《天然橡胶加工学》课程教学资源（参考资料）橡胶 Rubber（PPT讲稿）

Introduction to Polymer Science RUBBER 橡胶

RUBBER 橡胶 Introduction to Polymer Science

Part 1 CHARACTERISTICS OF THE RUBBER

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. o 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 cross-linkages 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

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 cross-linkages 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

CHARACTERISTIC OF ELASTOMERIC PROPERTY o small elastic modulus ·Steel:20000MPa; PE:200MPa(crystallized);PS:2500MPa; 。Rubber:0.2-8MPa o large strain 。Steel:<1% ·Rubber:300~1000% o 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. o The high elastic deformation of the rubber is time dependent,i.e. mechanical relaxation o The deformation process have obvious thermal effect

 small elastic modulus  Steel：20000MPa；  PE：200MPa (crystallized)； PS：2500MPa；  Rubber: 0.2-8MPa  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 。高弹态(high elastic state)是高分子运动的特点之一；大部分高分 子在Tg~Tf间都可表现出一定的高弹性。 glass glass high elastic viscous state transation state state II viscoelastic III transition Tg T Temperature (C) 。高弹态是聚合物特有的力学状态。在Tg以上的非晶态聚合物处于高 弹态，典型的代表是各种橡胶，因为其Tg≈-60~-20)℃，所以在一般 使用温度下均呈高弹态

RUBBER ELASTICITY  高弹态是聚合物特有的力学状态。在Tg以上的非晶态聚合物处于高 弹态，典型的代表是各种橡胶，因为其Tg≈-60 ~-20)℃，所以在一般 使用温度下均呈高弹态。  高弹态（high elastic state）是高分子运动的特点之一；大部分高分 子在Tg~ Tf间都可表现出一定的高弹性。 deformation Temperature (oC) I glass state high elastic state viscous state II III Tg Tf glass transation viscoelastic transition

RUBBER ELASTICITY 。橡胶带在绝热的情况 下拉伸时，其温度会 METAL heat 升高 。橡胶在负载重物下受 W 热过程中表现为收缩 而不是伸展。 。这种特性被称为热弹 效应 RUBBER heat thermoelastic effect W W

RUBBER ELASTICITY  橡胶带在绝热的情况 下拉伸时，其温度会 升高  橡胶在负载重物下受 热过程中表现为收缩 而不是伸展。  这种特性被称为热弹 效应 thermoelastic effect

RUBBER ELASTICITY dl 。长度为的橡胶试样，等温下受外力f作用拉 伸，伸长为d。 。根据热力学第一定律有： 一又 。其中：d名乙 而dVO,则： aAa 。整理后可得： 。实验证明在橡胶拉伸过程中内能基本不变，即： al 0f=-7 al

RUBBER ELASTICITY  长度为 l0 的橡胶试样，等温下受外力f 作用拉 伸，伸长为dl 。 d d d dd UQWTSW =− = − d d d WpV fl = − l0 dl f  根据热力学第一定律有：  其中： 而dV≈ 0，则：  整理后可得：  实验证明在橡胶拉伸过程中内能基本不变，即： d d d U TS fl = + TV TV , , U S f T l l       = −           , 0 T V U l          T V, S f T l    = −     

RUBBER ELASTICITY 。橡胶弹性体的聚合物分子链都是通过弱的。当拉伸时，分子链排列由于取 分子间色散力聚集在一起的，因此在外力 向作用变得规整，从而导致结 作用下分子链能快速相对滑动，产生明显 晶，进一步增加了材料的强度。 形变。 硫化反应引入了交联结构，使 Breakage 得链段一旦达到所能伸展的极 限，要继续产生形变必须使拉 伸力达到引起化学键的断裂或 结晶区破坏的程度。 Crystallization 。交联，将分子链通过化学键网 络固定，这使得橡胶能“记忆” Orientation 最初的形状，即在微观上保持 分子链的原位置。 Force applied

RUBBER ELASTICITY  当拉伸时，分子链排列由于取 向作用变得规整，从而导致结 晶，进一步增加了材料的强度。  硫化反应引入了交联结构，使 得链段一旦达到所能伸展的极 限，要继续产生形变必须使拉 伸力达到引起化学键的断裂或 结晶区破坏的程度。  交联，将分子链通过化学键网 络固定，这使得橡胶能“记忆” 最初的形状，即在微观上保持 分子链的原位置。  橡胶弹性体的聚合物分子链都是通过弱的 分子间色散力聚集在一起的，因此在外力 作用下分子链能快速相对滑动，产生明显 形变

THE PRINCIPLE OF VULCANIZED RUBBER 。硫化的主要作用简单地说，就是在分子链与分子链之间形成交联，从 而使分子链间作用力量增强。 。结构单元含有一个双键的聚合产物，这些双键可以与硫发生反应从而 交联形成网络状分子结构，得到硫化橡胶

THE PRINCIPLE OF VULCANIZED RUBBER  硫化的主要作用简单地说，就是在分子链与分子链之间形成交联，从 而使分子链间作用力量增强。  结构单元含有一个双键的聚合产物，这些双键可以与硫发生反应从而 交联形成网络状分子结构，得到硫化橡胶

Part 2 ORIGIN OF THE RUBBER

ORIGIN OF THE RUBBER Part 2