No abstract

Triple centrifuged natural rubber (NR) film was crystallized at room temperature by uniaxial drawing at draw ratio (l) 6.0. Morphologies of the induced crystals were studied by wide angle X-ray diffraction (WAXD). Using a special drawing apparatus for shifting the X-ray beam positions, crystalline orientation was surveyed all over the drawn sample. WAXD results show the biaxial orientation (BO) with the c-axis being parallel to the draw direction and the a-axis parallel to the film surface. By means of the WAXD pattern with the incident beam perpendicular to the film, the drawn NR film was separated into three regions: (200 þ 120) region indicating a low degree of BO, (200) region having a high degree of BO, and the intermediate region in between the above two regions. The degree of BO is enhanced from center to the clamping end depending on the increment of the sample width. At lower draw ratios (4.0 , l , 6.0), BO was developed with increasing draw ratio. In the intermediate region, BO increases sharply with a small increment of the width. The degree of BO is lowered at the periphery of the film.

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

No abstract

No abstract