低密度聚乙烯LDPE综述英文版

《通用高分子材料》课程期末论文

High-density Polyethylene (HDPE)

XXX

（School of Biological and Chemical Engineering Zhejiang University of Science and Technology, Hangzhou 310023）

Abstract: this article firstly introduces the HDPE ,gives it a definition (HDPE grade generally reach a molecular weight range of 40,000 to 300,000 weight average) and a classification according to the molecular weight. Then it describes the characteristics of high density polyethylene from Basic Characteristics and Combustion Characteristics, and analyses the advantages (HDPE has acid and alkali-resistant, organic solvent resistance and excellent electrical insulating properties.)and disadvantages of HDPE(HDPE has poor mechanical properties, poor ventilation, and too easy to deform, age, crisp ,stress cracking and scratch.).Then the author introduces three methods to produce HDPE :slurry polymerization, gas phase polymerization, solution polymerization. Slurry polymerization of HDPE is the main production technology in our country. Development of bimodal or multi-peak by using characteristics of the autoclave slurry products can achieve the balance of mechanical properties and processing performance. EMS slurry characteristics is used for the development of high-performance tubes and wide relative Molecular weight distribution of the product. Use of gas-phase process single line can force to form characteristics of stable production of generic products. Product of solution method process are homogeneity, and easy to switch characteristics and take advantange of which can develop high value-added production products. Then the article gives the application of the HDPE.: hollow container resin with the development of domestic packaging, food, cosmetic products and other industries. Finally, the article focuses on the Product of HDPE development .It mainly introduces two types: Bimodal high density polyethylene and Ultra-high molecular weight PE (UHWPE). Through the modify of HDPE, it can be of better properties and for better use.

Keywords：High-density polyethylene; produce; development

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《通用高分子材料》课程期末论文

1. Introduction

1.1 Definition

High density polyethylene (High Density polyethylene, referred to as \is a high degree of crystallinity, the non-polar thermoplastic resin. The appearance of the original state of HDPE is milky white and translucent in thin cross-section at a certain degree. PE has excellent resistance to most domestic and industrial chemicals. Certain types of chemicals will cause chemical corrosion, such as corrosive oxidizer (concentrated nitric acid), aromatics (xylene) and halogenated hydrocarbons (carbon tetrachloride). The polymer does not absorb moisture and has good water vapor resistence can be used for packaging purposes. HDPE has good electrical properties, especially high insulation of dielectric strength which make it very suitable for wire and cable. Medium to high molecular weight grade is of excellent impact resistance at room temperature or even in the low temperature of -40F. [1

1.2 HDPE Characteristics

－6]

1.2.1 Basic Characteristics

High-density polyethylene is an opaque white wax-like material.Specific gravity is lighter than water,and specific gravity is 0.941 to 0.960, soft and ductile.However, it is slightly stiffer than LDPE, and slightly stretchy, non-toxic, tasteless.[7]

1.2.2 Combustion Characteristics

HDPE is flammable, and even continue to burn away from fire. Top of flame is the yellow, and the bottom is blue. When burning, it’s melting, then dropping the liquid with no black smoke emission, at the same time emitting odor like paraffin wax when burning .[7]

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《通用高分子材料》课程期末论文

1.2.3 The Main Advantage

HDPE has acid and alkali-resistant, organic solvent resistance and excellent electrical insulating properties. It can maintain a certain toughness at low temperature.It’s surface hardness, tensile strength, stiffness and other mechanical strength higher than that of LDPE close to PP and tougher than PP, but the surface finish is worse than PP. [7]

1.2.4 The Main Disadvantage

HDPE has poor mechanical properties, poor ventilation, and too easy to deform, age, crisp ,stress cracking and scratch. Its brittle point lower than that of PP, and has low surface hardness. It’s difficult to print,when printing, surface need to be electroplated,but its surface is not matte.[7]

1.3 Molecular Weight

Rheology or molecular weight can be used to characterize the molecular weight of the material. HDPE grade generally reach a molecular weight range of 40,000 to 300,000 weight average. Molecular weight roughly corresponds to the melt index, ranging from 100 to 0. 029/10min.

The most common measurement of the MWD (molecular weight distribution) index irregularity index (HI), which is equal to the weight average molecular weight (MW) divided by the number average molecular weight (Mn). HDPE grade index range is 4-30.[8]

1.4 Classification

Based on denisity：

①Density of 0.91 ~ 0.925g/cm3, typeⅠPE-HD; ②Density of .926 ~ 0.94g/cm3,typeⅡPE-HD; ③Density of 0.94 ~ 0.965g/cm3 ,type Ⅲ PE-HD.[8]

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《通用高分子材料》课程期末论文

2. The Preparation Method of HDPE

Currently, HDPE production process mainly has three methods: slurry, gas phase, solution method．[9]

2.1 Slurry Polymerization

The slurry technology is to mix ethylene and aliphatic solvents, of which raw production suspend in the solvent. In the production process, pressure, temperature are low. The slurry polymerization is the main method of production of HDPE. And the slurry method put into Industrialized early, the technologyof it is mature.The use of the slurry production mainly are Hostalen Phillips, of Innovene S, Equistar,Borieas, CX, Equistar.Recornding to the slurry reactor,it can be devided in stirred tank bioreactor and tubular loop reactor . 2.1.1 stirred tank bioreactor

The characteristics of continuous polymerization process of the slurry tank reactor: ① Low operating pressure and operating temperature

② Dual-tank reactor can product unimodal and bimodal products with different forms in

parallel and i in series ; Uusing hexane as a solvent and simple recovery of unit.

③ High operating flexibility, grades change rapidly, and low purity requirements for raw

materials；Comonomers with propylene, 1 – butane

Fig. 1 Hostalen technology principle PFD

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《通用高分子材料》课程期末论文

2.1.2 Tubular Loop Reactor

The characteristics of tubular loop reactor process: ① Less equipment, short processes, low investment; ② Do not produce wax and oligomers to stick the wall; ③ Good powder shape, easy to transport;

④ Reaction heat relies on the jacket of the reactor cooling water, easy to remove the heat,

convenient adjustment;

⑤ Raw materials require more and need purification; ⑥ Hexene as comonomer;

⑦ Isobutane as solvent, easy to move out residual solvent.

Fig. 2 Phillips technology principle PFD

2.2 Gas-Phase Polymerization

Gas-Phase Polymerization process is characterized by:

① Low operating pressure power, low temperature ② Produce full-density Polyethylene

③ Catalyst system including Titanium, Chromium ,metallocene catalyst ④ High raw material purity requirements, all the raw materials need to be refined

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