Some structure-property relationships in oriented polychloroprene

TEM Studies on Thin Films of Natural Rubber and Polychloroprene Crystallized under Molecular Orientation

“…Figure 4(a) is a typical example of the ED patterns obtained from the CR thin film, which was crystallized at -5°C under no strain (e=0¾). This pattern is fairly similar to the wide-angle X-ray diffraction pattern for unoriented CR which was reported in ref 9. In Figure 4(a), the most intense reflection ring is determined as 120 and/or 200, and other two weak rings of 210 and 220 are also observed outside the innermost 120( + 200) ring.…”

“…Figure 4(b) is the bright-field image, taken by the defocus contrast method, 22 of the same area in the CR thin film that was used to take the ED pattern ( Figure 4(a)). This figure shows that the texture in our specimen film is essentially similar to that in the films crystallized under no strain in ref 9. The texture in this figure is composed of three different kinds of domains, namely A-, B-, and C-domains which are indicated, respectively, with the arrows and letters A, B, and C. The A-domains correspond to sheaf-like structures, namely immature spherulites in which the "filaments" are oriented in the radial direction (in subsequent paragraphs, these "filaments" will be identified as edge-on lamellae).…”

“…The texture in this figure is composed of three different kinds of domains, namely A-, B-, and C-domains which are indicated, respectively, with the arrows and letters A, B, and C. The A-domains correspond to sheaf-like structures, namely immature spherulites in which the "filaments" are oriented in the radial direction (in subsequent paragraphs, these "filaments" will be identified as edge-on lamellae). A fully developed spherulitic texture is, however, not recognized in Figure 4(b) though binocularly developed twodimensional spherulites were clearly observed in the film fully crystallized under no strain in ref 9. The greater population density of crystallization nuclei (possibly, heterogeneous nuclei) and thereby less space for the sheaves (namely, immature spherulites) to mature in our case is deduced to be a probable reason, 21 because the size of the sheaves in Figure 4 Shorter crystallization time (7 h) in our experiment than that (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) h) in ref 9 might be another reason.…”

“…8 Similar morphological results were also reported for crystallized thin films of polychloroprene (CR). 9 However, there still remain some morphological subjects to be solved, such as to establish the identity of the a-and }'-filaments in NR and that of the corresponding filamentous entities in CR and to elucidate the mechanism in oriented crystallization at a given amount of strain ( e ).…”

“…8 Similar morphological results were also reported for crystallized thin films of polychloroprene (CR). 9 However, there still remain some morphological subjects to be solved, such as to establish the identity of the a-and }'-filaments in NR and that of the corresponding filamentous entities in CR and to elucidate the mechanism in oriented crystallization at a given amount of strain ( e ).In this article, morphological studies on the NR and CR thin films which are moderately prestretched outside and then crystallized inside a TEM column, in particular, establishing the identity of the "a-filaments'" in NR and that of the corresponding filaments in CR will be presented as preliminary results for our future work by in situ TEM observation of the oriented-crystallization process of rubbers. …”