Effect of storage time on the characteristics of a waterborne polyurethane/tetraethoxysilane mixture and the properties of prepared films

Waterborne polyurethane (WPU) is one of the most important resins. The properties of WPU can be modified by introducing inorganic components. Tetraethoxysilane (TEOS) is a precursor for preparing inorganic polymers and can be used to prepare WPU/silica hybrids. In this study, WPU dispersion was synthesized by reacting polytetramethylene ether glycol and dimethylolpropionic acid with isophorone diisocyanate, followed by chain extension with ethylenediamine. After mixing WPU with TEOS, the mixture was sealed and stored at room temperature for different lengths of times. The influence of time on the characteristics of the WPU/TEOS mixture and the properties of films were investigated. The results showed that the viscosity, surface tension and average particle size of the mixture increased with prolonged storage time. ²⁹Si-NMR analysis indicated that the structure of silica exists in the WPU film. DSC, DMA and TGA results showed that WPU/silica films made from the mixture have less thermal activity, higher storage modulus, lower damping peak heights and better heat resistance after relatively long storage times.     

Preparation of polyurethane foam fine polishing wheel for stainless steel surface

Comparing with dry polishing, the wet-polishing of the stainless steel surface can significantly reduce dust, noise and other pollution, and improve the polished quality. Thus, it is important to develop new polishing tools. In this work, the effects of the foaming agent and diluents on the mechanical properties of the polyurethane foam (PUF) system were investigated, and then the effect of the filler of graphite on the structure and mechanical properties of PUF was studied. Furthermore, the PUF fine polishing wheel with aluminum oxide was prepared. Results show that the bi-component diluents combined cyclohexane and dimethylformamide significantly affects the porosity and hardness of the PUF matrix. The filler of graphite can decrease the mechanical properties of the polyurethane matrix and increase the porosity of PUF, consequently, improve the self-sharpening of the PUF polishing wheel. The PUF fine polishing wheel with aluminum oxide shows fine polishing performance.     

Biobased flexible polyurethane foams manufactured from lactide-based polyester-ether polyols for automotive applications

In this study, biobased polyester-ether polyols derived from meso-lactide and dimer acids were evaluated for flexible polyurethane foams (PUF) applications. Initially, the catalyst concentration was optimized for the biobased PUF containing 30% of biobased polyol (70% petroleum-based polyol). Then, the same formulation was used for biobased PUF synthesis containing 10%–40% of biobased polyols. The performance of biobased PUF was compared with the performance of the control foam made with 100% petroleum-based polyol. The characteristic times (cream, top of the cup, string gel, rise, tack-free) of biobased PUF were determined. The biobased PUF were evaluated for the mechanical (tensile and compressive) and morphological properties. As the wet compression set is important for automotive applications, it was measured for all biobased PUF. The thermal degradation behavior of biobased PUF was also evaluated and compared with the control foam. The effect of different hydroxyl and acid values of polyols on the mechanical properties of biobased PUF is also discussed. The miscibility of all components of PUF formulations is crucial in order to produce a foam with uniform properties. Thus, the miscibility of biobased polyols with commercial petroleum-based polyol was studied.     

Microstructure and tensile properties of injection molded thermoplastic polyurethane with different melt temperatures

The use of injection molding technology to prepare heterogeneous interlayer film of laminated glass holds strong applicable potential. This article aims to investigate the effects of melt temperature and melt flow on the microstructure evolution and tensile properties of thermoplastic polyurethane (TPU) specimens during the injection molding process. The tensile properties of the TPU specimens show dependency on the melt temperature and melt flow direction. The results of birefringence indicate that melt flow and lower melt temperature induce higher stretching deformation of the molecular chain network. Small-angle X-ray scattering analysis approves that besides the melt temperature and flow direction, the testing position on the cross section of the specimen has great influence on the microstructure of the TPU sheet. Further analysis and conclusions can be made using wide-angle X-ray scattering method. The above results demonstrate that both the tensile properties and microstructure of the injection molded TPU specimens tend to be isotropic with the increase of melt temperature. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48891.     

Influence of phenyl group number on enantioseparation performance of chitosan-based materials

In order to investigate the influence of phenyl group number on enantioseparation capability of a chitosan-based chiral selector (CS), in this study, two series of chitosan derivative and their enantioseparation were presented. According to the functional group at 2-position of glucosamine, the derivatives were classified as amido-type and ureido-type. In the amido-type CSs, the CS with two phenyl groups showed the best enantioseparation capability; the CS with one phenyl group exhibited the poorest enantioseparation; and the enantioseparation performance of the CS with three phenyl groups intermediated between those of the CSs with one and two phenyl groups. In the ureido-type, the CS bearing three phenyl groups was in the middle of two CSs with two phenyl groups in enantioseparation capability. Based on the results obtained in the present study, one phenyl group in a chitosan derivative is not enough for enantioseparation, and two or three phenyl groups are necessary. On the other hand, introducing three phenyl groups onto one glucosamine unit of chitosan, can not definitely result in a better enantioseparation capability, comparing with introducing two phenyl groups.     

Patterning of worm-like soft polydimethylsiloxane structures using a TiO2 nanotubular array

Patterned polydimethylsiloxane (PDMS) is an important structure for soft lithography. Various materials have been deployed as mold for patterning PDMS. Anodized nanotubular array has been sought after as cost-effective alternative for textured silicon. An array of TiO₂ nanotubes with characteristic diameter ≈140 nm and the length of ≈1.5 microns, created by anodic oxidation of a titanium substrate, was used here as a template for soft PDMS molding. The optimal molding process was developed by a combination of silanization, use of solvent, application of a vacuum, and hydraulic pressing. The silanization was confirmed by Fourier transform infrared spectroscopy and contact angle measurements while the PDMS structure was examined by scanning electron microscope and energy dispersive X-ray spectroscopy. Hydraulic pressing significantly improved the infiltration of PDMS into the pores of nanotubular array resulting in formation of PDMS nanobumps after separation of the polymer from the template. Complete infiltration of PDMS precursor into the cavity of nanotubes was observed on the hydraulic-pressed sample without toluene impurities. The hydraulic-pressed samples exhibited higher adhesion strength than nonpressed ones. The adhesive strength was measured by a simple experimental arrangement, in which the PDMS layer was stuck on a vertical glass surface followed by pulling it downwards.     

Correlating the 3D melt electrospun polycaprolactone fiber diameter and process parameters using neural networks

In the present work, we developed an artificial neural networks (ANN) model to predict and analyze the polycaprolactone fiber diameter as a function of 3D melt electrospinning process parameters. A total of 35 datasets having various combinations of electrospinning writing process variables (collector speed, tip to nozzle distance, applied pressure, and voltage) and resultant fiber diameter were considered for model development. The designed stand-alone ANN software extracts relationships between the process variables and fiber diameter in a 3D melt electrospinning system. The developed model could predict the fiber diameter with reasonable accuracy for both train (28) and test (7) datasets. The relative index of importance revealed the significance of process variables on the fiber diameter. Virtual melt spinning system with the mean values of the process variables identifies the quantitative relationship between the fiber diameter and process variables.     

Effect of the interphase properties on the fracture energy and fatigue behavior of thermoset resins containing spherical fillers

Interphase region in polymer based nanocomposites is a very thin layer that is created between the reinforcing phase and the matrix surface due to reaction forces between the nanoparticles and the matrix. The ability to determine the behavior of the interphase region can facilitate the understanding and prediction of the fracture toughness and fatigue behavior through multiscale modeling. In the present study, by using the fully analytical multiscale hierarchical modeling method, fracture toughness and also fatigue behavior of thermoset resins containing spherical fillers with consideration the influences of the main damage mechanisms and interphase properties (thickness and elastic modulus of the interphase region) were investigated. The novelty of this investigation is that it enables the application of a range of properties to the interphase zone and describes a technique for multiscale modeling based on this interphase zone. The present multiscale approach quantifies the dissipation energy due to main damage mechanisms at the nanoscale and accounts for the emergence of an interphase region as functionally graded (FG) properties surrounding nanofillers. Modeling of FG interphase power-varying properties, the derivation of governing equations, and the evaluation of the findings, all are parts of the achievements of this research. In addition, multiscale analyses have been carried out on fracture energy and fatigue behavior in various fiber volume fractions with and without interphase properties. It was found that the fracture toughness and fatigue behavior are significantly dependent on the interphase elastic properties and thickness. Furthermore, the critical debonding stress and the fracture energy were assessed with various interfacial fracture energy, elastic modulus, and thickness of interphase. Finally, the accuracy of the utilized multiscale approach with consideration of interphase properties was verified by comparing the modeling results with experimental tests on thermoset resins containing spherical fillers.     

Effect of auxiliary blowing agents on properties of rigid polyurethane foams based on liquefied products from peanut shell

The bio‐based rigid polyurethane (PU) foams were successfully prepared based on liquefied products from peanut shell with water as the blowing agent. The influence of reaction parameters on properties of rigid PU foams was investigated. Rigid PU foams showed excellent compressive strength and low shrinkage ratio, whereas their open‐cell ratio and water absorption were higher. Therefore, rigid PU foams were synthesized with petroleum ether, diethyl ether, and acetone as auxiliary blowing agents and their inner temperature, shrinkage performance, density, compressive strength, water absorption, and open‐cell ratio were determined. The results indicated that above rigid PU foams showed lower compressive strength than the original foam but their water absorption and close‐cell ratio were improved. Compared with the original foam, the highest inner temperature of rigid PU foams with petroleum ether, diethyl ether, and acetone as auxiliary blowing agents was reduced by 11, 19, and 23 °C, respectively. Typically, foams with petroleum ether as auxiliary blowing agent displayed better water absorption and swelling ratio in water and exhibited obvious improvement in close‐cell ratio. These foams were preferable for application in thermal insulation materials because of low thermal conductivity and better corrosion resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45582.     

Recycled polyester nanofiber as a reservoir for essential oil release

The importance of creating sustainable alternatives for products that can be easily recyclable, such as, poly (ethylene terephthalate) (PET), is not new, being textile fibers the product of greatest interest. The objective of this work is to propose a recycling alternative for PET bottles for fiber production as a reservoir of essential oils for aromatherapy applications. The fibers were obtained via coaxial and dual-jet electrospinning techniques. The material used in the impregnation and release of peppermint oil was PET originating from disposable bottles. The release of oil from the electrospun fibers was quantified by UV–vis spectroscopy. For the fibers produced by dual-jet electrospinning the cumulative release of peppermint reached around 70% after 30 days. The sample obtained by coaxial electrospinning had a core-shell structure and the amount of oil released was 33% after 30 days. In this investigation, a less aggressive process was introduced, making the electrospinning of PET a viable technique for essential oil impregnation. Dual-jet as well as coaxial electrospinning showed slower release than values reported in the literature. Thus, a procedure with more favorable working conditions was developed, making the process more feasible and serving as an alternative for recycling PET bottles to produce functional textiles.     

Synergistic effect of carbon nanofiber decorated with iron oxide in enhancing properties of styrene butadiene rubber nanocomposites

Elastomer nanocomposites reinforced with carbon nanofiber (CNF) decorated with metal nanoparticles exhibit excellent thermal, mechanical, and magnetic properties with low volume fraction of the reinforcement. Generally, metal nanoparticles are used to modify the surface of CNF, to improve their dispersion and contact resistance in the polymer matrix. In this study, Fe₂O₃ metal nanoparticles were decorated on CNF by electrostatic attraction via a green and facile solution‐based method. Interestingly, the CNF decorated with Fe₂O₃ (CNF‐Fe₂O₃)/elastomer improved both the tensile strength and the fatigue property of plain CNF/elastomer by as much as 57.2% and 27.2%, respectively. Moreover, the CNF‐Fe₂O₃/elastomer exhibited superior thermal conductivity, a twofold enhancement compared with carbon fibers. The elastomer nanocomposites consisting of CNF‐Fe₂O₃ also exhibited enhanced magnetic properties due to synergies between the Fe₂O₃ nanoparticles and the CNF. The elastomer nanocomposites prepared with CNF‐Fe₂O₃ will open significant new opportunities for preparing advanced elastomer nanocomposites for future engineering applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45376.     

Investigation of tensile behavior and molecular structure of the thermoplastic polyurethane sheets injection molded at different mold temperatures

This paper aims to investigate the influence of the mold temperature on the mechanical responses at different ambient temperature and molecular structure of the injection molded TPU sheets. The tensile properties of the TPU sheets prepared at different mold temperatures were obtained at different ambient temperatures. As the mold temperature increases, both the elongation at break and tensile strength of the specimens increase. The specimens show yield behavior during stretching at −30 and −50°C. The microstructure of the TPU sheets was characterized by DMA, AFM, and birefringence. The results show that the higher mold temperature can reduce the aggregation of hard domains because of the higher mobility of the hard segments. In-situ SAXS and WAXS measurements were carried out at −30°C test temperature to exhibit the evolution of the microstructure during stretching. When the specimens are prepared at 40°C mold temperature, the hard domains are destroyed and difficult to orient along the stretching direction. In contrast, the hard domains begin to be deformed and oriented along the stretching direction above the yield strain when the specimens molded at higher mold temperature. The above microstructure evolution is consistent with the tensile behavior of the TPU specimens.     

Synthesis and characterization of eugenol-based silicone modified waterborne polyurethane with excellent properties

A eugenol-based silicone-containing monomer 4,4′-(1,1,3,3-tetramethyldisiloxane-1,3-dipropyl)bis-2-methoxyphenol(EUSi) was synthesized from eugenol and 1,1,3,3-tetramethyldisiloxane via the hydrosilylation reaction. And waterborne polyurethane (WPU) with excellent properties was obtained by using EUSi as a type of diol chain extender. The unique combination of rigidity and flexibility in the chemical structure of EUSi greatly facilitated the mechanical properties, thermal properties, and water resistance of WPU. With only a 3% dosage of EUSi, the maximum tensile strength was increased from 6.2 to 22.4 MPa, while the water absorption was decreased from 31.3% to a surprisingly 7.6%. Our work provides a new convenient strategy for the preparation of organosilicon-modified WPU with improved performance.     

Boosting flame retardancy of epoxy resin composites through incorporating ultrathin nickel phenylphosphate nanosheets

Ultrathin nickel phenylphosphate (NiPP) nanosheets with layered structure are successfully synthesized through a mixed solvothermal method. The results indicate that NiPP is Ni(O₃PC₆H₅)·H₂O and has good thermal stability. To ameliorate the thermal stability and flame ratardancy of epoxy resin (EP), EP/NiPP nanocomposites are prepared by incorporating NiPP into EP matrix. The results show that adding NiPP can availably enhance thermal stability at high temperature due to the remarkable catalytic char performance of NiPP, and the residues yield of EP/NiPP nanocomposites with 6 wt% NiPP is 24.1% while the pure EP had only 14.2% at 700°C. In contrast with pure EP, the peak heat release rate, total heat release, smoke production rate, CO production, and CO₂ production of EP/6wt%NiPP nanocomposites reduced by 35.2%, 20.2%, 27.1%, 45.8%, and 35.5%. The synergistic effect of catalytic char performance and fire retardancy of NiPP make the EP/NiPP nanocomposites possess prominent flame retardancy, smoke suppression, and thermal stability.     

Fabricating and robust artificial neural network modeling nanoscale polyurethane fiber using electrospinning method

With regard to the fact that currently there is no comprehensive method to predict diameter of polyurethane/solvent fiber from electrospinning, in this study, diameter prediction of polyurethane/solvent fiber was conducted using neural networks and an error of 166 nm was observed. This error shows that artificial neural networks (ANNs) can predict diameter of electrospinning polyurethane fibers well. Then, considering weak repeatability nature of electrospinning in fabricating fibers with desired diameter, least mean square is used to improve stability of neural network model that shows an error of 113 nm, which represented better results compared to common ANN. To investigate the effect of each one of parameters affecting fiber diameter, sensitivity analysis was conducted. Along with this predicting model, sensitivity analysis can be used to reduce parameters space before conducting future studies. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45116.     

Characterization of the resistance to abrasive chemical agents of test specimens of thermoplastic elastomeric polyurethane composite materials produced by additive manufacturing

Currently the development of additive manufacturing and the emerging of new materials allows to manufacturing process obtaining functional models with properties and geometries adapted to each particular case with low production times and costs. Specifically, 3D printing by fused deposition modeling (FDM) that operates with polymers, is one of the most widespread and popular techniques. Among the numerous materials available, the elastomeric polymers, whose base composition is polyurethane, are becoming increasingly important since allow to obtain flexible pieces with good mechanical and chemical resistance. The objective of this work is to study the effect of an abrasive fluid (commercial automotive petrol) on test specimens made of two different elastomeric filaments commonly used in 3D printing, thermoplastic polyurethane and thermoplastic elastomers. To do this, some of the main physical and mechanical properties – hardness, weigh variation and tensile and bending tests - of these materials were analyzed after immersion of the samples in petrol for different periods of time. Specimens with different volume of material inside their structure were designed in order to determine the effect of the volume filling on the mechanical properties and the petrol effect.     

Structure and properties of bio-based polyurethane coatings for controlled-release fertilizer

Two kinds of bio-based polyurethane coatings for controlled-release urea were prepared by in-situ polymerization used castor oil and liquefied starch as raw materials, respectively. Scanning electron microscopy (SEM) showed that the section morphology of castor oil based polyurethane (Castor-PU) coating was uniform and dense, and that of liquefied starch based polyurethane (Starch-PU) coating had certain proportion of microporous. Infrared spectroscopy (IR) showed that the two coatings had typical urethane characteristic structure, but the difference was that the Starch-PU had obvious unreacted isocyanate structure. Differential scanning calorimetry (DSC) showed that the glass transition temperature of the two coatings was around 58°C, but the Castor-PU had a crystallization domain with obvious crystallization melting peak at 130°C. Thermogravimetric analysis (TG) showed that the thermal stability of Castor-PU was significantly higher than that of Starch-PU. The controlled-release property test showed that when the coating ratio was 2.8%, the nutrient release longevity of urea coated with Castor-PU was 49 days and that of urea coated with Starch-PU was 14 days. The reasons for the poor controlled-release performance of Starch-PU were analyzed, which probably caused by concentrated sulfuric acid and hydrophilic dispersant added in the liquefied starch.     

Fabrication and characterization of biorenewable plasma polymer films using sandalwood oil precursor

Sandalwood oil is a natural, biorenewable oil which has many beneficial properties such as being anticarcinogenic and cytotoxic to some viruses, while being safe for human consumption. Therefore, thin films derived from sandalwood oil are of interest in the biomedical field. Here, thin films using sandalwood oil as the precursor are deposited via plasma polymerization with the aim of minimizing degradation of the precursor structure. The chemical properties of the plasma phase were measured by optical emission spectroscopy and the degradation pathways of the precursor molecules were elucidated via mass spectrometry. Combined with surface analysis of the thin films, partial structural retention of precursor molecules is demonstrated.     

Reinforcement of agricultural wastes liquefied polyols based polyurethane foams by agricultural wastes particles

Four kinds of agricultural wastes particles (XS: oilseed rape straw [OS], rice straw [RS], wheat straw [WS], and corn stover [CS]) were used to reinforce agricultural wastes liquefied polyol (P-XS) based polyurethane (PU) foam. Different XS loading dosages (0% ~ 15%) are investigated to confirm suitable filler concentrations for modifying foams. RS particles show great promoting ability, OS particles reveal complex influence, while WS and CS particles display mild effect on foaming process. With 1% of OS, 6% of RS, 3% of WS, or 1% of CS incorporating in matrix materials, the reinforced foam could keep applicable density, reach better physical and mechanical property, display more uniform cellular structure, and show higher thermal stability with more excellent water absorption ability. Using of agricultural wastes as polymer filler is economical, simple, environmental, and wide applicable for biomass utilization and biopolymer preparation.     

Tensile deformation and morphology changes in segmented elastomer films and fibers including mechanical property modeling

Segmented polyether soft segment (SS) elastomers with different hard segments (HS) in film and fiber form were studied by birefringence, DSC, and tensile tests. To understand the morphological contributions to property differences, high resolution tapping AFM resolved ribbon-like highly anisotropic hard domain (HD) lamellae in low modulus Pebax (polyamide 12 HS) and polyetherester (PEE), films, while lower HS content high melting poly(urethane urea) (PUU) had much smaller less anisotropic but higher melting HDs, explaining its enhanced thermal and mechanical hysteresis properties. Stress–strain tensile data demonstrate the excellent strength and toughness of PUUs and some spun PEE fibers, and film and fiber birefringence data applied during strain cycling up to very high stresses provided the molecular basis for the varying properties. The parameters from non-Gaussian fits of tensile data provide insight into network properties for these systems exhibiting very high strengths and a large degree of strain hardening. Modeling of PEE and Pebax films also shows the effects of substantial plastic yielding of the HD networks. Tensile data were obtained as a function of strain rate and temperature to help understand the contributions of network restructuring and other factors. For fibers, strain rate data spanning seven decades show and unusual drop in strengths at very high strain rates. Temperature-dependent tensile data also show large differences between PUU materials versus lower melting PEEs.