高分子專業(yè)英語UNIT 10

1、UNIT 10 Tb脆化溫度 Tg玻璃化溫度Tf黏流溫度 Td分解溫度第一段An ordinary rubber ball if cooled below -70 becomes so hard and brittle(易碎的） that it will break into pieces like a glass ball falling on a hard surface!設(shè)想一個(gè)普通的橡膠球在零下70攝氏度冷卻會(huì)變得如此硬而脆以至于像一個(gè)玻璃球摔碎在堅(jiān)硬的表面成碎片。Why does a rubber ball become like glass below -70?This is be

2、cause there is a “temperature boundary（范圍）” for almost all amorphous（無定形的） polymers (and many crystallinepolymers結(jié)晶聚合物) only above which the substance remains soft,flexible(柔軟的） and rubbery（橡膠狀的） and below which it becomes hard,brittle and glassy.這是因?yàn)閷?duì)于幾乎所有的無定型聚合物（和許多結(jié)晶聚合物）有一個(gè)溫度范圍，這個(gè)范圍存在于軟的，橡膠狀物質(zhì)之上，

3、變成硬而脆，玻璃態(tài)的物質(zhì)以下。 This temperature ,below which a polymer is hard and above which it is soft,is called the “glass transition temperation” Tg.這個(gè)溫度被稱為“玻璃化轉(zhuǎn)變溫度Tg” ，低于該聚合物是硬的，高于是軟的。The hard,brittle state is known as the glassy state（玻璃態(tài) ）and the soft,flexible state as the rubbery or viscoelastic state（黏彈態(tài)

4、）.堅(jiān)硬，易碎的狀態(tài)被稱為玻璃態(tài)和溫和的，柔軟的狀態(tài)為橡膠或黏彈態(tài)。On further heating,the polymer(if it is uncross-linked非交聯(lián)的)becomes a highly viscous（黏的） liquid and starts flowing;this state is termed viscofluid state(黏流態(tài)）,and the another transition takes place at its flow temperature Tf.再進(jìn)一步加熱，聚合物（如果是非交聯(lián)的）成為一個(gè)高粘性液體開始流動(dòng)；這種狀態(tài)稱為黏流態(tài)，

5、另一個(gè)轉(zhuǎn)化發(fā)生在流動(dòng)溫度Tf。第二段Now，let us consider a polymer，say，polyethylene（聚乙烯）. At room temperature，polyethylene is solid，exhibiting all characterisitics of a low molecular weight substance. 現(xiàn)在,讓我們考慮一種聚合物,就說聚乙烯。在室溫下,聚乙烯是固態(tài)的,表現(xiàn)出的所有的分子量本質(zhì)的特性。At high temperatures，however，the characteristic difference between hi

6、gh and low molecular weight substance can be seen. 然而,在高溫下,這個(gè)特性的差異在高、低分子量本質(zhì)中可以看到。Deepending on（根據(jù)）the temperature，the molectures of a low molecular weight substance either move apart（分開，分離，移開）as a whole or do not move at all，i. e. ，there is a definite temperature ( melting point Tm ) below which the

7、 molecules do not move and above which they do move.根據(jù)溫度,低分子量的物質(zhì)要么整個(gè)分子移開,要么根本不運(yùn)動(dòng),有一個(gè)特定的溫度(熔點(diǎn)Tm)在低于這一溫度時(shí)分子不運(yùn)動(dòng),而在高于這一溫度時(shí)分子則運(yùn)動(dòng)。On the other hand，with polymers，if the temperature increases above Tg，localized units ( chain segments 鏈段) within the long chain molecture are first mobilized（運(yùn)動(dòng)，流動(dòng)）before the

8、whole molecture starts moving. 在另一方面,對(duì)于聚合物如果溫度高于Tg,在長分子鏈里的局部單元（鏈段）在整個(gè)分子開始運(yùn)動(dòng)之前先運(yùn)動(dòng)。In some parts within the molecule,there is aconsiderable localized motion，but not in other parts of the same molecture.在分子中的某些部分,有一個(gè)重要的局部運(yùn)動(dòng),但是不同于這個(gè)分子的其他部分。Thus，within the long chain of the polymer molecule，some segments

9、 have a certain freedom of movement，whereas others do not.因此,在聚合物的長鏈中,一些鏈段有確定的有規(guī)則的運(yùn)動(dòng),而其他的不會(huì)這樣。The molecule as a whole（作為一個(gè)整體，整體上）does not move although some of its segments do.分子作為一個(gè)整體不動(dòng),盡管分子的一些鏈段可以動(dòng)。第三段In the case of polymers, there is indeed an intermediate（中間的） state. If the temperature ranges be

10、tween Tg and Tf, the localized mobility（局部的流動(dòng)） is activated（被激活）, correspond to（相當(dāng)于） the mobility is not. 在聚合物的情況下，確實(shí)是一個(gè)中間狀態(tài)。如果溫度范圍之間的Tg和Tf，局部流動(dòng)被激活，與流動(dòng)性不對(duì)應(yīng)。The local segments（局部鏈段）, where mobility is already activated, correspond to the liquid state, while the molecule as a whole, where mobility is

11、forbidden（被禁止的）, is in the solid state. 在一條分子鏈上某些流動(dòng)性已經(jīng)被激活的局部鏈段相對(duì)應(yīng)著流體狀態(tài)，而沒有被完全激活的整體分子則處于固體狀態(tài)。This state,which is really a combination of liquid and solid,is called the rubbery state. 這個(gè)狀態(tài)，真的是一個(gè)液體和固體的組合，稱為橡膠態(tài)。Under the influence of an applied stress, it exhibits properties（屬性） of a viscous fluid （粘性的流

12、體）as well as an elastic（彈性的） solid and undergoes（經(jīng)歷） what is called viscoelastic deformation（變形）. 在外加應(yīng)力的作用下，聚合材料既顯示出黏性液體的性質(zhì)，也顯示出彈性固體的性質(zhì)，并發(fā)生所謂的黏彈形變。第四段The glass transition temperature Tg is an important parameter（參數(shù)） of a polymeric material.玻璃的轉(zhuǎn)變溫度Tg是聚合材料的一個(gè)重要參數(shù)。The Tg value of a polymer decides whet

13、her a polymer at the “use temperature” will behave like rubber or plastics.這個(gè)Tg表明，聚合物是否在這個(gè)“可用的溫度”決定著聚合物是橡膠態(tài)或是塑料態(tài)。The Tg value along with （連同）the Tm value gives an indication of （表明）the temperature region（范圍） at which a polymeric material trasforms from（由轉(zhuǎn)變成） a rigid（堅(jiān)硬的） solid to a soft viscous state.Tg值和Tm值表明了一個(gè)溫度范圍，在這個(gè)范圍內(nèi)聚合材料會(huì)由剛性固體變成黏流態(tài)。This helps in choosing the right processing temperature, i. e. , the temperature region in which