高分子材料英文-塑料PE

1、Polymer Materials -Plastic,Im surrounded by plastic!,What is the plastic ?,base material,A. resin,B. Add proper polymeric additive,C. With the aid of molding facility,D. Certain temperature and pressure plasticizing shape and size,E. Cooling and hardening -thermoplastics Cross-linking and Solidity-t

2、hermosets,基础材料-树脂,高分子助剂,成型设备,塑化,冷却硬化-热塑性塑料,交联固化-热固性塑料,PlasticsClassification,PE (Polyethylene)聚乙烯,PP(polypropylene)聚丙烯,PS(polystyrene)聚苯乙烯,PVC(polyvinyl chloride)聚氯乙烯,Other general plastics（commodity plastics）通用塑料,Engineering plastics 工程塑料,PE (聚乙烯),1. Overview,2. Structure,3. Properties,4. Applicati

3、ons,1. Overview 概述 molecular formula：CH2CH2n monomer：ethylene Synthesis method：free radical polymerization(自由基聚合)、coordination polymerization(配位聚合) Synthesis materials：petroleum; Ethylene monomer was obtained from petroleum cracking Production：Since the middle of 1960s, has been the highest in the f

4、irst place, accounting for 1/3 of the total amount of plastic Characteristics ：light quality、non-poisonous、Excellent chemical resistance、Electrical insulation、Low temperature resistance, Easy processing and forming Application：Appliance（家用电器）、Chemistry、Food、Machine building industry 、Agriculture etc

5、.,2. Structure,Polyethylene,Linear polymer ，Linear long chain 线性聚合物 Nonpolar group, Small intermolecular forces 非极性基团 Spatial arrangement- Planar zigzag (平面锯齿) The molecular chain-good flexibility and regularity(良好柔顺性规整性); Can be repeatedly folded and stacked to form a crystal Molecular chains conta

6、in short methyl groups and long alkyl chains. Both the crystalline structure, and amorphous structure exist,2.1 Structure of PE,2.2 Classification of PE,Polyethylene can be classified by its density: LDPE(低密度聚乙烯)、HDPE(高密度聚乙烯)、LLDPE(线性低密度聚乙烯).,HDPE,LLDPE,LDPE,20-30 branches of per 1000 carbon atoms,n

7、ot only contains ethyl, butyl short branched chain, but also contains a long chain, may be as long as the main chain,about 5 short branches per 1000 carbon atoms;,substantially linear polymer (polyethylene), with significant numbers of short branches,2.3 Molecular weight of PE,2.3.1 Representation o

8、f molecular weight,Melt flow rate (MFR熔体流动速率): the mass of PE melt heated to 190 degrees under 21.2N pressure from a hole in a certain pore size every 10 minutes, g/10min,The greater the MFR, the better the liquidity, the higher the melt viscosity.,2.3.2 Effect of PE molecular weight on mechanical p

9、roperties,The higher the molecular weight, the greater the entanglement and the attraction between macromolecular chains.,Tensile strength 、 surface hardness、Abrasion resistance、creep resistance、aging resistance、solvent resistance are improved.,3. Properties,Polyethylene film,Odorless、non-poisonous;

10、 Density: 0.91-0.96g/cm3 ; Milk white waxy solid, the material is translucent or opaque（半透明或不透明）, transparent (透明的), with the increase in the degree of crystallinity transparency is decreased; Permeability to water(透水) is low, permeability to gas(透气) is large, suitable for moisture proof packaging(防

11、潮包装); Flammable, the oxygen index of 17.4, low smoke when burning, a small amount of melt dripping（熔滴）, paraffin (石蜡) smell.,3.1 Mechanical properties,Polyethylene barrel, General mechanical properties（机械性能一般）,low strength, low hardness and rigidity; Soft and tough（软而韧）, strong creep （强的蠕变）under per

12、sistent force, high impact strength （冲击强度）as well as low friction（低摩擦）; Factors affecting mechanical properties 1) Crystallinity 2) molecular weight,The effects of crystallinity and molecular weight,The crystallinity increases, and the mechanical properties increase except for the impact strength. T

13、he degree of crystallinity is related to the degree of branching of the macromolecular chain, and the degree of branching depends on the polymerization method. HDPE with low degree of branching ,high crystallinity, high density, high mechanical properties and poor toughness. LDPE with high degree of

14、 branching,low crystallinity, low density, low mechanical property and good impact performance. The increase of molecular weight results in the increase of the entanglement and the attraction between macromolecular chains, and most of the mechanical properties are improved.,3.2 Thermal properties,No

15、t high heat resistance, low thermal deformation temperature, improved with the increase of molecular weight and crystallinity ; LDPE：80 HDPE：121 Good resistance to low temperature, the brittleness temperature(脆化温度)of -50 degrees Celsius. The higher the molecular weight, the more the branched chains,

16、 the lower the brittleness point; Thermal conductivity is higher, it is not suitable for the use of a good thermal insulation material(隔热材料) The linear expansion coefficient（线膨胀系数） is larger, the size of the product changes with the change of temperature.,1) Polyethylene consists of nonpolar, satura

17、ted, high molecular weight hydrocarbons; 2) Because of their symmetric molecular structure, they tend to crystallize; 3) Overall polyethylene is partially crystalline. Higher crystallinity increases density and mechanical and chemical stability. 4) Polyethylene absorbs almost no water. The gas and w

18、ater vapor permeability (only polar gases) is lower than for most plastics; oxygen, carbon dioxide and flavorings（调味品） on the other hand can pass it easily.,3.3 Chemical properties,Polyethylene anticorrosive tape,Good chemical stability At room temperature, there is no solvent to dissolve PE: resist

19、ant to dilute sulfuric acid(稀硫酸), nitric acid (硝酸)erosion, but not resistant to strong oxidizing agents such as fuming sulfuric acid(发烟硫酸), sulfuric acid(浓硫酸), chromic acid(铬酸); Below 60 ,insoluble in general solvent: long-term exposure to aliphatic hydrocarbons(脂肪烃), aromatic hydrocarbon(芳香烃), halo

20、genated hydrocarbon(卤代烃) will swell and crack; Above 60,a small amount of dissolution in toluene(甲苯), butyl acetate(乙酸戊酯), trichloroethylene(三氯乙烯), mineral oils(矿物油), paraffin wax (石蜡); Above 100 , soluble in tetraline(四氢化萘), decalin(十氢化萘) Low surface energy, poor adhesion, difficult to bond with ot

21、her materials.,Lined PE steel pipe,PE coated steel pipe,3.4 Electrical properties,cables,Good electrical insulator (nonpolarity 、Low moisture absorption) Dielectric loss (介电损耗) is very low, can be used for high frequency insulation, high voltage insulation materials Be easily electrostatically charg

22、ed (which can be reduced by additions of graphite, carbon black or antistatic agents).,PE can become brittle when exposed to sunlight. Carbon black is usually used as a UV stabilizer（紫外线稳定剂）;,3.5 Environmental performance,Poor resistance to environmental stress cracking: Active substances that cause

23、 environmental stress cracking: esters(酯类), metal soaps(金属皂类), alcohols(醇类), and organic silicon liquid(有机硅液体), moist soil(潮湿土壤),Improvement method: 1) Reduce the crystallinity of the material; 2) Increase the molecular weight and reduce the molecular weight dispersion; 3) Cause cross-linking betwee

24、n macromolecules.,3.6 Processability,Molding processing：Injection、extrusion、blowing 、pressing（模压） etc. Moisture absorption is very low. Before processing, raw materials can not have to dry; Molding process has great influence on the crystallinity of the product, such as the temperature and the distr

25、ibution of the mold; To avoid the melt s direct contact with oxygen, so as to avoid degradation; Avoiding the direct contact with aliphatic hydrocarbon(脂肪烃), aromatic hydrocarbon(芳香烃), mineral oil(矿物油), alcohol(醇类) and so on in the process of storing ,to avoid the environmental stress cracking.,Comp

26、arison of structure and properties of three kinds of polyethylene,Chain structure:HDPE(up)、 LDPE(middle)、LLDPE(down).,（1）Ultra high molecular weight polyethylene（UHMW-PE）（3.5 and 7.5 million）,Other kinds of PE,(2) Low molecular weight polyethylene（LMWPE）,（500-5000）,(3) Cross-linked polyethylene,Cabl

27、e coating,Radiation cross-link heat shrink wrapping tape,(4) Ethylene copolymer,LMWPE,4. Applications,Type,Abbreviation,Major uses,Low-density polyethylene,LDPE,Packaging film,wire and cable insulation,toys,flexible bottles,housewares,coatings,High-density polyethylene,HDPE,Bottles,drums,pipe,conduit（管道）,sheet,