Tie chain

The formation of the microstructure involves the folding of linear segments of polymer chains in an orderly manner to form a crystalline lamellae, which tends to organize into a spherulite structure. The SCB hinder the formation of spherulite. However, the volume of spherulite/axialites increases if the branched segments participate in their formation [59]. Heterogeneity due to MW and SCB leads to segregation of PE molecules on solidification [59-65], The low MW species are accumulated in the peripheral parts of the spherulite/axialites [63]. The low-MW segregated material is brittle due to a low concentration of interlamellar tie chains [65] and... 

Usually, crystallization of flexible-chain polymers from undeformed solutions and melts involves chain folding. Spherulite structures without a preferred orientation are generally formed. The structure of the sample as a whole is isotropic it is a system with a large number of folded-chain crystals distributed in an amorphous matrix and connected by a small number of tie chains (and an even smaller number of strained chains called loaded chains). In this case, the mechanical properties of polymer materials are determined by the small number of these ties and, hence, the tensile strength and elastic moduli of these polymers are not high. 

According to Hosemann-Bonart s model8), an oriented polymeric material consists of plate-like more or less curved folded lamellae extended mostly in the direction normal to that of the sample orientation so that the chain orientation in these crystalline formations coincides with the stretching direction. These lamellae are connected with each other by some amount of tie chains, but most chains emerge from the crystal bend and return to the same crystal-forming folds. If this model adequately describes the structure of oriented systems, the mechanical properties in the longitudinal direction are expected to be mainly determined by the number and properties of tie chains in the amorphous regions that are the weak spots of the oriented system (as compared to the crystallite)9). 

However, the use of this method on an industrial scale is cumbersome and the question arises whether it is reasonable to form the fibre and then melt it, in order to change its structure completely. Is it not better to form a structure with a great number of tie chains required for the attainment of high strength at once during crystallization of the melt ... 

In conclusion, the fundamental features of various methods for obtaining high strength systems from flexible-chain polymers should also be mentioned. Since the presence of ECC leads to an increase in the fraction of tie chains in crystallized samples (their number can be increased by other methods not related to a direct formation of ECC, e.g. by orientational drawing investigated by Marikhin and Myasnikova4)), the main tech-... 

Amorphous material often produces tie chains that connect two or more different crystals. These tie chains increase the properties of the solid resin by forming a temporary three-dimensional crosslinked system. As the resin is melted in an extruder, the crystals and the tie chains are destroyed, and the polymer acts like a... 

In these expressions, the subscript AB denotes the intrafibrillar amorphous tie-chains, AI the interfibrillar tie-chains and X is the volume fraction of the inter-fibrillar tie-molecules. 

It must be that iodine is sorted to be much condensed in the amorphous layers, and a substantial number of which participate in the complex formation, while in the interfibrillar space the soaking solution may take up part of the water which existed before soaking, and complex formation is hardly expected there. The increase in the SAXS intensity of the long spacing peak in Fig. 3 seems to support the condensation of the iodine in the amorphous layers. This means that most of the complex form in the amorphous layers with participation of tie chains. The change of Young s modulus of the specimens takes place so slowly that it lasts for 10 hours, which is related to some reinforcement of the chain networks due to the release of water and complex formation. 

This relation is not applicable to our heterogeneous network. We may, however, assume that the average molecular weight of tie chains may be larger in larger D.H. films than in smaller D.H. films as discussed in Sect. 2.1. This makes us suppose that the parameter A may depend on the freedom of tie chains in the... 

Furthermore, it is reasonable to assume that a tie chain whose freedom of movement is highly restricted by crystal interfaces can hardly form a helix to surround a polyiodine for making a complex. These considerations and expert-... 

In Sect. 2, a double network structure was proposed for the PVA films in the water-swollen state, i.e. an amorphous chain (tie chain) network and a fibrillar network. The blue color complex is considered to be formed mostly in the former network. Subsequently what happens in PVA films during soaking in aqueous solutions were discussed. The contractions of the volume and the long... 

In practice the structure of any given polymer sample is by no means as regular as the above classification would imply and in most cases defies description in terms of recognizable structural elements. For example, Wunderlich64 shows examples of cobweb structures which can be found in polymers. Clearly, for the purposes of research specific structures have been identified and studied - but this does not mean that a regular solid of macroscopic dimensions may be contracted with these structures. In polymers therefore, we always have to deal with statistical assemblies of elements more or less precisely defined as e.g. lamellar crystal, fibrous crystals, tie chains etc. 

Modulus. Jackson et al. (1) calculate the contribution of amorphous material to the shear modulus of a semicrystalline polymer by assuming that only tie chains (chains whose ends are attached to different crystallites) contribute to the modulus and that these chains follow Gaussian statistics. They assume that the chains deform affinely. The predicted modulus values are lower than the observed values. The... 

The most extensive ESR studies of polymers under tensile load have undoubtedly been carried out on drawn crystalline fibres, and this work has been reviewed recently by Kausch and De Vries It is clear that the morpholines of oriented crystalline fibres, with extensive tie-chain populations and hn d rees of molecular uncoiling, strongly favour the incidence of molecular hracture under tensile stress. 

Fig. 19. (A) Distributitm of tie chain lengths (B) correqwndiiig histogram for radical production (after Ref.

---