Polyurethane Content Research Articles

Self-gradient mechanism, morphology and damping analysis of a thickness continuous gradient epoxy–polyurethane interpenetrating polymer network

A simple and affordable gradient-distributing interpenetrating polymer network (IPN) composite was created that takes advantage of the relatively poor compatibility and the curing rate discrepancy between epoxy (EP) and polyurethane (PU) resins. Organic element content analysis (CHNS/O) and attenuated total reflection infrared spectroscopy (ATR-FTIR) reveal that the PU content is a gradient that changes along the direction of the thickness. Morphology analysis by scanning electron microscopy (SEM) and atomic force microscopy (AFM) proves that it has a continuously changing modulus with no stratified structure. Dynamic thermomechanical analysis (DMA) and fatigue testing demonstrate that the composite has better performances than traditional homogeneous IPNs with the same compositions.

Study on the poly(3‐hydroxybutyrate‐co−4‐hydroxybutyrate)‐based composites toughened by synthesized polyester polyurethane elastomer

ABSTRACTIn this study, polycaprolactone(PCL)‐based polyurethane (PU) elastomer containing 45 wt % hard segment component was synthesized and characterized by fourier transform infrared spectroscopy, gel permeation chromatography, and X‐ray diffraction. As a toughening agent, the as‐synthesized PU was incorporated into biodegradable poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) [P(3,4)HB] by solution casting to prepare P(3,4)HB/PU composites. The microstructure and properties of P(3,4)HB/PU composites were investigated using transmission electron microscopy, X‐ray diffraction, tensile testing, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and activated sludge degradation testing. The results show that PU can disperse well in a P(3,4)HB matrix. The elongation at break of P(3,4)HB/PU composites is remarkably increased while the yield strength and elastic modulus are decreased with an increase in PU content. At the same time, it is found that the fracture characteristic of P(3,4)HB is obviously transformed from brittleness into ductility with a gradual increase in PU loading. Moreover, the thermal stability of P(3,4)HB/PU composites is significantly improved compared with that of pure P(3,4)HB. In addition, the biodegradation rate of P(3,4)HB/PU composites is evidently reduced with the increase of PU content in the activated sludge degradation testing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42740.

Phase morphology, crystallization behavior and mechanical properties of poly(L-lactide) toughened with biodegradable polyurethane: Effect of composition and hard segment ratio

Polyester-based biodegradable polyurethane (PU) with different hard segment ratios was selected to modify the impact toughness of poly(L-lactide) (PLLA). The influence of blending composition and hard segment ratio of PU on the phase morphology, crystallization behavior and mechanical properties of PLLA/PU blends has been investigated systematically. The results showed that the PU particles were uniformly dispersed in PLLA matrix at a scale from submicrons to several microns. The glass transition temperature of PU within these blends decreased compared to that of neat PU, but rose slightly with its content and hard segment ratio. The presence of PU retarded the crystallization ability of PLLA, whereas enhanced its elongation at break and impact resistance effectively. As the PU content reaches up to 30 wt%, the phenomenon of brittle-ductile transition occurred, resulting in a rougher fracture surface with the formation of fibril-like structure. Moreover, under the same concentrations, the elongation at break and impact strength of PLLA blends decreased slightly with the increase of hard segment ratio of PU.

Strength Characteristics Of Polyurethane (PU) With Modified Sand

Soil stabilisation is defined as a technique to improve the engineering characteristics in order to improve the parameters such as shear strength, compressibility, density, hydraulic conductivity. There are many techniques that can be used for different purposes by enhancing some aspects of soil behaviour and improve the strength and properties of soil. One of the cheapest techniques is by using Polyurethane grout, which is workable for construction and enhances the performance of soil compressive strength. Polyurethane (PU) foam is non-toxic, having an indefinite life span and non-environment unfriendly. PU is a chemical substance that normally used in polymer industries for instance resilience foam seating, rigid foam insulation panels and microcellular foam seals. In this research, different percentages of PU content are mixed with sand to test the compressive strength of modified sand. The compressive strength of sand is determined by conducting the Unconfined Compression Test (UCT) with the mold samples of 50mm diameter and 100mm height. The test determines the compressive strength and generates the stress-strain relationship of the modified sand. It is shown that the compressive strength of modified sand will gradually increase with an increasing PU content percentage (varying from 10% (20 kPa) – 95% (500 kPa). Conclusively, this research could be used as the benchmark of ground improvement technique.

Preparation of High Density Polyethylene/Waste Polyurethane Blends Compatibilized with Polyethylene-Graft-Maleic Anhydride by Radiation

Polyurethane (PU) is a very popular polymer that is used in a variety of applications due to its good mechanical, thermal, and chemical properties. However, PU recycling has received significant attention due to environmental issues. In this study, we developed a recycling method for waste PU that utilizes the radiation grafting technique. Grafting of waste PU was carried out using a radiation technique with polyethylene-graft-maleic anhydride (PE-g-MA). The PE-g-MA-grafted PU/high density polyethylene (HDPE) composite was prepared by melt-blending at various concentrations (0–10 phr) of PE-g-MA-grafted PU. The composites were characterized using fourier transform infrared spectroscopy (FT-IR), and their surface morphology and thermal/mechanical properties are reported. For 1 phr PU, the PU could be easily introduced to the HDPE during the melt processing in the blender after the radiation-induced grafting of PU with PE-g-MA. PE-g-MA was easily reacted with PU according to the increasing radiation dose and was located at the interface between the PU and the HDPE during the melt processing in the blender, which improved the interfacial interactions and the mechanical properties of the resultant composites. However, the elongation at break for a PU content >2 phr was drastically decreased.

A New Approach for Synthesizing the Hybrid Silica Aerogels

Uniform Polyurethane/silica hybrid aerogels were achieved at ambient pressure via an approach in which an aqueous polyurethane dispersion was used and the hybridization step carried out before gelation step. The FT-IR spectra confirmed the incorporation of polymer chains into the silica network and hybrid network formation.As the H2O/TEOS molar ratio increased after hybridization in this method, the effect of H2O/TEOS molar ratio changes and PU content on the density of hybrid aerogels was investigated separately. The density of native silica aerogels decreases commonly with increasing the water content while increasing the aqueous PU dispersion content increases the density of hybrid aerogels. The density difference between the hybrid aerogel sample with a certain aqueous PU dispersion and the similar native silica aerogel with the same H2O/TEOS molar ratio demonstrated the intensive polyurethane chain effect on the aerogel density. The results showed that the simultaneous increase of H2O/TEOS molar ratio and PU content could be led to the uniform structure of hybrid aerogels. However, the effect of polyurethane on the aerogel density was more sensitive than H2O/TEOS molar ratio effect especially in high polyurethane content (≥10wt.%) that increased the density of hybrid aerogels.

CNT buckypaper/thermoplastic polyurethane composites with enhanced stiffness, strength and toughness

Abstract Carbon nanotube buckypaper/thermoplastic polyurethane elastomer composites were successfully fabricated. At certain polyurethane contents, the composites exhibited simultaneous improvements in stiffness (up to 6 GPa), strength (up to 120 MPa), ductility (up to 30%) and toughness (up to 36 MJ/m 3 ). The measured elastic modulus of the composites could be predicted by Mori–Tanaka model. The possible reinforcing mechanisms were discussed by Raman spectroscopy and SEM fractography. The results revealed that ductile polymers are very promising matrix in balancing the key mechanical properties of buckypaper, which are beyond the commonly used brittle thermosettings, e.g. epoxy resin.

Compatibility of Polyvinylidene Difluorid/Polyurethane and Preparation of Composite Tubular Membrane

The compatibility of polyvinylidene difluorid (PVDF) and polyurethane (PU), the thermodynamics of the PVDF/PU/DMF (N-N-Dimethylformamide) membrane-forming systems were studied, and the composite tubular membranes of PVDF/PU-PET knitted fabric tube were prepared by the immersion precipitation phase inversion method. The results showed that the PVDF/PU system was partly compatible by the measurements of the solubility parameter theory, the mixing enthalpy, the viscosity. With PU content increasing, the gelation values increased and the instantaneous liquid-liquid phase separation was preferred to occur. The water flux of the composite tubular membranes were enhanced from 1264.81 to 2165.35 L/m2.h with PU content increasing from 10wt% to 40wt%, which resulted from the an increment of the membrane porosity and the improvement of the hydrophilicity.

Synthesis, pore structure and properties of polyurethane/silica hybrid aerogels dried at ambient pressure

Polyurethane/silica hybrid aerogels were synthesized at ambient pressure drying conditions with the specific surface area, pore volume and pore diameter in the range of 530–850m2/g, 0.71–2.83cm3/g, and 5–13nm, respectively. TGA results showed that almost all polyurethane chains preserved as a part of gel network. The pore structure and properties of these hybrid aerogels showed an interesting dependence on the polyurethane content. The improved structure and properties compared to native silica aerogel was achieved with introducing 3v/v% aqueous polyurethane dispersion into silica sol. High polyurethane content led to low porosity (61%) and small surface area (535m2/g).

Influence of composition on the morphology of polyurethane/acrylic latex particles and adhesive films

Polyurethane (PU)/acrylic hybrid particles with different PU contents were synthesized by miniemulsion polymerization and subsequently dried to give solid adhesive films. The morphologies of the particles and the morphologies and mechanical properties of the resulting films were investigated by Transmission electron microscopy combined with selective staining of the PU and by uniaxial tension tests. Morphological investigations showed a clear change in the particle morphology as the PU weight fraction increased. While at 5wt% and 25wt% PU (with respect to total organic content) the particles were relatively homogeneous and mechanical properties of the films could be readily interpreted with molecular arguments, at 50wt% PU a core–shell structure was observed. This heterogeneous structure of the 50wt% PU particles persisted in the films, resulting in a percolating network of the harder PU phase. The low deformability and strain at failure of the 50% PU films suggest that, unlike the adhesives with lower PU content, the relatively weak interfaces between the original latex particles dominate the mechanical properties.

Risks related to car fire on innovative Poroelastic Road Surfaces—PERS

SummaryTo reduce tyre/road noise, the concept of poroelastic road surfaces (PERS) was invented. PERS is a road surface material that is porous, and at the same time, it is flexible because of the substantial amount of rubber granulate content (from 20% to 85%). The rubber and stone particles are bound by polyurethane resin instead of bitumen. It was feared that in case of fire, because of the high content of rubber and polyurethane, there may be considerable emission of potentially hazardous substances (such as hydrogen cyanide) from burning PERS. Tests performed by the Technical University of Gdansk show that the emission of toxic gases is rather small and that the surface does not promote car fire, even when soaked with fuel. Car fire with fuel spill on PERS is less dangerous for passengers than car fire on dense road surface as the fire is spreading much slower. The article presents results of laboratory and road experiments carried out within FP7 ‘PERSUADE’. Copyright © 2014 John Wiley & Sons, Ltd.

Characterization of solvent-filled polyurethane/urea–formaldehyde core–shell composites

Encapsulation of liquid phases is a crucial step in many self-healing material systems where a healing agent has to be protected during processing and then released during a damage event. In this work, the mechanical properties of polyurethane (PU) reinforced urea–formaldehyde (UF) shells are characterized. It was found that shell thickness is both a function of PU content in the core phase and of the microcapsule diameter. Furthermore, a saturation thickness was found for high PU contents or high capsule diameters and this phenomenon had direct implications on the bursting force under compression of single microcapsules. With help of an analytical model, the Young's modulus of the hybrid PU/UF was determined and in general, PU-reinforced shells had a lower modulus but higher ductility in terms of elongation at break, leading to more resistant microcapsules overall.

Preparation, properties, and applications of acrylic–polyurethane hybrid emulsions in extinction electrophoresis

ABSTRACTAqueous acrylic–polyurethane hybrid emulsions (PUA) were fabricated by semibatch emulsion copolymerization using a mixture of acrylic (AC) monomers in the presence of an isocyanate terminated polyurethane (PU). The effects of PU content on the morphology of the hybrid emulsions and film properties were here investigated in detail using FT‐IR, UV, TEM, and SEM. TEM images clearly showed that hybrid emulsions exhibited a core‐shell structure before neutralization. However, after neutralization with N,N‐dimethylethanolamine, the typical particles exhibited phase inversion, producing particles with irregular hemispheres shapes and diameters about 0.5 μm. SEM images showed that the film surface became rougher as PU content increased, peaking at 10 wt %, the gloss of this film was 23.1 (60°). The UV transmittance spectra of the PUA hybrid emulsion within a wavelength range 700–200 nm decreased as PU content increased. This was consistent with the changes in the surface roughness of the film. Electrophoresis took place on an aluminum alloy surface and the product was dried at 120°C. The film exhibited excellent mechanical performance due to curing reaction between the NCO group on PU and hydroxyl group on the AC copolymer. The gloss of the film was found to be as low as 4.0 after electrophoresis testing. These films may be useful in practical extinction electrophoresis. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40078.

Detailed study of distribution patterns of polycyclic aromatic hydrocarbons and isocyanates under different fire conditions

This study has examined the distribution patterns between gas phase and particle phase of some chemical compounds produced in fires. It has also addressed the question of the distribution of individual particle-associated species between the different size-ranges of particles. The chemical compounds studied and discussed in this paper are polycyclic aromatic hydrocarbons (PAHs), and isocyanates. The steady-state tube furnace, ISO/TS 19700, was chosen as the physical fire model in order to study the production of particles from different types of fire exposure, that is, oxidative pyrolysis, well-ventilated flaming fires and under-ventilated flaming post-flashover fires. Two materials were chosen for investigation, a polyvinyl chloride (PVC) carpet and a wood board. The particle production from the two materials investigated varied concerning both the amounts produced and the particle size distributions. The analysis of PAHs showed that volatile PAHs were generally dominant. However, when the toxicity of the individual species was taken into account, the relative importance between volatile and particle-associated PAHs shifted the dominance to particle-bound PAH for both materials. The substantial degradation in the tests of the low polyurethane content of the PVC carpet, and the (4,4′-methylenediphenyl diisocyanate)-based binder in the wood board resulted in no or very small amount of quantifiable diisocyanates. Copyright © 2013 John Wiley & Sons, Ltd.

Achieving shape memory: Reversible behaviors of cellulose–PU blends in wet–dry cycles

AbstractShape memory effect (SME) was achieved for cellulose–polyurethane (PU) blends of different compositions in wet–dry cycles, featuring that the amorphous cellulose and the PU content served as the fixing phase and the recovery phase, respectively. The dependence on the compositions of the fixity ratio and the recovery ratio was quantitatively measured by tensile tests. The morphological and thermal properties of the blends were further investigated by scanning electron microscopy and thermogravimetric analysis. The storage modulus of the blends varied reversibly in the wet–dry cycles, as determined by dynamic mechanical analysis. Furthermore, the microstructure of the blends reversibly changed correspondingly, as determined by wide‐angle X‐ray scattering diffraction and Fourier transform infrared. It was predicted that the reversible transition in different amorphous cellulose structures triggered by water led to the reversible variation in modulus as well as the wet–dry SME of the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Polyurethane (urea)/polyacrylates interpenetrating polymer network (IPN) adhesives for low surface energy materials

On the basis of the polymerization of the acrylate phase catalyzed by the oxidation of trialkylborane at room temperature, a series of polyurethane (urea)/polyacrylates adhesives with interpenetrating polymer network structure (IPNS) was synthesized. The crosslinking polyurethane (urea) phase was synthesized by the reaction between polymer diamine or triol and isocyanate. The resulting IPN adhesives as a function of the polyurethane (urea) or 2‐hydroxylethyl acrylate terminated polyurethane (HEA‐PU) (crosslinking agent of acrylate phase) content were explored. The adhesive morphology took on the IPNS that manifested as a finely dispersed polyurethane (urea) phase in the acrylate phase. Excellent adhesion to low surface energy materials was achieved within a wide range of polyurethane (urea) contents. The IPN adhesives also displayed better flexibility than polyacrylate adhesives with HEA‐PU as a crosslinking agent. Copyright © 2011 John Wiley & Sons, Ltd.

Damping, Thermal, and Mechanical Properties of Polycaprolactone-Based PU/EP Graft IPNs: Effects of Composition and Isocyanate Index

A series of polycaprolactone (PCL)-based polyurethane (PU)/epoxy resin (EP) graft interpenetrating polymer networks (IPNs) were prepared and their damping propertiesand thermal stability, as well as mechanical properties, were systematically studied in terms of composition and the values of the PU isocyanate index (R). The morphologies of the PU/EP IPNs were observed by scanning electron microscope (SEM) and atomic force microscope (AFM) characterization and the relationship between the morphologies and the properties is also discussed. The damping properties and thermal stability measurements revealed that the formation of PU/EP IPNs could significantly improve not only the damping properties but also the thermal stability. Meanwhile, the mechanical tests showed that the tensile strengths of the IPNs decreased, while their impact strengths increased with increasing PU content. The value of the PU isocyanate index also had significant impacts on the properties of the IPNs when the PU to EP ratio was fixed, which could be an effective means for manipulating the fabrication of PU/EP IPNs. From the results obtained, the PCL-based PU/EP IPNs hold promise for use in structural damping materials.

Effect of elastomeric additives on fabrication and properties of filled fiber materials formed from polymer solutions

We have studied the effect of elastomer additives on the properties of spin dopes for obtaining filled fiber materials by aerodynamic spinning from polymer solutions. We have obtained laboratory samples of materials with different polyurethane content. We have analyzed the results of physicomechanical, sorption, and physical tests of these materials. We show that modification of filled fiber materials by introducing elastomeric additives has only an insignificant negative impact on the sorption properties and markedly improves their physicomechanical characteristics.

Mechanical Properties of Adhesive Films Obtained from PU−Acrylic Hybrid Particles

The mechanical and adhesive properties of films made from novel hybrid urethane/acrylic dispersions have been investigated. The adhesive films were obtained from the drying of bicomponent acrylic urethane latexes prepared by miniemulsion polymerization. In the companion paper, phase separation at the macroscopic scale was avoided by using a NCO end-functionalized polyurethane (PU) prepolymer and a hydroxyethyl methacrylate (HEMA) reactive comonomer in the acrylic backbone. The effect of two compositional parameters on the mechanical and adhesive properties was specifically studied: the PU weight fraction and the degree of grafting of the PU prepolymer on the acrylic backbone, controlled by the ratio between grafting agent HEMA and chain extender Bisphenol A (BPA). Swelling, rheological, tensile, and probe tack tests were used in parallel with an analysis of the macroscopic adhesive properties of the films. Results show that the PU weight fraction modifies significantly the small-strain elastic modulus and the gel fraction in the latex particle while the ratio HEMA/BPA can be used to adjust the chain length of the PU incorporated in the network. This ratio affects significantly the finite extensibility of the PSA while causing only relatively small changes in the low strain elastic modulus and gel fraction. An increase in the degree of grafting at fixed PU content is found to improve the resistance to shear of the adhesive without reducing its adhesion energy in a peel or probe tack test.

Thermal and tensile properties of HTPB-based PU with PVC blends

Blends of HTPB (hydroxyl-terminated polybutadiene)-based polyurethane (PU) and polyvinyl chloride (PVC) membranes with various relative weight percentages were prepared by solution process. Different equivalent ratios of HTPB, 4,4′-dicyclohexyl methane diiscyanate (H 12MDI), and 1,4-butane diol were used to synthesize PU solution by two-stage process. The intermolecular bonding between N–H, C O groups of PU and C–Cl group of PVC was determined via FTIR analysis by the relative absorbance of the two N–H groups and was correlated to thermal/mechanical properties. Larger part of PVC has been found to disperse in the hard domain of PU resulting in the shift in IR frequency. Thermal property, tensile strength and intermolecular bonding of membranes were function of the contents of PVC and PU's hard segment. One-year aged butadiene-containing PUs and blends still exhibit higher tensile strength than that of as-prepared ones. Hence, it is promising to replace the plasticizer, such as DOP, in PVC by these HTPB-based PU for the prevention of PVC migration as well as the enhancement of mechanical and thermal properties of blends.