含两种异形二氧化硅填料的紫外光可固化聚氨酯柔性透明耐磨涂层的制备及性能

Preparation and properties of flexible,transparent,wear-resistant,and ultraviolet-curable polyurethane coating containing two heteromorphic silica fillers

以2~4μm的氮化硼(BN)和异丙醇配制成为3 g/L的BN溶液,在200 W功率的超声中振荡24 h,再先后以4 000 r/min离心10 min和8 000 r/min离心10 min,取上层清液将BN剥离。用少量的盐酸多巴胺和三羟甲基氨基甲烷包覆剥离后的BN,再以正硅酸乙酯(TEOS)生成纳米球沉积在BN片上,形成类似铠甲片的微纳结构耐磨剂(BN–SiO_(2)),随后与自制枝芽状二氧化硅粉体(L-SiO_(2))耐磨剂按照一定比例混合,加入自制柔性透明紫外光可固化聚氨酯(UV-PU)中,考察该复合粉体对聚氨酯涂膜透过率、柔韧性、耐磨性、热稳定性等性能的影响,并与商用柔性耐磨涂料进行了比较。结果表明:在复合粉体的总添加量固定为4%时,涂层的耐磨性和铅笔硬度随着BN–SiO_(2)与L-SiO_(2)质量比的增加而上升,透明性和韧性都呈下降趋势,BN–SiO_(2)与L-SiO_(2)的最佳质量比为3:2。BN–SiO_(2)与L-SiO_(2)耐磨剂协同使用,不仅增强了填料与基体树脂的界面作用,而且由于线形的L-SiO_(2)起到衔接片状BN–SiO_(2)的作用,形成了类似铠甲的结构,使复合涂层的耐磨性和柔韧性都得到了明显提升。在上述最佳条件下得到的UV-PU/BN–SiO_(2)/L-SiO_(2)复合涂层有高达7H的铅笔硬度,在1000g载荷下以60 r/min转500次后的质量损失为3.1 mg,抗折弯次数达到2 417次,在可见光波段的平均透过率为90.3%。在模拟柔性屏实际应用测试中,该复合涂料表现出比国内多种市售柔性屏涂料更为优异的耐磨性和耐折性,实现了透明、柔韧和耐磨3种性能的平衡。

A solution containing 3 g/L of boron nitride(BN,2-4μm in size)was prepared with isopropyl alcohol as solvent,and then ultrasonicated at a power of 200 W for 24 hours.The BN flakes formed thereby was separated from the clear upper liquid after centrifugation at 4000 r/min for 10 min and at 8000 r/min for 10 min successively.The stripped BN flakes were covered with a small amount of dopamine hydrochloride and tris(hydroxymethyl)aminomethane,and then deposited with nanospheres by using tetraethyl orthosilicate(TEOS),forming a wear inhibitor BN–SiO_(2) with a micro-nano structure similar to an armor sheet.The BN–SiO_(2) flakes were blended with a homemade wear-resistant dendritic powder L-SiO_(2) in different proportions,and the mixture was then added as a composite wear-resistant filler to a homemade flexible,transparent,and ultraviolet-curable polyurethane(UV-PU).The properties such as transmittance,flexibility,wear resistance,and thermal stability of the UV-PU coating containing the composite wear-resistant filler were examined and compared with those of some commercial counterparts.The results showed that the wear resistance and pencil hardness of the coating with 4%of the composite wear-resistant filler were increased with the increasing of the mass ratio of BN–SiO_(2) to L-SiO_(2),while the transparency and toughness were decreased.The optimal mass ratio of BN–SiO_(2) to L-SiO_(2) was determined to be 3:2.The coordination of BN–SiO_(2) and L-SiO_(2) not only enhances the interfacial compatibility between the filler and resin matrix,but also greatly improves the wear resistance and flexibility of the composite coating due to the formation of a armor-like structure brought from the bridging effect of the linear L-SiO_(2) between the BN-SiO_(2) flakes.The UV-PU/BN–SiO_(2)/L-SiO_(2) composite coating prepared under the optimized conditions had a pencil hardness of 7H,a weight loss of 3.1 mg after abrasionwith a load of 1000 g at 60 r/min for 500 cycles,and an average transmittance of 90.3%within the visible light wavelength range,and could endure 2417 times of bending.It showed superior resistance to abrasion and bending in a simulated application test for flexible screen as compared with the commercially available coatings in China,achieving a balance of transparency,flexibility,and abrasion resistance.