Papers by Keyword: Polyurethane

Abstract: This paper describes synthesis of a series of polyurethane (PU)/clay nanocomposites by using two different chain extenders ethylenediamine (ED) and 1,3-diamino-2-propanol (DAP). By using DAP as a chain extender, PU/clay nanocomposites show not only the stronger inter-and intrachain interactions through hydrogen bonding, but also exhibit enhanced clay exfoliation as evidenced by the disappearance of clay diffraction at 2θ = 2.5-10°.

Abstract: The paper describes synthesis and characterization of adamantane-modified polyurethanes (PU). The study shows that the number of hydroxy groups of adamantane additives plays a signifiant role in tuning polyurethane's properties. PU modified with adamantanetriol has relatively higher glass transition temperature than these with adamantanediol as an additive. Dynamic mechanical analysis (DMA) of PU with 0.5% adamantanetriol shows significant improvement in storage modulus and larger hardness than pure PU at low temperatures. In contrast, adamantanediol-modified PU exhibits lower storage modulus and smaller hardness than pure PU film. These remarkabe differences between two types of admantane-modified PUs originate from the low reactivity of adamantanediol as well as the formation of crosslinked structures in the presence of adamantanetriol.

Abstract: This paper describes the effect of multi walled carbon nanotubes (MWCNTs) on the properties, especially the strength properties of rigid polyurethane (PU) foams produced from palm oil based polyol (POP) and methylene diphenyl diisocyanate (MDI). The foam composites in the ratio of 1:1.1 (wt. %) mixed at speed 2000 rpm. The addition of MWCNTs into PU foam are varies from 0 wt. % to 3 wt. %. The properties evaluated were compressive strength, density and energy absorption. Compressive strength of PU foam composites with 0.5% of MWCNTs showed the highest value 1.162 MPa of compressive strength compared to other foam composites. It was proved by modeling displacement nodal magnitude using NX Software (version 8.5). The density was increased 15.69 % with addition of 0.5 % MWCNTs into the PU foam. Increasing the amount of MWCNTs in PU foam was found to improve the energy absorption from 22.89 J for pure PU to 24.53 J for foam composites with 3 % MWCNTs.

Abstract: Palm kernel oil based polyurethane (PU) electrolyte was prepared via prepolymerization method. The PU films was synthesized at 200/200 and 75/121 for PU1 and PU4 respectively according to the ratio of palm kernel oil polyol (PKO-p) with polyethylene glycol (PEG) as the chain extender to 2,4-methylene diphenyl diisocyanate (MDI). After that, lithium trifluoromethanesulfonate (LiCF₃SO₃) salt as the charge carrier was added to the system with different percentage at room temperature. The palm-based polymer electrolyte was casted onto teflon plate via solution casting technique and later was characterised by electrochemical impedance spectroscopy (EIS) to obtain ionic conductivity. The presence of PU-LiCF₃SO₃ complexes were observed by attenuated total reflection fourier transform infrared (ATR-FTIR) spectroscopy. Differential scanning calorimeter (DSC) was used to study the thermal property of the PU electrolyte. The highest conductivity achieved was 1.55×10^-5 S cm^-1 at 30 wt.% of LiCF₃SO₃ at room temperature. Infrared analyses showed the interaction between lithium ions and amine group (-N-H) at (3600-3100 cm^-1), carbonyl group (-C=O) at (1750-1650 cm^-1) and ether group (-C-O-C-) at (1150-1000 cm^-1).

Abstract: This study explored the feasibility of flexural performance of composite sandwich material composed of various low density polyurethane foam core thickness sandwiched between GFRP skins. The mechanical behaviour of this material was assessed by carrying out a flexural testing. Each spesimen had a nominal dimensions of 110 mm x 30 mm x (c + 4 mm). These spesimens with various core thickness (c) of 2 mm. 5 mm. and 8 mm were then tested in three point bending according to ASTM C 393-00. This study revealed that. by incorporating the thickest core ( 8 mm ) . the bending strength decreases by 42.3 % compared to 5 mm core and it further decreases by 72.6 % compared to 2 mm core. The material stiffness showed positive trend for the thickest core (8 mm). it increases by 53.1 % and 78.1 % compared to 5 mm core and 2 mm core respectively. Low shear modulus of polyurethane foam core contributed to the low bending strength of composite sandwich material with 8 mm core. This was further confirmed by failure analysis under optical microscope which revealed that core shear failure was the dominant failure mechanism for 8 mm core. Meanwhile the dominant failure mechanism for 2 mm core and 5 mm core was microbuckling which confirm the high modulus of GFRP skin. The material stiffness was affected by the high modulus of GFRP skin and the core thickness.

Abstract: The article deals with a problem of racking strength and stiffness of timber based two-by-four wall systems insulated with polyurethane foam. There are racking strength and rigidity tests described in the main part of the work. Results of performed tests are compared to calculation of the racking strength according to national standard.

Abstract: Polyurethane (PU)/multiwalled carbon nanotubes (MWCNTs) foam composites were produced by reaction of based palm oil polyol (POP) with methylene diphenyl diisocyanate (MDI). The MWCNTs were added into PU foam with the percentages varied from 0 wt.% to 3 wt.%. Sandwich composites were prepared using hand lay-up method where Aluminium (Al) sheet as skin were stacked onto PU foam using Araldite adhesives. The PU/MWCNTs foam composites (PMFC) and PU/MWCNTs foam sandwich composites (PMFSC) were characterized using flexural test analysis. Observation showed higher value of flexural strength for PMFC and PMFSC at 0.5% incorporation of MWCNTs. The flexural strength of sandwich PU foam is higher with an average value of 159.38% than control PU foam, due to Al sheet act as ductile skin and prevents samples from rupture rapidly. The modeling using finite element analysis (NX Software-version 8.5) showed the displacement nodal magnitude for 0.5% PMFC (2.537 mm) are higher than 0.5% PMFSC (0.288 mm).

Abstract: Trisilanolisobutyl polyhedral oligomeric silsesquioxane (TSI-POSS) with the humping semi-enclosed cage structure, was incorporated in concentrations of 7, 13 and 22 wt% into 4,4’-methylenebis (phenyl isocyanate) (MDI) and glycerol propoxylate to prepare TSI-POSS/PU hybrid composites, respectively. The polymer chain characteristics of these composites were investigated by wide angle X-ray scattering (WAXS) and molecular dynamics simulation approach. The results indicate that with TSI-POSS concentration increasing up to 22 wt% in hybrid composites, due to the humping semi-enclosed cage structure, distinct crystallite clusters are formed which lead to the micro-phase separation in composites. Meanwhile, the mobility of TSI-POSS cores and backbones in PU composites has been evaluated by the mean square displacement, which confirms that as the concentration of TSI-POSS increasing, the mobility of polymer chains are restricted apparently. Furthermore, it also indicates that the incorporation of TSI-POSS is as the rigid core in hybrid composites.

Abstract: A series of castor oil-based polyurethane (PU)/poly (methyl methacrylate-butyl methacrylate-styrene) (PA) grafted interpenetrating polymer networks (IPNs) were prepared. The effect of composition of the IPNs on the damping, thermal and mechanical properties were studied systematically. PU/PA (60:40, weight ratio) IPNs with methyl methacrylate/butyl methacrylate/styrene (MMA/BMA/St = 80/10/10, weight ratio). In the paper castor oil (CO) was used as PU’s branch units, the damping properties affected by the branch units ratio (ρ) were studied. Mechanical tests showed the tensile strength of the IPNs was improved after increasing the ρ value and PA content. The thermal stability was improved by incorporating heterocyclic imide rings into the PU molecular chains using isocyanate reacting with pyromellitic dianhydride (PMDA). It was found that the IPN composition with ρ value = 0.2 and PU/PA = 60:40 would be useful as structural damping materials, having tanδ values higher than 0.3 for a temperature range of 102°C (5.0-106.9°C).

Abstract: Elimination of the residual microorganisms from an infectious bone defects and the prevention of subsequent re-infection are of importance for chronic osteomyelitis treatment. The application of bone repair materials with antibacterial properties in such a condition has advantages. The present study reported a novel method to fabricate nanohydroxyapatite/polyurethane (n-HA/PU) based antibacterial porous scaffolds through immobilization "core-shell" silver-based mesoporous silica particles (Ag@SiO₂), i.e., silver nanoparticle as core and mesoporous silica as shell, on the surface of n-HA/PU scaffold. The samples were characterized by Scanning Electron Microscope (SEM) and antibacterial tests. The results revealed that the Ag@SiO₂ nanoparticles distributed uniformly on the surface of n-HA/PU porous scaffold. The Ag@SiO₂ could been kept on the surface of n-HA/PU porous scaffold more than 2 weeks, resulting in long-lasting the release of silver ions and antibacterial ability. The porous n-HA/PU scaffolds with an antibacterial surface may hold promise to be used in infectious bone defects repair.