Characterization of Natural Cellulosic Fiber Obtained from the Flower Heads of Milk Thistle (Silybum marianum) as a Potential Polymer Reinforcement Material

ABSTRACT

Natural fibers are being investigated as alternatives to synthetic fibers in composite materials. In this paper, the physical, chemical, thermal, and morphological characteristics of fibers derived from milk thistle flower heads were characterized as potential polymer reinforcement material using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The fibers were found to contain 42.9% cellulose, 21.2% hemicellulose, and a negligible lignin content. The fiber constituent functional groups were similar to those observed for other natural fibers. The crystallite size and the crystallinity index were found to be 2.23 nm and 84 ± 3%, respectively. The thermal stability of the fibers was found to be 220°C. The fibers start rapidly degrading above 290°C. Morphologically, the fibers appeared to have a nonporous surface with well-structured longitudinal parallel grooves. Cross sectionally, the fibers consisted of multiple hollow lumens interconnected with cell walls. The hollowed nature of the fibers explains the low value (0.33 ± 0.04 g mL⁻¹) of their density. The tensile strength of the fibers was determined to be 22 ± 1 MPa. In conclusion, the fibers of the flower heads of milk thistle can be used as effective reinforcements in polymer matrices.

摘要

天然纤维作为合成纤维在复合材料中的替代品正在被研究中. 本文利用傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）、热重分析（TGA）和扫描电子显微镜（SEM），对乳蓟花头纤维的物理、化学、热学和形态特征进行了表征，认为其是一种潜在的聚合物增强材料. 发现纤维含有42.9%的纤维素、21.2%的半纤维素和可忽略不计的木质素含量. 纤维组成官能团与观察到的其他天然纤维的组成官能团相似. 晶粒尺寸和结晶度指数分别为2.23 nm和84 ± 3%. 发现纤维的热稳定性为220°C. 纤维在290°C以上开始迅速降解. 从形态上看，纤维表面无孔，具有结构良好的纵向平行凹槽. 横截面上，纤维由多个与细胞壁互连的中空管腔组成. 纤维的中空特性解释了其密度的低值（0.33 ± 0.04 gmL − 1）. 纤维的抗拉强度测定为22 ± 1MPa. 总之，乳蓟花头的纤维可以作为聚合物基质中的有效增强剂.

KEYWORDS:

• Natural fiber
• cellulose
• polymer enforcement
• characterization
• chemical analysis
• Silybum marianum

关键词:

• 天然纤维
• 纤维素
• 聚合物强制执行
• 刻画
• 化学分析
• 水飞蓟

Acknowledgements

The authors would like to thank Eng. Rawan Hayajneh from the Nanotechnology Institute at JUST for her help in acquiring the SEM images. The authors are also grateful to Ramzi Munaiem for conducting the FTIR experiments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Highlights

• For the first time, fibers from the flower heads of milk thistle were characterized and identified as a potential polymer reinforcement material.

• The fibers obtained from the flower heads of milk thistle were found to have some favorable morphological properties, including having a longitudinally grooved surface, the presence of thorny anchors on the fiber sides, and the hollowed structure of the fibers that would enhance the anchoring of the fibers in polymer composites.

• The fibers obtained from the flower heads of milk thistle were found to have a low density, making it suitable for light weight applications.

Additional information

Funding

This research received funding from the Deanship of Scientific Research at the Jordan University of Science and Technology under grant number 20220605.