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

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.

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

“…5 summarizes the ID patterns of the 200 and 120 reflections as a function of f. As a result of BO, the intensity of the 200 reflection decreases, while that of the 120 reflection increases, with f. The ID patterns indicate that BO becomes sharper from positions to . This fact confirms the results observed in the previous article [1] by the qualitative analysis of the WAXD. It is possible to calculate the F 200 from the ID patterns.…”

“…For the longer distances (17 -23 mm), F 200 became 0.75 -0.85, saturated to the clamping position at 24mm. An increment of F 200 with respect to the sample width is consistent with the qualitative analysis in the previous article [1]. …”

“…The precise sample preparation was described in the previous article. [1] In the present experiment, we used the same sample, named Sample-1. The original gauge length, width, and thickness of Sample-1 were 8, 8, and 1 mm, respectively.…”

“…The ID pattern clearly demonstrates that 200 and 120 reflections are sharply distributed, having an opposite trend as shown in the previous article. [1] The ID indicates that rubber crystals have BO where the crystalline a-axis is preferentially aligned parallel to the film surface at position .…”

“…In 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:…”