Effect of PEG Molecular Weight on the Polyurethane-Based Quasi-Solid-State Electrolyte for Dye-Sensitized Solar Cells

Nanosilica was surface modified with polyaniline and incorporated into polyurethane to form a polymer matrix capable of entrapping a liquid electrolyte and functioning as quasi-solid-state electrolyte in the dye-sensitized solar cells. The effect on the S−PANi distribution, surface morphology, thermal stability, gel content, and structural change after varying the PEG molecular weight of the polyurethane matrix was analyzed. Quasi-solid-state electrolytes were prepared by immersing the polyurethane matrix into a liquid electrolyte and the polymer matrix absorbency, conductivity, and ion diffusion were investigated. The formulated quasi-solid-state electrolytes were applied in dye-sensitized solar cells and their charge recombination, photovoltaic performance, and lifespan were measured. The quasi-solid-state electrolyte with a PEG molecular weight of 2000 gmol−1 (PU−PEG 2000) demonstrated the highest light-to-energy conversion efficiency, namely, 3.41%, with an open-circuit voltage of 720 mV, a short-circuit current of 4.52 mA cm−2, and a fill factor of 0.63.

Experimental and numerical perspective on the fire performance of MXene/Chitosan/Phytic acid coated flexible polyurethane foam

Recent discoveries of two-dimensional transitional metal based materials have emerged as an excellent candidate for fabricating nanostructured flame-retardants. Herein, we report an eco-friendly flame-retardant for flexible polyurethane foam (PUF), which is synthesised by hybridising MXene (Ti[Formula: see text]) with biomass materials including phytic acid (PA), casein, pectin, and chitosan (CH). Results show that coating PUFs with 3 layers of CH/PA/Ti[Formula: see text] via layer-by-layer approach reduces the peak heat release and total smoke release by 51.1% and 84.8%, respectively. These exceptional improvements exceed those achieved by a CH/Ti[Formula: see text] coating. To further understand the fundamental flame and smoke reduction phenomena, a pyrolysis model with surface regression was developed to simulate the flame propagation and char layer. A genetic algorithm was utilised to determine optimum parameters describing the thermal degradation rate. The superior flame-retardancy of CH/PA/Ti[Formula: see text] was originated from the shielding and charring effects of the hybrid MXene with biomass materials containing aromatic rings, phenolic and phosphorous compounds.

Identifying competitive tin- or metal-free catalyst combinations to tailor polyurethane prepolymer and network properties

Polyurethane-based mastics, industrially obtained via a prepolymerization/crosslinking process, benefit from catalyst selection at both stages.

Microbial Conversion of Vegetable Oil to Hydroxy Fatty Acid and Its Application to Bio-Based Polyurethane Synthesis

New polyurethanes were synthesized based on dihydroxy fatty acid obtained by the microbial conversion of olive oil. Monounsaturated 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) was produced from olive oil by Pseudomonas aeruginosa PR3 and reacted with hexamethylene diisocyanate (HMDI) at different ratios to form polyurethanes. Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry confirmed the synthesis of DOD. The thermal and tensile properties of the polyurethanes were investigated by differential scanning calorimetry, thermogravimetric analysis, and a universal testing machine. At an isocyanate/hydroxyl ratio of 1.4, the polyurethane exhibited an elongation at break of 59.2% and a high tensile strength of 37.9 MPa. DOD was also mixed with polycaprolactone diol or polyethylene glycol at different weight ratios and then reacted with HMDI to produce new polyurethanes of various properties. These polyurethanes displayed higher elongation at break and good thermal stability. This is the first report on the synthesis of polyurethanes based on DOD produced by the microbial conversion of vegetable oil.

Fluoride-Catalyzed Deblocking: A Route to Polymeric Urethanes

We report a fluoride-catalyzed deblocking of urethanes as "blocked" isocyanates. Organic and inorganic sources of fluoride ion proved effective for deblocking urethanes and for converting polyurethanes to small molecules. Distinct from conventional deblocking chemistry involving organometallic compounds and high temperatures, the method we describe is metal-free and operates at or slightly above room temperature. The use of fluorescent blocking agents enabled visual and spectroscopic monitoring of blocking/deblocking reactions, and the selected conditions proved applicable to urethanes containing a variety of blocking groups. The method additionally enabled a one pot deblocking and polymerization with α,ω-diols. Overall, this deblocking/polymerization strategy offers a convenient and efficient solution to problems that have limited the breadth of applications of polyurethane chemistry.

3D porous polyurethanes featured by different mechanical properties: Characterization and interaction with skeletal muscle cells

The fabrication of biomaterials for interaction with muscle cells has attracted significant interest in the last decades. However, 3D porous scaffolds featured by a relatively low stiffness (almost matching the natural muscle one) and highly stable in response to cyclic loadings are not available at present, in this context. This work describes 3D polyurethane-based porous scaffolds featured by different mechanical properties. Biomaterial stiffness was finely tuned by varying the cross-linking degree of the starting foam. Compression tests revealed, for the softest material formulation, stiffness values close to the ones possessed by natural skeletal muscles. The materials were also characterized in terms of local nanoindenting, rheometric properties and long-term stability through cyclic compressions, in a strain range reflecting the contraction extent of natural muscles. Preliminary in vitro tests revealed a preferential adhesion of C2C12 skeletal muscle cells over the softer, rougher and more porous structures. All the material formulations showed low cytotoxicity.

High Throughput Screening of Rigid Polyisocyanurate Foam Formulations: Quantitative Characterization of Isocyanurate Yield via the Adiabatic Temperature Method

To reduce the time-to-market, a high throughput experimentation (HTE) method has been introduced at Bayer MaterialScience for the rapid development and optimization of polyurethane (PU) foam formulations and for the fast screening of new PU raw materials. The foam processor developed for this purpose allows automated PU foam production on a scale of 0.4 L, which is ten times smaller than the usual lab-scale foam volume. In order to optimize formulations for the increasing polyisocyanurate (PIR) foam market, a rapid in situ method has additionally been developed that is able to quantify isocyanurate concentration and yield. This method, the adiabatic temperature method (ATM), is based on the temperature profile measured within the foam bun in the HTE foam processor.

By comparison with attenuated total reflection (ATR)-FTIR spectra of the cured foams, it is shown that the isocyanurate concentration found in the 0.4 L foams is comparable with that of larger foams typically used in the laboratory (ca. 5 L). This demonstrates that the 0.4 L foams can be used to investigate the trimerization of isocyanates to form isocyanurate.

The suitability of the ATM is demonstrated and verified by ATR-FTIR spectroscopy for the influence of the index on isocyanurate yield and concentration for a pentane blown and a water co-blown PIR formulation. Isocyanurate yield is shown to be negligible at indices close to 100 but increases to an almost constant level at higher indices, the height of which depends on the type of the formulation. A level of approximately 70% has been observed for the physically blown formulations, whereas the water co-blown formulations only reach a level of around 40%.

Due to the successful implementation of the ATM, Bayer MaterialScience is increasingly using high throughput experimentation to optimize PIR recipes and to examine new raw materials and additives for polyisocyanurate foams. This has led to an increase in the efficiency of our polyurethane research and opened up possibilities that were not available to us before.

A Quantitative Investigation of the Effect of the Recipe on the Trimer-yield in Polyisocyanurate Foams

The effect of the recipe on the isocyanurate yield in polyisocyanurate (PIR) foams has been studied quantitatively using ATR—FTIR spectroscopy and the adiabatic temperature method based on the measurement of the reaction temperature during the course of the reaction. In this way, the effect of the index on the PIR reaction could be studied quantitatively. The significance of isocyanurate concentration and isocyanurate yield with respect to flammability properties is also investigated. It could also be shown that, for example, the presence of water reduces the isocyanurate yield dramatically. During an investigation of various commercially available PIR-catalysts, it is shown that potassium 2-ethylhexanoate in diethylene glycol (75: 25) leads to higher isocyanurate yields than potassium acetate in diethylene glycol (25: 75). Even when different concentrations of active components in commercially available catalysts are taken into account, this is still found to be the case.

Synthesis and characterization of polyurethanes made from copolymers of epoxidized natural oil and tetrahydrofuran

Polyols were synthesized from epoxidized natural oils and tetrahydrofuran through ring opening copolymerization catalyzed by Lewis acid. The properties of these polyols depend on the type of natural oils as well as the reaction conditions (monomer concentration, catalyst amount, reaction temperature and reaction time). These polyols were evaluated as a raw material for making polyurethane (PU) in order to understand the structure-property relationship between a natural oil and PU made from it. The tensile test analysis shows that the incorporation of natural oil moiety into the PU polymer network improves the elasticity of these PU samples when compared to a benchmark PU sample. In addition, the PU samples made from palm oil and soybean oil based polyols exhibit better tensile strength than benchmark PU. These polyols samples are suitable for making elastomeric PU, where high flexibility (high elongation at break) of PU is a common requirement.

Synthesis and characterization of biodegradable acrylated polyurethane based on poly(ε-caprolactone) and 1,6-hexamethylene diisocyanate

A series of biodegradable acrylic terminated polyurethanes (APUs) based on poly(ε-caprolactone) diol (PCL), aliphatic 1,6-hexamethylene diisocyanate (HDI) and hydroxyethyl methyl acrylate (HEMA) was synthesized as potential materials for hard tissue biomedical applications. PCLs with low molecular weights of 1000 and 2,000 g/mol were employed to provide different amounts of end capped urethane acrylate in APUs. To control crosslink density, a mixture of two different reactive diluents including mono-functional HEMA and bi-functional ethylene glycol dimethacrylate (EGDMA) with different weight ratios was incorporated into the APUs, called here PUAs. Morphological characteristics and mechanical properties were investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). DMA results indicated some degree of microphase separation between hard and soft segments; however, the microphase separation is more prominent for PUAs with higher molecular weight PCL. It was also found that the degree of crosslinking dominated greatly the formation of crystalline structure. PUAs with low crosslink density exhibited crystalline microstructure. The results also indicated that the mechanical properties of PUAs were governed considerably by crystalline microstructure, and hard segment content. All PUAs demonstrated hydrophobic behavior and were able to be degraded hydrolytically. The degradation process was closely related to the microstructure and surface tension of PUAs.

Incorporation of Modified Nano Montmorillonite (MMT) in Polyurethane Coatings Based on Acrylic Copolymer and Trimer of Isophorone Diisocyanate

This work presents the synthesis of acrylic copolymer and trimer of isophorone diisocyanate (IPDI) for preparation of polyurethane (PU) coatings. Further we have studied the effect of silane modified nano montmorillonite (MMT) on the properties of PU coatings. Nano MMT was modified by vinyltriethoxysilane (TEVS) coupling agent and incorporated in PU coatings made from acrylic copolymers and trimer of IPDI. Acrylic copolymer was synthesized in the laboratory using butyl acrylate (BA), methyl methacrylate (MMA), styrene and hydroxyl ethyl acrylate (HEA) monomers. Coating properties of prepared PU coatings studied are gloss, impact resistance, flexibility, cross hatch adhesion and physicochemical properties include chemical resistance. The experimental results revealed that polyurethane coatings based on MMT based acrylic polyol and IPDI trimer showed good gloss and excellent adhesion. Thermal stability of these PU samples was found upto 229 °C. Physicochemical properties reflected that these PU have excellent chemical and solvent resistance.

The Preparation and Performance of Phenolic Foams Modified by Active Polypropylene Glycol

A series of active polypropylene glycols (APPGs) were synthesized by the reaction of hexamethylene-1,6-diisocyanate (HDI) and polypropylene glycol (PPG). They were then mixed and reacted with resol resin in catalyst condition to prepare the phenolic foams. The structure of modified phenolic foams was investigated. The influence of Mn of PPG and proportion of APPG on mechanical and fire-retardant performances of foams was discussed. The research results showed that the flexible PPG can be inducted into the crosslink structure of phenolic foam by the together crosslink reaction of –NCO groups in APPG with –CH2–OH groups in resol resin. When the molecular weight of PPG was 2000 and the dosage of APPG was 15% the max strain increased by 87%, mass loss (friability) decreased by 52%, thermal conductivity decrease from 0.033 to 0.028 W/(m·K), meanwhile the LOI can maintain above 30.

Biocompatibility and chemical reaction kinetics of injectable, settable polyurethane/allograft bone biocomposites

Injectable and settable bone grafts offer significant advantages over pre-formed implants due to their ability to be administered using minimally invasive techniques and to conform to the shape of the defect. However, injectable biomaterials present biocompatibility challenges due to the potential toxicity and ultimate fate of reactive components that are not incorporated in the final cured product. In this study the effects of stoichiometry and triethylenediamine (TEDA) catalyst concentration on the reactivity, injectability, and biocompatibility of two component lysine-derived polyurethane (PUR) biocomposites were investigated. Rate constants were measured for the reactions of water (a blowing agent resulting in the generation of pores), polyester triol, dipropylene glycol (DPG), and allograft bone particles with the isocyanate-terminated prepolymer using an in situ attenuated total reflection Fourier transform infrared spectroscopy technique. Based on the measured rate constants, a kinetic model predicting the conversion of each component with time was developed. Despite the fact that TEDA is a well-known urethane gelling catalyst, it was found to preferentially catalyze the blowing reaction with water relative to the gelling reactions by a ratio >17:1. Thus the kinetic model predicted that the prepolymer and water proceeded to full conversion, while the conversions of polyester triol and DPG were <70% after 24h, which was consistent with leaching experiments showing that only non-cytotoxic polyester triol and DPG were released from the reactive PUR at early time points. The PUR biocomposite supported cellular infiltration and remodeling in femoral condyle defects in rabbits at 8weeks, and there was no evidence of an adverse inflammatory response induced by unreacted components from the biocomposite or degradation products from the cured polymer. Taken together, these data underscore the utility of the kinetic model in predicting the biocompatibility of reactive biomaterials.