The increase of the aromatic ring density in the Pu segment increases the rigidity of the segment and increases the intermolecular force, so that the thermal decomposition temperature of the polymer increases. Oxazolidinone can be synthesized from isocyanate groups with epoxy groups, the thermal decomposition temperature of 300 ℃ or more. The isocyanurate ring is an isocyanate trimerization product, and there is no unstable hydrogen atom and amide structure on the heterocycle, which makes it have good thermal stability. The polyimide is formed by the condensation polymerization of an acid anhydride and a diamine, which decomposes in air at a temperature of 400 to 450C, a decomposition temperature in N is 2400 to 500C, and an imide ring is introduced into a polyurethane material In the hard segment, the C = O content increases, increasing the hydrogen bonding between -NH and C = O and weakening the interaction between the hard segment -NH and the soft segment -O-, so that the interaction between the hard segments is enhanced, The hydrogen bond between the soft segment and the hard segment is deteriorated, and the degree of phase separation is increased, thereby improving the heat resistance of the polyurethane.
    Lu Liang, who through the bulk polymerization, synthesis of a new type of naphthalene-containing biphenyl structure of the PU plastic, the normal temperature shear strength of not less than 20MPa, with a high T (170 ~ 200 ℃), in a nitrogen atmosphere 250 ℃ without weight loss, g10% heat loss temperature of 300 ℃, and has a strong acid, hydrolysis resistance. The adhesive is suitable for use in high temperature environments.
    Solemnity and others through the introduction of high heat resistance and hydrolysis resistance of the structural unit to improve the molecular softening point, a reasonable control of intermediate indicators and other means to improve the resistance of PU plastic heat and humidity stability. The adhesive can be resistant to high temperature cooking at 135 ℃. With its production of composite bags PET / Al / CPP built by 135 ℃ cooking 40min, the bag is still intact.
    Petrova studied the borane-containing PU glue and found that only 20% of the total mass loss was heated to 600 ° C, while the loss of PU glue without borane was 80%. Russian scientists use kaplan to modify the polyurethane, made for steel, titanium, brass and steel bonded BK-20 adhesive, the use of temperature 500 ~ 800 ℃, up to 800 ~ 1000 ℃.
    Add filler
    PU glue to add the appropriate filler can reduce the shrinkage stress and thermal stress, thereby enhancing its heat resistance. Due to the interaction of organic and inorganic parts in the polyurethane to form a unique interfacial effect and synergistic effect, this material has higher thermal and oxygen stability. The interaction between the organic phase and the inorganic phase can be divided into two categories: the first type is organic and inorganic phase through the weak bond such as hydrogen bond, van der Waals force and electrostatic interaction, the other is the organic phase and The inorganic phase is bonded by covalent bonding. Commonly used fillers (such as glass fiber, mica, etc.), powders (such as cellulose, silica, aluminum oxide, etc.), sheet materials (such as talc), bulk materials (such as barite) and nanoparticles Or functional nanoparticles.
    SebastianClauβ and so on in the one-component PU glue by adding 30% of the volume of chalk, glued joint heat stability was significantly improved. B.S.Kim, respectively, with hydrophobic and hydrophilic groups modified two kinds of nano-silica enhanced UV curing polyurethane emulsion, found that with the increase in nano-silica, the degradation rate of polyurethane, especially hardened degradation of the temperature increase. Lee et al. Studied waterborne polyurethane / clay nanocomposites, and found that the higher the heat resistance of the system was.
    In the preparation and use of polyurethane adhesives should be fully understand the relationship between its structure and performance, according to the purpose and requirements of the rational design. At present, the development of new heat-resistant polyurethane adhesive, research and development of new synthetic technology, new additives and the corresponding mechanism of research has become the focus of polyurethane research.