09-高分子科學導論-橡膠-展示頁
2025-02-24 12:22本頁面
【正文】 ? 結(jié)構(gòu)單元含有一個雙鍵的聚合產(chǎn)物，這些雙鍵可以與硫發(fā)生反應從而交聯(lián)形成網(wǎng)絡狀分子結(jié)構(gòu)，得到硫化橡膠。 ? 橡膠彈性體的聚合物分子鏈都是通過弱的分子間色散力聚集在一起的，因此在外力作用下分子鏈能快速相對滑動，產(chǎn)生明顯形變。 ? 硫化反應引入了交聯(lián)結(jié)構(gòu)，使得鏈段一旦達到所能伸展的極限，要繼續(xù)產(chǎn)生形變必須使拉伸力達到引起化學鍵的斷裂或結(jié)晶區(qū)破壞的程度。 ? 這種特性被稱為熱彈效應 thermoelastic effect RUBBER ELASTICITY ? 長度為 l0 的橡膠試樣，等溫下受外力 f 作用拉伸，伸長為 dl 。 ? 高彈態(tài)（ high elastic state）是高分子運動的特點之一；大部分高分子在 Tg~ Tf間都可表現(xiàn)出一定的高彈性。RUBBER 橡膠 Introduction to Polymer Science 四川大學化學學院 CHARACTERISTICS OF THE RUBBER Part 1 PROPERTIES OF RUBBER/ELASTOMER ? An elastomer is a polymer with the property of elasticity. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred when referring to vulcanisates. ? Elastomers are amorphous polymers existing above their glass transition temperature, so that considerable segmental motion is possible. At ambient temperatures rubbers are thus relatively soft and deformable. ? The elasticity is derived from the ability of the long chains to reconfigure themselves to distribute an applied stress. The covalent crosslinkages ensure that the elastomer will return to its original configuration when the stress is removed. ? Their primary uses are for seals, adhesives and molded flexible parts. ? small elastic modulus ? Steel： 20230MPa； ? PE： 200MPa (crystallized)； PS： 2500MPa； ? Rubber: ? large strain ? Steel: ＜ 1% ? Rubber: 300~1000% ? elastic modulus of the rubber increased with the temperature ? The motion and retractive force of the chain segments increased with the temperature, resulted in a high resistance of deformation. ? The high elastic deformation of the rubber is time dependent , i. e. mechanical relaxation ? The deformation process have obvious thermal effect. CHARACTERISTIC OF ELASTOMERIC PROPERTY RUBBER ELASTICITY ? 高彈態(tài)是聚合物特有的力學狀態(tài)。在 Tg以上的非晶態(tài)聚合物處于高彈態(tài)，典型的代表是各種橡膠，因為其 Tg≈60 ~20)℃ ，所以在一般使用溫度下均呈高彈態(tài)。 deformation Temperature (oC) I glass state high elastic state viscous
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