Spherulitic deformation

Such theories may be used to determine the degree of spherulite deformation from experimental patterns, and have been used for interpreting rates of deformation from light scattering motion pictures. They have been used more recently for explaining the results of dynamic light scattering measurements where samples are subjected to an oscillatory strain. ... 

The theories of spherulite deformation have been based upon the model of a perfect spherulite. The change in patterns accompanying deformation are undoubtedly affected by truncation and by internal disorder. The effect of these has been investigated. ... 

Samuels has also observed spherulite deformation for these poly-... 

Erhardt P, Stein RS. A technique for the study of spherulite deformation Light scattering movies. J Polym Sci 1965 3B 553-555. 

Calculation of the Orientation Distribution Function from the Spherulite Deformation Model 470... 

Figure 14 Change in uniaxial orientation distribution function of the crystal grains, w(, 0, rj), with extension ratio of the spherulite, calculated from the spherulitic deformation model...

Stage I Continuous deformation of the spherulitic structure before the neck ... 

At very small strains within the viscoelastic region (e<0.5%), deformation within the PP solid is confined to disordered amorphous regions [97,98) due to their inherently low stiffness at temperatures above their Tg (-10 °C). In this deformation region, spherulites undergo affine deformation on the whole. Inside the spherulites, rotation of lamellae occurs [101]. The resulting orientation of lamellae depends on their position within the spherulite in respect to the orientation of the external deformation [102-104],... 

Our findings in regard to the effects of deformation on PTFE accord in some respects with observations on the deformation of polyethylene " and polypropylene, although PE and PP usually have a spherulitic morphology before drawing. 

Another technique used for obtaining macroscopically polar films involves mechanical extension of the material. Uniaxial plastic deformation induces a destruction of the original spherulitic structure into an array of crystallites in which the molecules are oriented in the deformation direction. In case of PVF2 when such deformation takes place below 90 °C the original tg+ tg chains are forced into their most extended possible conformation which is all-trans [32]. 

Such information offers an opportunity to study details of the fibrillation mechanism. The fibers formed by stretching the spherulitic polymer representing nothing other than ribbon formations plastically deformed and oriented towards the mechanical stress that is released by comparatively weak mutual interconditions existing in an earlier formation (Figure 3). This behavior points to the existence of some weak surfaces in the crystalline polymers. Elements of the super-molecular structure detached by action of the external mechanical forces can slide on the weak surfaces. Evidence for the strain-destruction relationship must come from studies of the modification of the contact surfaces of two neighboring spherulites under mechanical stress. 

Rupture occurs without important plastic deformation when the ribbons of some neighboring spherulitic formations show a parallel orientation in the contact zone. Conversely, considerable elongation occurs when the orientation is normal at the contact limit because of plastic deformation of the ribbons (Figures 4 through 6). 

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