Polyurethane Macromolecules Research Articles

Robust and self-healing under-liquid superlyophobic coating fabricated by a universal strategy for polar-nonpolar liquid separation

Surfaces showing desirable under-liquid superlyophobicity have attracted great interests due to their high potential applications, especially in the liquid separation. Nevertheless, it still remains a challenge to put forward a universal strategy to fabricate robust under-liquid superlyophobic surfaces with self-healing function. Herein, a highly durable and self-healing under-liquid superlyophobic coating is developed that can be applied onto various substrates (e.g., cotton, polyester, filter paper, wool, hemp, sponge, lyocell, etc.) via a two-step coating process, through depositing silica nanoparticles partially grafted by octadecylamine followed by crosslinking of polyurethane macromolecules containing polysorbate20. The obtained substrates show superamphiphilic in air, under-water superoleophobic and under-oil superhydrophobic properties. High-efficiency separations of polar-nonpolar liquids, e.g., water-heavy oil, water-light oil, immiscible organic liquid mixtures, can be achieved when the coated fabric was used as the separation membrane. Moreover, such under-liquid superlyophobic coating demonstrates excellent durability against repeated washing, long time UV irradiation, organic solvent attack, high temperature and plasma treatment. Even the coating surface is damaged chemically or physically, its original superwetting property can be recovered by a short time of heating treatment. This work could provide a guidance for developing durable under-liquid superlyophobic materials with self-healing ability for diversified applications, such as liquid separation, micro-fluid manipulation, anti-adhesive surfaces.

Composition based on one-component polyurethane modified with tetrapropoxysilane

The questions of interaction of one-component polyurethane and organosilicon compound from the group of alkoxysilanes - tetrapropoxysilane are considered. The composition is intended to obtain a hydrophobic coating with improved performance properties to protect building structures from the effects of technogenic and natural factors. The mechanisms of interaction of one-component polyurethane with tetrapropoxysilane have been studied using spectroscopy. The product of the interaction of the polymer and tetrapropoxysilane is a three-dimensionally crosslinked polymer in which polyurethane macromolecules are crosslinked by organosilicon molecules. The chemical reaction is based on the mechanism of interaction of isocyanate groups with reactive groups of alkoxysilane. The effect of the modifier on the surface structure of the cured coating was studied using a microscope. The contact angle of wetting of the modified and unmodified composition is determined, and the concentration of tetrapropoxysilane at which the coating acquires hydrophobic properties is determined. The effect of tetrapropoxysilane on the adhesive characteristics of the polymer composition has been studied. The change in the hardness of the composition at various concentrations of alkoxysilane was studied. Chemical modification of polyurethane allows you to vary its properties in the desired direction without deteriorating its other characteristics.

UV-resistant transparent lignin-based polyurethane elastomer with repeatable processing performance

Lignin, as a green and environmentally sustainable natural material, is indispensable to be reasonably developed and utilized. Herein, lignin macromolecules are used as raw materials of polyhydroxyl structure to synthesize polyurethane macromolecules. It is found that the optimal mass ratio of lignin to isocyanate group in the synthesis of polyurethane is 95/5. The lignin-based polyurethane putted the lignin as a fulcrum to form a hydrogen bond with the polyurethane macromolecular chain to form a hydrogen bond network structure, so that its elastic recovery rate attains 94.7%. Meanwhile, its tensile strength and breaking elongation rate reach 16.2 MPa and 1049.5% respectively. Furthermore, the lignin-based polyurethane synthesized in this work still maintain excellent mechanical properties after thermal reprocessing. Moreover, the lignin-based polyurethanes prepared by this approach also possess excellent transparency and UV resistance, and the average ultraviolet protection factor (UPF)value of the lignin-based polyurethane hot-pressed fabrics obtained by hot pressing is greater than 50. This work provides an innovative and sustainable strategy for the further application of lignin, a pure natural material, as a bio-based multifunctional additive to packaging, textiles, automotive trim and other fields.

Surface modification and disaggregation of detonation nanodiamond particles with biodegradable polyurethane

Nanodiamond(ND) is one of the most important carbon nanomaterials, which not only has the distinguishing feature of fundamental nanoparticles but also has intrinsic characteristics of diamond. Depending on its extraordinary properties, such as good biocompatibility, low toxicity and mechanical behavior, ND thus has been widely used in a variety of fields. However, pristine ND easily tends to aggregate in the form of micro-sized clusters. Therefore, two different approaches for surface modification of ND with biodegradable polyurethane by chemical of grafting-to and grafting-from are presented herein. The Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analyses (TGA) reveal that polyurethane has been covalently attached to ND surface, and the weight loss is 3.51% and 3.23%, which is equivalent to the grafted rate. Dynamic light scattering, transmission electron microscopic (TEM) and natural sedimentation experiment all demonstrate that modified ND with long PU chains can well disperse in organic solvents and CCD images (Charge Coupled Device Images) illustrate that modified ND render hydrophilic pristine ND good hydrophobic behavior. So ND functionalized with polyurethane broadens a new prospect of application in biomedical science. It is suggested that the polyurethane macromolecules covalently bonded onto the agglomerate surface play an important role on the colloidal stability against aggregation.

Quantitative separation of the influence of copper (II) chloride mass migration on the chemo-responsive shape memory effect in polyurethane shape memory polymer

Chemo-responsive shape memory effect in polyurethane shape memory polymer (SMP) composite triggered by mass migration of copper (II) chloride (CuCl2) has been experimentally demonstrated. In this study, we present a comprehensive study on quantitative separation of the effect of CuCl2 particle mass migration on the chemo-responsive shape recovery behavior of polyurethane SMP composites with different concentrations of CuCl2 particles. It is found that the SMP is featured with a critical release rate of the mechanical energy storage associated with the shape recovery behavior due to mass migration of the CuCl2 particle. A sequence of molecular interactions among CuCl2 particles, polyurethane macromolecules and water molecules, i.e., assembly of the CuCl2 particle with polyurethane macromolecules, and then disassembly and dissolution of the CuCl2 particle in water, results in an acceleration of water-induced shape recovery of polyurethane SMP. This study focuses on the quantitative separation of the influence of mass migration on the chemo-responsive shape recovery behavior of polyurethane SMP in response to water. It is expected to promote and achieve the actuation of chemo-responsive SMPs in a fully controllable manner.

Enhanced hydrophobicity of polyurethane via non-solvent induced surface aggregation of silica nanoparticles

Fabrication of superhydrophobic surfaces from hydrophilic polymers has always been regarded as a challenge. In this study, to achieve superhydrophobic polyurethane (PU) surfaces, silica nanoparticles and ethanol as non-solvent were simultaneously utilized during a solution casting-based process. Such modified version of phase separation process was found to be highly efficient, and also it required much lower concentration of nanoparticles to achieve superhydrophobicity as compared to the previously reported methods in the literature. According to the proposed mechanism, non-solvent induces a more profound aggregation of silica nanoparticles at the surface’s top layer causing the surface energy to be highly diminished, and thus, the water repellency is improved. Morphology and topography results showed that a unique “triple-sized” structure was formed on the surface of superhydrophobic samples. X-ray photoelectron spectroscopy results proved that both PU macromolecules and silica nanoparticles were concurrently present at the surface layer of the superhydrophobic sample. It was concluded that surface composition and roughness could be regarded as competing factors in achieving superhydrophobicity. Based on the obtained results, the proposed method exhibits a promising potential in large-scale fabrication of surface layers with superhydrophobic property. Moreover, a mechanism was also presented to further explicate the physics behind the suggested method.

Chemo-responsive shape memory effect in shape memory polyurethane triggered by inductive release of mechanical energy storage undergoing copper (II) chloride migration

In this study, 10% weight fraction of copper (II) chloride (CuCl2) was embedded into shape memory polyurethane (SMPU) by dissolving it in a solvent mixture of tetrahydrofuran and N,N-dimethyl formamide. It is found that CuCl2 particles migrate; they are released from the polymer in the water-driven shape recovery process of SMPU composites. SMPU composites, after various immersion times in water, were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Experimental results support that hydrogen bonding between polyurethane macromolecules and water molecules is the driving force, resulting from the inductive decrease in the glass transition temperature. Furthermore, the release of the stored mechanical energy in SMPU is demonstrated by means of tracking the migration of CuCl2 particles via x-ray diffraction and scanning electron microscopy tests. This study focuses on the mechanism of release of the stored mechanical energy of a polymer, which is identified as the driving force for the chemo-responsive shape memory effect and inductive decrease in glass transition temperature of SMPU in response to the water.

Stretchable conductive polyurethane elastomer in situ polymerized with multi-walled carbon nanotubes

The development of the wearable sensors for healthcare related applications requires mechanically stretchable, electrically conductive and biologically compatible elastomers. We have fabricated a conductive polyurethane (PU) elastomer by in situ polymerization with surface hydroxyl-modified Multi-Walled Carbon Nanotubes (MWNTs). The FT-IR and Raman spectroscopy results indicated that the successful incorporation of the MWNTs into PU macromolecules. The good dispersion of MWNTs in PU/MWNT elastomers was confirmed by transmission electron microscopy (TEM) and Raman spectroscopy. Thermogravimetric analysis (TGA) suggested improved thermal stability of the in situ polymerized PU/MWNT elastomers. The in situ polymerization with MWNTs led to a significant increase in the conductivity of PU/MWNT elastomers. The stretching facilitated the orientation of the MWNTs and further enhanced the conductivity of PU/MWNT elastomers. The in situ polymerized PU/MWNT elastomers were employed as electrodes to construct a pressure sensor demonstrating good sensitivity and consistency.

Study on the Pyrolytic Behaviors and Kinetics of Rigid Polyurethane Foams

Abstract In order to investigate the pyrolytic behaviors and kinetics of rigid polyurethane foams (PUFs), three samples named PUF01, PUF02 and PUF03 were synthesized with different [NCO]: [OH] ratios of 1.05, 1.1 and 2, respectively. Many techniques including thermogravimetric analysis (TGA), Fourier-transform infrared spectrometry (FTIR) and synchrotron radiation vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) were used to analyze their pyrolytic behaviors. The results show that the process of PUFs pyrolysis can divide into two stages in nitrogen atmosphere: one is from room temperature to 400, and the other is above 400 .The pyrolysis of PUFs mainly occurred at temperature between 200 and 400 . The activation energies of the copolymers at lower percent conversion () grow with the increase of the isocyanate index. The higher activation energies were obtained at higher isocyanate index. Mass spectra of pyrolytic products evolved at low pressure indicate that the fission of main chain of polyurethane macromolecules leads to the formation of primary product of isocyanate. Along with the increase of temperature, the chief breakage of polyurethane occurs in the bonds of C-O and C-N. Kinds of pyrolysis products reduce with the increase of isocyanate index.

Critical chromatography and mass spectrometry of macromolecules: Determination of the position of a functional group in a chain

The potentials inherent in the method of critical chromatography of macromolecules combined with mass spectrometry for the study of the most complicated characteristic of the macromolecular structure—the determination of the position (the number) of a defect unit or functional group in a sequence of chain units—are considered. Polyurethanes based on poly(propylene oxide) oligomers were used as research objects. Such macromolecules contain a small amount of urethane groups in a chain that differ from mainchain units in the energy of interaction with the surface. Variation in the molecular-mass distribution of the initial poly(propylene oxide) oligomers makes it possible to prepare linear polyurethane macromolecules with different positions of urethane groups. Critical chromatography offers a way to separate macromolecules with different amounts of urethane groups and positions of these groups in chains.

Novel elastomeric polyurethanes with pendant epoxy groups as highly reactive auxiliary groups for further derivatizations

AbstractThe introduction of pendant, reactive groups into polyurethane macromolecules is a challenging problem. A variant of the nondegradative modification of polyurethanes with epoxy groups attached to the urethane sites is proposed. Two types of commercial elastomeric segmented polyurethanes, represented by a poly(ether urethane) and a poly(urethane urea), were functionalized by base‐induced N‐glycidylation of the urethane hard segments with an excess of epibromohydrin in dimethylacetamide solutions at low temperatures. This resulted in the modification of polymers with 0.30–0.44 mmol/g of pendant epoxy groups. Lithium or potassium tert‐butoxides were used as bases to initiate the reaction. A nonpolymeric urethane model (ethyl N‐p‐tolylcarbamoate) was used to verify the course of glycidylation. One of the polymers was subjected to epoxy ring opening with 1‐propanethiol, demonstrating the versatility of pendant glycidyl groups as auxiliary groups for further bulk modifications of polyurethanes. These functionalized polyurethanes are useful for the further covalent attachment of suitable moieties (stabilizing or biocompatibility‐enhancing agents). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4378–4385, 2002

Strength of chemical bonds in the main fragments of polyurethane macromolecules

The paper is based on a theoretical evaluation of the relative stability of chemical bonds that are incorporated in functional groups of various polyurethanes and are destroyed during thermal degradation processes. The necessary calculations were done in accordance with a quantum-chemical method classed as MINDO/3. It is shown that the thermal stability of individual PU fragments depends on the strength of bonds forming the latter.

Nature and mechanism of the effect of thermal prehistory on the structure and molecular mobility in a polyurethane capable of crystallization

Various physical methods have been used to investigate the structure and molecular mobility of a crystallizable polyurethane based on diphenylmethanediisocyanate and 1,4-butanediol as a function of thermal prehistory. Various forms of molecular movement have been observed and identified: these are caused by the appearance of local and segmental forms of movement in the polyurethane macromolecules, and also by molecular mobility within crystalline regions. It has been established that the latter includes a number of processes of molecular motion caused by the melting of the initial assembly of crystallites that had been formed as a result of the previous thermal treatment and subsequent reorganization of the crystallites during heating of the specimen. These processes of molecular motion substantially affect the mechanical behaviour of the polyurethane at temperatures above the glass region. It has been shown that the system of hydrogen bonds in the crystallizable polyurethane investigated is directly connected with the characteristics of its structure and undergoes considerable changes when the latter is reorganized during annealing and heating.