X-ray Diffraction: An Efficient Method to Determine Microfibrillar Angle of Dry and Matured Cellulosic Fibers

ABSTRACT

Cellulose is a naturally occurring unbranched polymer containing microfibrils in the secondary cell wall of the plant fibers oriented at an angle called Microfibrillar Angle (MFA) with respect to the fiber axis. This important structural parameter influences the mechanical behavior and the tensile properties of these fibers and eventually their composites. This study discloses the technique to determine the mean MFA of dry and matured cellulosic fibers extracted from Cocos nucifera fruit by X-ray diffraction from the peak diffraction intensity and the values are compared statistically with the MFA obtained from the strain-induced during the tensile test. The mean MFA value of the fibers obtained using the X-ray diffraction technique is 27.32 ± 0.41°. This value is in accordance with the MFA value (29.91 ± 1.51°) obtained using the global strain equation and the slight disparity could be attributed to the non-uniformity of the fiber cross-section and the external pulling forces that could cause reorganization of amorphous and crystalline contents in the cell wall. This technique is simple, inexpensive, and fairly accurate with no cumbersome processing.

摘要

纤维素是一种天然存在的无支链聚合物，含有植物纤维次生细胞壁中的微纤维，其方向与纤维轴成一个角，称为微纤维角（MFA）. 这一重要的结构参数影响这些纤维的力学行为和拉伸性能，并最终影响其复合材料. 本研究公开了用X射线衍射法从椰子果实中提取的干纤维和成熟纤维素纤维的平均MFA的测定方法，并将其与拉伸试验中应变得到的MFA值进行了统计比较. 用X射线衍射技术得到的纤维的平均MFA值为27.32±0.41°. 这个值与用整体应变方程得到的MFA值（29.91±1.51°）相一致，这种微小的差异可能是由于纤维横截面的不均匀性和可能导致细胞壁中非晶态和晶体成分重组的外力所致. 这种方法简单、廉价、准确，无需繁琐的加工.

KEYWORDS:

• Cocos nucifera fibers
• matured cellulose fibrils
• X-ray diffraction
• tensile testing
• microfibrillar angle
• global strain equation

关键词:

• 椰子纤维
• 成熟纤维素纤维
• X射线衍射
• 拉伸试验
• 微纤丝角
• 整体应变方程

Acknowledgements

The authors are thankful to the retired Tamil Nadu State Government Forest Engineering Division Selection Grade Senior Draughting Officer, Mr. A. Balasubramanian, for his help in sample preparation and testing.