No abstract

Organic–inorganic hybrid foams were prepared by using metakaolin or diatomite as a partial (or total) replacement of metakaolin, as precursor and metal silicon and whipped protein as blowing agents. The foamed systems were cured at defined temperature and time and then characterized by chemical point of view through Fourier transformed infrared spectroscopy and X-ray diffraction and by mechanical and morphological point of view by compression tests and scanning electron microscopy. The experimental findings highlighted that the replacement of diatomite in the formulation affected the morphological structure of the foams and consequently their mechanical properties, due to a different chemism between the sodium silicate and the solid phase. In particular, the consolidation mechanism in the diatomite based-hybrid foams changed from geopolymerization to a silicate polycondensation. Consequently, mechanical performances enhanced with increase of the diatomite content.

A vegetable tannin, a flavonoid-type natural polyphenolic compound, was used to promote the stabilization of polyurethane foams against UV radiation. Several polyurethane foams were synthesized by using an isocyanate, and a mixture of ethoxylated cocoalkyl amine and vegetable tannin. The content of vegetable tannin was varied from 0 to 40 wt %. The effects of tannin and water (used as a blowing agent) on the foaming kinetics and cellular morphology of foams were investigated. Samples were subjected to accelerated weathering under UV radiation for 3 to 24 h, and FTIR and DMA analyses were conducted to assess the performance change. The former analysis revealed a strong inhibiting effect of tannin on urethane linkage degradation during the UV treatment. The mechanical properties were significantly affected by the addition of tannin. The capability of the foams to withstand UV radiation was dependent on the amount of tannin. At tannin contents higher than 20%, the decrease in mechanical properties under UV irradiation was almost avoided.