Gubała Dajana, Harniman Robert, Eloi Jean-Charles, Wąsik Patryk, Wermeille Didier, Sun Lili, Robles Eric, Chen Meng, Briscoe Wuge H
School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK; Bristol Centre for Functional Nanomaterials, HH Wills Physics Laboratory, University of Bristol, Bristol, BS8 1TL, UK.
J Colloid Interface Sci. 2020 Jul 1;571:398-411. doi: 10.1016/j.jcis.2020.03.051. Epub 2020 Mar 14.
Thermal through-air bonding process and slip additive treatment affect fibre surface structure and nanomechanical properties, which is extremely difficult to characterise on a single-fibre level.
Optical microscopy (OM) was applied to study the effect of air-through bonding, spunbonding, and crimping on fibre geometry and general appearance. A "spray-on" method developed here using a custom-designed fibre holder allowed a direct measurement of static contact angles of water droplets on single fibres. Scanning electron microscopy (SEM) showed different morphological features on the fibre due to the nonwoven fabric-making process and additive treatment. Synchrotron X-ray diffraction (XRD) was applied to study the effect of erucamide presence on polypropylene (PP) fibre crystal structure. Atomic force microscopy (AFM) imaging provided complementary characterization of fibre topographic features such as average surface roughness, along with adhesion force mapping by quantitative nanomechanical (QNM) AFM imaging.
Our results show the effect of nonwoven making process and surfactant additive treatment on the fibre surface structure and nanomechanical properties. Wettability experiment on the single fibre revealed the hydrophobic nature of all the synthetic fibres. For polyethylene/polyethylene terephthalate (PE/PET) bicomponent single fibres, the polyethylene sheath was found to possess fibrillar microstructure - typical for drawn fibres, whereas the fibres entangled in nonwoven fabrics exhibited a uniform, porous surface morphology attributed to the through-air process. Adhesion force mapping allowed us to correlate fibre nanomechanical properties with its topography, with surface pore interiors showing higher adhesion than the flat polyethylene region. Furthermore, on the polypropylene (PP) fibre surface treated with erucamide (13-cis-docosenamide; a common slip additive used in polyolefin film processing), we observed overlapping multilayers consisting of 4 nm erucamide bilayers, attributed to the slip additive migration onto the fibre surface. XRD measurements of the fibres did not detect the presence of erucamide; however, AFM imaging provided evidence for its migration to the fibre surface, imparting influence on the surface structure and adhesive properties of the fibre. Single-fibre AFM imaging also allowed a detailed analysis of different surface roughness parameters, revealing that both through-air bonding in the nonwoven making process and the slip additive (erucamide) treatment affected the fibre surface roughness. The wettability, surface morphology, and adhesion properties from this study, obtained with unprecedented resolution and details on single fibres, are valuable to informing rational design of fibre processing for fibre optimal properties, critically important in many industrial applications.
热穿透式空气粘合工艺和爽滑添加剂处理会影响纤维表面结构和纳米力学性能，而在单纤维水平上对其进行表征极为困难。
采用光学显微镜（OM）研究穿透式空气粘合、纺粘和卷曲对纤维几何形状和总体外观的影响。本文开发的一种“喷涂”方法，利用定制设计的纤维固定器，可以直接测量水滴在单根纤维上的静态接触角。扫描电子显微镜（SEM）显示，由于非织造布制造工艺和添加剂处理，纤维呈现出不同的形态特征。同步加速器X射线衍射（XRD）用于研究芥酸酰胺的存在对聚丙烯（PP）纤维晶体结构的影响。原子力显微镜（AFM）成像提供了纤维形貌特征的补充表征，如平均表面粗糙度，同时通过定量纳米力学（QNM）AFM成像进行粘附力映射。
我们的结果显示了非织造布制造工艺和表面活性剂添加剂处理对纤维表面结构和纳米力学性能的影响。单纤维润湿性实验揭示了所有合成纤维的疏水性质。对于聚乙烯/聚对苯二甲酸乙二酯（PE/PET）双组分单纤维，发现聚乙烯皮层具有原纤状微观结构——这是拉伸纤维的典型特征，而在非织造布中缠结的纤维呈现出均匀的多孔表面形态，这归因于穿透式空气工艺。粘附力映射使我们能够将纤维纳米力学性能与其形貌相关联，表面孔隙内部显示出比平坦的聚乙烯区域更高的粘附力。此外，在用芥酸酰胺（13-顺式二十二碳酰胺；聚烯烃薄膜加工中常用的爽滑添加剂）处理的聚丙烯（PP）纤维表面，我们观察到由4纳米芥酸酰胺双层组成的重叠多层结构，这归因于爽滑添加剂迁移到纤维表面。对纤维的XRD测量未检测到芥酸酰胺的存在；然而，AFM成像提供了其迁移到纤维表面的证据，这对纤维的表面结构和粘附性能产生了影响。单纤维AFM成像还允许对不同的表面粗糙度参数进行详细分析，结果表明非织造布制造工艺中的穿透式空气粘合和爽滑添加剂（芥酸酰胺）处理均会影响纤维表面粗糙度。本研究以前所未有的分辨率和单纤维细节获得的润湿性、表面形态和粘附性能，对于为获得纤维最佳性能而进行纤维加工的合理设计具有重要价值，这在许多工业应用中至关重要。
