Fibrillar structures, development

Dry spinning generates a fiber that initially appears different from typical wet-spun fibers as there is no opportunity for the spin bath to diffuse into the fiber. However, when the unoriented dry-spun fiber is stretched, an oriented fibrillar structure develops, indistinguishable from a stretched wet-spun fiber. Hence, all acrylic fibers, whether dry- or wet-spun are fundamentally similar. 

The neck is more or less fully developed and a fibrillar structure is obtained. This structure is less susceptible to degradation because of its high degree of orientation and high crystallinity. This explains the drop and then levelling off of the carbonyl content in this latter stage. 

When the slurry ages, the pH rises, and, consequently, the viscosity rapidly elevates, there appears to be a breakdown in the mechanism that binds the solid particles in the silica matrix. With a well-developed sol, this behavior is more controllable. We believe that, at longer aging times, the microgel development proceeds by mechanisms more favorable to a finely textured, fibrillar structure (19). Hence, catalysts bound with this gel are more attrition resistant. We suggest that the dependence of attrition on slurry age/viscosity may be a consequence of an inhibition to forming a strong matrix. The most important conclusion that can be drawn from... 

Another interesting question relates to the problem of cellular differentiation. The fact that undifferentiated cells contain their contractile protein in a nonstructured form might lead to the speculation that this represents the state of a precursor of the structured actomyosins in the course of cellular development. Actually, this does not seem to be true. Holtzer et al. (1957) working with fluorescent antimyosin antibodies were able to show that, whenever myosin appears in the cellular protoplasm of the chicken embryo myoblasts, it does so already incorporated into a fibrillar structure. 

Drawn fibrillar morphology (developed when a spherulitic polymer is stretched below its melting point and the original lamellar crystallites are fragmented and rearranged into an oriented fibrous structure) (29)... 

In practice, a short gauge length. 10 mm for a 2 mm thick specimen of unidirectionally reinforced material, or 25 mm for a 4 mm thick fabric or mat reinforced specimen, is most frequently used. A framework has been developed in order to rationalize the many test methods and the even greater number of loading fixtures jigs. The final failure will frequently be by local microbuckling. or kinking, of bundles of fibers. A similar failure occurs in individual carbon and aramid fibers, which have a fibrillar structure. 

Different types of crystalline structures develop Fibrillar or extended-chain crystals and lamellar crystalhtes. Development of the first mentioned stractures is an equilibrium process. We do not have an amorphous phase since both segments and chains are ordered. Extended-chain crystals develop only in polymers of low molecular mass M < 10 kg/mol) and in the range of low undercoolings, that is AT = T - T is small. 

In case of ionized Na-form of the sorbent globular structure disappears and developed fibrillar structure may be observed. 

Well developed fibrillar structures were formed when the polymerization was carried out with M0CI5 [27], whereas PPP aggregates of indefinite shape were observed with FeCE as catalyst. The formation of the fibrils was interpreted as resulting from simultaneous polymerization and crystallization, and was attributed to the fact that benzene reacts with polyphenylene chain ends aligned on the crystalline surface of already precipitated PPP [27]. In the case of FeCl3, the crystallinity of the PPP is less pronounced, and it was suggested that benzene could form polyphenyl side-chains or polynuclear structures, which would prevent the formation of the fibrillar structures [24]. 

---