材料專(zhuān)業(yè)英語(yǔ)-Lesson5

1、 Lesson 4 Radical Combination Reaction自由基偶合反應(yīng)自由基偶合反應(yīng) 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(膠束), 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. 膠束 surfactant sfkt()nt n. 表面活性劑

4、colloidal klidladj. 膠體的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. 權(quán)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. 表面活性劑 乳液聚合乳液聚合-單體在水中分散成乳液狀態(tài)的聚合。單體在水中分散成乳液狀態(tài)的聚合。 傳統(tǒng)（或經(jīng)典）乳液聚合體系的基本配方由單體、水、水溶傳統(tǒng)（或經(jīng)典）乳液聚合體系的基本配方由單體、水、水溶性引發(fā)劑和水溶性乳化劑四組分構(gòu)成。性引發(fā)劑和水溶性乳化劑四組分構(gòu)成。 Emulsion Polymerization 乳液聚合機(jī)理：乳液聚合機(jī)理：

10、 遵循遵循自由基聚合自由基聚合規(guī)律，但存在獨(dú)特的反應(yīng)機(jī)理和成粒機(jī)理：規(guī)律，但存在獨(dú)特的反應(yīng)機(jī)理和成粒機(jī)理： 在水相中引發(fā)、膠束成核，在膠束或膠粒的隔離環(huán)境下增長(zhǎng)，在水相中引發(fā)、膠束成核，在膠束或膠粒的隔離環(huán)境下增長(zhǎng)，自由基壽命長(zhǎng)，另一自由基進(jìn)入膠粒后，才終止；自由基壽命長(zhǎng)，另一自由基進(jìn)入膠粒后，才終止；兼具高速兼具高速率和高聚合度。率和高聚合度。優(yōu)點(diǎn)：優(yōu)點(diǎn)：v (1) (1)聚合反應(yīng)速度快，分子量高，可同時(shí)實(shí)現(xiàn)高聚合速率和高分子量；聚合反應(yīng)速度快，分子量高，可同時(shí)實(shí)現(xiàn)高聚合速率和高分子量； v (2)(2)聚合體系即使在反應(yīng)后期粘度也很低聚合體系即使在反應(yīng)后期粘度也很低, ,因而也適于制備高粘

11、性的聚合物；因而也適于制備高粘性的聚合物；v (3)(3)用水作介質(zhì)，生產(chǎn)安全及減少環(huán)境污染；用水作介質(zhì)，生產(chǎn)安全及減少環(huán)境污染；v (4)(4)聚合熱易擴(kuò)散聚合熱易擴(kuò)散, ,聚合反應(yīng)溫度易控制；聚合反應(yīng)溫度易控制； v (5)(5)可直接以乳液形式使用，聚合后乳膠直接用作涂料和粘結(jié)劑，如丁苯膠可直接以乳液形式使用，聚合后乳膠直接用作涂料和粘結(jié)劑，如丁苯膠乳、丙烯酸酯類(lèi)膠乳等。乳、丙烯酸酯類(lèi)膠乳等。缺點(diǎn)：缺點(diǎn)：v 產(chǎn)品中留有乳化劑等雜質(zhì)，難以完全除干凈，影響制品性能；產(chǎn)品中留有乳化劑等雜質(zhì)，難以完全除干凈，影響制品性能；v 為得到固體聚合物為得到固體聚合物, ,需經(jīng)過(guò)凝聚、分離、洗滌、干燥等工

12、序；需經(jīng)過(guò)凝聚、分離、洗滌、干燥等工序；v 反應(yīng)器的生產(chǎn)能力也比本體聚合時(shí)低。反應(yīng)器的生產(chǎn)能力也比本體聚合時(shí)低。 乳液聚合的優(yōu)缺點(diǎn)乳液聚合的優(yōu)缺點(diǎn)v mechanism meknizm n. 機(jī)制；機(jī)理v mechanistic meknistikadj. 機(jī)械論的；機(jī)理的v element elimnt n. 元素；要素；元件；電池；電極；小單位； Most of condensation polymerization belong to step polymerization mechanism.condensation ,kndensein n. 縮合，凝聚縮合，凝聚大部分縮聚縮聚屬于逐

13、步聚合逐步聚合機(jī)理v permitpmit vt.允許；許可： 使有可能(1)The large window permits light to enter the room. 大窗戶(hù)能讓光線(xiàn)進(jìn)入屋內(nèi)。(2)Their communication systems are inefficient in the extreme. in the extreme非常；極度 他們通訊系統(tǒng)的效率極其低下。v efficient ifint adj. 有效率的；有能力的；生效的 ; 效率高的v inefficient ,inifint adj. 無(wú)效率的，效率低的；無(wú)能力的v 1. not only but

14、 （also） ，also可以省略，“不但不但而且而且”，在句中常用來(lái)連接兩個(gè)對(duì)等的成分，連接主語(yǔ)、謂語(yǔ)動(dòng)詞、賓語(yǔ)、賓語(yǔ)補(bǔ)足語(yǔ)、表語(yǔ)、狀語(yǔ)、從句、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 英國(guó)人和美國(guó)人不但語(yǔ)言相同，而且有很多相同的風(fēng)俗習(xí)慣。v 不僅我，而且湯姆和瑪麗

15、都喜歡看電視。 這個(gè)可憐的人不僅被逮捕，而且被投進(jìn)監(jiān)獄。v Not only had the poor man been arrested（逮捕 ） but he had been sent to prison as well. not onlybut also用于連接兩個(gè)表示并列關(guān)系的成分，著重強(qiáng)調(diào)后者，其意為“不僅而且”；其中的also有時(shí)可以省略。若連接兩個(gè)句子，not only后面的句子要用倒裝 v The water absorbs much of the heat of polymerization and facilitates reaction control, and the

16、 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. 相對(duì)地non-viscous 無(wú)粘性的 form f:m n. 形式，形狀；表格readily redili adv. 容易地；無(wú)困難地

17、convert into 轉(zhuǎn)變；把轉(zhuǎn)化成coagulation kugjulein n. 凝聚，凝固，凝結(jié)；凝結(jié)物 Viscous visks adj. 粘性的；黏的v readily redili adv. 很快地；容易地；樂(lè)意地；無(wú)困難地 這些零件在五金商店容易買(mǎi)到。 (2)The humid（潮濕的） conditions that spread rust （病菌） most readily have recently been lacking in most places. 最有利于傳播病菌的濕潤(rùn)條件最近在大部分地區(qū)都不具備。 (1) The components are readil

18、y available in hardware stores(五金店).v (2) Emulsion polymerization are open to great variation, from variation,vriein n. 變化 open to: 對(duì)開(kāi)放；愿接受的 v 乳液聚合容易接受巨大的變化，從not open to visitors. 謝絕參觀 open to suggestions. 廣納建議 v ratio reiiu n. 比，比例 v rate reitn. 率；比率; 速度；速率; (利息等的)費(fèi)率（1）The ratio of domestic sewage（

19、生活污水） to textile wastes（紡織廢水） has no effect on the treatability（處理能力）.生活污水與紡織廢水的比例對(duì)處理能力無(wú)影響。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 monomer.

20、level levl n. 水平；標(biāo)準(zhǔn) approach prut vt. 接近；limit limit n. 限制;限度;vt. 限制； substantial sbstnl adj. 大量的； amount maunt n. 數(shù)量；總額 substantial amount of 大量 dissipate disipeit vt. 使消散 incremental ,inkrimentl adj. 增加的monomer mnm n. 單體；單體與水相比較高就會(huì)達(dá)到直接聚合允許的極限，由于反應(yīng)放出大量的聚合熱需要排散，所以此時(shí)往往只能用不斷補(bǔ)加單體的辦法來(lái)獲得聚合物. infrequently

21、 infri:kwntli adv. 很少發(fā)生地；稀少地 frequently fri:kwntli adv. 時(shí)常，屢次；頻繁地，經(jīng)常地 accompany by 伴隨； aggregation ,riein n. 聚合,聚集;聚集體 inadequate indikwit adj. 不適當(dāng)?shù)?stabilization ,steibilaizein n. 穩(wěn)定 coagulation kugjulein n. 凝固，凝結(jié)；凝結(jié)物 v This stage is not infrequently accompanied by an increase in the latex particle

22、 size by aggregation and when surface stabilization is inadequate by coagulation.這一階段常常伴隨著由聚集作用而導(dǎo)致膠乳粒子的增大，而且當(dāng)表面穩(wěn)定體系選擇不當(dāng)時(shí)也會(huì)產(chǎn)生凝聚。(1)He will not do it for nothing.他不會(huì)無(wú)緣無(wú)故做這件事。（他做這件事定有企圖。） (2)None of us will leave school without learning any thing.我們畢業(yè)時(shí)定會(huì)學(xué)有所成。 v frequently fri:kwntli adv. 頻繁地，經(jīng)常地；時(shí)常v in

23、frequently infri:kwntli adv. 很少發(fā)生地v not infrequently (1)Be sure to find a substantial amount of information to draw you conclusions.務(wù)必要找到大量的大量的資料去得出你的結(jié)論。(2) Curing agent mixed with the monomer will induce polymerization.curingkjuri 固化固化劑與這種單體單體混合將引起聚合反應(yīng)。vpolymerizationvcopolymerization ku,plmraizeinvcopolymer kuplimvcopolymerization theoryv