Thermal Properties Of Polyurethanes Research Articles

Structure–Property Correlation Study of Novel Poly(urethane–ester–siloxane) Networks

Novel poly(urethane–ester–siloxane) networks, based on hydroxypropyl terminated poly(dimethylsiloxane) (PDMS), 4,4′-methylenediphenyl diisocyanate, and hyperbranched polyesters (HBPs) of the second and third pseudogenerations, were synthesized by two-step polymerization. The effects of the PDMS content and pseudogeneration number of HBPs on the structural, thermomechanical, thermal, and surface properties of polyurethanes were investigated. Thermomechanical and thermal properties of polyurethanes and FTIR, SAXS, and SEM results indicated good microphase separated structure. SAXS data suggested that the difference in the HBP pseudogeneration number affects only the global properties of the structure and is much less pronounced than the dependence on the PDMS content, while local properties depend only on the PDMS content. Surface characterization of samples indicated the slightly amphiphilic nature of polyurethanes. The results revealed that the synthesized polyurethanes have good thermal, thermomechanical...

Physical and Thermal Properties of Polyurethane from Isophorone Diisocyanate, Natural Rubber and Poly(ε-caprolactone) with High NCO:OH Content

Physical and Thermal Properties of Polyurethane from Isophorone Diisocyanate, Natural Rubber and Poly(<i>ε</i>-caprolactone) with High NCO:OH Content

Thermal properties of poly(urethane-ester-siloxane)s based on hyperbranched polyester

Novel polyurethanes (PUs) were synthesized using hydroxy-terminated hyperbranched polyester (BH-20) and 4,4′-methylenediphenyl diisocyanate (MDI) as hard segments and hydroxy-terminated ethylene oxide-poly(dimethylsiloxane)-ethylene oxide triblock copolymer (PDMS-EO) as soft segment, with soft segment content ranging from 30 to 60 wt %. The PUs were synthesized by two-step solution polymerization method. The influence of the soft segment content on the structure, swelling behavior and thermal properties of PUs was investigated. According to the results obtained by swelling measurements, the increase of the hard segment content resulted in the increase of the crosslinking density of synthesized samples. DSC results showed that the glass transition temperatures increase from 36 to 65°C with increasing hard segment content. It was demonstrated using thermogravimetric analysis (TGA) that thermal stability of investigated PUs increases with increase of the soft PDMS-EO content. This was concluded from the temperatures corresponding to the 10 wt % loss, which represents the beginning of thermal degradation of samples.

Preparation, mechanical properties of waterborne polyurethane and crosslinked polyurethane‐acrylate composite

AbstractThe waterborne polyurethane (PU) prepolymer was first prepared based on isophorone diisocyanate, polyether polyol (NJ‐210), dimethylol propionic acid (DMPA), and hydroxyethyl methyl acrylate via in situ method. The crosslinked waterborne polyurethane‐acrylate (PUA) dispersions were prepared with the different functional crosslinkers. The chemical structures, optical transparency, and thermal properties of PU and PUA were confirmed by Fourier transform infrared spectrometry, ultraviolet–visible spectrophotometry, and differential scanning calorimetry. Some physical properties of the aqueous dispersions such as viscosity, particle size, and surface tension were measured. Some mechanical performances and solvent resistance of PUA films were systemically investigated. The experimental results showed that the particle sizes of the crosslinked PUA aqueous dispersions were larger than the PU and increased from 57.3 to 254.4 nm. When the ratios of BA/St, BA/TPGDA, and BA/TMPTA were 70/30, PUA films exhibited excellent comprehensive mechanical properties. The tensile strength and elongation at break of the film were 2.17 MPa and 197.19%. When the ratio of BA/St was 30/70, the film had excellent water resistance and was only 6.47%. The obtained PUA composites have great potential application such as coatings, leather finishing, adhesives, sealants, plastic coatings, and wood finishes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Investigation on the modification to polyurethane by multi‐walled carbon nanotubes

Purpose – The purpose of this paper is to investigate the effects of multi‐walled carbon nanotubes (MWNTs) on the mechanical, thermal and electrical conductivity properties of polyurethane (PU) by in situ polymerisation of MWNTs and PU.Design/methodology/approach – A number of analytical techniques, including Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy, were employed to assess the effects of acid treatment on MWNTs. The mechanical and thermal properties of PU, MWNTs and PU composites were characterised using a tensile tester machine and dynamic mechanical analysis. The electoral conductivity properties of the materials were characterised by ohmmeter.Findings – It was found that desirable modifications to MWNTs occurred after acid treatment, thus mainly carboxylic acid groups were introduced onto the surface of MWNTs. And the acid‐treated MWNTs could improve the mechanical, thermal and electrical conductivity properties of PU by in situ polymerisation of MWNTs and PU succes...

Novel nanocomposites based on polyurethane and micro fibrillated cellulose

The goal of this study was to fibrillate cellulose from micro to nano scale and evaluate how these microfibers and nanofibrils affected the mechanical and thermal properties of thermoplastic polyurethane. The source of cellulosic material was hard wood cellulose fibers and the fibrillation was done with a high pressure homogenizer. The composite materials were prepared using compression moulding, by stacking the cellulose fiber mats between polyurethane films. The results showed that both microfibers and nanofibrils reinforced the polyurethane and provided better heat stability. The addition of 16.5 wt% of cellulose nanofibrils to PU increased the strength nearly 500% and the stiffness by 3000%. These results are very promising in terms of obtaining fibrils with a novel processing method and by improving the mechanical and thermal properties of polyurethane. This is expected to expand the application areas of polyurethanes.

Use of new hydroxytelechelic cis-1,4-polyisoprene (HTPI) in the synthesis of polyurethanes (PUs): Influence of isocyanate and chain extender nature and their equivalent ratios on the mechanical and thermal properties of PUs

AbstractNew segmented polyurethanes (thermoplastic-elastomers) based on previously described hydroxytelechelic cis-1,4-polyisoprene (HTPI), miscellaneous isocyanates and chain extenders at various equivalent ratios were prepared by the classical one-shot method. The influence of the nature of isocyanate and chain extender, as well as their equivalent ratios, on the mechanical and thermal materials behavior was investigated. Thus, a comparative assessment of material properties was performed. Microphase separation of hard and soft segments was observed by DMTA, DSC and AFM. Moreover, according to Thermogravimetric Analysis (TGA), linear relationships depending on the isocyanate and chain extender nature were found between the weight loss (%) and the percentages of hard segments. A classification of thermal stability in terms of weight loss was established. With the aim of a thermo-mechanical comparative study, polyurethane elastomers based on HTPI and isocyanates without chain extender, were also synthesized.

Use of hydroxytelechelic cis-1,4-polyisoprene (HTPI) in the synthesis of polyurethanes (PUs). Part 1. Influence of molecular weight and chemical modification of HTPI on the mechanical and thermal properties of PUs

New telechelic cis-1,4-polyisoprene oligomers bearing an hydroxyl group at the end of the polyisoprene backbone and possessing controlled molecular weights were used as soft segments in the elaboration of polyurethane elastomers. Besides, the well defined hydroxytelechelic cis-1,4-polyisoprene (HTPI) structure obtained through a controlled methodology, was chemically modified leading to hydrogenated and epoxidized oligomers based polyurethanes. The influence of the structural changes of these precursors on the polyurethanes properties have been studied. Thus, mechanical parameters as well as glass transition and mechanical transition temperature measurements indicated an increase in PUs hardness when the length of soft segment decreases and when the degree of epoxidized and hydrogenated isoprenic moieties increases. Moreover, based on thermogravimetric analysis (TGA), a linear relationship was established between the weight loss in the urethane stage degradation and the amount of hard segments in the PUs. Otherwise, the hydrogenated soft segments were found more thermally stable than the epoxidized and the non modified ones. By comparison with similar investigations developed from commercial oligodienes (PBHT R20 LM ® and EPOL ®), this study mainly showed that the PUs based on hydrogenated hydroxytelechelic cis-1,4-polyisoprenes were more thermally stable and softer than the EPOL ® based analogues.

Utilization of By-product(Shiro-Kasu) from Wheat Starch Industry for Polyurethane.

Polyurethane (PU) foams and films were prepared from Shiro-kasu which was discharged from a commercial wheat starch and gluten production. PU foams were obtained by reacting the mixture of Shiro-kasu and polyol with diphenylmethane diisocyanate. Apparent density of PU foams decreased with increasing Shiro-kasu content because of increase of foaming ratio. The mechanical properties were measured by a tensile test machine. The compression stress of PU foams decreased and the tensile stress of PU films increased with increasing Shiro-kasu content. Thermal properties of PU's were measured by differential scanning calorimetry and thermogravimetry. Glass transition temperature(Tg) of PU's increased and decomposition temperature (T_??_) of those decreased with increasing Shiro-kasu content. Biodegradability of PU films was measured by activated sludge method. The weight of PU films in activated sludge remarkably decreased with increasing Shiro-kasu content. These results indicated that Shiro-kasu could be used as a polyol for biodegradable PU.

Mechanical and Thermal Properties of Biodegradable Polyurethanes Derived from Sericin.

In this study, from the viewpoint of biodegradable polymers and waste disposal, polyurethane (PU) foams and films containing sericin were prepared from sericin and diphenylmethane diisocyanate (MDI). Polyethylene glycol (PEG, diol type) and polypropylene glycol (PPG, triol type) were used as a part of the polyol. Mechanical and thermal properties of PU's containing sericin were measured by tensile test and thermal analysis. Sericin could be used as a polyol of PU's and the strength and the glass transition temperature of PU films containing sericin increased with increasing sericin content. The strength of PU foams depended strongly on their apparent density. From the dynamic mechanical analysis (DMA), loss modulus (E) and tan δ curves showed three peaks, α, β, γ in the region from high to low temperatures. The α and β peaks which are assigned to the main chain motion and local mode motion shifted to the higher temperature region with increasing sericin content. The γ peak was almost constant at -130°C.

Chlorinated polyethylene as a modifier of thermal stability of polyurethane

The effect of the addition of various amounts of chlorinated polyethylene (CPE) on the thermal properties of polyurethane was investigated. A significant improvement in thermal stability was observed on addition of 3 wt% of CPE. It has been found that specific interaction between homopolymers occurs at the phase boundaries, so strengthening the urethane linkage and retarding its dissociation.

Synthesis and characterization of polyurethanes containing arylene sulfone ether linkages

AbstractPolyurethanes containing arylene sulfone ether linkages were synthesized by solution polymerization of 4,4′‐bis(4‐isocyanatophenoxy)diphenylsulfone (SPI) and 4,4′‐bis(3‐isocyanatophenoxy)diphenylsulfone (SMI) with various aliphatic glycols such as ethylene glycol (EG), 1,2‐propylene glycol (PG), 1,4‐butylene glycol (BG), polyethylene glycol (PEG 300 and 1000), polypropylene glycol (PPG 300 and 1000) and polytetramethylene glycol (PTMG 1000. TERACOL) in dimethylacetamide (DMAC) at 120°C. The diisocyanates SPI and SMI were prepared from the corresponding diacid chlorides via Curtius rearrangement. The polyurethanes were obtained in high yields. The effect of structures of diisocyanate and aliphatic diols on the molecular weight and thermal properties of polyurethanes was also investigated. The polyurethanes prepared were characterized by infrared spectroscopy, solution viscosity, elemental analysis, thermogravimetric analysis and X‐ray diffraction. Physical and thermal properties of polyurethanes prepared from SPI and various aliphatic glycols were compared with the polyurethanes from SMI and various aliphatic glycols.

Chain‐extended polyurethanes—Synthesis and characterization

AbstractThermoset polyurethane (PU) elastomers were prepared using hydroxyl‐terminated polybutadiene (HTPB), toluene diisocyanate (TDI) and hexamethylene diisocyanate (HMDI). The effects of various diamines and diols on the mechanical and thermal properties of polyurethanes are discussed. The average molecular weight between crosslinks (M̄/c) was determined by swelling studies. The properties imparted by the extenders are explained on the basis of the groups present in the diamines and the number of methylene carbons in the diols.

Dynamic mechanical and thermal properties of polyurethane modified with poly(4,4?-diphenylsulphone terephthalamide)

Three conventional polyurethane (PU) elastomers were blended physically with various ratios of high-molecular weight poly(4,4'-diphenylsulfone terephtalamide) (PSA) to form 12 PU/PSA polyblends. Also three new polyurethanes were synthetized with a low-molecular weight PSA propolymer as a hydrogen donor for chemical extending

Synthesis and Thermal Properties of Polyurethane, Poly(butyl methacrylate), and Poly(methylmethacrylate) Multi-Component IPN’s

Three component interpenetrating polymer networks (IPN’s) of polyurethane (PU)–poly(n-butyl methacrylate) (PBMA)–poly(methyl methacrylate) (PMMA) were prepared by the combined synthesis of simultaneous polymerization and sequential polymerization. Two types of IPN’s, (PU–PMMA)–PBMA and (PU–PBMA)–PMMA, were obtained by forming PU–PMMA (or PU–PBMA) simultaneous IPN’s first and then swelling the network in BMA (or MMA) and ethylene dimethacrylate (EDMA) monomer mixtures followed by sequential polymerization of the imbibed monomers. The glass transition behavior studied by DSC and DMA showed three separate but broad Tg’s for (PU–PMMA)–PBMA IPN’s, while two Tg’s (one broad Tg for PU. transition and the other broad Tg at intermediate temperature of PMMA and PBMA transition) were observed for (PU–PBMA)–PMMA IPN’s. Both three component IPN’s showed high damping characteristics (tanδ=0.2—0.4) in the temperature range of −30—90°C. The TGA analysis revealed enhanced thermal stability in all of the two-component and three-component IPN’s of polyurethane and polymethacrylate.