This study brokes new ground to understand the insulation and permeability performances of rigid polyurethane foams (RPUFs) containing the different contents of micron-sized turkey feather powders (TFPs) depending on the free volume change for the first time. The effects of TFPs loading on the RPUFs were investigated by the examination of their structural and chemical features (particle size and ATR-FTIR analyses), free volume property (PALS analysis), insulation features (thermal conductivity and sound absorption tests), permeability performance (air and water vapor permeability tests) and cellular topology (SEM). PALS analysis results revealed that the addition of TFPs into the foams led to the sharp decrease in all free volume parameters since TFPs caused the formation of the disordered cells by occupying the holes in the matrix. Furthermore, both thermal conductivity and acoustic performance of the resulting foams get worse when compared to unfilled RPUF. This results were attributed to the formation of thinner and weaker cells during polymerization, reduction in the amount of CO2 inside the cells, enhancement in the solid-phase level in the matrix due to the increasing of volumetric density. Additionally, the foam samples with high content of TFPs showed considerably lower air and water vapor permeabilities when compared to neat RPUFs due to the dominant hydrophobic character of the keratin and reduction in the degree of vacancies in the matrix. SEM analysis also revealed that TFPs showed good compatibility with RPUF, but the distorted and irregular shaped cellular morphology was obtained at high contents.

In this work, glycerol was chemically modified into novel toluene diisocyanate (TDI) based trifunctional polyol (NTP) by a two step process, involving the reaction of TDI with glycerol to form an isocyanate-terminated pre-polymer, followed by the reaction with glycol. A thermal and mechanical property of water-blown rigid polyurethane foam (WB-PUF) was enhanced by the partial substitution (30 & 50 wt%) of castor oil with glycerol or synthesized NTP. The effects of glycerol content and NTP on the WB-PUF properties were investigated using various characterization techniques including ATR-FTIR, TGA, SEM, compression test, and Shore-A hardness test. Notably, the introduction of NTP substitution into the formulation of WB-PUF foams had beneficial impact on the structure of materials enhancing foam density from 77 kg/m3 to 117 kg/m3 and also exhibited superior thermal and mechanical properties compared to those with glycerol and unmodified foams. Shore A hardness and compression strength of those foams ranged from 50 to 69.5 °Sh A and 1.88-3.28 MPa, respectively. These findings suggest potential applications of the modified WB-PUF in areas such as rigid tissue engineering.

Fabricating low-density elastomeric foams with a homogenous cell structure has been challenging because of foam shrinkage. The low modulus of the elastomers and the high diffusivity of blowing agents lead to foam shrinkage and poor surface quality. Using N2 as a physical blowing agent (PBA) is an eco-friendly foaming method to overcome foam shrinkage. In this study, PTMEG-MDI/BD-based TPU with a hardness of 85A, 90A, and 95A were foamed using N2. Nitrogen as a blowing agent created a homogeneous cell structure with an expansion ratio of more than five times, an average cell size of less than 25 μm, and a cell density of more than 109 cells/cm3. The shrinkage ratio and cellular morphology of CO2- and N2-blown TPU foam were compared at their maximum expansion ratio. At the maximum expansion ratio, the N2-blown foams exhibited a fine cell structure with a shrinkage ratio of less than 4%. However, the CO2-blown TPU foam showed a shrinkage ratio of 12.7% with significant cracks in the sample. The results demonstrate that using N2 as a blowing agent can achieve an expansion ratio similar to that of CO2-blown foam, and the shrinkage problems of elastomeric foams can be significantly eliminated, which may help to maintain the physical properties of the foam.

This paper presents the experimental works on rigid palm oil-based polyurethane (PU) foam reinforced with sodium-montmorillonite (Na-MMT). Filler loading was varied between 1 and 10 wt %., and the obtained foam was characterized for its combustibility, morphology, thermal stability, and mechanical response. Exfoliated clay microstructure was exhibited at lower Na-MMT loadings. Addition of nanoclay into the PU foam failed to impart any discernable improvement with regards to its flammability, believed due to stronger influence of low-functionality palm oil polyol used. Apparent improvement in thermal stability was observed at low clay amounts. Foam with finer cell size was obtained in the presence of Na-MMT, however only until a certain loading limit. Compressive strength generally increases with increasing clay content, but after 3 wt % the property deteriorated. Peculiarly, compressive strength rose again at 5 wt % and 6 wt % – postulated due to additional load-bearing effect of ‘integral skin’ – before plummeting back again beyond this value.

In this research, a new method to increase the mechanical properties of the low-density polyurethane foams (PUFS) has been described. Chloroprene rubber (CR) is used as reinforcing the mechanical properties of the foam. Polyurethane foam (PUF) containing CR (PUF/CR) and pure PUF were characterized by mechanical testing, Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Differential scanning calorimeter (DSC), Thermogravimetric analysis (TGA). The results of mechanical properties show the tensile strength of PUFS containing 0, 1, 2, 3, 4 and 5 wt% CR are 38.2, 42, 56.4, 61.48, 77.3 and 77.18 kPa, respectively. Also the morphological studies show by increasing the amount of CR in the foam structure, the foam cells are smaller and more closed.

The study developed and designed polyvinyl acetate (PVAc) foams using advanced freeze-drying technology, which exhibited good heat-insulating ability, flame retardancy, and mechanical properties. Different combinations of bleach kraft pulp, water-soluble chitosan, and zinc borate were used to reinforce the foams. The foams exhibited desirable compression and flexural properties, with compression strength and compression modulus ranging from 0.01 MPa to 0.08 MPa and 0.05 MPa to 0.29 MPa, respectively, while flexural strength and flexural modulus ranged from 0.12 MPa to 5.37 MPa and 9.86 MPa to 260,85 MPa, respectively. The use of zinc borate as a reinforcement resulted in improved thermal properties and reduced mass loss at 600°C by 20.69%. Thermal conductivity tests indicated that the foams had low thermal conductivity values ranging from 0.037 W/mK to 0.074 W/mK. The foams with zinc borate (60  g/L) and high molecular weight water-soluble chitosan (70  g/L) reinforcement exhibited high limiting oxygen index (LOI) of 28.72%. Overall, the results suggest that the PVAc foams could serve as a promising sustainable alternative in thermal insulation and construction fields.

An increased awareness of sustainability among the population leads, from an industrial point of view, to efforts to act more ecologically as well as to the aim for lower production costs and an increased efficiency. With this in mind, a new process has been developed for foaming without blowing agents in rotational molding. Process related air inclusions in the polymer melt are expanded to form the cell structure by means of vacuum application. In the presented study, the influence of different particle sizes as well as the arising potential of deploying microgranules in the otherwise powder-based process is investigated with regard to the resulting foam cells. The results confirm that particle size and form greatly influence the existence and size of air inclusions in the polymer melt. It could be proven that these differences, caused by the particle characteristics, propagate during the foaming process and lead to different cell morphologies in the resultant foam. Furthermore, it is indicated that qualitative predictions of the resulting cell dimensions can be made on the basis of bulk density measurements and the analysis of the sintering behaviour of the initial particles.

Using small amounts of multi-walled carbon nanotubes (MWCNTs) functionalized with carboxyl groups, methyldiethanolamine and triethanolamine (from 0.005 to 0.1%), a series of rigid composite polyurethane-polyisocyanurate (PIR) and polyurethane (PUR) foams was obtained. The influence of these additives on the morphology of the cellular structure of the synthesized foams, as well as the change in their physical-mechanical and thermophysical characteristics, was analyzed. The effect of additions of functionalized MWCNTs on the change in compressive strength, Young’s modulus, thermal conductivity index, and mass loss during combustion of the synthesized foams has been studied. Based on the results obtained, the introduction of small amounts (up to 0.05%) of functionalized nanotubes in the foam composition improves the characteristics described above. The greatest effect was achieved using 0.05% carboxylated MWCNTs functionalized with triethanolamine.

In this study, cellular polypropylene based composite foams were prepared using an universal injection moulding machine. The chemical foaming agent was added to neat polypropylene (PP) polymer, talc filled polypropylene (PP-T) composite and talc filled polypropylene/ethylene-propylene-diene blend (PP-T-EPDM) composite materials at the ratio of 1% and 2% by weight. The influence of foaming agent content on the mechanical and cellular properties of both neat PP polymer and PP composites was investigated. The results showed that the tensile strength, tensile modulus, impact strength, hardness, cell diameter, foam density and viscosity values and skin layer thickness decreased while volume expansion ratio increased with the increment in chemical blowing agent content.

In this current study, rigid polyurethane foams (RPUFs) composites were prepared using different percentage (3, 6, 9 and 12%) of the hemp fibers via one-shut one-step polymerization method. The influences of the hemp fiber addition on the RPUFs were investigated meticulously by means of Fourier-transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), thermal conductivity measurement and scanning electron microscopy (SEM) techniques by evaluating the alternations in the chemical structures of the component, thermal stability, apparent density, insulation performance and cellular topology of the produced samples. The structural analysis revealed that there existed the strong secondary chemical bonds between the functional groups belonging to the components and, depending on that, the improvement in the thermal stability of the foam samples was recorded accompanied by the formation of the better interfacial adhesion. Furthermore, thermal conductivity values of the hemp fiber-loaded RPUFs were observed to increase regularly with the increasing of the content level of the hemp fibers. This was explained by enhancement in the bulk phase conduction level depending of the apparent density rising, reduction in CO2 concentration inside cells as well as the formation of the distorted cellular structures. The obtained air permeability results displayed that the hemp fibers incorporated successfully with RPUF structure, which provides the occurrence of the novel micro barriers and pathways limiting the passage of the air throughout the matrix. The taken scanning electron microscopy images also indicated that the cellular morphology and dimensional stability of the produced foams affected negatively by the hemp fiber addition. At high contents, the wrinkled, non-uniform and irregular cellular structures were observed with ruptured and collapsed walls and struts.