Synergetic Enhancement of Mechanical Properties for Silk Fibers by a Green Feeding Approach with Nano-hydroxyapatite/collagen Composite Additive

ABSTRACT

In the current study, a novel intrinsic functionalization approach based on composite feeding additive for silkworms to produce silk fibers (SFs) with enhanced mechanical properties has been successfully developed. Effect of single feeding additive by either nano hydroxyapatite (Nano-HA) or collagen, and composite feeding by both additives on the silkworm larvae growth and cocooning, crystalline structure, molecular conformationas as well as mechanical properties of SFs have been systematically investigated. Experimental results demonstrated that feeding additive strategy could greatly facilitate the growth and cocooning of the silkworms. Surface and cross-section morphology observation suggested the additive has been absorbed into silkworm body and eventually embedded in SFs. Meanwhile, the basic structure of SFs still kept integrity after feeding additive from X-ray diffraction (XRD) analysis. Furthermore, fourier transform infrared (FTIR) spectrum demonstrated that random coil/α-helix and β-sheet content of SFs by feeding additive presented an increase and decrease change than natural SFs. More importantly, mechanical properties of SFs exhibited an obvious enhancement by composite additive than single additive feeding due to the nanoconfined crystallite toughening and polymer physical blending mechanism. Inspired by this approach, the composite additive feeding may open a novel and green strategy to fabricate SFs with enhanced mechanical properties.

摘要

在本研究中，一种新的基于复合饲料添加剂的功能化方法被成功地应用于蚕丝生产，以提高蚕丝的力学性能. 系统地研究了纳米羟基磷灰石（纳米-HA）和胶原单一饲料添加剂和复合饲料添加剂对家蚕幼虫生长、结茧、晶体结构、分子构象和力学性能的影响. 试验结果表明，饲料添加剂策略对家蚕的生长和结茧有很大的促进作用. 表面和横截面形貌观察表明，该添加剂已被蚕蛹吸收，并最终包埋在SFs中. 同时，X射线衍射（XRD）分析表明，添加添加剂后SFs的基本结构仍保持完整. 此外，傅立叶变换红外光谱（FTIR）分析表明，饲料添加剂对SFs的无规卷曲/α-螺旋和β-片含量的影响比天然SFs有增有减的趋势. 更重要的是，由于纳米晶粒的增韧作用和聚合物的物理共混机制，复合添加剂对SFs的力学性能有明显的提高. 受此启发，复合添加剂的加入为制备力学性能优良的SFs开辟了一条新的绿色途径.

KEYWORDS:

• Silk fibers
• nano hydroxyapatite
• collagen
• green feeding
• composite additive
• mechanical properties

关键词:

• 蚕丝纤维
• 纳米羟基磷灰石
• 胶原蛋白
• 绿色喂养
• 复合添加剂
• 机械性能

Acknowledgments

Z. Guo and Y. Chi contributed equally to this work.

Additional information

Funding

This work was supported by the National Key R&D Program of China (Grant 2018YFC1106400, 2018YFA0108200); National Natural Science Foundation of China (Grant 81671829); and Technology Program of Guangzhou (Grant 201803010086).