材料专业英语-Lesson5

1、 Lesson 4 Radical Combination Reaction自由基偶合反应自由基偶合反应 LESSON 4 RADICAL COMBINATION REACTIONv The rate of combination of simple radicalsv Simple collision theoryv The rate of atom combinationv Diatomic moleculev The bond dissociation energyv Activated speciesv Collision v Vibration and rotationLesson

2、5 Emulsion Polymerization 乳液聚合v Emulsion polymerization is a method for the production of polymers.v Water acts as the continuous phase in which the monomers can polymerize and the monomer is present in monomer droplets in the water. The monomers are polymerized in micelles(胶束), that are formed by s

3、urfactant. v The reaction is started with a water-soluble initiator. After the reaction has come to completion the formed product is called a latex. This latex consists of a colloidal dispersion of the polymer particles in water. droplet drplt n. 小滴，液滴 micelle mseln. 胶束 surfactant sfkt()nt n. 表面活性剂

4、colloidal klidladj. 胶体的Emulsion Polymerizationv An important feature of emulsion polymerization is the possibility to combine the properties of two or more monomers into one polymer. v This process is called copolymerization and is usually carried out in two steps: first one monomer is polymerized t

5、o form a seed latex containing the first polymer and after that the seed latex is further polymerized with the other monomer(s) to make polymer chains with the desired properties.Emulsion Polymerization Advantages of emulsion polymerization include:v Emulsion polymerization can produce high molecula

6、r weight polymers at high polymerization rates. By contrast, in bulk polymerization, there is a tradeoff between molecular weight and polymerization rate. tradeofftred,f n. 权衡v A high conversion can be reached without the use of toxic and flammable solvents, the use of water provides a very good hea

7、t transfer and thus a good temperature control.v Since polymer molecules are contained within the particles, the viscosity of the reaction medium remains close to that of water and is not dependent on molecular weight.v The molecular weight can be easily controlled by the use of chain transfer agent

8、s.v The final product can be used as is and does not generally need to be altered or processed. Disadvantages of emulsion polymerization include:v Surfactants remain in the polymer or are difficult to remove.v For dry (isolated) polymers, water removal is an energy-intensive(耗能的 ) processv Can not b

9、e used for condensation, ionic or Ziegler-Natta polymerization, although some exceptions(例外) are known. surfactant sfkt()nt n. 表面活性剂 乳液聚合乳液聚合-单体在水中分散成乳液状态的聚合。单体在水中分散成乳液状态的聚合。 传统（或经典）乳液聚合体系的基本配方由单体、水、水溶传统（或经典）乳液聚合体系的基本配方由单体、水、水溶性引发剂和水溶性乳化剂四组分构成。性引发剂和水溶性乳化剂四组分构成。 Emulsion Polymerization 乳液聚合机理：乳液聚合机理：

10、 遵循遵循自由基聚合自由基聚合规律，但存在独特的反应机理和成粒机理：规律，但存在独特的反应机理和成粒机理： 在水相中引发、胶束成核，在胶束或胶粒的隔离环境下增长，在水相中引发、胶束成核，在胶束或胶粒的隔离环境下增长，自由基寿命长，另一自由基进入胶粒后，才终止；自由基寿命长，另一自由基进入胶粒后，才终止；兼具高速兼具高速率和高聚合度。率和高聚合度。优点：优点：v (1) (1)聚合反应速度快，分子量高，可同时实现高聚合速率和高分子量；聚合反应速度快，分子量高，可同时实现高聚合速率和高分子量； v (2)(2)聚合体系即使在反应后期粘度也很低聚合体系即使在反应后期粘度也很低, ,因而也适于制备高粘

11、性的聚合物；因而也适于制备高粘性的聚合物；v (3)(3)用水作介质，生产安全及减少环境污染；用水作介质，生产安全及减少环境污染；v (4)(4)聚合热易扩散聚合热易扩散, ,聚合反应温度易控制；聚合反应温度易控制； v (5)(5)可直接以乳液形式使用，聚合后乳胶直接用作涂料和粘结剂，如丁苯胶可直接以乳液形式使用，聚合后乳胶直接用作涂料和粘结剂，如丁苯胶乳、丙烯酸酯类胶乳等。乳、丙烯酸酯类胶乳等。缺点：缺点：v 产品中留有乳化剂等杂质，难以完全除干净，影响制品性能；产品中留有乳化剂等杂质，难以完全除干净，影响制品性能；v 为得到固体聚合物为得到固体聚合物, ,需经过凝聚、分离、洗涤、干燥等工

12、序；需经过凝聚、分离、洗涤、干燥等工序；v 反应器的生产能力也比本体聚合时低。反应器的生产能力也比本体聚合时低。 乳液聚合的优缺点乳液聚合的优缺点v mechanism meknizm n. 机制；机理v mechanistic meknistikadj. 机械论的；机理的v element elimnt n. 元素；要素；元件；电池；电极；小单位； (1)Most of condensation polymerization belong to step polymerization mechanism.condensation ,kndensein n. 缩合，凝聚缩合，凝聚大部分缩聚缩聚

13、属于逐步聚合逐步聚合机理v permitpmit vt.允许；许可： 使有可能(1)The large window permits light to enter the room. 大窗户能让光线进入屋内。(2)Their communication systems are inefficient in the extreme. in the extreme非常；极度 他们通讯系统的效率极其低下。v efficient ifint adj. 有效率的；有能力的；生效的 ; 效率高的v inefficient ,inifint adj. 无效率的，效率低的；无能力的v 1. not only

14、but （also） ，also可以省略，“不但不但而且而且”，在句中常用来连接两个对等的成分，连接主语、谓语动词、宾语、宾语补足语、表语、状语、从句、句子等。v Not only I but also Tom and Mary are fond of watching television. v The Americans and the British not only speak the same language but also share a large number of social customs.v 英国人和美国人不但语言相同，而且有很多相同的风俗习惯。v 不仅我，而且汤姆

15、和玛丽都喜欢看电视。 这个可怜的人不仅被逮捕，而且被投进监狱。v Not only had the poor man been arrested（逮捕 ） but he had been sent to prison as well. not onlybut also用于连接两个表示并列关系的成分，着重强调后者，其意为“不仅而且”；其中的also有时可以省略。若连接两个句子，not only后面的句子要用倒装 v The water absorbs much of the heat of polymerization and facilitates reaction control, and

16、the product is obtained in a relatively non-viscous and easily handled form, to be used as such or readily to be converted into solid polymer after coagulation, washing and drying.facilitate fsiliteit vt. 使容易 relatively reltivli adv. 相对地non-viscous 无粘性的 form f:m n. 形式，形状；表格readily redili adv. 容易地；无困

17、难地 convert into 转变；把转化成coagulation kugjulein n. 凝聚，凝固，凝结；凝结物 Viscous visks adj. 粘性的；黏的v readily redili adv. 很快地；容易地；乐意地；无困难地 这些零件在五金商店容易买到。 (2)The humid（潮湿的） conditions that spread rust （病菌） most readily have recently been lacking in most places. 最有利于传播病菌的湿润条件最近在大部分地区都不具备。 (1) The components are rea

18、dily available in hardware stores(五金店).v (2) Emulsion polymerization are open to great variation, from variation,vriein n. 变化 open to: 对开放；愿接受的 v 乳液聚合容易接受巨大的变化，从not open to visitors. 谢绝参观 open to suggestions. 广纳建议 v ratio reiiu n. 比，比例 v rate reitn. 率；比率; 速度；速率; (利息等的)费率（1）The ratio of domestic sewa

19、ge（生活污水） to textile wastes（纺织废水） has no effect on the treatability（处理能力）.生活污水与纺织废水的比例对处理能力无影响。v The higher levels approach the limit which can be achieved by direct polymerization and owing to the substantial amount of heat to be dissipated can often only be obtained by incremental addition of monom

20、er.level levl n. 水平；标准 approach prut vt. 接近；limit limit n. 限制;限度;vt. 限制； substantial sbstnl adj. 大量的； amount maunt n. 数量；总额 substantial amount of 大量 dissipate disipeit vt. 使消散 incremental ,inkrimentl adj. 增加的monomer mnm n. 单体；单体与水相比较高就会达到直接聚合允许的极限，由于反应放出大量的聚合热需要排散，所以此时往往只能用不断补加单体的办法来获得聚合物. infrequen

21、tly infri:kwntli adv. 很少发生地；稀少地 frequently fri:kwntli adv. 时常，屡次；频繁地，经常地 accompany by 伴随； aggregation ,riein n. 聚合,聚集;聚集体 inadequate indikwit adj. 不适当的 stabilization ,steibilaizein n. 稳定 coagulation kugjulein n. 凝固，凝结；凝结物 v This stage is not infrequently accompanied by an increase in the latex parti

22、cle size by aggregation and when surface stabilization is inadequate by coagulation.这一阶段常常伴随着由聚集作用而导致胶乳粒子的增大，而且当表面稳定体系选择不当时也会产生凝聚。(1)He will not do it for nothing.他不会无缘无故做这件事。（他做这件事定有企图。） (2)None of us will leave school without learning any thing.我们毕业时定会学有所成。 v frequently fri:kwntli adv. 频繁地，经常地；时常v

23、 infrequently infri:kwntli adv. 很少发生地v not infrequently (1)Be sure to find a substantial amount of information to draw you conclusions.务必要找到大量的大量的资料去得出你的结论。(2) Curing agent mixed with the monomer will induce polymerization.curingkjuri 固化固化剂与这种单体单体混合将引起聚合反应。vpolymerizationvcopolymerization ku,plmraizeinvcopolymer kuplimvcopolymerization theoryv