Inter-crystalline links

Figure 3.21 Sketch of inter-crystalline links near the surface of a growing spherulite. (a) Plan view of lamellar faces (b) edge view of the lamellae.

These materials tend to be very brittle because, although they are highly crystalline, there are few inter-crystalline linking molecules. Figure 5.9 shows an electron micrograph of a replica of a fracture surface of extended-chain crystalline material of polychlorotrifluoroethylene. The lamellae are about 1-2 pm thick and there appears to be no limit on the lateral dimensions of the crystallites except space and availability of material. 

The linking macromolecules, having more or less strength conformations, traverse the inter-crystalline domains. Under the deformation conditions, these ones gradually adopt stretched conformations, are tensioned, and suffer the homolytical splitting. Therefore, under the creep fatigue conditions, the fracture process is directly influenced not by the applied stress but the induced deformation. An important effect is played by the increase of solicitation rate, due to the fact that the stress duration becomes comparable with the relaxation time. The overtensioned macromolecules are not able... 

This has the same form as Eq. (7.1) the renamed constants are a Young s modulus , and a viscosity 17. It is not possible to directly link these constants to the modulus of the crystalline phase and the viscosity of the amorphous inter-layers in a semi-crystalline polymer. Hence, the Voigt model is an aid to understanding creep, and relating it to other viscoelastic responses, rather than a model of microstructural deformation. 

Noncoplanar aromatic monomers, such as 2,2 -disubstituted biphenylene derivatives and 4,4 -functionalized 1,1 -binaphthyl derivatives (Fig. 14) have been used as comonomers in para-linked aromatic polyesters with remarkable effects on the phase transition temperatures, the crystallinity, and the solubility. The incorporation of these noncoplanar monomers will not initially reduce the chain stiffness. The phenyl rings are forced by the 2,2 -substitution into a noncoplanar conformation which strongly decreases the intermolecular inter-... 

Of course, inter- and intramolecular electron transport cannot be rigorously separated from each other. For example, intermolecular electron passage is facilitated by molecular chains being in a high state of order. Thus, the specific conductivity of crystalline poly(acetylene) is four orders of magnitude higher than for the amorphous polymer. The electronic conductivity of amorphous polymers is promoted by molecular cross-linking. 

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