Sound absorption properties of polyurethane/nano‐silica nanocomposite foams

In this study, polyurethane (PU)/nano‐silica nancomposite foams were prepared. The effects of isocyanate index, cell size, density, and molecular weight of polyols on the sound absorption ratio of PU/nano‐silica foams were investigated. With increasing nano‐silica content, the sound absorption ratio of PU/nano‐silica foams increases over the entire frequency range investigated in this study. Decrease of isocyanate index, cell size, and increase of density leads to the increase of sound absorption ratio of PU/nano‐silica foams. PU/nano‐silica foams have a broad T_g centered around room temperature by decreasing molecular weight of polyol resulting in good sound absorbing ability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

High improvement in the properties of exfoliated PU/clay nanocomposites by the alternative swelling process

In this work, a stable de-aggregated solvent-swollen organic modified clay, ALA-MMT, suspension is prepared by an efficient solvent swelling process using a home-made shaking mixer. It is found that the estimated average size of the as-prepared organoclay particles in the suspension is reduced to about 155 nm, which has not been reported before. The X-ray diffraction (XRD) patterns confirm that the d-spacing of the silicate layers of the solvent-swollen ALA-MMT expands from 1.4 nm to about 2.1 nm. The de-aggregated solvent-swollen ALA-MMT suspension is then used with polyurethane (PU) to prepare a series of highly exfoliated and high-organoclay-loading nanocomposites, PU/ALA-MMT. Both the XRD patterns and the TEM photographs of the as-prepared PU/ALA-MMT nanocomposites indicate that the organoclay is uniformly dispersed in the PU matrix with a highly exfoliated morphology structure of up to 7 wt% loading. Meanwhile, the TEM photographs give the first report for PU/clay nanocomposites which are almost completely exfoliated, and ∼1-nm thin silicate nanolayers are homogeneously dispersed in the polymer matrix with a high aspect ratio of 30-100. The thermal, mechanical, and anti-corrosion properties are all tremendously enhanced for the as-prepared nanocomposites. The results obtained for the PU nanocomposite with 7 wt% ALA-MMT loading (PUC7) reveal a 19 °C increment in T_g, a 48 °C increment in T_5%, a 248% increase in the tensile strength, and a 123% increase in the elongation. The stainless steel disk (SSD) coated with PUC7 shows the lowest corrosion rate of 2.01 × 10⁻⁶ mm/year, which is 469% lower than that of the SSD coated with pure PU. The reinforcements are much greater than the previously reported PU/clay nanocomposites with comparable clay loadings ascribed to the exceptional homogeneity of as-prepared nanocomposites, which are accredited largely to the stable de-aggregated solvent-swollen organoclay suspension generated by the efficient solvent swelling process.     

Influence of structure of organic modifiers and polyurethane on the clay dispersion in nanocomposites via in situ polymerization

Influence of polyurethane (PU) structure on the nature of PU/clay nanocomposite was studied using varying amounts of trimethylol propane (TMP) as branching agent. The effect of hydroxyl groups in the modifier of organoclays on the structure of PU/clay nanocomposites was studied. Nanocomposites were characterized using wide‐angle X‐ray diffraction measurements (WAXD) and transmission electron microscopy (TEM). The results show that formation of completely exfoliated and well dispersed polyurethane/clay nanocomposites via in situ polymerization, is facilitated by the presence of tethering groups on the clay surface and an ability to form branched and crosslinked structures. Incorporation of long alkyl chains in addition to tethering hydroxyl groups in the modifier structure of the clay did not significantly improve the compatibility of linear PU with the clay. Intercalated thermoplastic polyurethane/clay nanocomposites, prepared using poly(caprolactone diol) as soft segment and isophorone diisocyanate and 1,4‐butanediol as hard segments show increase in storage tensile moduli at temperatures before glass transition temperature when functional groups capable of chemically reacting with the growing polymer chains are present in the clay modifier. This is indicative of improved interaction of the polymer with the clay surface when the modifier has larger number of hydroxyl groups. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Analysis of the structure and mass transport properties of nanocomposite polyurethane

In this work, nanocomposite adhesives obtained using an organically modified montmorillonite (OMM) in a polyurethane matrix were studied. The basal distance of OMM before and after mixing with the polyol and after curing was characterized by X‐Ray diffraction. The viscosity of polyols‐OMM systems was studied as function of shear rate in a cone‐plate rheometer in order to correlate the viscosity with the aggregation state of OMM. A simple model accounting for an apparent increase of rheological units size associated with the intercalation of macromolecules into OMM galleries is proposed. Curing was performed at room temperature for 1 week. The basal distances of crosslinked PU nanocomposites were obtained by X‐ray diffraction. The glass transition temperature, T_g, of PU nanocomposites, as measured using differential scanning calorimetry, increases with increasing volume fraction of OMM. Finally, the permeability to oxygen and water vapor of polyurethane clay‐nanocomposites was measured. The gas permeation through the composites was correlated to the volume fraction of the impermeable inorganic part of the OMM. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Synthesis and characterization of elastomeric polyurethane and PU/clay nanocomposites based on an aliphatic diisocyanate

This investigation reports preparation of polyurethane and polyurethane/clay nanocomposites based on polyethylene glycol, isophorone diisocyanate (IPDI), an aliphatic diisocyanate and 1,4‐ Butanediol as chain extender by solution polymerization. In this case PU/clay nanocomposites were prepared via ex‐situ method using 1, 3, and 5 wt % of Cloisite 30B. Thermogravimetric analysis showed that the maximum decomposition temperature (T_max) of the PU/clay nanocomposite is much higher than the pristine PU. The tensile properties improved upon increasing the organoclay (Cloisite 30B) content upto 3 wt %, and then decreased to some extent upon further increasing the nanoparticle loading to 5 wt %. Optical properties of the nanocomposites were studied by UV‐vis spectrophotometer. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the morphology of the nanocomposites. It was observed that with the incorporation of 3 wt % nanoclay the crystallinity in PU nanocomposite increases, then diminishes with further loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3328–3334, 2013     

Synthesis and Thermal Characterization of Polyurethane/Clay Nanocomposites Based on Palm Oil Polyol

Polyurethanes (PUs) are very versatile polymeric materials with a wide range of physical and chemical properties. PUs also have desirable properties, such as high abrasion resistance, tear strength, shock absorption, flexibility, and elasticity. Although they have poor thermal stability, it can be improved by using treated clay.

The objective of the present work is to study the thermal stability of polyurethane, polyurethane/montmorillonite (PU CTAB-mont 3% wt), and polyurethane/montmorillonite containing moca (PU Moca CTAB-mont 3% wt) nanocomposites based on palm oil polyol.

The interest of investigating the synthesis of polyurethane/clay nanocomposites based on palm oil polyol is to explore the use of palm oil polyol to partially replace petrochemical-based polyol.

Polyurethane/clay nanocomposites were prepared by a pre-polymer method and evaluated by Fourier Transform Infrared Spectra (FTIR) to determine micro-domain structures of segmented PU, PU CTAB-mont 3% wt, and PU Moca CTAB-mont 3% wt. The morphology of the nanocomposites was characterized by X-ray diffraction (X-RD), and flame retardant was investigated with thermogravimetric analysis (TGA). The result showed that in comparison with the virgin polyurethane, adding clay and moca demonstrated better thermal stability.     

Preparation and crystalline morphology of biodegradable starch/clay nanocomposites

An organically modified clay (o-clay) and a pristine clay (p-clay) were used to prepare biodegradable thermoplastic starch (TPS)/clay nanocomposites by melt processing. The gelatinization behaviour of starch with glycerol/H₂O was investigated and the gelatinized temperature (T_gel) was determined using a polarized optical microscopy (POM) equipped with a hot stage. The morphologies of gelatinized starch and extruded starch were revealed by scanning electron microscopy (SEM). Thermal stabilities of starch/clay nanocomposites were evaluated under N₂ atmosphere using thermogravimetric analysis (TGA). Transparent films of starch/clay hybrids were fabricated by hot pressing. Intercalation of starch into clay galleries and crystalline structure of starch were investigated using X-ray diffraction (XRD). It was found that the increase in d-spacing of organically modified clay was due to starch molecular intercalation while the increase in d-spacing of pristine clay was mostly caused by glycerol intercalation because of the narrow valid d-spacing of pristine clay and special ring-like monomer of starch. The mechanism of starch intercalation in clay galleries was discussed.     

Water‐blown polyurethane–clay nanocomposite foams from biopolyol—effect of nanoclay on the properties

The present work deals with the development of polyurethane–clay nanocomposite foams by replacing part of the synthetic polyol with castor oil derivative. Hydroxylated castor oil was converted into diethanol amide by transamidation and the resulting polyol was formulated into water‐blown foams. Modified montmorillonite clay was used as nanofiller in different amounts viz. 0.5%, 1.0%, 2.0%, and 5.0% by total weight of the foam formulation. Rheological measurements on the polyol–clay mixtures indicated that up to 1% clay loading there is no significant change in the viscosity with shear rate and beyond 2%, shear thinning occurred. X‐ray diffraction studies further substantiated these results. The effect of the modified clay on the density, mechanical properties such as compression strength, compression modulus, and microstructure of the foams were investigated. The filler thus added had a reinforcing effect on the foam as observed in the density and compression strength measurements. Differential scanning calorimetric studies on T_g and dynamic mechanical analyses on the modulus clearly indicated that 1% clay loading and above led to exfoliation and plasticizing effect. Exfoliated nanocomposites in compositions containing 1% clay and more yielded a much higher nucleation rate than intercalated ones leading to reduced cell size as observed by optical and scanning electron microscopy. Thus, castor oil, which is readily available, relatively inexpensive, and environmentally benign nonedible oil, has been successfully used to prepare filled semirigid foams which can find application in insulation and packing. POLYM. COMPOS. 34:1306–1312, 2013. © 2013 Society of Plastics Engineers     

Effects of a silane coupling agent on the exfoliation of organoclay layers in polyurethane/organoclay nanocomposite foams?

An attempt was made to synthesize polyurethane (PU)/organoclay nanocomposite foams with high thermal insulation properties. The organoclay was modified by polymeric 4,4′‐diphenylmethane diisocyanate (PMDI) with a silane coupling agent. The structure of the organoclay‐modified PMDI with the silane coupling agent was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Transmission electron micrographs and wide‐angle X‐ray diffraction patterns showed that the interlayer distance increased for the PU/organoclay nanocomposites with the addition of the silane coupling agent. It was expected that the distance between the organoclay layers would increase and that the organoclay would be dispersed on a nanoscale in the PU matrix because of the organic/inorganic hybrid bond formation between the organoclay and silane coupling agent. Compressive and flexural strengths of the PU/silane coupling agent/organoclay nanocomposite foams were similar to those of the PU/organoclay nanocomposite foams. However, the thermal conductivity appreciably decreased from 0.0250 to 0.0230 W/m h °C in the PU/silane coupling agent/organoclay nanocomposite foams. Scanning electron micrographs showed that the cell size of the PU/silane coupling agent/clay nanocomposite foams also decreased. On the basis of these results, it is suggested that the smaller cell size and lower thermal conductivity of the PU/silane coupling agent/organoclay nanocomposite foams were mainly due to enhanced exfoliation of the organoclay layers by the silane coupling reaction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and Characterization of Sustainable Polyurethane Foams from Soybean Oils

Polyol derived from soybean oil was made from crude soybean oil by epoxidization and hydroxylation. Soy-based polyurethane (PU) foams were prepared by the in-situ reaction of methylene diphenyl diisocyanate (MDI) polyurea prepolymer and soy-based polyol. A free-rise method was developed to prepare the sustainable PU foams for use in automotive and bedding cushions. In this study, three petroleum-based PU foams were compared with two soy-based PU foams in terms of their foam characterizations and properties. Soy-based PU foams were made with soy-based polyols with different hydroxyl values. Soy-based PU foams had higher T _g (glass transition temperature) and worse cryogenic properties than petroleum-based PU foams. Bio-foams had lower thermal degradation temperatures in the urethane degradation due to natural molecular chains with lower thermal stability than petroleum skeletons. However, these foams had good thermal degradation at a high temperature stage because of MDI polyurea prepolymer, which had superior thermal stability than toluene diisocyanate adducts in petroleum-based PU foams. In addition, soy-based polyol, with high hydroxyl value, contributed PU foam with superior tensile and higher elongation, but lower compressive strength and modulus. Nonetheless, bio-foam made with high hydroxyl valued soy-based polyol had smaller and better distributed cell size than that using low hydroxyl soy-based polyol. Soy-based polyol with high hydroxyl value also contributed the bio-foam with thinner cell walls compared to that with low hydroxyl value, whereas, petroleum-based PU foams had no variations in cell thickness and cell distributions.     

Preparation and characterization of polyurethane–organoclay nanocomposites

Nanocomposite polyurethane (PU)–organoclay materials have been synthesized via in‐situ polymerization. The organoclay is first prepared by intercalation of tyramine into montmorillonite (MMT)‐clay through ion exchange process. The syntheses of polyurethane–organoclay hybrid films containing different ratios of clay were carried out by swelling the organoclay into diol and diamine followed by addition of diisocyanate and then cured. The nanocomposites with dispersed and exfoliated structure of MMT were obtained as evidenced by X‐ray diffraction and scanning electron microscope. X‐ray diffraction showed that there is no peak corresponding to d₀₀₁ spacing in organoclay with the ratios up to 20 wt%. SEM images confirmed the dispersion of nanometer silicate layers in the polyurethane matrix. Also, it was found that the presence of organoclay leads to improvement in the mechanical properties. The tensile strength was increased with increasing the organoclay contents to 20 wt% by 221% in comparision to the PU with 0% organoclay. POLYM. COMPOS. 28:108–115, 2007. © 2007 Society of Plastics Engineers     

Study on the effect of ultrasonication time on transport properties of polyurethane/organoclay nanocomposite coatings

In this study, a series of polyurethane (PU)/organically modified montmorillonite (OMMT) clay nanocomposites were synthesized by in situ polymerization technique through an ultrasonication-assisted process at various processing times. Wide angle X-ray diffraction (WAXD) was employed to investigate the effect of processing time on degree of delamination of clay platelets. In order to evaluate the effect of ultrasonication time on transport properties of the PU/OMMT composites, diffusion coefficient and maximum water uptake were determined through a water permeation test. Electrochemical impedance spectroscopy (EIS) was carried out to analyze the barrier properties and to evaluate the corrosion performance of these composite coatings on carbon steel panels. It was found that by increasing sonication time, the barrier property of nanocomposites against diffusion of water molecules was improved. This is due to further separation of clay platelets and enhancement of the traveling pathways for water molecules.     

Surface‐modifiers of clay on mechanical properties of rigid polyurethane foams/organoclay nanocomposites

Three different surface modifiers, octadecyl trimethyl ammonium (ODTMA), octadecyl primary ammonium (ODPA), and decanediamine (DDA) were used to modify Na⁺? montmorillonite (MMT), and the resultant organoclays were coded as ODTMA‐MMT, ODPA‐MMT, DDA‐MMT, respectively. Rigid PU foams/organoclay composites were prepared by directly using organoclay as the blowing agent without the addition of water. Investigation shows that the morphology of the nanocomposites is greatly dependent on the surface modifiers of clay used in the composites. In detail, DDA‐MMT is partially exfoliated in the PU matrix with the smallest cell size, while two others are intercalated in the PU matrices with smaller cell sizes. The sequence of their cell sizes is pristine PU foams > rigid PU foams/ODTMA‐MMT > rigid PU foams/ODPA‐MMT > rigid PU foams/DDA‐MMT, and the average cell size of rigid PU foams/DDA‐MMT composites decreases evidently from 0.30 to 0.07 mm. Moreover, all rigid PU foams/organoclay composites show remarkable enhanced compressive and tensile strengths as well as dynamic properties than those of PU foams, and the enhancement degree coincides well with the relative extent of internal hydrogen bonding of materials and gallery spacing of organoclay. For example, in the case of rigid PU foams/DDA‐MMT composite, 214% increase in compressive strength and 148% increase in tensile strength compared with those of pure PU foams were observed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effect of clay exfoliation and organic modification on morphological,dynamic mechanical,and thermal behavior of melt‐compounded polyamide‐6 nanocomposites

Polyamide‐6/clay nanocomposites were prepared employing melt bending or compounding technique followed by injection molding using different organically modified clays. X‐ray diffraction and transmission electron microscopy were used to determine the molecular dispersion of the modified clays within the matrix polymer. Mechanical tests revealed an increase in tensile and flexural properties of the matrix polymer with the increase in clay loading from 0 to 5%. C30B/polyamide‐6 nanocomposites exhibited optimum mechanical performance at 5% clay loading. Storage modulus of polyamide‐6 also increased in the nanocomposites, indicating an increase in the stiffness of the matrix polymer with the addition of nanoclays. Furthermore, water absorption studies confirmed comparatively lesser tendency of water uptake in these nanocomposites. HDT of the virgin matrix increased substantially with the addition of organically modified clays. DSC measurements revealed both γ and α transitions in the matrix polymer as well as in the nanocomposites. The crystallization temperature (T_c) exhibited an increase in case of C30B/polyamide‐6 nanocomposites. Thermal stability of virgin polyamide‐6 and the nanocomposites has been investigated employing thermogravimetric analysis. POLYM. COMPOS., 28:153–162, 2007. © 2007 Society of Plastics Engineers     

Reaction kinetics and characteristics of polyurethane/clay nanocomposites

The reaction behavior and physical properties of polyurethane (PU)/clay nanocomposite systems were investigated. Organically modified clay was used as nanofillers to formulate the nanocomposites. Differential scanning calorimetry was used to study the reaction behavior of the PU/clay nanocomposite systems. The reaction rate of the nanocomposite systems increased with increasing clay content. The reaction kinetic parameters of proposed kinetic equations were determined by numerical methods. The glass transition temperatures of the PU/clay nanocomposite systems increased with increasing clay content. The thermal decomposition behavior of the PU/clay nanocomposites was measured by using thermogravimetric analysis. X‐ray diffractometer and transmission electronic microscope data showed the intercalation of PU resin between the silicate layers of the clay in the PU/clay nanocomposites. A universal testing machine was used to investigate the tensile properties of the PU/clay nanocomposites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1641–1647, 2005     

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     

Thermal Stability and Flame Retardancy of Rigid Polyurethane Foams/Organoclay Nanocomposites

The thermal stability and flame retardancy of a new kind of rigid polyurethane (PU) foams/organoclay nanocomposites developed by our research group were investigated by using thermogravimetry analysis (TGA) and cone calorimeter test. Results indicate that compared with pure PU foams, rigid PU foams/organoclay composites show significantly enhanced thermal stability and flame retardancy. The reasons leading to the results were discussed in detail by relating with the morphology of the composites. The discussion suggests that the enhancement degree of thermal stability and flame retardancy of composites compared with that of PU foams coincides well with the sequences of gallery spacing of organoclay in the PU matrix.     

Study on effect of duration of the ultrasonication process on solvent‐free polyurethane/organoclay nanocomposite coatings: Structural characteristics and barrier performance analysis

In this study, effect of duration of ultrasonication process on structural characteristics and barrier properties of solvent‐free castor oil‐based polyurethane (PU)/organically modified montmorillonite (OMMT) nanocomposites was investigated. A series of PU/OMMT composites were synthesized by in situ polymerization technique through an ultrasonication‐assisted process at various processing durations. Effect of ultrasonication duration on de‐agglomeration of clay stacks in castor oil dispersions was evaluated by optical microscopy, sedimentation test, and viscosity measurement. Wide angle X‐ray diffraction and Fourier‐transform infrared spectroscopy were employed to investigate the effect of processing time on degree of delamination of clay platelets and interfacial strength between clay layers and PU matrix. Also, surface morphology of the nanocomposites was analyzed by atomic force microscopy. The results showed that by increasing the ultrasonication time up to 60 min, the size of clay agglomerates decreased and the interlayer spacing of clay platelets increased. To evaluate the effect of ultrasonication duration on transport properties of the PU/OMMT composites, diffusion coefficient and permeability were determined through water uptake test. Electrochemical impedance spectroscopy was carried out to analyze the barrier properties and to evaluate the corrosion performance of these composite coatings on carbon steel panels. It was found that by increasing sonication time, the barrier property of nanocomposites against diffusion of water molecules improved, which is due to further separation of clay platelets, enhancement of the traveling pathways for water molecules and improvement of interactions between the two components. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Improvement of nanoclays dispersion through microwave processing in polyurethane rigid nanocomposite foams

Polyurethane rigid nanocomposite foams were synthesized by in situ‐polymerization using both pristine and organically modified layered silicates. The effect of synthesis conditions, in particular the effect of different dispersing techniques, on morphology and mechanical properties of polyurethane nanocomposite foams was studied. To promote dispersion, clays were dispersed either in polyols or isocyanate and were subjected to a well known dispersion method, like ultrasonication, but also to a new dispersion method, based on microwaving. The morphological characterization of the foams, carried on using X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy, proved that the technology based on microwave processing is able to provide very good silicates dispersion and requires very short application time to be effective. Further confirmations of the importance of the clay organo‐modifier are still present. Mechanical characterization of foams show that clay interferes with H‐bond formation and then the overall compressive performance of PU nanocomposite foams depends on the competition between the positive reinforcing effect of clay and the negative effect on H‐bond formation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of chain-extended organifier and properties of polyurethane/clay nanocomposites

Clay organifier with hydroxyl end-group and relatively high molecular weight was synthesized. The clay treated with the organifier was suspended in DMF and the dispersibility of organoclay in polyurethane matrix was enhanced by applying the sonication to the suspension of organoclay in DMF. The d-spacing of organoclay was found to be 2.29 nm compared to 1.18 nm of pristine montmorillonite. The polyurethane/clay nanocomposites formed an intercalated structure with some disorder and their d-spacings were about 2.6-2.7 nm. The barrier property, thermal stability and tensile properties significantly increased with increasing the dispersibility of organoclay. A 2.9-fold increase in tensile strength with 1 wt% of well-dispersed organoclay, a 41% decrease in oxygen permeability and a 1.7-fold increase in Young's modulus at 5 wt% of well-dispersed organoclay were achieved.