Ester-based Polyurethane Research Articles

Preparation of Polyurethane-Modified Epoxy Coating Materials Based on Vegetable Oil Derivated Ester

This study utilize vegetable oil derivatives as a polyol in polyurethane. A modification of epoxy using polyurethane was done using ester derivative of vegetable oils as polyols, which was polyethylene glycol monooleate (PEGMO). The PEGMO was synthesized via an esterification reaction. The synthesis of polyurethane-modified epoxy using polyethylene glycol monooleate ester (PME-PEGMO) was conducted by reacting epoxy, tolonate and PEGMO. Analysis results of FTIR and H-NMR showed a new absorption peak derived from the urethane bond. The mechanical and thermal properties were characterized by a universal testing machine (UTM) and thermogravimetry analysis (TGA), respectively. According to the analysis results, it is shown that the addition of polyethylene glycol monooleate ester-based polyurethane on epoxy improved the mechanical properties of the epoxy, from 69.61 kgf/cm2 to139.80 kgf/cm2. However, it decreased the thermal stability of the epoxy. At 500°C, the mass of epoxy was remaining 28%, while the PME-PEGMO was only 13%.
 
 

Microbial enzymes will offer limited solutions to the global plastic pollution crisis.

Global economies depend on the use of fossil-fuel-based polymers with 360-400 million metric tons of synthetic polymers being produced per year. Unfortunately, an estimated 60% of the global production is disposed into the environment. Within this framework, microbiologists have tried to identify plastic-active enzymes over the past decade. Until now, this research has largely failed to deliver functional biocatalysts acting on the commodity polymers such as polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), ether-based polyurethane (PUR), polyamide (PA), polystyrene (PS) and synthetic rubber (SR). However, few enzymes are known to act on low-density and low-crystalline (amorphous) polyethylene terephthalate (PET) and ester-based PUR. These above-mentioned polymers represent >95% of all synthetic plastics produced. Therefore, the main challenge microbiologists are currently facing is in finding polymer-active enzymes targeting the majority of fossil-fuel-based plastics. However, identifying plastic-active enzymes either to implement them in biotechnological processes or to understand their potential role in nature is an emerging research field. The application of these enzymes is still in its infancy. Here, we summarize the current knowledge on microbial plastic-active enzymes, their global distribution and potential impact on plastic degradation in industrial processes and nature. We further outline major challenges in finding novel plastic-active enzymes, optimizing known ones by synthetic approaches and problems arising through falsely annotated and unfiltered use of database entries. Finally, we highlight potential biotechnological applications and possible re- and upcycling concepts using microorganisms.

Plastics: Environmental and Biotechnological Perspectives on Microbial Degradation.

Plastics are widely used in the global economy, and each year, at least 350 to 400 million tons are being produced. Due to poor recycling and low circular use, millions of tons accumulate annually in terrestrial or marine environments. Today it has become clear that plastic causes adverse effects in all ecosystems and that microplastics are of particular concern to our health. Therefore, recent microbial research has addressed the question of if and to what extent microorganisms can degrade plastics in the environment. This review summarizes current knowledge on microbial plastic degradation. Enzymes available act mainly on the high-molecular-weight polymers of polyethylene terephthalate (PET) and ester-based polyurethane (PUR). Unfortunately, the best PUR- and PET-active enzymes and microorganisms known still have moderate turnover rates. While many reports describing microbial communities degrading chemical additives have been published, no enzymes acting on the high-molecular-weight polymers polystyrene, polyamide, polyvinylchloride, polypropylene, ether-based polyurethane, and polyethylene are known. Together, these polymers comprise more than 80% of annual plastic production. Thus, further research is needed to significantly increase the diversity of enzymes and microorganisms acting on these polymers. This can be achieved by tapping into the global metagenomes of noncultivated microorganisms and dark matter proteins. Only then can novel biocatalysts and organisms be delivered that allow rapid degradation, recycling, or value-added use of the vast majority of most human-made polymers.

High modulus hydrogels for ophthalmic and related biomedical applications.

This paper presents three families of semi-interpenetrating polymer network (SIPN) hydrogels based on an ester-based polyurethane (EBPU) and hydrophilic monomers: N,N-dimethylacrylamide (NNDMA), N-vinyl pyrrolidone (NVP) and acryloylmorpholine (AMO) as potential materials for keratoprosthesis, orthokeratology and mini-scleral lens application. Hydrogels sheets were synthesized via free-radical polymerization with methods developed in-house. SIPN hydrogels were characterized for their equilibrium water content, mechanical and surface properties. Three families of optically clear SIPN-based hydrogels have been synthesized in the presence of water with >10% of composition attributable to EBPU. Water contents of SIPN materials ranged from 30% to 70%. SIPNs with ≤15% EBPU of total composition showed little influence to mechanical properties, whereas >15% EBPU contributed significantly to an increase in material stiffness. In the hydrated state, SIPNs with ≤15% EBPU of total composition show little difference in polar component (γp ) of surface free energy, whereas for >15% EBPU there is a decrease in γp . The EBPU SIPN hydrogels display complementary material properties for keratoprosthesis, orthokeratology, and mini-scleral applications. © 2018 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1645-1653, 2019.

Phase separation and electrical conductivity of nanocomposites made of ether-/ester-based polyurethane blends and carbon nanotubes

Nanocomposites made of blends of ether-based thermoplastic polyurethanes (TPUs) and ester-based TPUs with multi-walled carbon nanotubes (MWCNTs) were studied. The TPU blend/MWCNT nanocomposites had higher electrical conductivities than those containing a single TPU. At a specific MWCNT loading, quenched or annealed TPU blend nanocomposites exhibited electrical conductivities three to four orders of magnitude larger than single TPU samples. Using Lorentz corrections, invariant quantity, Q inv , in small-angle X-ray scattering (SAXS) analysis, MWCNTs were found to retard phase separation. Raman spectra indicated the existence of interactions between phenyl rings in the TPUs and the MWCNT. Good dispersion of MWCNTs in the TPU blend was observed with transmission electron microscopy (TEM); both isolated droplet and co-continuous phase-separated morphologies were shown. Fourier transform infrared spectroscopy (FTIR) analysis and differential scanning calorimetry (DSC) measurements were performed to investigate the changes in morphology. Dynamic mechanical analysis (DMA) results were consistent with the DSC results.

Polyurethane/polyhedral oligomeric silsesquioxane shape memory nanocomposites with low trigger temperature and quick response

Ester-based polyurethane (PU) was found to have excellent shape memory properties with low trigger temperature. Polyhedral oligomeric silsesquioxanes (POSS) have drawn considerable interest due to their hybrid organic–inorganic structures consisting of a silica cage surrounded by eight organic groups. Incorporation of functional POSS in polymers normally improves the mechanical properties of polymer matrix. For the purpose of obtaining shape memory materials with low trigger temperature and quick response, octa(3-hydroxypropyl) polyhedral oligomeric silsesquioxane (POSS-(OH)8) was incorporated into polyurethane by solution casting. The chemical structures and microstructures were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD) and field emission scanning electron microscope (FESEM). The thermal properties and dynamic mechanical properties were investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The mechanical properties were also evaluated. Shape memory properties were characterized by cyclic thermal mechanical tests and physical shape recovery tests. The results show that the nanocomposites with low POSS-(OH)8 loading content (1 and 3 wt.%) possess higher breaking strength and elastic modulus, resulting in higher shape fixity, recovery ratios and faster recovery. The nanocomposites might have potential applications for controlling tags or proof marks in the area of low temperature storage.

Biomimetic myocardial patches fabricated with poly(ɛ‐caprolactone) and polyethylene glycol‐based polyurethanes

The production of efficient heart patches for myocardium repair requires the use of biomaterials with high elastomeric properties and controllable biodegradability. To fulfil these design criteria we propose biodegradable poly(ester urethanes) and poly(ether ester urethanes) from poly(ɛ-caprolactone) (PCL) and poly(ethylene glycol) (PEG) as macrodiols, 1,4-diisocyanatobutane as diisocyanate, l-Lysine Ethyl Ester and Alanine-Alanine-Lysine (AAK) as chain extenders. This peptide was used to tune biodegradability properties, since the Alanine-Alanine sequence is a target for the elastase enzyme. Enzymatic degradation tests demonstrated the feasibility of tuning biodegradability properties due to the introduction of AAK peptide in polyurethane backbone. Two formulations have been processed into porous scaffolds by Thermally-Induced Phase Separation (TIPS). Scanning Electron Microscopy micrographs revealed promising microstructures, which were characterized by stretched and unidirectional pores and mimicked the striated muscle tissue. Tensile tests showed that, although scaffolds are characterized by lower mechanical properties than films, these substrates have suitable elastomeric behaviors and elastic moduli for contractile and soft tissue regeneration. Viability tests on cardiomyocytes revealed the best cell response for dense film and porous scaffold obtained from PCL and Lysine Ethyl Ester-based polyurethane, with an increased viability for the porous substrate, which is ascribable to the morphological features of its microstructure. Future works will be addressed to study the in vivo behavior of these constructs and to confirm their applicability for myocardial tissue engineering.

Carbon nanotube–polyurethane shape memory nanocomposites with low trigger temperature

Ester-based polyurethane (PU) with low glass transition temperature was used to develop shape memory nanocomposites with low trigger temperature. Pristine carbon nanotubes (CNTs) and oxidized CNTs (ox-CNTs) were introduced by melt mixing to improve the mechanical and shape memory properties of the PU matrix. The dispersion of CNTs on the mechanical properties and shape memory behaviors of the nanocomposites were also investigated. The results show that better dispersion of ox-CNTs contributes to more stiffness effect below glass transition temperature (Tg) while lower storage modulus (E′) above Tg. The nanocomposites exhibit high shape fixity and recovery ratio above 98%. The ox-CNT/PU nanocomposite shows higher shape recovery ratio for the first cycle, faster recovery due to better dispersion of CNTs and have potential applications for controlling tags or proof marks in the area of frozen food. The trigger temperature can be tailored by controlling the Tg of the PU matrix or the content of the nanofillers.

Collision induced dissociation study of ester-based polyurethane fragmentation reactions

A combination of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) collision induced dissociation (CID) and ion mobility separations (IMS) was used to study a complex mixture composed of unreacted polyester starting material (polybutylene adipate) and polyurethane (PUR) end products. Collision induced dissociation fragmentation identified two primary fragmentation mechanisms of PURs, which were used to generate a general fragmentation model. Predicted fragment ions were used to distinguish: (1) linear and cyclic PURs, (2) hard-block and soft-block PURS, (3) the degree of “blockiness” within hard- and soft-block PURs, (4) the location of the MDI linkages within each PUR chain, and (5) the relative intensities of various isobars intermingled within a precursor mass peak. These results were consistent with the observed IMS separations.

Structure-Property Relationships in Polyoxymethylene/Thermoplastic Polyurethane Elastomer Blends

A series of blends of polyoxymethylene (POM) / thermoplastic ester-based polyurethane elastomer (TPU) has been obtained by using a double screw extruder (L/D = 25) in the temperature range of 175-190°C. Differential scanning calorimetry (DSC) was applied to investigate the influence of TPU on the melting and crystallisation of POM; it was found that there is a decrease of the enthalpy of melting with an increase of TPU amount in the blend (up to 10 wt %); enthalpy of fusion also decreases. X-ray diffraction patterns confirm that the crystalline structure of POM remains unaffected after blending with multiphased TPU. Morphology of the blends, investigated by scanning electron microscopy (SEM), showed that TPU is distributed rather uniformly in POM and forms cylindrical-shaped domains of ca. 10 μm length. Homogeneous distribution may be the consequence of existence of specific interactions in form of hydrogen bonding between ether oxygen (POM) and hydrogen from urethane group (TPU) as evidenced by FTIR measurements. Modified morphology contributes to the better mechanical properties; elongation at break increases with an increase of the TPU content in the blend (for TPU content > 10%).

Extraction Preconcentration of Naphthols and Phenol with Solvent Mixtures Impregnated into Polyurethane Foam

The extraction of phenol and naphthols with isomolar mixtures of nonane and tributyl phosphate, dibutyl phthalate, or hexane impregnated in ester-based polyurethane foam was studied. The optimum conditions for the extraction–adsorption preconcentration (equilibration time, the pH of the solution, the volume of the test sample, the mass of the adsorbent pellet, and the nature and composition of the mixture applied to polyurethane foam) were determined. A procedure providing the 250- to 350-fold preconcentration of phenol and naphthols is proposed for quantitative extraction.

Biodegradation of a colloidal ester-based polyurethane by soil fungi

Four species of fungi were isolated from soil and found to degrade ester-based polyurethane in a polyurethane-agar clearing assay. One of these isolates, Curvularia senegalensis, secreted an extracellular enzyme-like factor with esterase properties, as determined by fluorescein diacetate hydrolysis, and this active factor was partially purified by ammonium sulfate fractionation. The polyurethane-clearing factor had an isoelectric point of 5·1 and a molecular weight of 28 kDa. It was stable to heating at 100°C for 10 min and was inhibited by phenylmethylsulfonyl fluoride.

Biodegradation of Polymer Coatings

AbstractConventional paint removal methods include chemical stripping with VOCs, blasting with plastic media, and delamination with high pressure water. These methods have many limitations, in that they are labor intensive, pose human health risks, are relatively expensive and pose significant waste disposal problems. However, polymeric coatings are known to contain structural components, such as ester, amide and urea linkages, that can be degraded biologically. We are working to develop a stable, enzyme-based, non-toxic paint stripping strategy that will be environmentally safe and cost effective.The specific objectives are to identify and characterize microbial systems capable of degrading polymeric coatings, to develop a quantitative degradation assay and to optimize activity levels for subsequent purification and concentration of the biological products required for rapid degradation of coatings.A water-dispersed colloid of an ester-based polyurethane polymer has been used in solid growth medium to screen about 100 different bacteria for microbial degradation activity. Those with demonstrable activity have been grown in the presence of epoxypolyamide paint- and polyester polyurethane paint-coated aluminum coupons. We have demonstrated delamination under certain conditions and have developed a spectrophotometric method for quantitating degradation activity as a function of dye release.

Crosslinking studies of polyether–ester‐based polyurethane systems

AbstractEther‐ and ester‐based prepolymeric diols suitable for polyurethane elastomer formation were prepared from polyoxytetramethyleneglycol and polyoxytetramethylene–oxypropyleneglycol with dicarboxylic acids like adipic acid, maleicacid, and phthalic acid. Crosslinked polyurethane elastomers were prepared from these prepolymers using various concentrations of trimethylolpropane as a crosslinker and toluenediisocyanate as the curing agent. Crosslinked polyurethanes were also prepared by a method taking excess toluenedisocyanate other than that of the stochiometric requirement and curing it at a comparatively higher temperature. The data on mechanical properties of these elastomers show that both methods of crosslinking in polyurethane imparts a similar effect on mechanical properties.