Production method of toughened polyurethane film

Abstract

The invention provides a production method of a toughened polyurethane film. The production method of the toughened polyurethane film comprises the following steps of (1) producing a casting solution,wherein a poor solvent of polyurethane, N,N-dimethylformamide and a solvent with polarity lower than that of the N,N-dimethylformamide are mixed to form a ternary mixed solvent, and then vacuum defoamation is conducted after a polyurethane prepolymer and the ternary mixed solvent are stirred evenly by a machine so as to produce the polyurethane casting solution; (2) producing a coagulation bath;(3) conducting blade coating on the polyurethane casting solution to coat a mold with the polyurethane casting solution; (4) conducting thermal treatment on the mold in an environment at 40-80 DEG C for 30-60 s; (5) sequentially conducting immersion precipitation and solvent evaporation treatment on the mold; and (6) conducting thermal treatment on a polyurethane film at 80-100 DEG C to obtain thetoughened polyurethane film. According to the production method of the toughened polyurethane film, the poor solvent of the polyurethane, the N,N-dimethylformamide and the solvent with polarity lowerthan that of the N,N-dimethylformamide are adopted, and are mixed to form the ternary mixed solvent system, and the polyurethane film formation speed and a distribution mode of polyurethane moleculechains are improved, so that the polyurethane film excellent in mechanical performance is obtained.

Description

technical field [0001] The invention relates to the technical field of polymer film preparation, in particular to a method for preparing a toughened polyurethane film. Background technique [0002] Polyurethane is a block polymer composed of alternating soft and hard segments. The soft segment is in a highly elastic state at room temperature and can produce large tensile deformation, while the hard segment provides nodes for the elongation and deformation of the soft segment. The unique chemical structure of polyurethane makes it have excellent properties such as high elasticity, abrasion resistance, solvent resistance, water resistance, fatigue resistance and aging resistance, so it is widely used in textile, national defense, transportation, sports, construction, medical, Fields such as machinery and energy occupy a very important position in the national economy. [0003] At present, the commonly used methods for preparing high-tough polyurethane films include chemical m...

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Problems solved by technology

Although this method uses ammonium salt as a coagulation bath, the micro-crosslinked structure formed in the form of hydrogen bonds between the ammonium salt molecules in the polyurethane film after film formation and the amorphous region molecules in the polyurethane, or in the pores of the polyurethane film The formation of nano-needle structure and nano-spherical structure can increase the tensile stress and strain of the polyurethane film at the same time, but its disadvantage is that on the one hand, the toughening range of the polyurethane film prepared by this method is not large enough; The polyurethane film prepared by the method introduces the second phase material, not a single-component pure polyurethane film

However, its shortcoming is that the toughening effect of this method on polyurethane is not significant enough, and the film-making method adopted in this article does not give full play to the excellent structure and performance of polyurethane bulk material

[0009] The public doctoral thesis "Research on the Phase Transformation Control Mechanism and Performance of High Tough Polyurethane and Its Composite Materials" was published in April 2018. In this doctoral thesis, different proportions of N,N-dimethylformamide and toluene were used as mixed solvents. The polyurethane film has been prepared, although it uses a binary mixed solvent of different components to toughen the polyurethane, but its disadvantage is that this method has no effect on the toughening of the polyurethane film while improving the elongation at break of the polyurethane. Significantly, no greater limit for toughened polyurethane membranes

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