Biaxial Orientation Mechanism of Drawn Natural Rubber. II. Quantitative Analysis of the Biaxial Orientation

Abstract

Natural rubber film was prepared from triple centrifuged latex. The film was uniaxially drawn at room temperature and the induced crystalline orientation was quantitatively studied by wide angle X-ray diffraction. The intensity distribution of 200 and 120 reflections confirmed that the induced crystals have a biaxial orientation with the c-axis parallel to the draw direction. The orientation of the a-axis was evaluated by using an orientation function of the (200) plane. The function (F 200 ) indicated that the crystalline a-axis is parallel to the film surface depending on the draw ratio and on positions in the film. The experimental results are possible to explain by shish-kebab-like crystallization developed from a highly oriented fibril. The secondary crystallization grows perpendicularly to the draw direction along the a-axis. The population of the secondary crystals is controlled by an ellipsoidal free space. The shape of the ellipsoid is changed by the fibril distribution depending on width and thickness of the sample film. In this study, the quantitative biaxial orientation is consistently explained by the shish-kebab-like crystallization and the ellipsoidal free space. IntroductionIn the previous article, [1] we made a qualitative analysis of the biaxial orientation (BO) of uniaxially drawn natural rubber (NR) film. The features of BO are summarized as follows:(1) uniaxial drawing of bulk NR film at room temperature resulted in the appearance of BO of the induced crystals with the c-axis parallel to the draw direction and a-axis parallel to the film surface; (2) the degree of BO increased toward the clamping end, having correlation with the increment of the sample width; (3) the degree of BO also increased with the draw ratio.In this article, the degree of BO is quantitatively evaluated by using an orientation function. The intensity distributions of the 200 and 120 reflections were measured precisely by rotation of the film around the draw direction. The orientation function of

Biaxial Orientation Mechanism of Drawn Natural Rubber. I. Appearance of the Biaxial Orientation

“…We will make further quantitative analyses in the following article. [21] The resulting film width of Sample-1 is listed in Table 1. The (200) region appears when the width is larger than 4.0 mm.…”

Biaxial Orientation Mechanism of Drawn Natural Rubber. IV. The Effect of Aspect Ratio

“…9. [8] From the nuclei of the PF, SC are developed by the shish kabab-like transcrystallization mechanism.…”

“…7. [8] The point of R th ¼ 1 corresponds to p/q ¼ 2. As shown in Figure 7, the shape of the ellipsoid is determined by the evaluated value of p/q.…”

“…The observed BO was quantitatively evaluated using the orientation function of the (200) plane, F 200 . Finally, the results of BO were explained by a free space model for the primary and secondary crystallization: [8] 5. The theoretical F 200 was calculated as a function of the ratio of radii, (p/q), of the ellipsoid, where p and q are the radii parallel and perpendicular to the sample film surface, respectively.…”