Uniaxial Tensile Deformation of Poly(ε-caprolactone) Studied with SAXS and WAXS Techniques Using Synchrotron Radiation
Uniaxial Tensile Deformation of Poly(ε-caprolactone) Studied with SAXS and WAXS Techniques Using Synchrotron Radiation
复制标题
DOI：
10.1021/ma301714f
复制
发表时间：
2012-11-13
期刊：
影响因子：
5.5
通讯作者：
Park, Soo-Young
中科院分区：
文献类型：
--
作者：
Kamal, Tahseen;Shin, Tae Joo;Park, Soo-Young
采用小角和广角x射线散射（SAXS和WAXS）技术研究了聚e-己内酯（PCL）在25℃单轴拉伸变形过程中的结构演变。在最近升级的浦项同步辐射源上的高能x射线束揭示了PCL的完全层状变形行为。基于坡度的S-S曲线划分显示了三个不同的区域：弹性（区域I）、屈服（区域II）和塑性变形（区域III）。在具有弹性变形的I区，由于非晶态链沿拉伸方向的伸长，WAXS的模式是各向同性的，而SAXS的模式则是扁圆形的。在屈服变形的II区，WAXS模式表现出轻微的定向，而SAXS模式则表现出由扁圆形到四点和六点的变化，这是由于链折叠片层同时破碎和融化（导致四点模式）以及随后形成的链延伸片层（沿子午线又增加了两个最大值）。在III区，WAXS模式显示了PCL晶体的取向发展，而SAXS模式显示了两点模式。II区和III区新形成的延伸链片可能产生网络结，可以将施加的力转移到PCL晶体上以增加取向。在过去的单轴拉伸变形实验中，没有观察到或报道过PCL II区的六点模式。这可能是由于在机械制图过程中使用同步辐射快速获取x射线模式。
The structural evolution of poly(e-caprolactone) (PCL) during uniaxial tensile deformation at 25 degrees C Was examined using small- and wide angle X-ray scatterings (SAXS and WAXS) techniques with simultaneous stress and strain (S-S) curves. A high-energy X-ray beam at the recently upgraded Pohang synchrotron radiation source revealed the complete lamellar deformation behavior of PCL. Slope-based division of the S-S curves indicated three distinct regions of elastic (region I), yielding (region II) and plastic deformations (region III). In region I, which showed elastic deformation, the WAXS patterns were isotropic, whereas the SAXS patterns became oblate due to elongation of the amorphous chains along the draw direction. In region II, which showed yielding deformation, the WAXS patterns showed a slight orientation, whereas the SAXS patterns exhibited a change from oblate to four point and to six point patterns due to the simultaneous fragmentation and melting of the chain-folded lamellae (leading to the four-point pattern) and the subsequent formation of chain-extended lamellae (adding another two maxima along the meridian). In region III, the WAXS patterns revealed the development of the orientation of PCL crystals, whereas SAXS patterns exhibited a two-point pattern. The newly formed chain-extended lamellae in regions II and III might produce network junctions that can transfer an applied force to the PCL crystals for increased orientation. The six-point pattern in region II for PCL was not observed or reported in the past during the uniaxial tensile deformation experiment. This might be due to fast acquisition of the X-ray patterns during mechanical drawing using synchrotron radiation.