The study investigated properties of particleboards resinated with PMDI modified with polyethylene glycols with varying molar masses (PEG 200 and 400). The conducted investigations showed that PMDI resin modification with both PEG 200 and PEG 400 causes an increase in mechanical properties of manufactured boards. In turn, modulus of elasticity decreases with an increase in plasticity of the modified resin. Then, water resistance of the tested boards, measured by their tear resistance after the boiling test, irrespective of the type and the amounts of applied modifiers, is very high and considerably exceeds the requirements specified in the respective standard. Particleboards exhibiting better mechanical properties and considerably improved water resistance may be obtained by the modification of PMDI resin with polyethylene glycol of a higher molar mass.

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