Abstract In order to efficiently protect plastic cover of 5G mobile phones, a novel hyperbranched polyurethane acrylate-based hard coating (HBPUA) having highly rigid hyperbranched cores was prepared and used as the protective film. For purpose of researching the structure and property relationship, two more hyperbranched cores (Hyper-6OH) and corresponding HBPUA oligomers were also synthesized. The structures of Hyper-6OH and HBPUA were characterised by proton nuclear magnetic resonance, and the molecular weight of HBPUA was confirmed by gel permeation chromatography. To further enhance the crosslinking and lower the internal stress, pentaerythritol tetra(3-mercaptopropionate) (PETMP) was introduced into the film system. The curing behaviours of the prepared HBPUA coatings were determined by Fourier-transform infrared spectroscopy. The results indicated that the double bond conversion was associated with the rigidity of the hyperbranched core and the content of thiol groups. The properties of HBPUA-based films were characterized by the test of gel content, swelling ratio and water absorption and as well as dynamic mechanical property, mechanical property, thermogravimetry and surface property. The results reveal that the pencil hardness of the prepared coatings reaches 5H that is higher than the commercially available resin PUA-6, enabling potential application in the protection of plastic cover. The rigidity of the hyperbranched cores and the introduction of PETMP remarkably affect the Tg value of the films, and the addition of thiol groups increases the gel content, swelling ratio, toughness and adhesion of coatings, but decreases the water absorption and tensile strength. Moreover, all coatings exhibit good thermal properties.

中文翻译：

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紫外光固化超支化聚氨酯丙烯酸酯硬涂层的制备及性能

摘要 为了有效保护5G手机的塑料外壳，制备了一种具有高刚性超支化核的新型超支化聚氨酯丙烯酸酯基硬涂层（HBPUA），并将其用作保护膜。为了研究结构和性能关系，还合成了另外两个超支化核（Hyper-6OH）和相应的HBPUA低聚物。Hyper-6OH和HBPUA的结构通过质子核磁共振表征，HBPUA的分子量通过凝胶渗透色谱法确定。为了进一步增强交联并降低内应力，将季戊四醇四（3-巯基丙酸酯）（PETMP）引入薄膜体系中。制备的HBPUA涂层的固化行为通过傅里叶变换红外光谱测定。结果表明，双键转化与超支化核的刚性和硫醇基团的含量有关。HBPUA基薄膜的性能通过凝胶含量、溶胀率和吸水率的测试以及动态力学性能、力学性能、热重和表面性能的测试进行表征。结果表明，所制备涂层的铅笔硬度达到5H，高于市售树脂PUA-6，在塑料盖保护方面具有潜在应用。超支化核的刚性和PETMP的引入显着影响薄膜的Tg值，硫醇基团的加入增加了涂层的凝胶含量、溶胀率、韧性和附着力，但降低了吸水率和拉伸强度。