Abstract: Polyurethane, as an emerging organic synthetic polymer material, is known as the "fifth largest plastic" and is widely used in chemical, electronics, textile, medicine, construction, automobile, and many other fields because of its excellent performance. Polyurethane is broadly categorized as solvent-based one, water-based one and solvent-free one. Traditionally produced polyurethane is mostly solvent-based one. Solvent-based polyurethane seriously jeopardizes the physical and mental health of producers because of the addition of organic solvents such as N,N dimethylformamide and acetone to the production process, and the presence of residual organic solvents in the finished product may also be harmful to the physical and mental health of consumers. And water-based polyurethane replaces organic solvents with water, solving the problem of solvent pollution. However, because of the existence of hydrophilic groups, the coating's water resistance decreases, which makes it easier to dissolve abd affects the mechanical properties. Meanwhile, the water evaporation is slow, resulting in a long drying time and heavy energy consumption. Solvent-free polyurethane (reactive polyurethanes) solves the above problems of polyurethane by virtue of the absence of solvent incorporation. Mechanical properties are an important index of coatings, and it is necessary for the article to investigate the effect of hydroxyl silicone oil on the mechanical properties of solvent-free polyurethane coatings.
     Polyurethane coatings with high strength, high-temperature thermal stability, low-temperature resistance, hydrophobicity, and softness were comprehensively designed. Diphenylmethane diisocyanate and 1,3 propylene glycol were used as hard segments, and poly(tetrahydrofuran ether diol), castor oil, and bis-hydroxy-capped polydimethylsiloxane (PDMS) were used as soft segments. The two-component method was used for prepolymerization, followed by mixing, scraping, and reaction molding. A series of solvent-free polyurethane coatings were synthesized by partially replacing castor oil with PDMS, and the effects of PDMS content on the mechanical and thermal properties, low-temperature resistance, hydrophobicity, and feel of the coatings were investigated. The effect of hydroxyl silicone oil on the mechanical properties of polyurethane was investigated in a solvent-free system. The tensile strength and elongation at break of reactive polyurethane (Si-PU) coatings modified by silicone were effectively enhanced, with a maximum increase of 51.9% in tensile strength and 99.3% in elongation at break. With the increase in PDMS mass fraction, the mixing degree of soft and hard segments of Si-PU increased, and the degree of microphase separation weakened. As the mass fraction of PDMS increased, Tmax moved toward high temperature, and the thermal stability of the coating was enhanced; the glass transition temperature (Tg) of the coating gradually decreased, and its low-temperature resistance was significantly improved; at the same time, the hydrophobicity was improved, and the handfeel became softer, thus the serviceability was improved.
    The silicone-modified polyurethane coating prepared by the above method overcomes the shortcomings of solvent-based polyurethane and water-based polyurethane, and at the same time, its breaking strength, elongation at break, high-temperature thermal stability, low-temperature resistance, hydrophobicity, and softness have been improved to a certain extent. As the national requirements for environmental protection in the chemical industry become higher and higher, further research on solvent-free polyurethane technology is expected to be more in-depth and comprehensive in the future, so that it can be more widely used in various industries.

Key words: reactive polyurethane, coating, organosilicon, solvent free, microphase separation

摘要： 为改善聚氨酯(PU)材料的力学性能，以聚四氢呋喃醚二醇、蓖麻油、双羟基封端聚二甲基硅氧烷(PDMS)为软段，二苯基甲烷二异氰酸酯(MDI)为硬段，采用绿色环保的无溶剂体系制备了有机硅改性的反应性聚氨酯(Si-PU)涂层，考察了PDMS质量分数对PU涂层的拉伸强度、断裂伸长率、高温热稳定性、耐低温性能、手感等的影响。结果表明：与未改性PU涂层相比，Si-PU涂层的拉伸强度、断裂伸长率均得到明显提升。当PDMS质量分数为7.6%时，改性涂层的拉伸强度较未改性PU涂层增长了51.9%；当PDMS质量分数为9.9%时，改性涂层的断裂伸长率较未改性PU涂层增长了99.3%；随着PDMS质量分数提高，质量损失速率最大的温度有一定提高，涂层的玻璃化温度逐渐降低，耐低温性能提高，同时疏水性提高，手感变得更加柔软，综合性能得到显著改善。

关键词: 反应性聚氨酯, 涂层, 有机硅, 无溶剂, 微相分离