Chain contour length between

The first molecular variable to be considered is chain entanglement density. It is known that this factor, as well as a related parameter, viz. the average chain contour length between entanglements, can have an appreciable effect on deformation modes observed in thin films and on various aspects of crazing such as the craze stress and the craze fibril extension ratio. Examples of these effects will be presented and dis-... 

As the chain contour length between physical entanglements is reduced, so too is the maximum craze fibril extension ratio, Provided the entanglement network remains intact upon straining, X is given by... 

Figure 8.5. Schematic showing fine structure within domains for an IPN. The solid black circles represent crosslinks. The distance between phase domains is less than half the chain contour length between crosslinks in the network, thus permitting phase separation to occur. At the same time, some network segments provide the requisite interconnection between the phase domains.

Effective molecular mass between crosslinks tvtc/kg mol 1 Tensile yield strength cry/MPa Energy release rate Gic/Jm 2 Half crack opening displacement w = 6/2 = Gic/2cry w/pm Chain contour length (Eq. 7.9) lc/nm... 

The chain contour length 1 between entanglements is given by le = lo Me/Mo... 

In Eq. (29.23) W 0) is the distribution of constraints among different points along the network chain and 0 = i/n is the position of the /th segment of the chain as a fraction of the contour length between two crosslinks. If the distribution is uniform, then W 0) = 1 inside the integrand of Eq. (29.23). In the case when constraints are assumed to affect only fluctuations of junctions (as in the constrained-junction theory), 0 is limited to 0 = 0 or 0 = 1 only. [95] It is important to note that this theory does not reduce identically to the constrained-chain theory, because the latter characterizes the deformation-dependent fluctuations of the centers of mass of the chains and not the deformation-independent fluctuations of the midpoints [95]. 

X 10 N and the value obtained by the simplest form, 1.45 X 10 " N m n = 918 and a = 0.31 nm for Equation 21.1). These comparisons imphed that the measurements were consistent with the theoretical predictions. The deviation between the rupture length of 260.9 nm and the fitted-contour length indicated that the polymer chain was not fully stretched at the rupture event. The reason for this was that the rupture event was a stochastic process and was dependent on many factors such as pulling speed, bond strength, and temperature. The vahdity of the freely jointed (FJC) model (dashed fine) was also checked ... 

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