Pulverized polyurethane foam particles reinforced rigid polyurethane foam and phenolic foam

Polyurethane consumption has been increasing in recent years, raising concerns about how to deal with the polymer waste. Post‐consumer rigid polyurethane foams or polyurethane foam scraps (PPU) ground into particles were utilized to strengthen mechanical properties of rigid polyurethane foam (PUF) and phenolic foam (PF). Viscosity of prepolymer with PUF was measured and PPU was well dispersed in prepolymer, as observed by optical microscope. Microstructures and morphologies of the reinforced foam were examined with scanning electron microscope (SEM) while cell diameter and density were measured by Scion Image software. Universal testing machine was employed to optimize compressive properties at various weight ratios of PPU. Both PUF and PF with 5 wt % PPU, respectively, exhibited considerable improvement in mechanical properties especially compressive property. The compressive modulus of PUF with 5 wt % PPU was 12.07 MPa, almost 20% higher than pure PUF while compressive strength of PF with 5 wt % PPU reached 0.48 MPa. The thermal stability of the reinforced foam was tested by thermal gravity analysis (TGA) and the result shows no obvious impact with PPU. The decomposition temperatures of PUF with PPU and PF with PPU were 280°C, because PPU has relatively weak thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39734.     

Thermoplastic polyurethane composites prepared from mechanochemically activated waste cotton fabric and reclaimed polyurethane foam

In this study, thermoplastic polyurethane (PU) composites were successfully prepared from waste cotton fabric (WCF) and reclaimed PU foam derived from the shoe manufacturing industry through melt mixing. A pan‐mill‐type mechanochemical reactor made in our laboratory was applied to determine the mechanochemical activation of WCF. The intramolecular and intermolecular hydrogen bonds of WCF could be broken up through pan milling because of the fairly strong shearing and squeezing forces. Moreover, the simultaneous reduction of particle size and the large increment of the specific surface area of pan‐milled WCF benefitted its dispersion and the interfacial adhesion with the PU matrix. Mechanochemically activated WCF could be used as a low cost but effective functional additive to enhance the melt processability and mechanical properties of PU/WCF composites. With the addition of 75‐phr WCF, the heat shrinkage of the melt‐reprocessed PU decreased sharply from its original 11.4 to 0.3%. Meanwhile, the tensile strength of the composites was enhanced from 10.3 to 23.2 MPa. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of ultrasound on the synthesis and properties of polyurethane foam/clay nanocomposites

Polyurethane foam (PUF)/clay nanocomposites were synthesized with clay modified by polymeric 4,4′‐diphenylmethane diisocyanate (PMDI) with the application of ultrasound. Transmission electron micrographs showed that the interlayer distance increased for the polyurethane (PU)/clay nanocomposites where ultrasound was applied. The results of the transmission electron microscopy and X‐ray measurements suggest that the application of ultrasound to the clay modification with PMDI improved the efficiency of the clay modification by the effective breakup of the clay agglomerates and intercalation of the silicate layers. In the mechanical tests of the PUF/clay nanocomposites, the flexural and tensile strengths of the PUF/clay nanocomposites showed the maximum value at 3.0 wt % clay content based on PMDI. These results suggest that the increases in the flexural and tensile strengths were perhaps due to the uniform dispersion of the clay by the application of ultrasound. At the same modified clay content, the fire resistance properties were increased for the PUF/clay nanocomposites with the application of ultrasound compared to the PUF/clay nanocomposites without the application of ultrasound. The cell size and thermal conductivity were decreased for the PUF/clay nanocomposites with the application of ultrasound compared to the PUF/clay nanocomposite without the application of ultrasound. Because of these results, we suggest that the smaller cell size and lower thermal conductivity of the PUF/clay nanocomposites were mainly due to the enhanced dispersion of the clay by the application of ultrasound to the mixture of PMDI and clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3764–3773, 2006     

New applications for foam composites of polyurethane and recycled rubber

In Portugal, most end‐of‐life tires are recycled through a process involving a cryogenic grinding technology. The purpose of this work was to envisage new applications for recycling rubber from end‐of‐life tires. In this work, rubber was supported in a polyurethane matrix generating two new products of distinct characteristics and properties. The choice of these products was ruled by the requests of potential clients: (a) Floating trays to withstand the load of plants capable of cleansing polluted water from lagoons, ponds, or basins; (b) Compression‐absorbing buoys to dampen the shocks and the compressive stresses between ships and docks. The polyurethane formulations developed herein were based on methylene diphenyl diisocyanate and a trifunctional polyol such that the final foam would be flexible. As the floating trays' density should be lower than the water density, the best formulation found comprised 150% of rubber, 4% of water (relative to the polyol mass), with an isocyanate index of 105% and a density of 89 kg m^?3. The foam that presented the optimal compression behavior to be applied in compression absorbing buoys, comprised 200% of rubber, 3% of water, with an isocyanate index of 105% and a density of 121 kg m^?3. In both cases, the composite foam materials obtained showed final properties compatible with the envisaged applications, pointing out that the implied methodology may be used in the future to recycle rubber from end‐of‐life tires. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mixed‐matrix membranes based on polyurethane containing nanohydroxyapatite and its potential applications

In this study, new asymmetric polyurethane (PU) mixed‐matrix membranes with different nanohydroxyapatite loadings were prepared via a dry–wet phase inversion method by the dispersion of hydroxyapatite (HA) nanoparticles in the PU matrix. The HA nanopowder was obtained by a wet chemical precipitation method; it showed an average crystallite size of 58.3 nm, a specific surface area of 261 m²/g, and a pore size of about 1.6 nm. The effects of the HA loading (10–50 wt %) on the PU membrane characteristics were studied. The scanning electron microscopy images revealed that the HA nanoparticles were well dispersed enough in the PU matrix. The average pore size in the top layer and porosity of the membranes slowly decreased, whereas the hydrophilicity and water permeability increased with increasing content of HA. The evaluation of the nanofiltration performance was performed by investigation of the NaCl rejection. The composite membranes had a higher salt‐removal capacity than the unfilled PU membrane. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41813.     

Synthesis and characterization of crosslinked polyurethane/clay nanocomposites

A series of glycerin‐crosslinked polyurethane (XPU)‐clay nanocomposites were prepared by in situ polymerization followed by solution casting and thermal treatment. The weight percent (wt %) of clay in the nanocomposites was varied between 0.25 and 10. The structural, rheological and dynamic mechanical properties of the nanocomposites were investigated. X‐ray diffraction (XRD) analysis showed that well dispersed clay platelets were formed in nanocomposites containing up to 1 wt % of clay. Scanning electron microscopy (SEM) showed that poorly dispersed and non‐exfoliated clays were present in composites containing >2 wt % of clay and resulted in phase‐separated disparities within the matrix. Rheological studies demonstrated that processability of polyurethane was significantly improved after clay addition such that solution viscosity decreased by between 76 and 90%. Furthermore, the presence of chemical and physical crosslink networks within the matrix resulted in a remarkable enhancement in the rubbery plateau storage modulus. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43346.     

Preparation and characterization of polyurethane/silica aerogel nanocomposite materials

In this investigation, silica aerogel (SA)/Rigid Polyurethane (PUR) foam composites and silica aerogel/Polyurethane (PU) composites were prepared by dry mixing of granular and grinded silica aerogels with polyol part. They were then combined with diisocyanate part. Three different types of PUR foams and an elastomeric coating grade of PU were studied as well. Results show that thermal conductivity of foams did not decrease by adding silica aerogel. It even increased for some grades which is assumed to be due to the change in cell configuration of these foams. It was also found that sound insulation performance of these cellular composites did not improve significantly. Unlike foam composites, addition of silica aerogel into elastomeric PU improved its thermal and acoustic insulation properties. Because of the more promising properties of elastomeric PU composites, further examinations including measurements of compression strength and water contact angle of silica aerogel/PU composites were also taken. Final results showed a significant improvement in general properties of PU coatings by adding little amounts of silica aerogel (1–4 wt %). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44521.     

Recycling of waste poly(ethylene terephthalate) into flame‐retardant rigid polyurethane foams

Waste poly(ethylene terephthalate) (PET) textiles were effectively chemical recycling into flame‐retardant rigid polyurethane foams (PUFs). The PET textile wastes were glycolytically depolymerized to bis(2‐hydroxyethyl) terephthalate (BHET) by excess ethylene glycol as depolymerizing agent and zinc acetate dihydrate as catalyst. The PUFs were produced from BHET and polymeric methane diphenyl diisocyanate. The structures of BHET and PUFs were identified by FTIR spectra. The limiting oxygen index (LOI) of the PUFs (≥23.27%) was higher than that of common PUFs (16–18%), because the aromatic substituent in the depolymerized products improved the flame retardance. To improve the LOI of the PUFs, dimethyl methylphosphonate doped PUFs (DMMP‐PUFs) were produced. The LOI of DMMP‐PUFs was approached to 27.69% with the increasing of the doped DMMP. The influences of the flame retardant on the foams density, porosity, and compression properties were studied. Furthermore, the influences of foaming agent, catalyst, and flame retardant on the flame retardation were also investigated. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40857.     

Preparation and characterization of colloidal carbon sphere/rigid polyurethane foam composites

Sucrose decomposed under hydrothermal conditions, generating colloidal carbon spheres (CCSs) with a perfectly spherical morphology. X‐ray diffraction indicated that the main component of the CCSs was disordered carbon, and massive hydroxyl groups existed on the surface, as confirmed by Fourier transform infrared spectroscopy. CCSs were first introduced into polyurethane foams (PUFs), and CCS‐reinforced PUF (PUF/CCS) composites were synthesized. The introduction of CCSs did not increase the viscosity of polyol/CCS blends significantly. The good dispersion of CCSs and the compatibility between CCSs and polyurethane were confirmed by transmission electron microscopy measurements. The results of mechanical testing showed that PUF/CCS composites exhibited greatly improved mechanical properties in comparison with neat PUFs, and this could be ascribed to the finer cell structure of the PUF/CCS composites, which was inspected with scanning electron microscopy. Thermogravimetric analysis indicated that the effects of CCSs on the thermal stability of the foams were slight. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Oil absorption performance of polymer/clay aerogel materials

Oil absorption performance of aerogels produced from poly(amide‐imides), epoxies, and acrylic polymers were dependent upon freezing conditions, which in turn dictated solid state structures of these materials. Denser aerogels have less void space, and are more efficient at filling that space with oil, supporting the hypothesis that capillary spacing plays a vital role in determining oil absorption. Lower molecular weight epoxy‐based polymers produced aerogels with small capillary radii, again allowing increasing amounts of the liquid to penetrate between the aerogel layers. Aerogels produced from acrylic emulsions outperformed the other two systems tested in terms of volume per volume absorption. The initial difficulty with these materials, the fact that they still retain some hydrophilicy and absorb water, was overcome by simple post curing treatment, which was able to reduce water absorption to near zero levels. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45844.     

Effect of organoclays on the properties of polyurethane/clay nanocomposite coatings

Linear, one‐binding‐site or two‐binding‐site (N⁺) organifiers with two hydroxyl end groups were synthesized, and novel organoclays were prepared through a cation‐exchange reaction between pristine sodium montmorillonite and the synthesized organifiers. After sonication of the as‐prepared organoclay in N,N′‐dimethylformamide for 10 min, the average size of the clay decreased to about 1 μm. The X‐ray diffraction patterns confirmed that the d‐spacing of the silicate layers of the organoclay expanded from 1.1 to about 1.9 nm and the peak intensity decreased with the molecular weight of the organifier increasing. Polyurethane/clay nanocomposites were synthesized by a one‐shot polymerization method. Both intercalated and exfoliated structures of the layered silicates in the polyurethane matrix were observed from transmission electron microscopy micrographs, and the d‐spacing ranged from 4 to 10 nm. The thermal and mechanical properties of the nanocomposite were enhanced by the introduction of the organoclay into the polyurethane matrix. An approximately 40–46°C increase in the onset decomposition temperature, a 200% increase in the tensile strength with a 0.5 wt % clay loading, and a 49% increase in Young's modulus with a 3 wt % clay loading were achieved. The effects of the molecular weight and the number of binding sites of the organifier on the properties of the nanocomposites were also evaluated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Optimization of sound absorption property for polyurethane foam using adaptive simulated annealing algorithm

Polyurethane foam is one of the sound absorbing materials because of its advantage in lightweight, sound absorption and low cost. Therefore, it is important to optimize the formulation for better sound absorption performance. In this study, experimental optimization was carried out with a response surface methodology to investigate the effects of different variables including catalyst triethanolamine, catalyst A33, and additive polyethylene fiber. The mathematical model was developed for correlating experimental data. The model parameters were optimized by adaptive simulated annealing algorithm. The maximum acoustic property of the foams was found to be 0.68 by adding 3.2 g triethanolamine, 1.0 g A33, and 0.1 g polyethylene fiber. Then, the polyurethane foam was synthesized according to the optimization results. The sound absorption coefficient of it is within the allowable error of the optimization result. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46426.     

Preparation and characterization of waterborne polyurethane/clay nanocomposite: Effect on water vapor permeability

A series of waterborne polyurethane (WBPU)/clay nanocomposite coating materials were prepared by prepolymer process with different clay contents (0–2 wt %). The study investigated surface structure as well as water resistance, thermal, mechanical, and water vapor permeability (WVP) of composite materials as a function of clay contents. The glass transition temperature of composite materials was higher than pristine WBPU and also increased with increasing clay contents. Thermal stability, and water resistance of the nanocomposite films also increased, when compared with pristine WBPU, and these properties increased with an increase in clay content. The maximum tensile strength was found with optimum clay content (1 wt %) of composite films. The WVP of coated nylon fabrics depend on the clay content and temperatures. The rate (%) of WVP of coated nylon fabrics decreased with increasing clay content at a fixed temperature. However, at a fixed clay content the WVP increased with the increase of temperatures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigations on the adhesion and interfacial properties of polyurethane foam/thermoplastic materials

The adhesion and interfacial properties of polyurethane (PU) foams with thermoplastic (TP) materials were investigated using different techniques. The adhesion performance of PU foam with TP materials was evaluated using the peel test method, and the adhesion durability was checked after different climate treatments. X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements were used to study the surface and interface morphology of PU foam and TP material system. Three types of PU foam samples which differ in their composition and also five commercially available TP blends systems, based on poly(carbonate), poly(styrene‐co‐maleic anhydride), poly(acrylonitrile‐butadiene‐styrene), and silicone acrylate rubber have been used. The slow reacting foam shows the best adhesion properties with all the TP materials. The climate treatments strongly effected the PU foam adhesion durability with poly(carbonate) containing TP materials (70–80% loss in adhesion), but nearly no effect with poly(styrene‐co‐maleic anhydride). The samples with lowered adhesion could be separated by peeling without visible foam residues on the TP surface. AFM, XPS, and surface tension studies have shown that the surface properties of the TP material are still governed by the PU foam. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 479–488, 2007     

Synthesis and properties of polyurethane/clay nanocomposite by clay modified with polymeric methane diisocyanate

A polyurethane (PU)/clay nanocomposite was synthesized from polyol, polymeric 4,4′‐diphenyl methane diisocyanate (PMDI), and modified clay with PMDI. To achieve the modified clay with PMDI, the silanol group of the clay and the NCO group of the PMDI were reacted for 24 h at 50°C to form urethane linkage. Fourier transform IR analysis of the clay modified with the PMDI demonstrated that the NCO characteristic peak was observed in the clay after a modification reaction with PMDI. The results of the X‐ray pattern suggested that the clay layers were exfoliated from the PU/clay nanocomposite. From the results of the mechanical properties, the maximum values of the flexural and tensile strength were observed when 3 wt % clay based on PMDI was added into the PU/clay nanocomposites. The glass‐transition temperature and change in the heat capacity at glass transition temperature (ΔC_p) of the PU/clay nanocomposite decreased with an increase in the modified clay content. We suggested that the decrease in the ΔC_p with the modified clay content might be due to the increase of steric hindrance by the exfoliated clay layers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2879–2883, 2006     

Preparation and characterization of water‐absorbing polyurethane foam composites with microsized sodium polyacrylate particles

This article introduces the preparation of rigid polyurethane foam (PUF) and studies the effect of various mass percentages of sodium polyacrylate (PAAS, microsized) on PUF hydrophilicity. The characterization of PUF (with 0–5.5 wt % PAAS) was conducted via scanning electron microscopy, contact angle analysis, differential scanning calorimetry, and pore size distribution. All modified foams showed an improvement in their water sorption and water maintenance capacities, and the PU foam content of 5.5 wt % PAAS showed a water absorption of 891%, and the water retention performance was 408% (96 h) compared to the pure PU foam. Through contact angle measurements, the relationship between the hydrophilicity of the modified foams and PAAS content was investigated. The compression strength of the samples was also tested. When the PAAS is 2.6 wt %, the compression strength of the composites decreased about 50% compared with the pure PU foam. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46702.     

Incorporation of theophylline in a chitosan/chondroitin sulfate hydrogel matrix: In vitro release studies and mechanical properties according to pH changes

Hydrogels based on natural polymers have been widely applied as vehicles for controlled drug release because of their advantages and interesting properties. In this study, a physical hydrogel based on chitosan and chondroitin sulfate (CS) was formed under mild conditions to act as a potential device for the controlled release of theophylline (TH). In vitro CS and TH release studies at pH 2 and 8 were performed. Under acid conditions (pH 2), the fraction of TH released (ca. 0.87) was higher than that of CS (ca. 0.13). On the other hand, under basic conditions, the fractions released of both substances were similar (ca. 0.57). In addition, the system presented in this work was able to sustain the TH release in a controlled way for 30 h. The variation of the pH affected the mechanical properties and contributed to form ordered regions within the hydrogel network, as observed through compression tests and wide‐angle X‐ray scattering analysis. The experimental data and discussion presented in this article will contribute to the development of a new vehicle for controlled TH release; this ensures the efficacy of the drug and reduced the number of daily doses administered. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The thermoresponsive shape memory characteristics of polyurethane foam

The purpose of this study is to develop a protective and thermally intelligent filler by optimizing the preparing conditions and the thermoresponsive property of PU foam. The specimens were polyurethane synthesized by a one step process with 4,4′‐diphenylmethane diisocyanate, polycaprolactone and 1,4‐butanediol. After dissolving the polyurethane in tetrahydrofuran, the polyurethane foam was manufactured by the salt leaching method. The appearance, compressive property, and thermal property of the manufactured foam as well as the shape memory effects were evaluated. In addition, air and water vapor permeabilities and the thermal insulation property were measured to examine the basic properties of the foam. The cell sizes of the completed foam were distributed in the range of 400–1,000 μm. The compressive stress of the foam was low in the initial compressive strain but increased dramatically above a compressive strain of 70%. However, the foam showed a very low capacity for compressive stress compared with an electrospun web or a film manufactured by using the identical shape memory polyurethane. The transition temperature of the foam was 30°C. The shape recovery and shape retention were 98% or higher. The foam, with a porous structure, was found to be generally good in both air and water vapor permeability. In the case of the foam that maintained its compressed shape below the transition temperature, these permeabilities of the foam decreased slightly, but not significantly. Because of the porous structure of the foam, the shape memory effect did not noticeably influence the permeability change with a change in temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Water‐blown polyurethane/polyisocyanurate foams made from recycled polyethylene terephthalate and liquefied wood‐based polyester polyol

Depolymerized polyethylene terephthalate and liquefied wood polyesters can be used as a polyol for the production of polyurethane/polyisocyanurate foams. In this research, liquefied wood was synthesized by using a combination of diethylene glycol and glycerol and due to the possibility of using glycerol that is a by‐product in biodiesel production, our goal was to use as much glycerol in the liquefaction reagent as possible. We determined the properties of the polyols, properties of produced foams, and explained their correlation. Greater amount of glycerol in the liquefaction reagent resulted in higher OH number, molecular weight, functionality, and viscosity of the polyol, as well as in longer cream time and tack free time in foam preparation. Glass transition temperature, density, and water absorption of the foam increased with increasing amount of glycerol in liquefied wood. Compressive stress increased up to 30% of the glycerol in the reagent and then reduced, while thermal conductivity was not affected. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41522.     

Mechanical properties of blocked polyurethane/epoxy interpenetrating polymer networks

The mechanical properties of blocked polyurethane(PU)/epoxy interpenetrating polymer networks (IPNs) were studied by means of their static and damping properties. The studies of static mechanical properties of IPNs are based on tensile properties, flexural properties, hardness, and impact method. Results show that the tensile strength, flexural strength, tensile modulus, flexural modulus, and hardness of IPNs decreased with increase in blocked PU content. The impact strength of IPNs increased with increase in blocked PU content. It shows that the tensile strength, flexural strength, tensile modulus, and flexural modulus of IPNs increased with filler (CaCO₃) content to a maximum value at 5, 10, 20, and 25 phr, respectively, and then decreased. The higher the filler content, the greater the hardness of IPNs and the lower the notched Izod impact strength of IPNs. The glass transition temperatures (T_g) of IPNs were shifted inwardly compared with those of blocked PU and epoxy, which indicated that the blocked PU/epoxy IPNs showed excellent compatibility. Meanwhile, the T_g was shifted to a higher temperature with increasing filler (CaCO₃) content. The dynamic storage modulus (E′) of IPNs increased with increase in epoxy and filler content. The higher the blocked PU content, the greater the swelling ratio of IPNs and the lower the density of IPNs. The higher the filler (CaCO₃) content, the greater the density of IPNs, and the lower the swelling ratio of IPNs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1826–1832, 2006