Polymer Science

Rigid polyurethane (PU) foams were successfully filled with different weight ratios of melamine (1 wt%, 5 wt%, 10 wt%), silica (0.1 wt%) and ionic liquid, 1-Ethyl-3-methylimidazolium chloride, [EMIM]Cl (0.3 wt%). The aim of this study was to improve the flame retardancy of PU foams and to develop the synergistic effect between melamine, silica and ionic liquid on the flame-retardant PU foams. The influence of different loadings of the fillers was examined. The results showed that in comparison with unfilled foam, all modified compositions are characterized by higher density (41–46 kg m−3), greater compression strength (134–148 kPa), and comparable thermal conductivity (0.023–0.026 W m−1 K−1). Moreover, the reaction to fire of the PU composites has been investigated by the cone calorimeter test. The results showed that the fire resistance of PU foams containing as little as 1 wt% of melamine is significantly improved. For example, the results from the cone calorimeter test showed that the incorporation of the melamine, silica and ionic liquid significantly reduced the peak of heat release rate (pHRR) by ca. 84% compared with that of unmodified PU foam. SEM results showed that incorporated fillers can form an intumescent char layer during combustion which improves the reaction to fire of the composite foams.

Polyurethane (PU) composite foams were successfully reinforced with different concentrations (1 wt%, 2 wt%, 5 wt%) of nutmeg filler. The effect of nutmeg filler concentration on mechanical, thermal, antimicrobial and anti-aging properties of PU composite foams was investigated. PU foams were examined by rheological behavior, processing parameters, cellular structure (Scanning Electron Microscopy analysis), mechanical properties (compression test, impact test, three-point bending test, impact strength), thermal properties (Thermogravimetric Analysis), viscoelastic behavior (Dynamic Mechanical Analysis) as well as selected application properties (thermal conductivity, flammability, apparent density, dimensional stability, surface hydrophobicity, water absorption, color characteristic). In order to Disc Diffusion Method, all PU composites were tested against selected bacteria (Escherichia coli and Staphylococcus aureus). Based on the results, it can be concluded that the addition of 1 wt% of nutmeg filler leads to PU composite foams with improved compression strength (e.g. improvement by ~19%), higher flexural strength (e.g. increase of ~11%), improved impact strength (e.g. increase of ~32%) and comparable thermal conductivity (0.023–0.034 W m−1 K−1). Moreover, the incorporation of nutmeg filler has a positive effect on the fire resistance of PU materials. For example, the results from the cone calorimeter test showed that the incorporation of 5 wt% of nutmeg filler significantly reduced the peak of heat release rate (pHRR) by ca. 60% compared with that of unmodified PU foam. It has been also proved that nutmeg filler may act as a natural anti-aging compound of PU foams. The incorporation of nutmeg filler in each amount successfully improved the stabilization of PU composite foams. Based on the antibacterial results, it has been shown that the addition of nutmeg filler significantly improved the antibacterial properties of PU composite foams against both Gram-positive and Gram-negative bacteria.

In the study walnut shells (WS) and silanized walnut shells (S_WS) were used as cellulosic fillers for novel polyurethane (PU) composite foams. The impact of 1, 2 and 5 wt% of WS and S_WS on the foaming parameters, mechanical and thermo-mechanical properties of obtained materials were evaluated. The results have shown that compared to untreated WS filler, the application of S_WS leads to PU foams with more regular structure and improved physico-mechanical behavior of PU materials. For example, compared to controlled WS_0 foam, PU foams enhanced with 1 wt% of the S_WS exhibited better mechanical properties, such as higher compressive strength (~15% of improvement), better impact strength (~6% of improvement), and improved tensile strength (~9% of improvement). The addition of S_WS improved the thermomechanical stability of PU foams. This work provides a better understanding of a relationship between the surface modification of the walnut shell filler and the mechanical, insulating and thermal properties of the PU composites. Due to these positive and beneficial effects, it can be stated that the use of WS and S_WS as natural fillers in PU composite foams can promote a new application path in converting agricultural waste into useful resources for creating a new class of green materials.

This paper presents the effect of natural compound (E,E)-1,7-bis(4-Hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (curcumin) on the antibacterial, anti-aging, mechanical and morphological properties of polyurethane (PU) rigid foams. Concentrations of 1 wt%, 2 wt% and 5 wt% of antibacterial compound was used, and the infection reduction capacity was evaluated for different types of bacteria (Escherichia coli (G-) and Staphylococcus aureus (G+). In order to determine all assumed properties the synthesized PU foams were characterized by analytical (Fourier Transform Infrared Spectroscopy, FTR), morphological (Scanning Electron Microscopy, SEM), bactericidal effects (Disc Diffusion Method), thermal characteristic (Thermogravimetric Analysis, TGA), mechanical techniques (three-point bending test and compressive test) and physical properties (apparent density, dimensional stability, contact angle, water uptake, color characteristics). Compared to the reference foam, compositions modified with 1 and 2 wt% of the curcumin showed greater compressive strength (increase of 10 and 7%, respectively), higher flexural strength (increase of 17 and 7%, respectively), less water uptake (decrease by 12 and 10%, respectively), as well as, better thermal properties. On the other hand, it has been shown, that in all cases, curcumin can be used as a natural anti-ageing additive for polymers. The addition of curcumin in the amount of 1, 2 and 5 wt% considerably improved the stabilization of the polymer. Moreover, based on the microbiological results, it has been shown that the addition of 5 wt% of the extract is suitable for the manufacturing of PU foams with enhanced antibacterial properties.