The main composition and classification of TPU material




The main composition of TPU material:

According to the chemical structure, TPU belongs to the block copolymer, the soft segment is usually composed of polyester or polyether segment, commonly used polyester polyol, polyether polyol, polycarbonate diol, polysiloxane diol and polycaprolactone with hydroxyl at both ends, polylactic acid, hydroxyl-terminated polybutadiene and the like. The hard segment of polyurethane includes the urethane and chain extender part of the molecular chain, and a variety of diisocyanates and polyureas are commonly used. Due to the composition of the soft segment and the hard segment of a wide variety of monomers, can be condensed into different hardness and performance and use of TPU.

Because the hard segment of TPU is incompatible with the soft segment in terms of polarity and interfacial properties, TPU is easy to form a microscopic phase separation structure, the hard segment usually has a strong polarity, and it is easy to form hydrogen bonds between them. In addition, the crystallization of the hard segment also leads to phase separation, and the micro-domain structure generated by phase separation is the fundamental reason why TPU becomes a thermoplastic elastomer.

In general, the soft segments form a continuous phase, imparting elasticity to the TPU, while the hard segments act as a physical crosslinking point and reinforcing filler. When heated to the melting point or dissolved by the solvent, this physical crosslinking point disappears, and can be processed by thermoplastic processing technology or form a uniform solution. After cooling or solvent volatilization, the soft and hard segments are re-phase separated to form a crosslinked network, thereby restoring elasticity.

classification of tpu material:

TPU is classified according to different standards. According to the soft segment structure, it can be mainly divided into polyester type and polyether type, which contain ester group, ether group and butylene group respectively. According to the hard segment structure, TPU is divided into urethane type and urethane urea type, which are obtained by diol chain extension or diamine chain extension respectively.

According to the process is divided into bulk polymerization and solution polymerization. In bulk polymerization, it can be divided into pre-polymerization method and one-step method according to the presence or absence of pre-reaction. The pre-polymerization method is to react diisocyanate with macromolecular diol for a certain period of time and then add chain extender to generate TPU, and the one-step diisocyanate and macromolecular diol and chain extender are mixed and reacted at the same time to generate TPU. Solution polymerization is to dissolve diisocyanate in solvent first, then add macromolecular diol to make it react for a certain time, and finally add chain extender to generate TPU.

Application of TPU material in electronic digital accessories:

TPU material is widely used in the manufacture of protective sleeves in mobile phones. The general process is injection molding, and the surface treatment process is UV varnish after electroplating. However, in the process of surface treatment of TPU material, if a mold release agent is used in the injection molding process, resulting in oil stains such as mold release agent on the surface of TPU material, oil spots and oil spots will appear on the surface after electroplating with varnish oil, and the adhesion of 100 cells will not pass. The method of soaking and removing oil with white electric oil is mostly used in the industry, but it is dangerous and inefficient. The effective method is to spray TPU treatment agent developed by Yangsheng treatment agent on the surface of the material to cover the oil stain, improve the adhesion of the coating, and solve the defect problem caused by the oil stain on the surface.