343 nm飞秒激光制备微孔阵列以增强聚氨酯合成革透湿性

为了提高聚氨酯(PU)合成革透湿性，分别使用343 nm飞秒激光和作为对比的1030 nm飞秒激光及1064 nm纳秒激光制备微孔阵列。采用扫描电镜(SEM)和3D激光扫描显微镜对比研究了微孔形貌。结果表明，343 nm飞秒激光可以制备出效果最佳的微孔。此外，分析了3种激光与PU涂层的作用机理，揭示了343 nm飞秒激光合成革微钻孔过程仅表现为光化学烧蚀，光化学和光热烧蚀同时发生于1030 nm飞秒激光钻孔过程，而1064 nm纳秒激光只显示了光热烧蚀。激光合成革表面钻孔后，测量其透湿性和抗张力。结果显示: 微孔密度越大，皮革透湿性(WVP)越大而抗张力越低，脉冲重叠的增加会导致WVP的增加和抗张力的下降；同时，随着脉冲重叠从91.7%降到50%，微孔直径从45 μm降低到30 μm，而微孔锥度从0.7°增加到12.1°；当脉冲重叠率为91.7%，微孔密度为2550/cm2时，最大的WVP增长率为306%。

Improving water vapor permeability of polyurethane synthetic leather by drilling micro-hole arrays with 343 nm femtosecond laser

In this paper, 343 nm femtosecond laser and as a comparison, 1030 nm femtosecond and 1064 nm nanosecond lasers were used for improving water vapor permeability (WVP) of polyurethane (PU) synthetic leather. The morphologies of micro-hole were comparatively studied via a scanning electron microscope (SEM) and a 3D laser scanning microscope. The results indicated that 343 nm femtosecond laser was optimal to obtain excellent and small drilled micro through-holes. Moreover, analysis of interaction mechanism between laser beam and PU film revealed that the micro-drilling by 343 nm femtosecond laser exhibited photochemical ablation only, micro-drilling by 1030 nm femtosecond laser caused both photochemical and photothermal ablation, while micro-holes drilled by 1064 nm nanosecond laser resulted in photothermal ablation. By measuring the WVP and tensile resistance of the laser-drilled leather, it was concluded that the higher micro-hole density, the higher WVP value and lower tensile resistance, and the increase of pulse overlap led to an increase of WVP and a decrease of tensile resistance. The diameter of micro-hole decreased from 45 μm to 30 μm and taper of micro-hole increased from 0.7° to 12.1° with pulse overlap decreased from 91.7% to 50%. And, the highest WVP growth ratio was 306% at 2550 per sq. cm and the pulse overlap was 91.7%.