Scientific studies have focused on environmentally friendly solutions as effective as the reuse of crop products owing to plastic-waste problems in recent years. This issue is the main driving force for upcoming academic research attempts in waste valorization-related studies. Herein, we integrated an aqua-waste, mussel shell (MS), as a bioadditive form into green thermoplastic polyurethane (TPU) green composites. Tuning of the MS surface was performed to achieve strong adhesion between composite phases. The surface functionalities of MS powders were evaluated via infrared spectroscopy and scanning electron microscopy (SEM) images. Composite samples were prepared by melt-compounding followed by injection molding techniques. It was confirmed by morphological analysis that relatively better adhesion between the phases was achieved for composites involving surface-modified MS compared to unmodified MS. Tensile strength and Young’s modulus of surface-modified MS-filled composites were found to be higher than those of unmodified MS, whereas the elongation at break shifted to lower values with MS inclusions. The shore hardness of TPU was remarkably improved after being incorporated with silane-treated MS (AS-MS). Stearic acid-treated MS (ST-MS) additions resulted in an enhancement in the thermal stability of the composites. Thermo-mechanical analysis showed that the storage moduli of composites were higher than those of unfilled TPU. ST-MS additions led to an increase in the characteristic glass transition temperature of TPU. Melt flow index (MFI) of neat TPU was highly improved after MS loading regardless of modification type. According to the wear test, surface modification of MS displayed a positive effect on the wear resistance of TPU. As the water absorption data of the composites were evaluated, the TPU/AS-MS composite yielded the lowest water absorption. The silane layer on MS inclusion promoted water repellency of composites due to the hydrophobicity of silane. The results of the biodegradation investigation demonstrated that adding unmodified and/or modified MS to the TPU matrix increased the biodegradation rate. The test results at the end of a 7-week period of biodegradation with a soft-rot fungus implied that the composite materials were more biodegradable than pure TPU. Silane modification of MS exhibited better performance in terms of the characterized properties of TPU-based composites.

Graphical abstract

中文翻译：

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通过水性废物的增值，有效利用贻贝壳作为 TPU 绿色复合材料的生物添加剂

近年来，由于塑料废物问题，科学研究重点关注与农作物产品再利用一样有效的环保解决方案。这个问题是即将进行废物增值相关研究的学术研究尝试的主要驱动力。在此，我们将水产废物贻贝壳 (MS) 作为生物添加剂形式整合到绿色热塑性聚氨酯 (TPU) 绿色复合材料中。对 MS 表面进行调节，以实现复合相之间的强粘附。通过红外光谱和扫描电子显微镜 (SEM) 图像评估 MS 粉末的表面功能。复合材料样品通过熔融复合和注射成型技术制备。通过形态分析证实，与未改性的 MS 相比，涉及表面改性 MS 的复合材料在相之间实现了相对更好的粘附。研究发现，表面改性的 MS 填充复合材料的拉伸强度和杨氏模量高于未改性的 MS，而断裂伸长率随着 MS 夹杂物的变化而降低。与硅烷处理的MS（AS-MS）结合后，TPU的肖氏硬度显着提高。添加硬脂酸处理的 MS (ST-MS) 可以提高复合材料的热稳定性。热机械分析表明复合材料的储能模量高于未填充的TPU。ST-MS 的添加导致 TPU 的特征玻璃化转变温度升高。无论改性类型如何，纯 TPU 的熔体流动指数 (MFI) 在 MS 加载后均得到显着改善。根据磨损测试，MS的表面改性对TPU的耐磨性表现出积极的影响。在评估复合材料的吸水率数据时，TPU/AS-MS 复合材料的吸水率最低。由于硅烷的疏水性，MS 夹杂物上的硅烷层提高了复合材料的防水性。生物降解研究的结果表明，在 TPU 基质中添加未改性和/或改性的 MS 可提高生物降解率。使用软腐真菌进行为期 7 周的生物降解后的测试结果表明，该复合材料比纯 TPU 具有更高的生物降解性。MS 的硅烷改性在 TPU 基复合材料的特性方面表现出更好的性能。

图形概要