Mechanical properties,thermal stability,sound absorption,and flame retardancy of rigid PU foam composites containing a fire‐retarding agent: Effect of magnesium hydroxide and aluminum hydroxide

Isocyanate, polyether polyol, a flame retardant (10 wt%), and aluminum hydroxide/magnesium hydroxide (0, 5, 10, 15, and 20 wt%) are used to form the rigid polyurethane (PU) foam, while nylon nonwoven fabrics and a polyester aluminum foil are combined to serve as the panel. The rigid PU foam and panel are combined to form the rigid foam composites. The cell structure, compressive stress, combustion resistance, thermal stability, sound absorption, and electromagnetic interference shielding effectiveness (EMI SE) of the rigid foam composites are evaluated, examining the effects of using aluminum hydroxide and magnesium hydroxide. Compared with magnesium hydroxide, aluminum hydroxide exhibits superior performance to the rigid foam composites. When aluminum hydroxide is 20 wt%, the rigid foam composite has an optimal density of 0.153 g/cm³, an average cell size of 0.2466 mm, a maximum compressive stress of 546.44 Kpa, an optimal limiting oxygen index (LOI) of 29.5%, an optimal EMI SE of 40 dB, and excellent thermal stability and sound absorption.     

Compressive response of composite ceramic particle-reinforced polyurethane foam

Quasi-static and dynamic compressive tests are undertaken on the polyurethane (PU) foam and fumed silica reinforced polyurethane (PU/SiO₂) foam experimentally. The ceramic microspheres with varying mass fractions are adopted to mix with the PU/SiO₂ foam to fabricate the composite particle-reinforced foams. The effects of strain rate and particle mass fraction are discussed to identify and quantify the compressive response, energy-absorbing characteristic, and the associated mechanisms of the composite foams. The results show the initial collapse strength and plateau stress of the foams are improved significantly by reinforcing with the ceramic microsphere within 60 wt% at quasi-static compression. The rate sensitivity is observed on all the foams, but in different patterns due to the influence of ceramic microsphere. The compressive response affected by ceramic microsphere can be attributed to the particle cluster effect and stress wave propagation. Together with the deformation, the compressive characteristic experiences non-monotonic change from the low to high strain rates. The specific energy absorption (SEA) of the foam with 41 wt% ceramic microsphere show the largest magnitude at quasi-static compression. With the increasing strain rate, the ceramic reinforced foam exhibits superior energy absorption efficiency at high strain rates to that of the pure foams.     

Mechanical,acoustical and flammability properties of SBR and SBR-PU foam layered structure

In this work a layer structure from styrene butadiene rubber (SBR) composites and PU foam with improved flame retardancy property and high sound absorption coefficient at frequency range (200–500 Hz). Different types of flame retardants; iron (acrylic-co-acrylamide) as metal chelate (MC), magnesium hydroxide (MOH) and sodium tripolyphosphate (STP) were blended with SBR. The type and loading level of flame retardant had a great effect on filler dispersion and consequently on mechanical properties of SBR. MOH exhibited the best dispersion as indicated from scanning electron microscope (SEM), and SBR/MOH samples had almost the highest crosslink density (16.04*10⁻⁵ g⁻¹ mol) and the best mechanical properties where the tensile strength was improved by 32.7% at 40 phr MOH. Horizontal burning rate of SBR composites indicated that MC and MOH reduced the rate of burning of SBR at all loading levels. TGA data presented that the addition of flame retardants to SBR increased the maximum decomposition temperature in all composites. A double and triple layer structures of SBR composite and PU foam was designed. The effect of 2.5 cm air cavity on the sound absorption coefficient of SBR-PU foam layered structure was studied. The presence of air cavity behind the layered structure improved the sound absorption in the range of (200–500 Hz) better than the existence of it between the layers. The triple-layer structure gave higher sound absorption coefficient at lower frequencies than that obtained with the double-layer structure where it reached to ≥0.98 at 315 Hz.     

Compressive stress relaxation of metallocene‐based polyolefin foams: Effect of gamma‐ray‐induced crosslinking

Metallocene‐based polyolefin (MPO) foams possess a closed‐cell structure which is in contrast to the open‐celled structure of polyurethane (PU) foams. In this study, we investigate the effects of gamma‐irradiation on the mechanical behavior of MPO foams using PU foam behavior as a basis. Compressive step‐strain experiments reveal a two‐step relaxation process in MPO foams, dominated by polymer chain relaxation at short times and gas diffusion from the closed cells at longer times. On the other hand, the relaxation in PU foams is similar to fully crosslinked polymers with the relaxation modulus reaching an equilibrium value after an initial decay. The closed‐celled structure of MPO foams lends to rapid stress relaxation and low structural recoverability upon application of compressive loads. Exposure to gamma radiation induces crosslinking in MPO foams and improves their resilience and recoverability. Stress relaxation tests reveal that nonradiated MPO foams show complete relaxation and structural loss at high temperatures. In contrast, radiated MPO foams show a significant retardation in relaxation kinetics and structural stability attributed to radiation‐induced crosslinking. Dynamic rheology and solvent‐extraction studies also support the results obtained from stress‐relaxation experiments. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1045–1056, 1999     

Lanthanum phenylphosphonate–based multilayered coating for reducing flammability and smoke production of flexible polyurethane foam

In the present work, lanthanum phenylphosphonate (LaPP)–based multilayered film was fabricated on the surface of flexible polyurethane (PU) foam by layer‐by‐layer self‐assembled method. The successful deposition of the coating was confirmed by scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX). Subsequently, the thermal decomposition and burning behavior of untreated and treated PU foams were investigated by thermogravimetric analysis (TGA) and cone calorimeter, respectively. The TGA results indicated that T_max2 of treated PU foams were increased by approximately 15°C to 20°C as compared with untreated PU foam. The peak heat release rate (PHRR) and total heat release (THR) of PU‐6 (with 19.5 wt% weight gain) were 188 kW/m² and 20.3 MJ/m², with reductions of 70% and 15% as compared with those of untreated PU foam, respectively. Meanwhile, the smoke production of treated PU foam was suppressed after the construction of LaPP‐based coating.     

Rigid polyurethane foams reinforced with disilanolisobutyl POSS: Synthesis and properties

This work reports the synthesis of rigid polyurethane (PU) foams modified by disilanolisobutyl polyhedral oligomeric silsesquioxane (DSIPOSS). This open‐cage nanostructure silsesquioxane has 2 hydroxyl groups and therefore can be chemically built directly in the PU backbone to form hybrid polyurethane‐POSS foam. Synthesis procedure using polymeric 4,4′‐diphenylmethane diisocyanate, polyetherol, and DSIPOSS has been elaborated, and the influence of POSS on the cell structure, closed cell content, apparent density, thermal conductivity, and compression strength of the rigid polyurethane composites has been evaluated. The hybrid composite foams containing 1.5 and 2.0 wt% DSIPOSS showed a reduced number of cells and an increased average area of foam cells in comparison with the unmodified PU, while the addition of 0.5wt% of DSIPOSS causes an increase in the number of cells of the foam as compared with the reference and thus a reduction in the average area of cells. X‐ray microtomography provided data on the porous structure of polyurethane hybrid materials, including reduction of the pore surface area. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy analysis revealed a good homogenization of DSIPOSS in polyurethane matrix. Thermogravimetric analysis results have shown that incorporation of POSS nanoparticles into PU foam does not significantly change the degradation process. The compressive strength of PUF‐POSS hybrids in the direction parallel and perpendicular to the direction of foam rise is greater than the strength of the reference foam already for the lowest DSIPOSS content.     

Enhancement of the thermal and mechanical properties of a surface‐modified boron nitride–polyurethane composite

Thermoplastic polyurethane (PU) elastomer, prepared from poly(tetramethylene glycol) and methyl diphenyl diisocyanate, was blended with boron nitride (BN) to fabricate a thermally conductive interface material. BN treated by a silane coupling agent (BN―NH₂) and PU‐grafted BN were prepared to fabricate a composite that has better thermal conductivity and mechanical strength. The surface‐modified filler showed enhanced dispersibility and affinity because of the surface treatment with functional groups that affected the surface free energy, along with the structural similarity of the doped crystallized diisocyanate molecule with the matrix. The thermal conductivity increased from 0.349 to 0.467 W mk^?1 on 20 wt% PU‐grafted BN loading that is a 1.34‐fold higher value than in the case of pristine BN loading at the same weight fraction. Moreover, the number of BN particles acting as defects, thereby reducing the mechanical strength, is decreased because of strong adhesion. We can conclude that these composite materials may be promising materials for a significant performance improvement in terms of both the thermal and mechanical properties of PU‐based polymers. Copyright © 2014 John Wiley & Sons, Ltd.     

Energy‐damping behaviors of poly(methyl acrylate‐co‐divinylbenzene) microspheres coated with a porous nickel–phosphorus layer

Hybrid microspheres of poly(methyl acrylate‐co‐divinylbenzene) (PMADVB) with a thin and porous nickel–phosphorus (Ni–P) alloy layer were prepared via suspension polymerization and electroless nickel plating. The characterization of pristine and nickel‐coated microspheres was carried out with a differential scanning calorimeter and a scanning electron spectroscope equipped with an energy‐dispersive system. The glass‐transition range of Ni–P‐coated PMADVB was broadened and extended in the higher temperature direction. This effect allowed the PMADVB network to embrace more diversified energy states of the segment motion, this being a desired feature for damping sound waves. The low‐frequency (100–1000‐Hz) sound absorption behavior of the microspheres was tested with a sound attenuation kit. Besides the testing of their low‐frequency damping performance, an investigation into the ultrasonic‐wave (～35 kHz) absorption feature of the microspheres was conducted through chemical means; that is, the attenuation to the ultrasonic wave with respect to the unprotective situation was assessed through the chemisorption extent of copper ions on a biomass adsorbent. The Ni–P deposition layer was found to augment the damping capacity of the polymer network. The alloy layer was determined to cause an expansion of the glass‐transition range of PMADVB and its wave‐scattering capability because this layer was made up of submicrometer metallic grains. In this work, the particulars of the metal–polymer interactions were associated with a core–shell structure. The metal outer layer was thought to create a spherical temperature field inside the PMADVB network, and concerted motions of the polymer segments resulted. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2710–2723, 2004     

Influence of caged bicyclic phosphate and CaCO3 nanoparticles on char-forming property of PU rigid foams

Char-forming property of PU rigid foams, which can be assessed by char residue (%) when PU is burned at certain temperature, was studied by TG and DTG. The results showed that pure PU rigid foam had low char residue of only 17%, while 33% of char residue was achieved when PU rigid foam was modified by adding 8 wt% of 1-oxo-2,6,7-trioxa-1-phosphabicyclo[2,2,2] octane (PEPA), which is a caged bicyclic phosphate. The experiment results of FTIR and XPS showed that the PEPA modified PU rigid foam could be dehydrogenated and dehydrated at temperature between 380 and 450 °C, resulting in the increase of char residue of PU rigid foam. Further study also revealed that the addition of CaCO₃ nanoparticles could enhance the char stability when the PEPA modified PU rigid foam was being burned. The mechanism was investigated and it was found that the enhanced char stability could be attributed to the limited permeation of oxygen caused by the formation of calcium phosphate and calcium pyrophosphate by the reaction of PEPA and CaCO₃ at high temperature, which were covered on or buried in the char layer.     

Sound absorption behavior of flexible polyurethane foams including high molecular‐weight copolymer polyol

Noise pollution is an important issue for automotive industries. In this article, the high molecular‐weight copolymer polyol is blended in the polyol mixtures for fabricating flexible polyurethane foams to improve sound absorption efficiency. Changes of cavity size and material density of the foams are negligible by inclusion of copolymer polyol in the polyol mixture, but the closed pore ratio and specific airflow resistance increase for the copolymer polyol content higher than 20 wt% because of changes of phase separation behavior from drainage flow rate reduction that occurs with increased viscosity. Sound absorption efficiency increases with increasing copolymer polyol content up to 20 wt%, but it decreases beyond this point. The sound absorption property mainly results from the closed pore ratio, not from the cavity size. The compression strength increases with increasing copolymer polyol contents by increased amount of hard segments. Therefore, an optimum amount of high molecular‐weight polyol is recommended for enhanced sound absorption property.     

Synthesis and morphology of rigid polyurethane foams with POSS as pendant groups or chemical crosslinks

This work reports on the preparation of polyurethane foams (PUFs) chemically modified by functionalized 1,2‐propanediolisobutyl polyhedral oligosilsesquioxane (PHI‐POSS) as pendant groups and octa(3‐hydroxy‐3‐methylbutyldimethylsiloxy) POSS (OCTA‐POSS) as chemical crosslinks. The resulting foams, which contain 0 to 15 wt% POSS (versus polyol), were characterized in terms of their structure, morphology, density, thermal conductivity, compressive strength, and water absorption. Fourier transform infrared‐attenuated total reflectance revealed good reaction rate between POSS and PUF. PHI‐POSS suppresses the formation of the hydrogen bonds in the soft phase. The composite foams with OCTA‐POSS showed a reduced number of cells and increased average area of foam cells in comparison with the PUF, while the addition of PHI‐POSS causes an increase in the number of cells of the foam as compared with the reference, and thus a reduction in the average area of cells. Scanning electron microscopy–energy‐dispersive X‐ray spectroscopy analysis revealed that POSS moieties form lamellae‐shaped crystals of different sizes, distributed homogeneously in the bulk (PHI‐POSS) or close to the self surfaces (OCTA‐POSS). The compressive strength of PUF/POSS hybrids in the direction parallel and perpendicular to the direction of foam rise is greater than the strength of the reference foam. PHI‐POSS improves monotonically the compressive strength in the studied loading range. About 5 wt% OCTA‐POSS also provides reinforcement, but further loading reverses the phenomenon. PUF/POSS hybrids absorb less water than the pristine foam because of an increase of foam density. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of surface modification of montmorillonite on the properties of rigid polyurethane foam composites

<正>This study investigated the influence of various organically modified montmorillonites(organoclays) on the structure and properties of rigid polyurethane foam(RPUF) nanocomposites.The organoclays were modified with cetyltrimethyl ammonium bromide(CTAB),methyl tallow bis(2-hydroxyethyl) quaternary ammonium chloride (MT2ETOH) and tris(hydroxymethyl)aminomethane(THMA) and denoted as CMMT,Cloisite 30B and OMMT, respectively.MT2ETOH and THMA contain hydroxyl groups,while THMA does not have long aliphatic tail in its molecule. X-ray diffraction and transmission electron microscopy show that OMMT and Cloisite 30B can be partially exfoliated in the RPUF nanocomposites because their intercalating agents MT2ETOH and THMA can react with isocyanate.However, CMMT modified with nonreactive CTAB is mainly intercalated in the RPUF matrices.At a relatively low filler content,the RPUF/CMMT composite foam has a higher specific compressive strength(the ratio of compressive strength against the apparent density of the foams),while at relatively high filler contents,RPUF/Cloisite 30B and RPUF/OMMT composites have higher specific compressive strengths,higher modulus and more uniform pore size than the RPUF/CMMT composite.     

Preparation and properties of negative ion/polyurethane flexible foam composites

Abstract

In this study, negative ionpowder was modified with a silane coupling agent and then added to the polyurethane flexible foam to prepare NI/PU flexible foam composites by the one-step foaming method. The effects of the amount of negative ion powder on the mechanical properties, thermal properties and release of negative ions were investigated using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and negative ion detectors. The SEM results showed that modified negative ion powder could be more uniformly distributed around the cell walls of the polyurethane flexible foam. The thermal stability, tensile strength and resilience of the NI/PU flexible foam composite were improved with the increase of the amount of modified negative ion powder. Increasing the amount of modified negative ion powder could also result in an increase in the release of negative ions, and it reached 5500/cm³ or higher at a negative ion content of 3%.     

A novel method for manufacturing of aluminum foam sandwich panels

In this study, a novel method for manufacturing aluminum foam sandwich (AFS) panels via self‐propagating high temperature synthesis (SHS) has been introduced and investigated. In this method, a powder mixture of metallic aluminum and copper oxide was placed in core–sheet interface. Sandwich panel was then heated under static pressure. During heating, SHS reaction (3CuO + 2Al = Al₂O₃ + 3Cu, ΔH < 0) occurred in the interface. The generated heat from this exothermic reaction caused sheets to join the core by melting the interface and nearby. In order to evaluate the shear strength of the interface, the shear test was applied on manufactured sandwich panels, and its results were compared with those obtained from testing the sandwich panels which were produced by diffusion bonding process. Furthermore, by the aid of energy dispersive spectrometer (EDS) and X‐ray diffraction (XRD) analyses, the formation of copper in the core–sheet interface and its diffusion into the sheets and the core were investigated. In addition, by plotting the hardness values of the panels' sheets across distance, it was found that the generated heat of the exothermic reaction caused a local melting of the panel sheets and the core. These results approved that core to sheet joining in metal foam sandwich panels took place because of the SHS reaction. Significantly, this new method could be applied as a proper and alternative method for production of AFS panels. Copyright © 2010 John Wiley & Sons, Ltd.     

The discovery of polymer‐clay hybrids

The first successful example of a polymer‐clay hybrid was nylon‐clay hybrid (NCH), which is a nano‐meter‐sized composite of nylon‐6 and 1‐nm‐thick exfoliated aluminosilicate layers of the clay mineral. NCH was found and developed at Toyota Central Research and Development Laboratories over 17 years ago. The NCH containing a few weight percentages of clay exhibits superior properties such as high modulus, high strength, and good gas‐barrier properties. The key for the discovery of NCH was the polymerization of a nylon monomer in the interlayer space of the clay. This highlight presents the development of NCH from its discovery to its commercialization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 819–824, 2004     

A ToF‐SIMS investigation of a buried polymer/polymer interface exposed by ultra‐low‐angle microtomy

The interfacial region of a model multilayer coating system on an aluminium substrate has been investigated by high‐resolution time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Employing ultra‐low‐angle microtomy (ULAM), the interface between a poly(vinylidene difluoride) (PVdF)‐based topcoat and a poly(urethane) (PU)‐based primer ‘buried’ >20 µm below the PVdF topcoat's air/coating surface was exposed. Imaging ToF‐SIMS and subsequent post‐processing extraction of mass spectra of the ULAM‐exposed interface region and of the PVdF topcoat and PU primer bulks indicates that the material composition of the polymer/polymer interface region is substantially different to that of the bulk PVdF and PU coatings. Analysis of the negative ion mass spectra obtained from the PVdF/PU interface reveals the presence of a methacrylate‐based component or additive at the interface region. Reviewing the topcoat and primer coating formulations reveals that the PVdF topcoat formulation contains methyl methacrylate (MMA)–ethyl acrylate (EA) acrylic co‐polymer components. Negative ion ToF‐SIMS analysis of an acrylic co‐polymer confirms that it is these components that are observed at the PVdF/PU interface. Post‐processing extraction of ToF‐SIMS images based on the major ions of the MMA–EA co‐polymers reveals that these components are observed in high concentration at the extremities of the PVdF coating, i.e. at the polymer/polymer interface, but are also observed to be distributed evenly throughout the bulk of the PVdF topcoat. These findings confirm that a fraction of the MMA–EA acrylic co‐polymers in the formulation segregate to the topcoat/primer interface where they enhance the adhesive properties exhibited by the PVdF topcoat towards the underlying PU primer substrate. Copyright © 2004 John Wiley & Sons, Ltd.     

New type of spherical pore Al alloy foam with low porosity and high strength

The Ultra Light Metal Structure with variouskinds of pores (open, close) realizes the lightness andmultifunction of structural material. The functionsinclude lightness (ρ < 1), high specific strength, highenergy absorption, sound insulation, heat insulationand electromagnetism shield. It is one of the hotspotsin material research nowadays[1— . The requirements 6]of high speed movement and high technology make Alalloy foam, which has higher specific st…     

An Elastic Monolithic Catalyst: A Microporous Metalloporphyrin‐Containing Framework‐Wrapped Melamine Foam for Process‐Intensified Acyl Transfer

The advent of conjugated microporous polymers (CMPs) has had significant impact in catalysis. However, the presence of only micropores in these polymers often imposes diffusion limitations, which has resulted in the low utilization of CMPs in catalytic reactions. Herein, the preparation of a foam‐supporting CMP composite with interconnective micropores and macropores and elastic properties is reported. Metalloporphyrin‐based CMP organogels are synthesized within the melamine foam by a room‐temperature oxidative homocoupling reaction of terminal alkynes. Upon drying, the CMP‐based xerogels tightly wrap the framework skeletons of the foam, while the foam cells are still open to allow for the preservation of elasticity and macroporosity. Such a hierarchical structure is efficient for acyl transfer, facilitates substrate diffusion within interpenetrative macropores and micropores, and could be used to intensify catalytic processes.     

Effect of EVM/EVA‐g‐MAH ratio on the structure and properties of nylon 1010 blends

The nylon 1010/ethylene‐vinyl acetate rubber (EVM)/maleated ethylene‐vinyl acetate copolymers (EVA‐g‐MAH) ternary blends were prepared. The effect of EVM/EVA‐g‐MAH ratio on the toughness of blends was examined. A super tough nylon 1010 blends were obtained by the incorporation of both EVM and EVA‐g‐MAH. Impact essential work of fracture (EWF) model was used to characterize the fracture behavior of the blends. The nylon/EVM/EVA‐g‐MAH (80/15/5) blend had the highest total fracture energy at a given ligament length (5 mm) and the highest dissipative energy density among all the studied blends. Scanning electron microscopy images showed the EVM and EVA‐g‐MAH existed as spherical particles in nylon 1010 matrix and their size decreased gradually with increasing EVA‐g‐MAH content. Large plastic deformation was observed on the impact fracture surface of the nylon/EVM/EVA‐g‐MAH (80/15/5) blend and related to its high impact strength. Then with increasing EVA‐g‐MAH proportion, the matrix shear yielding of nylon/EVM/EVA‐g‐MAH blends became less obvious. EVM and EVA‐g‐MAH greatly increased the apparent viscosity of nylon 1010, especially at low shear rates. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 877–887, 2009     

Polyurethane/polyaniline and polyurethane‐poly(methyl methacrylate)/polyaniline conductive core‐shell particles: Preparation,morphology, and conductivity

Polyurethane/polyaniline (PU/PANI) and polyurethane‐poly(methyl methacrylate)/polyaniline (PU‐PMMA/PANI) conductive core‐shell particles were synthesized by a two‐stage polymerization process. The first stage was to produce a core of PU or PU‐PMMA via miniemulsion polymerization using sodium dodecyl sulfate (SDS) as the surfactant. The second stage was to synthesize the shell of polyaniline over the surface of core particles. Hydrogen chloride (HCl) and dodecyl benzenesulfonic acid (DBSA) were used as the dopant agents. Ammonium persulfate (APS) was used as the oxidant for the polymerization of ANI. Different concentrations of HCl, DBSA, and SDS would cause different conformations of PANI chains and thus different morphologies of PANI particles. UV–visible spectra revealed that the polaron band was blue‐shifted because of the more coiled conformation of PANI chains by increasing the concentration of DBSA. Besides, with a high concentration of DBSA, both spherical‐ and rod‐shape PANI particles were observed by transmission electron microscope, and the coverage of PANI particles onto the core surfaces was improved. The key point of formation of rod‐type PANI particles was that DBSA was served with a high concentration accompanied with the existence of HCl or SDS. The better coverage of PANI particles over the core surfaces by charging higher DBSA concentrations resulted in a higher conductivity of hybrid particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3902–3911, 2007