Production principle of polyurethane insulation board and distinction
polyurethane insulation board very not bad mainly lies in his density and crispness. In general, 4 - 5 cm of polyurethane board density around 40, such as polyurethane board with high altitude, it is not easy deformation, bibulous rate is lower, heat preservation effect is good. Some manufacturers in order to reduce costs, save raw material density adjustment to the 30 or so, such a cubic less 10 kg, the weight of the single chip products looks no difference, but after time of precipitation, low density polyurethane board will & other; Shrink & throughout; 。 What is a shrink? To say for a long time in the sun, high temperature environment, polyurethane plate deformation, becomes rugged, also some 4 original shrink into 3 cm or 2 cm thickness. 5cm。 As everybody knows, polyurethane foam need high temperature, so some people use heat to do a special low density polyurethane plate, but always can not stand the test of time! Again the high temperature will be asked to show his true colors.
sheet as our price cheap, but really not an option. Building is one hundred, repeated construction not only cost is high, and did a lot of inconvenience to the life of people.
in the process of the preparation of waterborne polyurethane plate, it is the main reaction of isocyanate with reaction, which contains the active hydrogen compounds, and isocyanate intermolecular and some other crosslinking reaction and the reaction. Chemistry is based on isocyanate polyurethane board based on chemical reactions. The organic isocyanate compound containing a highly unsaturated isocyanate group ( - NCO, structured to - N = C = O) And chemical properties of particularly lively.
it is generally believed that isocyanate polyurethane board base charge distribution is as follows, the resonance structure is: the electronic because of oxygen and nitrogen atoms on the electron cloud density is larger, the electronegativity is bigger also, - Oxygen atoms of NCO group electronegativity, the largest as the nucleophilic center, with compounds containing active hydrogen molecules on the reaction and the generated hydroxyl hydrogen atoms, but of the hydroxyl groups on the unsaturated carbon atoms is very unstable, will rearrange for carbamate ( When the reactants is alcohol) Or urea base ( When the reactants is amine) 。
due to the electron cloud density on the lowest carbon atoms, thus rendering strong electropositive, as electrophilic center, and vulnerable to the attack of the nucleophilic reagent. Isocyanate react with active hydrogen compounds, it is because the active hydrogen compounds intramolecular nucleophilic center attack - NCO based on carbon atoms.
( 1) The reactive group - isocyanate NCO can with active hydrogen of polyester polyol, polyether polyol, the reaction of organic silicon, which thus can introduce organic silicon in the pre polymers, which improves the performance of the polyurethane board.
( 2) Isocyanate react with active hydrogen compounds is due to the molecules of the active hydrogen compounds - nucleophilic center attack NCO based carbon atoms.
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