Development of high ductility and tensile properties by a two-stage draw of poly(acrylonitrile): Effect of molecular weight

✍ Scribed by Daisuke Sawai; Akira Yamane; Hiroshi Takahashi; Tetsuo Kanamoto; Masayoshi Ito; Roger S. Porter

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 265 KB
• Volume: 36
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(199803)36:4<629::aid-polb9>3.0.co;2-j

✦ Synopsis

Ultradrawing of atactic poly(acrylonitrile) (PAN) was investigated for a M v series, ranging 8.0 1 10 4 -2.3 1 10 6 . Samples for the draw were prepared from 0.5-30 wt % solutions of PAN in N,N-dimethylformamide. The solutions were converted to a gel by quenching from 100 to 0ЊC. The dried gel films were initially drawn uniaxially by solid-state coextrusion (first-stage draw) to an extrusion draw ratio (EDR) of 16, followed by further tensile draw at 100-250ЊC (second-stage draw). The maximum total draw ratio (DR t ,max ) and tensile properties achieved by two-stage draw increased remarkably with sample M v . Other factors affecting ductility were the solution concentration from which gel was made and the second-stage draw temperature. The effects of these variables became more prominent with increasing M v . The temperature for optimum second-stage draw increased with sample M v . Both the initial gel and the drawn products showed no small-angle X-ray long period scattering maximum, suggesting the absence of a chain-folded lamellae structure, which had been found in our previous study on the drawing of nascent PAN powder. The chain orientation function ( f c ) and sample density ( r s ) increased rapidly with DR t in the lower range (DR t õ 30) and approached constant values of f c Å 0.980-0.996 and r s Å 1.177-1.181 g/cm 3 , respectively, at higher DR t ú 30-100. The tensile modulus also showed a similar increase with DR t . The tensile strength increased linearly with DR t , reaching a maximum, and decreased slightly at yet higher DR t . The highest modulus of 28.5 GPa and strength of 1.6 GPa were achieved with the highest M v of 2.3 1 10 6 .