The production of LLDPE is initiated by transition metal catalysts, particularly Ziegler or Philips types of catalyst. The actual polymerization process can be done either in solution phase or in gas phase reactors. Usually, octene is the comonomer in solution phase while butene and hexene are copolymerized with ethylene in a gas phase reactor. LLDPE has higher tensile strength and higher impact and puncture resistance than does LDPE. It is very flexible and elongates under stress. It can be used to make thinner films, with better environmental stress cracking resistance. It has good resistance to chemicals. It has good electrical properties. However, it is not as easy to process as LDPE, has lower gloss, and narrower range for heat sealing.

Processing
LDPE and LLDPE have unique rheological or melt flow properties. LLDPE is less shear sensitive because of its narrower molecular weight distribution and shorter chain branching. During a shearing process, such as extrusion, LLDPE remains more viscous and, therefore, harder to process than an LDPE of equivalent melt index. The lower shear sensitivity of LLDPE allows for a faster stress relaxation of the polymer chains during extrusion, and, therefore, the physical properties are susceptible to changes in blow-up ratios. In melt extension, LLDPE has lower viscosity at all strain rates. This means it will not strain harden the way LDPE does when elongated. As the deformation rate of the polyethylene increases, LDPE demonstrates a dramatic rise in viscosity because of chain entanglement. This phenomenon is not observed with LLDPE because of the lack of long-chain branching in LLDPE allows the chains to slide by one another upon elongation without becoming entangled. This characteristic is important for film applications because LLDPE films can be downgauged easily while maintaining high strength and toughness. The rheological properties of LLDPE are summarized as "stiff in shear" and "soft in extension". LLDPE can be recycled though into other things like trash can liners, lumber, landscaping ties, floor tiles, compost bins, and shipping envelopes

Application
LLDPE has penetrated almost all traditional markets for polyethylene; it is used for plastic bags and sheets (where it allows using lower thickness than comparable LDPE), plastic wrap, stretch wrap, pouches, toys, covers, lids, pipes, buckets and containers, covering of cables, geomembranes,[1] and mainly flexible tubing. In 2013, the world market for LLDPE reached a volume of $40 billion.[339]

LLDPE manufactured by using metallocene catalysts is labeled mLLDPE.