同步辐射对SAXS和WAXS技术研究聚（ε-己内酯）单轴拉伸变形的影响,Macromolecules

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同步辐射对SAXS和WAXS技术研究聚（ε-己内酯）单轴拉伸变形的影响
Macromolecules ( IF 5.1 ) Pub Date : 2012-11-01 00:00:00 , DOI: 10.1021/ma301714f
Tahseen Kamal ₁ , Tae Joo Shin ₂ , Soo-Young Park ₁

Affiliation

聚（ε-己内酯）（PCL）在25°C单轴拉伸变形过程中的结构演变使用小角度和广角X射线散射（SAXS和WAXS）技术同时进行应力和应变（S–S）检验曲线。最近升级的浦项同步加速器辐射源上的高能X射线束揭示了PCL的完整层状变形行为。S-S曲线的基于坡度的划分显示了三个不同的弹性区域（区域I），屈服区域（区域II）和塑性变形（区域III）。在显示出弹性变形的区域I中，WAXS图案是各向同性的，而SAXS图案由于沿拉伸方向的无定形链的伸长而变得扁圆。在显示屈服变形的区域II中，WAXS图案显示出轻微的方向，而由于链折叠薄片同时断裂和熔化（导致形成四点样式）以及随后形成的链扩展薄片，SAXS样式显示出从扁形到四点和六点模式的变化。（沿子午线再增加两个最大值）。在区域III中，WAXS模式显示了PCL晶体取向的发展，而SAXS模式显示了两点模式。在区域II和III中新形成的扩链薄片可能会产生网络结，可以将施加的力传递到PCL晶体上以增加取向。过去在单轴拉伸变形实验中未观察到或报道过PCL II区的六点图案。

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Uniaxial Tensile Deformation of Poly(ε-caprolactone) Studied with SAXS and WAXS Techniques Using Synchrotron Radiation

The structural evolution of poly(ε-caprolactone) (PCL) during uniaxial tensile deformation at 25 °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.

更新日期：2012-11-01

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