UNIT 22 Mechanical Properties of Polymers
吴国山
聚合物的力学性能铁莲花
The mechanical properties of polymers are of interest in all applications where polymers are ud as structural materials. Mechanical behavior involves the deformation of a material under the influence of applied forces.
聚合物的力学性能感兴趣的所有应用中聚合物被用作结构材料。机械行为涉及材料形变的影响下，施加的力。
The most important and most characteristic mechanical properties are called moduli. A modulus is the ratio between the applied stress and the corresponding deformation. The re-ciprocals of the moduli are called compliances. The nature of the modulus depends on the nature of the deformation. The three most important elementary modes of deformation and the moduli (and compliances) derived from them are given in Table 22.1, where the definitions of the elastic parameters are also given. ® Other very important, but more compl由里及外的按摩
icated, de-formations are bending and torsion. From the bending or flexural deformation the tensile modulus can be derived. The torsion is determined by the rigidity.
最重要和最具特色的机械特性被称为模。一个模之间的比例应力和相应的变形。该re-ciprocals的称为弹性模量。性质的模量取决于钠¬真实的变形。三个最重要的基本模式和变形模量（和依从性）来自他们在表22.1中给出的定义，给出了弹性参数。®其他非常重要，但更为复杂，de-formations是弯曲和扭转。从弯曲或弯曲变形，拉伸模量可导出。扭转是由僵硬。
Cross-linked elastomers are a special ca. Due to the cross-links this polymer class shows hardly any flow behavior. The kinetic theory of rubber elasticity was developed by Kuhn , Guth, James, Mark, Flory, Gee and Treloar. It leads, for Young's modulus at low strains, to the following equation s
交联弹性体是一种特殊情况。由于这类的交联聚合物显示几乎没有任何流动行为。橡胶弹性动力学理论是由库恩，杰姆斯，马克，古思，弗洛里，吉和特雷洛尔。它的领导，为杨氏模量低的菌株，对以下方程
E=3RTp/Mcrl = 3zcrlRT/V=3C0
The paragraphs above dealt with purely elastic deformations, i. e. deformations in which the strain was assumed to be a time-independent function of the stress. In reality, materials are never purely elastic: under certain circumstances they have nonelastic properties. This is especially true of polymers, which may show nonelastic deformation under circum-stances in which metals may be regarded as purely elastic. ® It is customary to u the ex-pression viscoelastic deformations that are not purely elastic. Literally the term viscoelastic means the combinations of viscous and elastic properties. As the stress-strain relationship in viscous deformations is time-dependent, viscoelastic phenomena always involve the change of properties with time. Measurement of the respon in deformation of a viscoelastic material to periodic forces, for instance during forced vjbration, shows that stress and strain are not in pha; the strain lags behind the stress by a pha angle 8, the loss angle. So the moduli of the materials, the complex moduli, include the storage moduli which determine the amount of recoverable energy stored as elastic energy, and the loss moduli which determine the dissipation of energy a
s heat when the material is deformed.
藏族民俗以上段落红石峡景区处理纯粹的弹性变形，即变形，应变假定时间独立功能的应力。在现实中，材料是不纯粹的弹性：在某些情况下他们的非弹性性能。这是特别真实的聚合物，这可能表明非弹性变形情况下，金属可能被视为纯粹的弹性。®通常使用粘弹性变形的表达式，并不是纯粹的弹性。粘弹性是指粘性和弹性性能的结合。由于应力应变关系的粘性变形的时间依赖性，粘弹现象总是涉及的性能随着时间的变化。测量反应在变形的粘弹性材料定期部队，例如在被迫vjbration，表明应力和应变不阶段；应变滞后的压力的相位角8，损耗角。因此，模量的材料，复模量，包括储存模量的确定数额的可恢复能源存储弹性能量，和损失模量确定能耗的热量时，材料的变形
UNIT 23 Thermal Properties of Polymer
热性能的聚合物
The heat stability is cloly related to the transition and decomposition temperature, i. e. to intrinsic properties. By heat stability is exclusively understood the stability (or re-tention)
of properties (weight, strength, insulating capacity, etc. ) under the influence of heat. The melting point or the decomposition temperature invariably form the upper limit; the "u temperature" may be appreciably lower.
热稳定性是密切相关的过渡和分解温度，即内在特性。热稳定性是完全理解的稳定性（或re-tention）性能（体重，强度，绝缘能力，在热的影响等。）。熔点或分解温度总是形式的上限；“使用温度可明显降低。
香港宝莲禅寺>缺土的名字The way in which a polymer degrades under the influence of thermal energy in an inert atmosphere is determined, on the one hand, by the chemical structure of the polymer itlf, on the other hand, by the prence of traces of unstable structures.
方式，聚合物降解的影响下，热能在惰性气氛是确定的，一方面，通过化学结构的聚合物本身，另一方面，存在的痕迹不稳定结构。
Thermal degradation does not occur until the temperature is so high that primary chemi-c
年夜饭几点吃al bonds are parated. For many polymers thermal degradation is characterized by the breaking of the weakest bond and is conquently determined by a bond dissociation energy. Since the change in entropy is of the same order of magnitude in almost all dissociation reac-tions, it may be assumed that also the activation entropy will be approximately the same. This means that, in principle, the bond dissociation energy determines the phenomenon. So it may be expected that the temperature at which the same degree of conversion is reached will be virtually proportional to this bond dissociation energy. ®
热降解不会发生，直到温度较高，主要化学债券分离。对许多聚合物热降解的特点是打破最薄弱的债券，从而确定一个键的离解能。由于熵的变化是相同的数量级在几乎所有的解离反应，可以假定，同样的活化熵是大致相同的。这意味着，在原则上，键离解能确定的现象。因此可以预计，温度在相同转化率达到将几乎成正比这个键离解能。®
The process of thermal decomposition or pyrolysis is characterized by a number of ex-perimental indices, such as the temperature of initial decomposition, the temperature of h
alf decomposition, the temperature of the maximum rate of decomposition, and the average en-ergy of activation. The heat resistance of a polymer may be characterized by its "initial" and "half" decomposition.
热分解过程或裂解的特点是一些试验指标，如初始分解温度，温度的分解温度的一半，最大分解速率，和平均能量活化。耐热聚合物的特点是其“初始”和“半”分解。
There are two types of thermal decomposition: chain depolymerization and random de-composition. The former is the successive relea of monomer units from a chain end or at a weak link, which is esntially the rever of chain polymerization; ® it is often called deprop-agation or unzippering. This depolymerization begins at the ceiling temperature. Random degradation occurs by chain rupture at random points along the chain, giving a disper mix-ture of fragments which are usually large compared with the monomer unit. The two types of thermal degradation may occur parately or in combination; the latter ca is rather nor-mal. Chain depolymerization is often the dominant degradation process in vinyl polymers, whereas the degradation of condensation polymers is mainly due to random chain rupture.
