Composites of Rigid Polyurethane Foams Reinforced with POSS

Comparison of Biowaste Fillers Extracted from Fish Scales and Collagen on the Mechanical Properties of High-Density Polyurethane Foams

The utilization of biowaste fillers in the development of high-density polyurethane (PU) foams has gained significant attention due to environmental and economic benefits. This study investigates the mechanical properties of PU foams reinforced with biowaste fillers extracted from fish scales (FS) and fish scale-derived collagen (FSC). The fish scales and collagen were characterized for their composition and integrated into PU foams at various loadings. Mechanical properties such as tensile strength, hardness, and density were evaluated. ANOVA was used to analyze the mean values. Bonferroni tests were used to identify differences between the filler materials (α = 0.05). The tensile strength increases with an increase in filler content for both FS (59.48 Kpa) and FSC (65.43 Kpa). No differences were observed between FS and FSC in tensile strength. Significant differences were observed between the FS and FSC in both hardness and density (p < 0.001). The results demonstrated that both fillers enhanced the mechanical properties of PU foams, with collagen-reinforced foams showing superior performance. This suggests that collagen and fish scales can be effective biowaste fillers for developing environmentally friendly PU foams with enhanced mechanical properties.

Effect of Selected Bio-Components on the Cell Structure and Properties of Rigid Polyurethane Foams

New rigid polyurethane foams (RPURFs) modified with two types of bio-polyols based on rapeseed oil were elaborated and characterized. The effect of the bio-polyols with different functionality, synthesized by the epoxidation and oxirane ring-opening method, on the cell structure and selected properties of modified foams was evaluated. As oxirane ring-opening agents, 1-hexanol and 1.6-hexanediol were used to obtain bio-polyols with different functionality and hydroxyl numbers. Bio-polyols in different ratios were used to modify the polyurethane (PUR) composition, replacing 40 wt.% petrochemical polyol. The mass ratio of the used bio-polyols (1:0, 3:1, 1:1, 1:3, 0:1) affected the course of the foaming process of the PUR composition as well as the cellular structure and the physical and mechanical properties of the obtained foams. In general, the modification of the reference PUR system with the applied bio-polyols improved the cellular structure of the foam, reducing the size of the cells. Replacing the petrochemical polyol with the bio-polyols did not cause major differences in the apparent density (40-43 kg/m3), closed-cell content (87-89%), thermal conductivity (25-26 mW⋅(m⋅K)-1), brittleness (4.7-7.5%), or dimensional stability (<0.7%) of RPURFs. The compressive strength at 10% deformation was in the range of 190-260 and 120-190 kPa, respectively, for directions parallel and perpendicular to the direction of foam growth. DMA analysis confirmed that an increase in the bio-polyol of low functionality in the bio-polyol mixture reduced the compressive strength of the modified foams.

Recent Advances in Development of Waste-Based Polymer Materials: A Review

Limited petroleum sources, suitable law regulations, and higher awareness within society has caused sustainable development of manufacturing and recycling of polymer blends and composites to be gaining increasing attention. This work aims to report recent advances in the manufacturing of environmentally friendly and low-cost polymer materials based on post-production and post-consumer wastes. Sustainable development of three groups of materials: wood polymer composites, polyurethane foams, and rubber recycling products were comprehensively described. Special attention was focused on examples of industrially applicable technologies developed in Poland over the last five years. Moreover, current trends and limitations in the future “green” development of waste-based polymer materials were also discussed.

Bio-Based Rigid Polyurethane Foam Composites Reinforced with Bleached Curauá Fiber

This study aims to evaluate the influence of using a bleached Curauá fiber (CF) as filler in a novel rigid polyurethane foam (RPUF) composite. The influence of 0.1, 0.5 and 1 wt.% of the reinforcements on the processing characteristics, cellular structure, mechanical, dynamic-mechanical, thermal, and flame behaviors were assessed and discussed for RPUF freely expanded. The results showed that the use of 0.5 wt.% of CF resulted in RPUF with smoother cell structure with low differences on the processing times and viscosity for the filled pre-polyol. These morphological features were responsible for the gains in mechanical properties, in both parallel and perpendicular rise directions, and better viscoelastic characteristics. Despite the gains, higher thermal conductivity and lower flammability were reported for the developed RPUF composites, related to the high content of cellulose and hemicellulose on the bleached CF chemical composition. This work shows the possibility of using a Brazilian vegetable fiber, with low exploration for the manufacturing of composite materials with improved properties. The developed RPUF presents high applicability as enhanced cores for the manufacturing of structural sandwich panels, mainly used in civil, aircraft, and marine industries.

Chlorine-Functional Silsesquioxanes (POSS-Cl) as Effective Flame Retardants and Reinforcing Additives for Rigid Polyurethane Foams

The subject of the research was the production of silsesquioxane modified rigid polyurethane (PUR) foams (POSS-Cl) with chlorine functional groups (chlorobenzyl, chloropropyl, chlorobenzylethyl) characterized by reduced flammability. The foams were prepared in a one-step additive polymerization reaction of isocyanates with polyols, and the POSS modifier was added to the reaction system in an amount of 2 wt.% polyol. The influence of POSS was analyzed by performing a series of tests, such as determination of the kinetics of foam growth, determination of apparent density, and structure analysis. Compressive strength, three-point bending strength, hardness, and shape stability at reduced and elevated temperatures were tested, and the hydrophobicity of the surface was determined. The most important measurement was the determination of the thermal stability (TGA) and the flammability of the modified systems using a cone calorimeter. The obtained results, after comparing with the results for unmodified foam, showed a large influence of POSS modifiers on the functional properties, especially thermal and fire-retardant, of the obtained PUR-POSS-Cl systems.

Silicon-Containing Polymeric Materials

When thinking about a chemical element that has contributed to the technological progress over the last two centuries, carbon and all carbon-based materials immediately come to mind [...].

Effects of Polyhedral Oligomeric Silsesquioxane (POSS) on Thermal and Mechanical Properties of Polysiloxane Foam

The thermal and mechanical properties of polysiloxane foam are greatly improved by the addition of acrylolsobutyl polyhedral oligomeric silsesquioxane (MA0701, hereinafter referred to as MAPOSS), which has double bonds. The morphologies and properties of the polysiloxane composite foam were characterized. The average cell diameter of the composite foams decreased, while the cell density increased with increasing MAPOSS. Meanwhile, MAPOSS can enhance thermal conductivity and thermal stability. Thermal conductivity increased by 25%, and the temperature at the maximum weight loss rate increased from 556 °C to 599 °C. In addition, MAPOSS also promoted heterogeneous nucleation by functioning as a nucleating agent, which can increase cell density to improve the mechanical properties. The compressive strength of the composite foam increased by 170% compared with that of pure foam. In the composite, MAPOSS increased the cross-linking density by acting as a physical cross-linking point and limited the movement of the segments.

Mendes J, de O. Souto Silva KK, Zille A. Dog Wool Microparticles/Polyurethane Composite for Thermal Insulation

A polyurethane (PU)-based eco-composite foam was prepared using dog wool fibers as a filler. Fibers were acquired from pet shops and alkaline treated prior to use. The influence of their incorporation on the PU foams’ morphological, thermal, and mechanical properties was investigated. The random and disorganized presence of the microfibers along the foam influence their mechanical performance. Tensile and compression strengths were improved with the increased amount of dog wool microparticles on the eco-composites. The same occurred with the foams’ hydration capacity. The thermal capacity was also slightly enhanced with the incorporation of the fillers. The fillers also increased the thermal stability of the foams, reducing their dilatation with heating. The best structural stability was obtained using up to 120 °C with a maximum of 15% of filler. In the end, the dog wool waste was rationally valorized as a filler in PU foams, demonstrating its potential for insulation applications, with a low cost and minimal environmental impact.

Effects of Chemically Treated Eucalyptus Fibers on Mechanical, Thermal and Insulating Properties of Polyurethane Composite Foams

In this work, rigid polyurethane (PUR) foams were prepared by incorporating 2 wt% of eucalyptus fibers. The eucalyptus fibers were surface-modified by maleic anhydride, alkali, and silane (triphenylsilanol) treatment. The impact of the modified eucalyptus fibers on the mechanical, thermal, and fire performances of polyurethane foams was analyzed. It was observed that the addition of eucalyptus fibers showed improved mechanical and thermal properties and the best properties were shown by silane-treated fibers with a compressive strength of 312 kPa and a flexural strength of 432 kPa. Moreover, the thermal stability values showed the lowest decline for polyurethane foams modified with the silane-treated fibers, due to the better thermal stability of such modified fibers. Furthermore, the flame resistance of polyurethane foams modified with the silane-treated fibers was also the best among the studied composites. A cone calorimetry test showed a decrease in the peak of heat release from 245 to 110 kW∙m⁻² by the incorporation of silane-treated fibers. Furthermore, total heat release and total smoke release were also found to decrease remarkably upon the incorporation of silane-treated fibers. The value of limiting oxygen index was increased from 20.2% to 22.1%. Char residue was also found to be increased from 24.4% to 28.3%. It can be concluded that the application of chemically modified eucalyptus fibers has great potential as an additive to incorporate good mechanical, thermal, and fire properties in rigid polyurethane foams.

Bio-Based Polyurethane Composite Foams with Improved Mechanical, Thermal, and Antibacterial Properties

Among different organic fillers, the chemical composition of Syzygium aromaticum, commonly known as cloves, has great potential as a sustainable reinforcement for polymeric materials. In the study, grounded cloves were used as cellulosic filler for a novel polyurethane (PU) composite foams. Soybean oil-based PU composite foams were successfully reinforced with different concentrations (1, 2, and 5 wt%) of clove filler. 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), thermal properties (thermogravimetric analysis), viscoelastic behavior (dynamic mechanical analysis) as well as selected application properties (apparent density, dimensional stability, surface hydrophobicity, water absorption, color characteristic). In order to undertake the 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 and 2 wt% of clove filler leads to PU composite foams with improved compression strength (improvement by ≈18% for sample PU-1), greater flexural strength (increase of ≈11%), and improved impact strength (increase of ≈8%). Moreover, it has been proved that clove filler may be used as a natural anti-aging compound for polymeric materials. Based on the antibacterial results, it has been shown that the addition of clove filler significantly improved the antibacterial properties of PU foams and is suitable for the manufacturing of antimicrobial PU composite foams. Due to these positive and beneficial effects, it can be stated that the use of cloves as a natural filler 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.

Polystyrene Nanocomposites Reinforced with Novel Dumbbell-Shaped Phenyl-POSSs: Synthesis and Thermal Characterization

Two series of novel dumbbell-shaped polyhedral oligomeric silsesquioxanes (POSSs), fully functionalized with phenyl groups at the corner of the silicon cages, were used to prepare polystyrene (PS) nanocomposites through the method of in situ polymerization. The percentage of the molecular filler reinforcement was set as 5% w/w of POSS and was checked by ¹H-NMR spectroscopy. The obtained nanocomposites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Thermal and morphological properties were evaluated and compared among the nanocomposites obtained using the two different series of dumbbell-shaped POSSs and with the net PS. The thermal parameters for the prepared nanocomposites were very high when compared with those of neat PS, and they evidenced significant differences when an aliphatic or aromatic bridge was used to link the silicon cages. SEM analysis results allow us to hypothesize a justification for the different resistance to thermal degradation showed by the two series of molecular reinforcement.

Investigation of the Constitutive Model of W/PMMA Composite Microcellular Foams

Investigating the constitutive relationship of a material can provide better understanding of the mechanical properties of a material and has an irreplaceable effect on optimizing the performance of a material. This paper investigated a constitutive model for tungsten/polymethyl-methacrylate (W/PMMA) composite microcellular foams prepared by using melt mixing and supercritical carbon dioxide foaming. The stress-strain relationships of these foams with different W contents were measured under static compression. The elastic modulus and compressive strength values of the foams were remarkably greater than those of the pure PMMA foams: at a W content of 20 wt %, these values were increased by 269.1% and 123.9%, respectively. Based on the Maxwell constitutive model, the relevant coefficients were fitted according to the experimental data of different relative densities and W contents in quasi-static compression. According to the numerical relationships between the relevant coefficients and the relative densities and W contents, the quasi-static mechanical constitutive model of W/PMMA composite microcellular foams with W contents of 0~60 wt % and relative densities of 0.15~0.55 were predicted. This study provided basic data for the optimal design of the W/PMMA composite microcellular foams and proposed a method for investigating the mechanical properties of composite microcellular foam materials.