Organoclay nanoparticles interaction in PU:PMMA IPN foams: Relationship between the cellular structure and damping-acoustical properties

Abstract

The present article seeks to characterize open-cell flexible interpenetrating polymer network (IPN) foams with a polyurethane-polymethylmethacrylate (PU-PMMA) ratio of 75:25 comprising organoclay nanoparticles. The effects of different nanoclay contents ranging from 0.3% to 1.5% (wt) in PU:PMMA (75/25) IPNs were investigated on mechanical properties such as storage modulus, loss modulus, and Tan delta. Thermal properties were also examined in a wide range of temperature using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), flow resistivity analyses determined that the optimized content of nanoclay leads to highest air permeability. The scanning electron microscopy (SEM) results showed semi-spherical micro-cell formed in the frame of foams using nanoclay below 1 mm in average diameter. The interaction between nanoclay and polymeric IPN chains observed in dynamic mechanical thermal analysis (DMTA) can be attributed to increases in the storage modulus in the neighborhood of Tg. Moreover, increasing and optimizing the percentage of nanoclay in IPNs widened the range of Tan δ peaks. An IPN containing 1.2% wt of nanoclay corresponded with the highest storage modulus and the widest peak of Tan δ. TGA thermograms also confirmed that thermal stability is directly proportional to the percentage of nanoclay in IPNs. The results revealed air permeability from IPN samples have been increased with increasing the amount of nanoclay and also, air permeability enhancement leads to a reduction of sound waves reflection and an increase of sound waves absorption. The sound absorption coefficient has been increased with the presence of the nanoclay.The results showed that sound absorption experiments attributed the interaction between nanoclay hydroxyl groups and urethane bonds of IPN to the higher sound absorption of IPNs. Furthermore, an IPN with 1.2% wt of nanoclay showed the best mechanical properties and highest sound absorption over the measured frequency ranges.