58 research outputs found
1,2-Bis(4-aminoÂphenÂoxy)ethane
The molÂecule of the title compound, C14H16N2O2, is located on a crystallographic twofold rotation axis. The central O—C—C—O bridge adopts a gauche conformation. One of the amine H atoms is disordered over two equally occupied positions. The crystal structure is stabilized by N—Hâ‹ŻO and N—Hâ‹ŻN hydrogen bonds
Synthesis and characterization of siloxane-based polyurethane elastomers using hexamethylene diisocyanate
Synthesis and characterization of polydimethyl siloxane-based polyurethane elastomers using toluene diisocyanate
Nanoclay Dispersion and its Effect on Properties of Waterborne Polyurethanes
In recent years, waterborne polyurethanes as in coatings and adhesives formulations have attracted considerable attention because they are non-toxic, non-flammable and friendly to environment. Besides environmental management, the flexibility, low temperature property, high tensile strength, good adhesion and improved rheological property are specific properties of waterborne polyurethanes. Also low production cost of water borne polyurethanes over solvent-borne polyurethanes is also a reason for their applications. However, these materials have some defects such as weak water resistance and low adhesion in the moisture environment due to sensitivity of their hydrophilic ionic bonds, ether groups, urethane and ester groups to hydrolysis which need to be improved. Also, low heat resistance of these materials is due to a relatively low crystalline melting point or glass transition temperature of hard segments. One of the ways to solve this problem and improve its properties for different applications is the addition of inorganic fillers especially nano-sized layered silicates within polyurethane matrix. In this way water resistance, heat resistance, mechanical properties and modulus increase simultaneously. In this research, waterborne polyurethane nanocomposites with PTMG polyol, IPDI, DMPA (internal emulsifier), TEA (neutralizer) and 1, 3 and 5weight % of Cloisite 30B as reinforcement were synthesized and characterized. Polarity of the samples was investigated by contact angle test and dispersion of nano particles in the samples was characterized by X-Ray and TEM, Thermal properties and dynamic mechanical properties were measured by TGA and DMTA, respectively. The results showed that incorporation of clay into polyurethanes did reduce water absorption and increased heat resistance, modulus, particle size and contact angle.In recent years, waterborne polyurethanes including coatings and adhesives have attracted considerable attention because they are non-toxic, non-flammable and friendly to environment. Besides environmental management, flexibility, low temperature property, high tensile strength good adhesion and improved rheological property are specific evidence of waterborne polyurethanes. Also low production cost of water borne polyurethane over solvent-borne polyurethanes is also a reason for their applications. However, these materials have some defects such as weak water resistance and low adhesion in the moisture environment due to sensitivity of their hydrophilic ioned bonds, ether groups, urethane groups and ester groups to hydrolysis which are needed to be improved. Also, low heat resistance of these materials is due to relatively low crystalline melting point or glass transition temperature of hard segments. One of the ways to solve this problem and improve its properties for different application is the addition of inorganic fillers especially nanosized layered silicates within polyurethane matrix. In this way water resistance, heat resistance, mechanical properties and modulus increase. In this research, waterborne polyurethane nanocomposites with PTMG polyol, IPDI, DMPA (internal emulsifier), TEA (neutralizer) and 1, 3 and 5weight % of cloisite 30B as reinforcement were synthesized and characterized. Polarity of the samples was investigated by Contact angle test, dispersion of nano particles in the samples were characterized by X-Ray and TEM, Thermal properties and dynamic mechanical properties were measured by TGA and DMTA respectively. Results showed that incorporation of clay into polyurethane samples caused the reduction of water absorption, increasing of heat resistance, modulus, particle size and contact angle
Comparison between Properties of Polyurethane Nanocomposites Prepared by Two Different Methods
In this work, a thermoplastic polyurethane elastomer (TPUE) model based on polytetramethylene glycol, toluene diisocyanate and 1,4-butanediol was selected and synthesized. According to this model two types of polyurethane nanocomposites were prepared by in situ polymerization and melt intercalation procedures. The organo-modified nanoclay was used in nanocomposites samples in 0.4 weight percent level. The prepared nanocomposites were studied by WAXD, tensile and thermal analysis. Thermal properties of the nanocomposites were higher than those of pure polyurethane elastomers. Nanocomposites prepared via melt intercalation method showed a lower tensile strength and hardness than those prepared through in situ polymerization method.
Fire Behavior of Rigid Polyurethane Foam and Metal Faced Polyurethane Sandwich Panels and Its Fire Hazard Assessment
Reaction to fire of fire-retarded rigid PUR foams and two types of metal faced rigid polyurethane foam core sandwich panel was evaluated by using cone calorimeter test method. The tests were carried out in various radiative heat fluxes from 15 to 75 kW/m2. The radiation rate effect on reaction to fire parameters, including time to ignition (TTI), peak of heat release rate (PRHR), total heat release (THR), average heat release rate (Av.RHR) and average heat of combustion (Av.EHC) was investigated. The phenomenon of char forming, when the foam is exposed to heat, leads to the formation of a protective layer on the surface of foam and hence no direct relation exists between Av.RHR and average specific mass loss rate (Av.Spec.MLR) of foam with increased radiation rate. In addition, the increased PRHR with foam density was also very smooth. The relation between TTI and heat flux was investigated for the foam and its corresponding correlation has been achieved with a specified density. Fire hazard assessment of foams and sandwitch panels was carried out by adopting Petrella and Richardson fire risk classification methods. The assessment results showed that rigid PUR foam and PUR sandwich panels may have a high contribution to bring the room to critical flashover condition, but the risk is intermediate from the viewpoint of fire endurance. The reasons of these risk levels are attributed to a very short TTI, relative high PRHR and an intermediate amount of THR. Decrease in foam density reduces heat release but it shows no significant effect on reducing flashover hazard
The Role of Polymeric Additives on the Morphology and Performance of a Porous Layer of Nanofiltration Composite Membranes Based on Polyether Sulfone
The role of polymeric additives such as PVP and PEG is studied with respect to the morphology of PES porous layer as a sublayer of nanofiltration composite membranes based on PES/PA. Results show that by phase inversionprocess of quaternary systems comprised of four components of polymer/solvent/non-solvent/additive and the diffusion of intertwined polymers some changes occur in membrane morphology with changes in their concentration. With addition of PVP, tear-like pores, finger-like and channel-like morphology change to enlarged channel cavities and by adding more PVP, membrane morphology changes further and spongy regions are extended in the membrane. Presence of PEG in casting solution delayed the precipitation time. By adding PEG, the solution viscosity is increased which is followed by decreases in diffusion rates of solvent/non-solvent in coagulation bath.Therefore, membrane morphology shifts to small pores and spongier region. Another effect of increased PEG content would be deformed PA layer formation in PES sublayer which affects membrane performance. However, PVP as an additive does not change membrane salt rejection very much while it leads to higher fluxes. A membrane with 2.5 percent PVP would perform by 40 percent flux increases, while a membrane with 5% PVP shows flux reductions even below the initial value. Contrary to PVP, the PEG content of 20 percent leads to 4 folds flux increases and in a membrane with 50 percent PEG, there is a flux increase by 7 folds and drop in salt rejection occurs by 50 percent and 70 percent, respectively
Effect of layered silicate nanoclay on the properties of silane crosslinked linear low-density polyethylene (LLDPE)
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