Nonwoven needle-punched fabrics with nano-sized polyurethane reinforcing sheaths for construction application

The novel star shaped benzoxazine-co-urethane prepolymers are first synthesized from the natural resource castor oil, hydroxyl terminated benzoxazine and diisocyanate through the facile one-pot formulation method. Then the cured benzoxazine copolymers can be obtained by the ring-opening polymerization of oxazine groups of the prepared prepolymers. Both hexamethylene diisocyanate and 4,4′-methylenediphenyl diisocyanate are employed as aliphatic and aromatic diisocyanate, respectively, to clarify their effects on the chemical structure and high-frequency dielectric properties of copolymers. In comparison with the pure polybenzoxazine, the copolymer films occupy the improved high-frequency dielectric properties owing to the introduction of three branching aliphatic castor oil, leading to the reduction of molecular polarity and the improvement of free volume. It should be noted that the aliphatic diisocyanate not only decreases the polarity of the copolymer, but also enhances the intermolecular interaction and intermolecular entanglement between castor oil and benzoxazine for the copolymers. Accordingly, the aliphatic diisocyanate based poly(benzoxazine-co-urethane) occupies the minimum high-frequency dielectric constants (2.94, 5 GHz; 2.96, 10 GHz) and relatively high glass transition temperature (220 °C). Therefore, this work not only provides a simple path for improving high-frequency dielectric properties of benzoxazine, but also gives some insight into the effects of diisocyanates on the formation and high-frequency dielectric properties of poly(benzoxazine-co-urethane)s.

Seeded emulsion polymerization of methyl methacrylate using aqueous polyurethane dispersion: effect of hard segment on grafting efficiency

Aqueous polyurethane dispersions (PUDs) have recently emerged as important alternatives to their solvent-based counterparts for various applications due to increasing health and environmental awareness. A series of aqueous polyurethane dispersions containing carboxylate anion as hydrophilic pendant groups were synthesized through step growth polymerization reaction using hexamethylene diisocyanate (HDI), 1,4-butanediol (1,4-BDO), dimethylol propionic acid (DMPA) and polyethylene glycol (PEG) of different molecular weight. Effect of PEG molecular weight was investigated on molecular structure, contact angle measurement, and physical and adhesive properties of PU emulsions. Fourier transform infrared spectroscopy (FT-IR) was used to check the completion of polymerization reaction. Contact angle measurement indicated that the hydrophilicity of polymer increases by increasing molecular weight of PEG with a corresponding decrease in contact angle. Results of T-peel test showed a decrease in peel strength by increasing molecular weight of PEG. Moreover, solid contents%, drying time and storage stability suggested fast drying properties and greater stability of aqueous PU dispersions.

At present, the modern society utilizes composite materials in various branches of the national economy. The properties of such materials depend on their composition and structure, and may considerably differ from the properties of source materials. In turn, texture and structure of crystals, their packing order, size and level of sophistication affect the structure of materials. This is particularly demonstrated by hydration curing materials on the basis of gypsum and magnesia binding materials, as well as portland cement. Structuring control is one of the key problems of composite materials. Gypsum binding materials with various modification composition are suggested as a model system to study the influence of texture and structure of materials on their properties. One of them is the construction gypsum – an anhydrite binder and a multiphase gypsum binder (MGB). Scanning electron microscopy (SEM) was chosen as the main method of study. It is found that gypsum crystals that are formed during hydration and curing of gypsum binders with various modification composition have different texture and structure. It prevents from getting the optimal packing of a material. It is justified and confirmed that the MGB consisting of several modifications of calcium sulfate allow choosing the best material composition due to the combination of crystals having different size and form. Besides, MGB contains significant amounts of insoluble anhydrite that reduces the water-gypsum ratio of a binder and compacts its structure. Considerable attention is paid to microfillers, which significantly affect the texture and structure of materials based on gypsum binders. Iron ore concentrate of the Lebedinsky GOK generally consisting of magnetite, as well as impalpable flour cullet waste of sodium and potassium glass were used as microfillers in the given study. Ultra- and nanodispersed powders at their introduction to gypsum and anhydrite compositions change the size and morphology of crystal newgrowths and ensure the formation of ordered, denser and uniform fine-crystalline structures of composite materials, which leads to the reduction of structure imperfection, porosity and increase in contact areas of crystalline hydrates increasing physical and mechanical performance of gypsum materials. Efficient composite construction materials are obtained on the basis of MGB and microfillers.

Rheology of aqueous polyurethane dispersion (PUD) has a significant influence on the industry process. In this study, the aqueous PUD used in warp knitted vamp printing was characterized by Fourier transform infrared (FTIR) spectra, dynamic light scattering and laser Doppler electrophoresis. Characterization results reveal that aqueous PUD shows bimodal and broad particle size distributions as well as negative surface charges. Aiming at studying the influence of rheological property on industrial applications of aqueous PUD, dynamic oscillating shear experiments were performed, and its constitutive equation was deduced. Experimental results suggest that temperature has no distinct effect on the linear viscoelastic range, in which aqueous PUD shows a solid‐like behavior. In view of advantages of fractional order constitutive equation describing the viscoelasticity of fluid, this paper optimize the fractional order element to derived fractional Zener (FZ) and Poynting‐Thomson models, and FZ model performs the better. Furthermore, the application and analysis of fractional order model provide theoretic guide for industrial process in warp knitted vamp printing.

A simple approach for morphology tailoring of alginate particles by manipulation ionic nature of polyurethanes

Development of biocompatible aqueous polyurethane dispersions using chitosan and curcumin to improve physicochemical properties of textile surfaces

A series of aqueous polyurethane dispersions containing pendant carboxylate anion as the hydrophilic were synthesized, and the particle size and the mechanical properties of the dispersions were measured. The effects of the molar ratio of NCO/OH groups or the other functional groups on the chemical structure and the properties were discussed. The particle size mainly depended on the molar ration of the functional groups. The NH groups in urethane and urea linkage formed hydrogen bonding with the carbonyl group (CO) of other urethane group in the hard segments or ether group (COC) in the soft segments. Fourier transform infrared (FTIR) analysis showed that the higher molar ratio of NCO/OH concentrated the NH group, leading to the hydrogen bonding, which resulted in the increasing mechanical strength of the polyurethane. The tensile testing and dynamic mechanical analysis measurement revealed that the pendant carboxylate anion made the modulus and the stiffness of the polyurethane increase. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3461–3465, 2002

A new curing agent for self-curable system of aqueous-based PU dispersion

Aqueous polyurethane dispersions were prepared with 4-10 wt% of functionalized polyhedral oligomeric silsesquioxanes (POSS) via homogeneous solution polymerization in acetone followed by solvent exchange with water. The use of acetone as the initial polymerization solvent allowed for the facile incorporation of both diamino and dihydroxy functional POSS monomers in a homogeneous reaction environment. After addition of water and removal of the acetone, stable dispersions with unimodal particle sizes were obtained. The incorporation of the POSS monomers did not have a significant effect on the dispersion's properties; however, the physical properties of the isolated polymers did display significant changes, with notable increases in storage modulus, T-g, complex viscosity, and surface hydrophobicity. These changes were attributed to the incorporation of the POSS residues into the polyurethane hard segment domains found. Though no sign of any gross phase heterogeneity due to the inclusion of POSS moieties was detected by either thermal characterization or wide-angle X-ray diffraction (WAXD), a significant change was observed by atomic force microscopy (AFM) when the samples were recast from organic solvent.

Effect of the chain extender and selective catalyst on thermooxidative stability of aqueous polyurethane dispersions

Modern science and technology constantly require new and novel materials with special properties. Over the past decade, Nanocomposites materials have received significant attention as active materials in components ranging from sensors to biomaterials, electronics devices to structural parts. These novel composites have applications in many areas, such as energy, insulation, manufacturing, and the modern building industry. However, not all applications have the same requirements in terms of acoustic insulation, so it is useful to adapt the kind of core materials and their product specifications, such as particle size and porosity, to the different applications. Furthermore, in some applications, cheaper core materials, like precipitated silica, would be a reasonable alternative to replace the time-consuming series of measurements. Because of many bad conditions that affect acoustic insulation properties in modern buildings. And to summarize recent applications of nanotechnology as they relate to textile fibers, yarns, and fabrics for improving acoustic insulation in modern buildings and civilian communities, this paper discusses the ability to apply 3D woven spacer fabric (3DWSF) composite materials reinforced with epoxy, rigid polyurethane foam, and silica nanoporous particles, which were prepared by the sol-gel technique. Four samples had been prepared, all of these samples were textile composite materials, and reinforced with two types of nano silica 99.8% SiO2; mesoporous Ns particles with porosity up to 83%, true density 0.08 g/cm³, and particle size between 100 and 2000 nm and pore size 70–150 nm, which had been prepared by Sol-gel technique, and nonporous Aerosil®200 particles with surface area 200–225 m2/g, true density 0.25 g/cm³, and particle size between 2 and 20 nm. We used rigid polyurethane foam as core material, and epoxy resin for laminating the fabric. 3D spacer E-glass fabrics, and chopped E-glass microfibers had been used. The weight percentage of silica nano particles which were used in this research was 5% by weight, which was better for economic reasons, and enough, to enhance the acoustic absorption coefficient up to [Formula: see text] = 99.79%. The best sound absorption could be achieved by using mesoporous silica nanoparticles, and soundproofing of an insulator using this porous structure is better than using a nonporous one. We found in this research that the thickness 45 mm and semi-porosity structure of the 3DWSF composite insulator material were enough to make a difference, with reference to the thermal and acoustic insulation guide of buildings.

Demands for Composite materials is increasing more and more because of their specific mechanical properties, especially in aerospace industry. Due to the porous structure of composite materials, there is the negligible probability of breaking up and defects in the internal structure. Detection of deep defects is a challenging subject in the field of Non-destructive testing. Due to the large size of composite components in the aerospace industry, line scanning thermography (LST) coupled with a robot arm is used to inspect large composite materials. In this paper, an innovative optimization procedure has been employed using analytical model, 3-D simulation using COMSOL Multiphysics, experimental setup and signal processing algorithms. The goal is to maximize the detection depth and signal to noise value as the criteria to evaluate the inspection quality and performance. the proposed algorithm starts searching to find the optimization variables of robotized LST such as scanning speed, source power and distance considering all technical and mechanical constraints. The optimal values are dependent on the material structure, thermal specifications of the composite, defect shape and infrared camera resolution. Using the proposed optimization algorithm, the detection depth was increased to 3.5 mm in the carbon fiber reinforced polymer and the signal to noise ratio was enhanced to 95%.

Novel organoboron polymers were prepared by alkoxyboration polymerization of diisocyanates with mesityldimethoxyborane. The polymers obtained have boronic carbamate in their repeating units and can be expected as a novel type of reactive polymers. First, alkoxyboration polymerization between mesityldimethoxyborane and 1,6-hexamethylene diisocyanate was examined, and the best reaction condition was optimized to be 140 °C in bulk. Both aliphatic and aromatic diisocyanates gave the corresponding polymers. When aromatic diisocyanates were employed, the reactions required severe reaction conditions (150 °C). The polymers prepared from aromatic diisocyanates have a high stability toward air. Among various boron monomers, mesityldimethoxyborane was found to be the most suitable monomer for the present polymerization system.

The distinct interaction of adsorbate-adsorbent pair is attributed to the characteristics of heterogeneous surface and structure of porous materials. In material science, the porous structure is modified in response to certain applications. Backed by the chemical recipes, such conventional approach rely on the material characterization techniques to verify the resultant porous structure and its interaction with the adsorbate molecules. Such a practice is best assisted by a theoretical approach that can pre-define the required heterogeneous structure of porous surfaces and its role in selective adsorbate-adsorbent interaction, to facilitate material scientists for the synthesis of only those energy sites which can enhance or tailor its responses for a certain application or target. It has been reported here that the understanding of porous structure in terms of energy sites and their distribution, which controls the adsorbate-adsorbent interaction, is the key for porous surface engineering. Understanding of such porous surface characteristics empower the scientists to alter kinetics and thermodynamics of material according to the ‘sweet spots’ of an application. Therefore, a theoretical framework, to express the energy sites and their distribution over the porous heterogeneous surface, is demonstrated here as a prerequisite criterion for porous material development and characterization.