Molecular draw ratio

Affine deformation takes place when molecular draw ratio (MDR) = This is true in the... 

It has been shown that the elastic recovery in drawn HDPE can be a sensitive measure for the efficiency of draw (11,12). The correlations between this property and morphology (14) and tensile modulus (11) have been discussed. Thus, we measured thermally induced elastic recovery for each sample portion separated from the characteristic deformation components in the low and the high MW HDPE extruded at 90 and 110°C to EDR 12 and 25. When a drawn specimen was immersed and freely floated in a silicon oil bath kept at 160 C, the elastic shrinkage quickly occurred and completed within a few seconds. The shrinkage was evaluated in terms of % recovery (R) and molecular draw ratio (MDR) defined previously (11,12). 

However, the structure and properties of oriented polymers are characterised much more adequately by the molecular draw ratio mol [125]. The following expression relating and D to one another has been obtained [123] ... 

MDR molecular draw ratio MI/MO multi-input/ multi-output... 

Let us note that within the frameworks of the cluster model of polymers amorphous state structure [18] chains deformation in loosely packed matrix only is assumed and since the Eq. (4.42) gives molecular drawing ratio, which is determined in the experiment according to the relationship [81] ... 

FIGURE 7.2 The dependence of local overloading coefficient k, calculated according to the Eq. (7.3), on molecular draw ratio l j for UHMPE (1) and UHMPE/Al (2). The shaded region indicates literary values range [10]. 

The greatest molecular draw ratio is reached at complete orientation of chain between entanglements nodes and, hence, it corresponds to the conditions =1.0 and k = 1.0, as it has been noted above. In Fig. 7.2, the shaded region indicates literary values Q range for polyethylenes from Q = 5.4 [24] up to Q = 7.0 [25]. As one can see, exactly in this range of values max... 

Kozlov, G. V, Gazaev, M. A., Bloshenko, V. A., Varyukhin, V. N., Slobodina, V. G. (1995). Intercommunication of Molecular Characteristics and Molecular Draw Ratio for Oriented Polyethylene and Compositions on its Basis. Ukrainskii Fizicheskii Zhumal, 40(8), 883-886. 

However, the attempts to describe o - A curve for nanocomposite SBR-S with the help ofthe Eq. (A.3) were unsuccessful (see Fig. A. 1). Already at A = 3 the essential discrepaney of theory and experiment (theoretical result are lower than experimental) is observed and this diserepancy grows at A increasing. Let us note, that o calculation according to the Eq. (A.3) for SBR-S was earried out in two variants. The first used the nominal value A and the second used real (molecular) draw ratio determined according to the equation [12] ... 

Sadler and Barham (1990) also recorded the change in molecular draw ratio during the post-necking... 

Figure 9.21 Young s modulus of cold-drawn polyethylene as a function of the post-necking molecular draw ratio. The molecular draw ratio precisely after necking is close to 8. Drawn after data from Sadler and Barham (1990).

Most properties are strongly influenced by chain orientation. Birefringence, thermal expansivity, thermal conductivity and the elastic modulus depend on the Hermans orientation function according to relatively simple formulae. However, the elastic modulus of ultra-oriented polymers depends more directly on the macroscopic and molecular draw ratio. The latter reflects the extension of the end-to-end vector and the axial chain continuity. 

The definition of the molecular draw ratio may be illustrated as in Fig. 13.23. The molecular draw ratio (A) is defined, based on the notation used... 

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