化工专业英语 unit 9 polymers

Teaching plan for Unit 9
Teaching aims 能够用英语描述高聚物材料种类、性能、应用及生产技 术问题，掌握相关专业术语。 Contents ： 0. Outline of polymers 1. Commodity Polymers 2. Engineering Polymers 3.Advanced Polymeric Materials 4.Making of Polymers Teaching hours ：4 Points： 0,1,2,3,4 Methodology: lecture Teaching steps and points :
This definition excludes（排除） simple organic and inorganic compounds, e.g. CH4, NaCl, and also excludes materials like diamond（金钢石）, silica（硅胶） and metals（金属） which appear to have the properties of polymers, but are capable of being vaporized（蒸发） into monomer units.
No distinction is made between biopolymers and synthetic polymers. Indeed many of the early synthetic polymers were based upon naturally occurring polymers, e.g. celluloid (cellulose nitrate), vulcanization(硫化) of rubber, rayon (人造纤 维)(cellulose acetate).
1. Commodity Polymers
Examples of these are: Polyethylene low density polyethlene (LDPE) high density polyethlene (HDPE) linear low density polyethylene (LLDPE) Polypropylene (PP) Poly vinyl chloride (PVC) Polystyrene (PS) Each of these is prepared on the 10 million tonnes/year scale. The price is <＄1500/tonne.
By definition（按照定义；当然地；明显地 ）, 1 mole of a polymer contains 6×1022 polymer molecules and therefore 1mole = MW of the polymer in grams, which, in theory, can be>106g. However, by convention（按照惯例）, 1g mole usually refers to the MW of the repeat unit; thus 1g mole of polyethylene –(CH2)n- is taken as 14g ( the end groups, being negligible（可以 忽略的）, are ignored（忽略）).
Prelude
Polymers are all around us. They are the main components of food (starch, protein), clothes (silk, cotton, polyester, nylon) dwellings（民居） (wood-cellulose, paints) and also our bodies (nucleic acids, polysaccharides, protein).
Polymers are really effect chemicals in that they are use as materials, e.g. plastics, fibers, films（薄膜）, elastomers （弹性体）, adhesives（粘合剂）, paints（油漆）, etc… with each application requiring different polymer properties. Many of the initial uses of plastics were inappropriate（不 适当的）, which led to the belief that plastics were ―cheap and nasty（不值钱的，低劣的）”.
10 to the power of 3 is 1000.
It therefore has the appearance of cooked spaghetti or worms (or more correctly, worms of different length). The movements of these polymer chains are determined by several factors, such as:
The molecular weight (MW) (strictly relative molecular mass) can be obtained from the MW of the monomer (or repeat unit) multiplied（乘以） by n. Thus the MW of CH4 or NaCl is 18 or 58.5 respectively, whereas the MW of a polymer can be > 100. When the value of n is small, say 2-20, the substances are called oligomers（低聚 体）, often these oligomers are capable of further polymerizations and are then referred to （被提到）as macromers（大分子 单体）.
2. Engineering Polymers
The materials have enjoyed the highest percentages growth of any polymers in the last ten years and are principally used as replacements for metals for moderate temperature (< 150℃) and environmental conditions or they may have outstanding chemical inertness and/or special properties e.g. low friction polytetrafluoroethylene (PTFE).These engineering polymers include
I. Temperature II. Chemical make-up of the backbone（脊椎, 中枢, 骨干, 支柱） –C-C-C- chain; whether the chain is flexible (aliphatic structure) or rigid (aromatic). III.The presence or absence of side-chain on the backbone IV.The inter-polymer（互聚物） chain attraction （吸引力） (weak-dipole/dipole（弱偶极子/偶子）, H-bonding- or strong covalent bonds, crosslinking（交联）) V. The MW and molecular weight distribution (MWD) of the polymer
A polymer with a MW of 107, if fully extended, should have a length of ~1mm and a diameter of ~ 0.5 nm. This is equivalent in size to uncooked spaghetti (意大利式细面条) ~ 2km in length. However, in reality（事实上）, in bulk（散装的） polymers the chain is never fully extended— —a random coil configuration（随机盘绕构型） is adopted sweeping out （占掉，扫除）a space of diamerer ~200 nm.
Polymers are constructed from monomer（单体） units, connected by covalent bonds.
The definition of a polymer is: “a substance, —R—R—R—R— or, in general：—[R]n—， where R is a bifunctional（两功能的） entity （实体） (or bivalent二价的 radical) which is not capable of a separate existence”, Where n is the degree of polymerization, DPn .
河 南 城 建 学 院 化 学 与 化 学 工 程 系
Unit 9 Polymers
By Zhao Ya-qi Henan University of Urban Construction
河 南 城 建 学 院 化 学 与 化 学 工 程 系
Unit 9 Polymers
By Zhao Ya-qi Henan University of Urban Conecent legislation on product liability（责任，义务，债务，倾向） and a better understanding of the advantages and disadvantages of plastic have changed this position. Economics, that is the cost of making and fabricating（制作） the polymer is prime importance。 This has led to a rough grouping of polymers into commodity polymers. Engineering polymers, and advanced polymeric materials.
Nearly all of the properties of polymers can be predicted if the above factors are known, e.g. whether the polymer is amorphous or partially crystalline; the melting temperature of the crystalline phase (Tm) (actually it is more of a softening temperature over several degrees); is the polymer brittle（易碎的） or tough（坚硬的）; its rigidity or stiffness (called modulus), whether the polymer dissolves in solvents, etc.