Thermal Properties Of Polyurethanes Research Articles

Scalable design of uniform oligourethanes for impact study of chain length, sequence and end groups on thermal properties.

The full potential of sequence-defined macromolecules remains unexplored, hindered by the difficulty of synthesizing sufficient amounts for the investigation of the properties of such uniform structures and their derived materials. Herein, we report the bidirectional synthesis and thermal behavior analysis of sequence-defined oligourethanes. The synthesis was conducted on a large scale (up to 50 grams) using a straightforward protocol, yielding uniform macromolecules as validated by NMR, ESI-MS and SEC. With this approach, a library of uniform oligourethanes (up to the octamers) was produced using two structural units: a hydrogen-bonding carbamate and a methyl-substituted alternative structure. By varying the chain length, monomer sequence and functionality, we were able to perform a systematic study of the impact of hydrogen bonding on the thermal properties of polyurethanes. Thermal analysis of the discrete oligomers using DSC revealed that both the molecular weight and microstructure significantly affect the glass transition and melting temperatures. TGA measurements also revealed differences in the thermal stability of the oligomers, underscoring the significance of the primary structure of polyurethanes. Additionally, the influence of the terminal groups on the degradation pathway was assessed via pyrolysis-GC-MS, which specifically highlighted the increased thermal stability in the absence of hydroxyl end groups. This work shows the interest of using sequence-defined synthetic macromolecules for the elucidation of structure-property relationships and thereby facilitates their fine-tuning towards specific material applications.

Mechanical and Thermal Properties of Polyurethane-Palm Fronds Ash Composites

The aim of the article is to study the influence of environmentally friendly palm frond ash on the mechanical and thermal properties of polyurethane used as filler. Various weight filler ratios with particle sizes around (125 μm) were examined and characterized using elongation, tensile strength, Young's modulus, compressive strength, average burning time, and infrared spectroscopy. The results showed that the addition of 20 wt.% palm frond ash powder significantly improved the hardness mixture by about 2.83 MPa. In addition to that, the highest value of the compressive strength of the polymer with the additive was recorded at 10 wt.%. Also, the most excellent value of Young’s modulus was 2 MPa at a ratio of 50 wt. %, as was the average burning time of about 33 sec. The mechanical properties of polyurethane were affected by adding palm frond ash, which increases the tensile and compressive strengths, making it suitable for use in many applications. Moreover, the environmentally friendly material reflects the benefits of waste recycling. The addition of filler affects the morphology and strengthens the brittleness. Additionally, the use of fly ash from palm frond combustion in the technology of polyurethane materials complies. Partial replacement of petrochemical components with waste filler also reduces the total energy consumption in producing PU composites.

The Mechanical and Thermal Properties of Polyurethanes/Precipitated Calcium Carbonate Composites

The properties of polyurethane containing precipitated calcium carbonate (PCC) were studied. The PCC were produced from acetylene gas waste, and its usage as filler material for polymer were explored in this study. Present findings suggested the addition of 5 per hundred gram of PU(phr) significantly increases the shore A hardness to 39.2, in addition to improve the degradation mperature and specific gravity with decrease in water and oil absorptions capacity. The addition of 5 phr PCC to polyurethane improves the material structure and the morphology as calcium carbonate were dispersed when observed using microscopes. This research extends our knowledge of the addition of PCC to strengthen the mechanical and thermal properties of polyurethanes.

Synthesis and characterization of boron and phosphorus-containing phenol formaldehyde resin-modified polyurethane composites

Composite films with polyurethane (PU), phenol formaldehyde resin (PFR) and boron, phosphorus-containing phenol formaldehyde resins (P-PFR and B, P-PFR), were synthesized using sol–gel and copolymerization techniques. These composite films were deposited via spin-coating onto an aluminum alloy (AA) for improve the corrosion protection. The effects of different types of PFR on the structural, thermal and mechanical properties and corrosion resistance of the composites were investigated. The structures and morphologies of the composites were investigated by the gel permeation chromatography (GPC), Fourier transform infrared (FTIR), scanning electronic microscopy (SEM) and atomic force microscopy (AFM). It was shown from the dynamic mechanical analysis (DMA) and thermal gravimetric analysis (TGA) that the mechanical and thermal properties of PU were improved by incorporation of PFR, P-PFR and B, P-PFR. In addition, the PU/PFR composites provided an excellent corrosion protection in comparison with PU according to potentio-dynamic and salt-spray analyses.

Vpliv oblikovanja sinteze na termične lastnosti poliuretana

Vpliv oblikovanja sinteze na termične lastnosti poliuretana

Castor oil‐based polyols with gradually increasing functionalities for biopolyurethane synthesis

ABSTRACTIn this research, castor oil‐based polyols with gradual increasing functionalities were prepared using thiol‐ene photo click reaction. The polyols were prepared by facile and efficient photo‐click reaction using thiols with different number of hydroxyl groups. The polyols were successfully synthesized using a modified bio‐oxygen demand (BOD) reactor and their structures were characterized. The hydroxyl number of the prepared polyols gradually increased depending on the thiol used for preparation. The increased hydroxyl number resulted in increased crosslinking densities for the prepared polyurethanes. The effect of the increasing crosslinking density and structure of the polyols on the mechanical and thermal properties of polyurethane were investigated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48304.

Preparation, Characterization, and Antioxidant Activity of β-Carotene Impregnated Polyurethane Based on Epoxidized Soybean Oil and Malic Acid

A new polyol was synthesized based on epoxidized soybean oil (ESO) and malic acid (MA) for the formulation of a bio-based polyurethane. The synthesized polyol was characterized by Fourier transform-infrared spectroscopy, nuclear magnetic resonance spectroscopy, and mass spectrometry. Polyurethanes were formed by reacting the synthesized ESO-MA polyol with 1,6-hexamethylene diisocyanate at different isocyanate/hydroxyl ratios. The tensile and thermal properties of the prepared polyurethanes were analyzed by differential scanning calorimetry, thermogravimetric analysis, and universal testing machine. The polyurethanes exhibited a tensile strength of 1.34–5.56 MPa, an elongation at break of 20–41%, and a glass transition temperature of − 2.7 to 0.6 °C. In addition, β-carotene, a natural antioxidant, was impregnated on the polyurethane surface and its effect on the tensile and thermal properties of polyurethane was investigated. An increase in tensile strength and a reduction in elongation at break were observed in these β-carotene impregnated polyurethane films. They also showed up to 61% radical scavenging activity against 2,2-diphenyl-1-picryhydrazyl radical in methanol. Moreover, these films retained radical scavenging activity for more than 50 days.

Linear polyurethanes with imidazoquinazoline rings: preparation and properties evaluation

In this work, research concerning the synthesis and properties of linear polyurethanes (PUs) with the imidazoquinazoline rings was represented. Reaction conditions of 2,6-bis(2-hydroxyethyl)-1-phenylimida-zo[1,5-c]quinazoline-3,5-dione (BHPIQ) with 1,6-hexamethylene diisocyanate were determined and optimized. These conditions are adapted to reaction of BHPIQ with 4,4′-diphenylmethane diisocyanate and 2,4-toluene diisocyanate. New PUs with imidazoquinazoline rings were characterized by spectral methods (1H-NMR and IR spectroscopies), which confirm their structures. Their molar masses and dispersity index were measured by size exclusion chromatography method. The wide-angle X-ray scattering and differential scanning calorimetry (DSC) studies have shown that all PUs based on BHPIQ are amorphous. Moreover, thermal properties of PUs were investigated by thermogravimetry analysis, standard DSC, and temperature-modulated DSC methods. During thermogravimetric measurements, the exhaust gases were analyzed by FTIR method. Incorporation of imidazoquinazoline ring into the PU chains escalates their glass transition temperature; thus, their heat resistance was enhanced. Furthermore, their degradation rate and the amount of released degradation products were reduced. The investigated properties of the obtained PUs with imidazoquinazoline rings were compared with those ones of suitable PUs based on 1,4-butanediol.Graphical abstractLinear polyurethanes were obtained in reaction of 1-phenyl-2,6-bis(2-hydroxyethylimidazo[1,5-c]quinazoline-3,5-dione with hexamethylene 1,6-diisocyanate, 4,4′-diphenylmethane diisocyanate and toluene 2,4-diisocyanate. Their composition and structure were confirmed. The phase contents and thermal properties were investigated

Enhancement of nonlinear optical and thermal properties of polyurethanes by modifying the chromophores with fused heterocyclic and pyrimidine rings

This article describes the synthesis of substituted triazolo[3,4‐b]‐thiadiazole heterocycles based nonlinear optical (NLO) responsive chromophores. To enhance the NLO properties of the chromophores, the pyrimidine ring was introduced with an appropriate π‐bonding. With these chromophores, different series of polyurethanes were prepared by condensation with tolylene‐2,4‐diisocyanate and 3,3′‐dimethoxy‐4,4′‐biphenylene diisocyanate. The structure of the resulting chromophores and polyurethanes was confirmed using Fourier transform infrared, proton nuclear magnetic resonance, and Carbon Hydrogen Nitrogen (CHN) analyzer. The inherent viscosities (ηinh) of the polyurethanes measured by Ubbelohde viscometer were in the range of 0.2324–0.2760 dl/g. Thermal behavior of the polyurethanes was investigated using differential scanning calorimetry and thermogravimetric analysis. The molecular orientation in polyurethane films was induced by a corona poling, and this was ascertained using ultraviolet‐visible spectrophotometer and atomic force microscope. The thicknesses and refractive indices of thin films were determined by an Ellipsometer. Polyurethanes exhibited excellent solubility in most of the common organic solvents. The second harmonic generation (SHG) coefficients (d33) of the poled polyurethanes ranged from 63.20 and 95.32 pm/V at 532 nm. None of the polyurethanes showed SHG decay below 100°C, and retained 95% of the signal even up to 500 h. The resulting enhanced NLO efficiency and longer temporal stability make these polyurethanes as promising candidates for photonic devices. POLYM. ENG. SCI., 59:500–509, 2019. © 2018 Society of Plastics Engineers

Incorporation of silica nanoparticles and polyurethane into hybrid composites for increase of char residue

Effect of different chain extenders, silica nanoparticle loading, and using sol–gel method on the thermal properties of polyurethane (PU) hybrid composites was investigated from the viewpoint of increase of char residue and decomposition temperature. Two different chain extenders were used for this purpose, and the PU products were modified with (3-aminopropyl) triethoxysilane to obtain PUI (ethoxysilane-terminated PU with pyromellitic dianhydride chain extender) and PUBD (ethoxysilane-terminated PU with butanediol chain extender), respectively. Fourier-transform infrared spectroscopy was used for confirmation of synthesis of PUI and PUBD. Thermogravimetric analysis showed that char residue and thermal degradation temperature of PU hybrid composites were increased after incorporation of silica nanoparticles. Also, using pyromellitic dianhydride as chain extender resulted in higher char contents and also thermal stabilities in comparison with butanediol. By the addition of 4 and 8 mass% silica nanoparticles in PUBD hybrids, char residue increased to 15.1 and 16.3%, respectively. In the case of PUI hybrids, addition of 4 and 8 mass% of silica nanoparticles resulted in char residue of 20.8 and 25.7% and Tmax of 409.3 and 411.8 °C, respectively. X-ray diffraction showed an amorphous peak for cross-linked PU at 2θ = 21.7°. Transmission electron microscopy showed dispersion of silica nanoparticles in the hybrid composite of PUI.

Investigation on Thermal Properties of Kenaf Fibre Reinforced Polyurethane Bio-Composites

This research focuses on the effect of Kenaf fibre on thermal properties of Polyurethane (PU) reinforced kenaf bio-composites. The samples were prepared using the polymer casting method with different percentages of kenaf fibre content (5 wt%, 10 wt%, 15 wt%). The thermal properties of Kenaf/PU bio-composite are determined through the Thermogravimetric Analysis and Differential Scanning Calorimeter test. The TGA results revealed that 10 wt% Kenaf/PU bio-composite appeared to be more stable. DSC results show that the glass transition temperature (Tg) value of 10 wt% Kenaf/PU composite is significant to pure polyurethane. It can be said that the thermal stability of 10 wt% Kenaf/PU bio-composite exhibits higher thermal stability compared to other samples.

The influence of chemical structure on thermal properties and surface morphology of polyurethane materials

The surface morphology and thermal properties of polyurethanes can be correlated to their chemical composition. The hydrophilicity, surface morphology, and thermal properties of polyurethanes (differed in soft segments and in linear/cross-linked structure) were investigated. The influence of poly([R,S]-3-hydroxybutyrate) presence in soft segments and blending of polyurethane with polylactide on surface topography were also estimated. The linear polyurethanes (partially crystalline) had the granular surface, whereas the surface of cross-linked polyurethanes (almost amorphous) was smooth. Round aggregates of polylactide un-uniformly distributed in matrix of polyurethane were clearly visible. It was concluded that some modification of soft segment (by mixing of poly([R,S]-3-hydroxybutyrate) with different polydiols and polytriol) and blending of polyurethanes with small amount of polylactide influence on crystallinity and surface topography of obtained polyurethanes.

Sustainable production of polyurethane from castor oil, functionalized with epoxy- and hydroxyl-terminated poly(dimethyl siloxane) for biomedical applications

A sustainable method has been employed for the production of a biomedical material in an economical way. Among biomedical polymers, two mostly used polymers are silicones (PDMS) and polyurethanes (PU). PDMS can outperform other polymers due to its biocompatibility and flexibility, but its high cost became a major roadblock for many applications. PU can be produced from a variety of sustainable resources in a cost effective manner. In this work, vegetable oil-based PU is blended with PDMS to produce a biomedical material which can contribute to the economy and environment. In this method, siliconized epoxy-terminated polyurethanes (EPDMS) were prepared from castor oil, 4,4’ methylene-bis-(cyclohexyl isocyanate), glycidol, and hydroxy-terminated poly-(dimethyl siloxane) (HTPDMS). The properties of the resulting products were compared with virgin PU with a NCO/OH ratio of 1.2:1 and epoxy-terminated PU (EPU) with a polyol/diisocyanate/glycidol ratio of 1:3:3. The structural elucidation of PU, EPU, and EPDMS were carried out by FTIR and 1HNMR spectroscopic techniques. The effect of incorporation of siloxane and glycidol on the thermal properties of PU was analyzed by thermogravimetric analysis and differential scanning calorimetry analysis. The improved hydrophobicity of the EPDMS was observed from water contact angle measurements. The surface morphology was examined using atomic force microscopy analysis. In vitro cytotoxicity analysis revealed the cytocompatibility of the EPDMS which makes them suitable for biomedical applications.

Synthesis and properties of polyurethane/epoxy copolymers by UV curing

ABSTRACTTo improve the mechanical and thermal properties of polyurethane, two prepolymers, polyurethane acrylate (PUA) and epoxy acrylate (EPA) which have acrylate-ended groups, were synthesized. The obtained prepolymers were homogeneously mixed with various compositions and cured by UV. After UV curing, the properties of PU/EP copolymers were investigated by using Fourier-transform infrared spectroscopy, universal testing machine, dynamic mechanical thermal analysis and thermogravimetric analysis. The thermal and tensile properties of PU/EP copolymers gradually increased with the amount of EP due to the intermolecular interaction whereas their elongation properties decreased. These results indicate that the copolymerization of PU with EP could control their mechanical properties.

SYNTHESIS AND CHARACTERIZATION OF NATURAL FIBRE REINFORCED POLYURETHANE COMPOSITES BASED ON CARDANOL

In recent studies importance has been given to the use of natural products from renewable resources due to the decrease in the supply and price escalations of petroleum raw materials. Cardanol based resole type phenolic resin has been synthesized by condensing cardanol with furfural in a particular mole ratio using dicarboxylic acid catalyst such as phthalic acid. Polyurethane sheets were prepared by treating cardanol furfural resin with 4,41 – methylene bis(cyclohexyl isocyanate) and the catalyst dibutyltin dilaurate. Natural fibres are prospective reinforcing materials and their use until now has been more traditional than technical. Among the various fibres sisal is of particular interest in that its composites have high impact strength besides having moderate tensile and flexural properties compared to other fibres. Fibre reinforced polyurethane composites have been prepared by treating sisal fibre (10%) into polyurethane. The physico chemical, spectral and thermal properties of polyurethane and fibre reinforced polyurethane composites have been studied.

Synthesis and properties of segmented polyurethanes with hydroquinone ether derivatives as chain extender

Two series of 4, 4′-diphenylmethane diisocyanate (MDI) type polyurethanes based on poly(tetramethyleneoxide) glycol (PTMO) and polybutylene adipate glycol (PBA) as soft segments were synthesized by one-step bulk polymerization process. Various hard segments were obtained from hydroquinone ether derivatives with or without ether oxygen structure bonded with the aromatic units in main chain, including hydroquinone (HQE), hydroquinone bis(b-hydroxyethy) ether (HQEE), and 4-hydroxyethyl ethyl oxygen-1-hydroxy ethyl benzene ether (HQEE-L) as chain extenders. The effect of chain extender structure on aggregation structure, thermal and mechanical properties was studied. ATR-FTIR suggested that hydrogen bonding interactions were significantly changed in the presence of flexible ether oxygen structure in hard segment. HQEE-based polyurethanes and HQEE-L-based polyurethanes displayed microphase separation and microphase mixing behavior respectively based on DMA and DSC results. XRD curves confirmed that flexible ether oxygen chain bonded with the rigid aromatic units played a balancing role in the steric effect caused by aromatic chain extender. Thermal properties of polyurethanes were affected mainly by the hard segment packing while mechanical properties were influenced by both phase separation and phase mixing which possess strong hydrogen bonding interactions. The excellent elongation in PTMO/HQEE-L and the high ultimate tensile strength in PBA/HQEE-L can be attributed to the phase mixing with strong hydrogen bonding interactions presented in HQEE-L-based polyurethanes.

Simultaneous Improvement of Mechanical Properties and Thermal Stability of Polyurethane by Polyethylene Glycol Grafted Cellulose Nanocrystals

A study of the effect of the addition of polyethylene glycol grafted cellulose nanocrystals on the properties of a polyurethane matrix was carried out. The resulting nanocomposite films were characterized by scanning electron microscopy, Fourier transform infrared spectrometry, micro–control electronic universal testing machine and thermal gravimetric analysis. Remarkable improvements in the mechanical and thermal properties of polyurethane could be attributed to well–dispersion of nanofillers in polyurethane matrix and the formation of hydrogen bonding network within the polymer matrix.

Polyols and polyurethanes prepared from epoxidized soybean oil ring‐opened by polyhydroxy fatty acids with varying OH numbers

AbstractBio‐based polyols from epoxidized soybean oil and different fatty acids were successfully prepared using a solvent‐free method in order to investigate the effect of the polyols' OH numbers on the thermal and mechanical properties of the polyurethanes prepared using them. Epoxidized soybean oil/epoxidized linseed oil was ring‐opened by methanol/glycol followed by saponification to prepare polyhydroxy fatty acids. These fatty acids and epoxidized soybean oil were then used for further solvent‐free ring‐opening reactions with DBU as catalyst, which facilitated the carboxylic ring‐opening. Gel permeation chromatography revealed that a molar ratio of carboxylic acid from polyhydroxy fatty aicds and epoxy group of 0.5 : 1 resulted in optimized polyols containing the smallest amounts of residual starting materials. The obtained polyols had varying OH numbers and the acquired polyurethane films were comprehensively characterized. With increasing OH number of the polyols the PUs displayed an increase in crosslinking density, glass transition temperature (Tg), tensile strength and Young's modulus, and a decrease in elongation and toughness. This work provides Supporting Information on the effect of OH number of polyols obtained via a solvent‐free ring‐opening method on the mechanical and thermal properties of polyurethanes, of particular interest when designing PU products for specific purposes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41213.

Study of structural morphology, thermal degradation and surface charge decay in PU + PSF + CNTs polymer hybrid nanocomposite

Abstract Polyurethane (PU)/Polysulfone (PSF)/Multi Wall Carbon Nanotubes (CNTs) hybrid nanocomposite films were prepared by solution grown method with different wt% of functionalized CNTs. The structural and thermal properties of PU, PSF and PU + PSF + CNTs nanocomposite films were studied by various techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), FTIR and TGA/DTG. The dispersion of CNTs in polymer was studied by SEM spectra, which indicates the presence of CNTs on the surface of the polymeric material. XRD results show the increases of crystallinity with different weight percentage of CNTs in polymer matrix. FTIR spectra reveal the position of different chemical bonds in pure and hybrid nanocomposite films. TGA and DTG show that the thermal stability of hybrid nanocomposite is better than PU and PSF due to reinforcement of CNTs in PU–PSF matrix. Surface charge decay study represents the charge stability in hybrid nanocomposite is due the localization of charge carriers in deeper traps.

From cellulosic waste to nanocomposites. Part 2: synthesis and characterization of polyurethane/cellulose nanocomposites

New polyurethane (PU)-based nanocomposites were synthesized through two-step in situ polymerization by incorporating low loading levels of spherical cellulose nanoparticles (CNs). Structural, mechanical, thermal, and morphological characterization of the nanocomposites was done with infrared spectroscopy, X-ray diffraction, tensile test, dynamic mechanical thermal analysis, thermogravimetry, differential scanning calorimetry, and field emission scanning electron microscopy. The results showed with incorporation of CNs there was no significant change in the structure of PU. However, the addition of 1 % CNs into PU increased the modulus nearly 42 % and tensile strength by 112 %. On the contrary, elongation at break decreased with increasing nanoparticles contents, but the nanocomposites maintained an elongation of greater than 800 %, which was still a large elongation. The thermal stability of PU enhanced with increasing the small amounts of nanoparticles. Also, incorporating of the CNs improved the phase separation between the soft and hard domains which led to an upward shift in melting temperatures and enthalpy of crystalline phase melting. These results were very encouraging in terms of using CNs as an inexpensive nanofiller and improving the mechanical and thermal properties of PU without using solvents in nanocomposite preparation.