formulation of two-component solvent-free polyurethane adhesive there are also many kinds, such as:
① more terminal nco prepolymers are used as component a, and component b is polyol or polyol/polyamine compound, similar to the cast polyurethane elastomer system;
②more a mixture of oligomer polyols such as polyether polyols and additives constitute component a, and component b uses low molecular weight polyisocyanate such as papi;
③polyether polyol and additives (including fillers, etc.) constitute component a, containing nco's polyether polyurethane prepolymer is used as component b. these two-component solvent-free polyurethane adhesives can be used to bond solvent-sensitive substrates such as polystyrene, plexiglass, etc., can be used as potting glue for electronic components, and can be used as bonding sealant, etc. here are some recipe examples.
【example1]
composed of phthalic anhydride, adipic acid, ethylene glycol, 1,2-propanediol , branched polyester prepared from trimethylolpropane is used as component a, with a viscosity of about 3.1 pa·s. use papi as component b.
a. mix component b according to the calculated proportion, stir vigorously and mix well , vacuum to remove bubbles, and leave it at room temperature for a week to stabilize the performance, and obtain a polyurethane cured product with a hardness above shore a90 and a tensile strength of about 10mpa.
【example2]
polyester diol is prepared from phthalic anhydride, adipic acid, ethylene glycol, diethylene glycol and catalyst. add a small amount of small molecule diol and coupling agent to the polyester diol and mix evenly to obtain component a. a castor oil polyurethane prepolymer with an nco content of about 3.3% is prepared from castor oil and excesstdi (or mdi).
component a/component b is prepared at a mass ratio of 1/(1~2). the tensile strength of the cured product can reach 10.7mpa, and the elongation can reach 450 %, good temperature resistance. the pot life of the formulated adhesive is approximately 5 hours. the glue can be used in industries such as composite films, cement bags and shoemaking industries.
【example3]
prepolymer is synthesized from dehydrated polyether polyol and polyisocyanate, nco at 9% ~13%, as component a. the dehydrated and dried polyol, various fillers and catalysts are ground evenly to form a uniform and stable paste as component b. the two components are mixed according to a certain ratio and cured at room temperature for 5 hours to achieve higher strength.
there are also polyester polyol as a component and polyether polyol-mdi prepolymer as a component, which are used for composite film adhesives and other purposes.
