Transparent,flexible, and high‐strength regenerated cellulose/saponite nanocomposite films with high gas barrier properties

Regenerated cellulose‐saponite nanocomposite films were prepared from LiOH/urea solutions, and exhibited high optical transparency and flexibility. The saponite platelets formed intercalated nanolayered structures in the composites. The longitudinal directions of both the cellulose II crystallites and the saponite platelets were preferentially oriented parallel to the film surface in the composites. The good nanodispersibility and high orientation of the saponite platelets in the composite films resulted in high mechanical strength, high Young's modulus, and good thermal dimensional stabilities, and gas barrier properties in the composites, compared with a reference cellulose film. Moreover, the tensile strength and Young's modulus of the composite film reached 241 MPa and 7.7 GPa, respectively, when a simple drawing process was applied to the wet composite film; this is probably owing to the improvement in the orientation of the cellulose II crystallites and saponite platelets in the composites. The composite films also showed high toughness and ductility. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3168–3174, 2013     

Syndiotactic polypropylene/microfibrous cellulose composites: Effect of filler size on tensile properties

Syndiotactic polypropylene (SPP)/ethanol swelled microfibrous cellulose (MFC) composite was prepared by a melting mixer, and its morphology and tensile properties were studied. The scanning electron microscope microphotograph did not show the aggregated MFC part up to the 40 wt % MFC loading content, and the Young's modulus was exponentially increasing with the increase of the MFC loading content. These results suggested that the MFC was well‐dispersed in the SPP matrix by an ethanol surfactant work. The Young's modulus was much higher than that of the composite with commonly used fibrous cellulose and moreover, exceeded the theoretical one obtained from the Halpin‐Tsai equation. The differential scanning calorimetry and wide‐angle X‐ray diffraction measurements showed that the MFC acted as a good α‐nucleation agent for SPP. It was found that the excessive Young's modulus of the MFC composite was originated from an increase of that of the SPP matrix induced by the α‐nucleation effect. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

High‐tensile‐strength polyvinyl alcohol films prepared from freeze/thaw cycled gels

The mechanical properties and molecular structure of a poly(vinyl alcohol) (PVA) film, which was obtained by eliminating water from a PVA hydrogel using repeated freeze/thaw cycles, were investigated by tensile tests, thermal analysis, and X‐ray diffraction measurements. The mechanical properties of PVA with 99.9% saponification were measured as a function of the number of freeze/thaw cycles performed. The tensile strength and Young's modulus increased and the elongation at break decreased with increasing freeze/thaw cycles. The tensile strength and Young's modulus of PVA films obtained after seven freeze/thaw cycles were as high as 255 MPa and 13.5 GPa after annealing at 130°C. Thermal analysis and X‐ray diffraction measurements revealed that this is because of a high crystallinity and a large crystallite size. A good relationship between the tensile strength and the glass transition temperature was obtained, regardless of the degree of saponification and annealing conditions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40578.     

Regenerated cellulose/layered double hydroxide nanocomposite films with improved mechanical property

Construction of environment-friendly biomass-based nanocomposites with high performance is in great demand for developing of a sustainable low-carbon society. Here, transparent and flexible regenerated cellulose (RC)/layered double hydroxide (LDH) nanocomposite films were prepared from aqueous NaOH/urea solutions. The obtained nanocomposite films were characterized using AFM, SEM, FTIR, XRD, tensile testing, water contact angle, and thermogravimetric analysis. The results show that LDH nanoplatelets were individually dispersed with a thickness of 1 nm and surface diameter of 100 nm after ultrasonic treatment. Strong interaction existed between LDH nanoplatelets and cellulose molecules, leading to the improved thermal stability and mechanical strength of RC together with the original good properties of LDH. In particular, the nanocomposite films with 10 wt% LDH showed a 135% and 234% increase in the tensile strength and Young's modulus than those of the neat RC film. Meanwhile, the nanocomposite films exhibited high transparency. Therefore, these RC/LDH nanocomposites are promising in the fields of high-performance packaging materials, flexible display panels, and high-temperature dielectric materials.     

Crosslinked poly(vinyl alcohol) composite films with cellulose nanocrystals: Mechanical and thermal properties

In this work, poly(vinyl alcohol) (PVA) and cellulose nanocrystals (CNCs) were crosslinked using sodium tetraborate decahydrate (borax) to improve the mechanical and thermal properties of the neat PVA. The results showed that the CNCs affected the crystallization behavior of the crosslinked PVA. The crystallization temperature of the crosslinked PVA with CNCs increased considerably from ～152 to ～187 °C. The continuous improvement of the thermal stability was observed with the increasing content of CNCs in the crosslinked PVA films. Additionally, the strong interaction between the CNCs and PVA was theoretically estimated from the Young's modulus values of the composites. Thermodynamic mechanical testing revealed that the crosslinked PVA composite films with CNCs could bear higher loads at high temperature compared to the films without the CNCs. At 60 °C, 2.7 GPa was reported for the storage modulus of the crosslinked composites with 3 wt % of CNCs, twice as high as that for the crosslinked films without CNCs. Moreover, creep results were improved when CNCs were added in the crosslinked nanocomposites. The materials prepared in this work could broaden the opportunities for applications in a wide range of temperatures. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45710.     

Improved mechanical properties of SnO2:F thin film by structural modification

This study reports the improvement in the mechanical properties of SnO₂:F (FTO) thin films through the modification of the structure and surface morphology. The FTO thin films are deposited on glass substrates by the atmospheric pressure chemical vapor deposition method on an industrial production line. Both the average grain size and the surface roughness were progressively increased by increasing the flow rate of metal organic monobutyltin trichloride (MBTC). The hardness and Young's modulus of the FTO films increased from 9.01 GPa to 15.08 GPa, and from 125.24 GPa to 206.93 GPa, respectively, according to the nanoindenter results. Post-heat treatment at 650 °C for 10 min resulted in a further increase in the hardness and Young's modulus, reaching maximum values of ~15.89 GPa and ~235.9 GPa, respectively. The enhancement in mechanical properties can be attributed to the reduced grain boundaries and the improved structural densification.     

Effect of incorporation of graphene oxide and graphene nanoplatelets on mechanical and gas permeability properties of poly(lactic acid) films

Nanocomposite thin films of poly(lactic acid) (PLA) were produced incorporating small amounts (0.2 to 1 wt%) of graphene oxide (GO) and graphene nanoplatelets (GNP). The films were prepared by solvent‐casting. Mechanical properties were evaluated for plasticized (by residual solvent) and unplasticized films. Plasticized nanocomposite films presented yield strength and Young's modulus about 100% higher than those of pristine PLA. For unplasticized films improvements in tensile strength and Young's modulus were about 15 and 85%, respectively. For both film types, a maximum in mechanical performance was identified for about 0.4 wt% loadings of the two filler materials tested. Permeabilities towards oxygen and nitrogen decreased, respectively, three‐ and fourfold in films loaded with both GO or GNP. The glass transition temperature showed maximum increases, in relation to unloaded PLA films, of 5 °C for 0.4 wt% GO and 7 °C for 0.4 wt% GNP, coinciding with the observed maxima in mechanical properties. Copyright © 2012 Society of Chemical Industry     

ON THE DRYING MECHANISM OF SHRINKAGE MATERIALS

ABSTRACT

Effects of moisture content on Liquid transport properties (Permeability and suction pressure) and mechanical properties (Young's modulus, yield stress and tensile strength) of drying shrinkage materials (Kibnshi, IIaido and mixed clay) were measured and a strong dependence was found. When glass beads are added to the Kibushi, permeability increase and Young's modulus and yield stress decrease in spite of the same suction pressure and tensile strength. Changes in local moisture content and stress during drying was calculated by using finite-element method, taking into account the stress gradient in addition to the pressure gradient due to osmotic suction.     

Mechanical behavior of sheets prepared from sugar beet cellulose microfibrils

The mechanical behavior of films cast from sugar beet cellulose microfibrils was investigated through tensile tests. The obtaining of these microfibrils by chemical and mechanical treatments from the raw beet pulp is described. Depending on their purification level, individualization state, and moisture content, differences in tensile modulus are observed. It is found that pectins act as a binder between the cellulose microfibrils, which tends to increase the Young's modulus in dry atmosphere and to decrease it in moist conditions. The extraction of the cellulose microfibrils from the sugar beet cell wall and the obtainment of microfibril suspensions with partial individualization of the microfibrils by a mechanical treatment lead to the formation of a network of cellulose microfibrils within the film, which in turn increases the tensile modulus. Furthermore, the effect of the remaining pectins is compared with the effect of pectins previously removed and added to completely purified cellulosic microfibrils. As expected, once removed and so partly degraded, those pectins have nearly no influence on the mechanical properties. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1185–1194, 1997     

Electronic Structure and Mechanical Properties of NiB: A Promising Interphase Material for Future UHTCf/UHTC Composites

Weak interphases play a pivotal role by acting as mechanical fuse to deflect matrix cracks in future ultrahigh‐temperature ceramic fiber reinforced ceramic matrix (UHTC_f/UHTC) composites. However, the interphase materials are not available yet. In this work, the electronic structure, chemical bonding, and mechanical properties of NiB, which is a promising interphase material for UHTC_f/UHTC composites, were investigated. NiB has relatively low shear modulus of 116 GPa, moderate Young's modulus of 307 GPa, but high bulk modulus of 287 GPa. The Pugh's ratio G/B is only 0.404 and the micro hardness is predicted to be 8.2 GPa, indicating that NiB belongs to “soft” and “ductile” UHTCs. The possible slip systems are [100](001), [010](001), and [001](010) due to the presence of metallic Ni–Ni and weak Ni–B bonding. Details on the electronic structure and directional dependence of shear and Young's moduli are disclosed to highlight the mechanisms that underpin the properties.     

Influence of processing parameters on the electric conductivity and on the mechanical properties of thick polypyrrole films

The electric conductivity and the mechanical properties of electrochemically synthesized polypyrrole/p‐toluene sulfonic acid (PPy/pTSA) as a function of its processing parameters were investigated. The influence of polymerization current density, pyrrole concentration, and counter ion concentration on the electric conductivity of thick (?100 μm) polymer films was examined and the electric conductivity was found to be in a range between 1.6 and 97 S · cm^?1. Analysis of the polymer's chemical composition delivered a result in agreement with literature data of one counter ion for every 2.97 pyrrole rings for the best conducting samples. In mechanical tests, maximum values for Young's modulus, tensile strength, and elongation at break, were found to be 4.0 GPa, 72.6 MPa, and 11.2%, respectively. POLYM. ENG. SCI., 47:662–666, 2007. © 2007 Society of Plastics Engineers.     

Evaluation of mechanical properties and hydrophobicity of room-temperature,moisture-curable polysilazane coatings

Polysilazane coatings have a broad need in real-life applications, which require low processing or working temperature. In this work, five commercially available polysilazanes have been spin-coated on polycarbonate substrates and cured in ambient environment and temperature to obtain transparent, crack-free, and dense films. The degree of crosslinking is found to have a significant impact on the hardness and Young's modulus of the polysilazane films but has a minor influence on the film thickness and hydrophobicity. Among all five polysilazane coatings, the inorganic perhydropolysilazane-based coating exhibits the largest hardness (2.05 ± 0.01 GPa) and Young's modulus (10.76 ± 0.03 GPa) after 7 days of curing, while the polyorganosilazane-derived films exhibit higher hydrophobicity. The molecular structure of polysilazanes plays a key role in mechanical properties and hydrophobicity of the associated films, as well as the adhesion of coatings to substrates, providing an intuitive and reliable way for selecting a suitable polysilazane coating material for a specific application.     

Effects of process conditions on Young's modulus and strength of extrudate in short‐fiber‐reinforced polypropylene

We examined the effects of process conditions on Young's modulus and tensile strength of extruded short‐fiber reinforced thermoplastics. With increasing extrusion ratio and decreasing extrusion temperature, the fiber alignment increases, the mean fiber length decreases, and the mechanical properties of the matrix are improved. The orientation parameter, mean fiber length, Young's modulus, and tensile strength of the matrix are described as a function of extrusion ratio and extrusion temperature. The models proposed by Fukuda and Kawata, and Fukuda and Chou are applied to predict Young's modulus and tensile strength of the composites using orientation parameter. By comparing the predicted Young's modulus and tensile strength with experimental results, the validity of the models is examined. The prediction of Young's modulus agreed quit with the experimental results. The tensile strength of composite extruded below the melting point nearly matched that of the neat matrix. There is no the strengthening effect of the fiber since the angle between fracture surface and fiber direction is very small. POLYM. COMPOS. 28:29–35, 2007. © 2007 Society of Plastics Engineers     

On the UV Curability and Mechanical Properties of Novel Binder Systems Derived from Poly(ethylene terephthalate) (PET) Waste for Solventless Magnetic Tape Manufacturing, 2. Methacrylated Oligoesters

Recycling of poly(ethylene terephthalate) PET waste by chemical methods is a well‐known process that generates value‐added products. Depolymerization products of PET recycling were commonly applied as starting materials for the synthesis of polyurethanes, saturated and unsaturated polyester resins. In this current work we are reporting on a novel application of the depolymerized products obtained by glycolysis of PET by converting the hydroxyl functional groups to methacrylate groups. The obtained methacrylated oligoesters were tested for UV curability by UV irradiation, in the presence of 2‐benzyl‐2‐dimethylamino‐1‐(4‐morpholinophenyl)‐1‐butanone (BDMB) as a photo initiator. This gave cured films of high mechanical properties when these methacrylated oligoesters were either cured alone or as mixtures with other commercially available diacrylate/dimethacrylate monomers. The measured tensile properties were in the range of 7.21–43 MPa for maximum tensile strength and 0.90–3.0 GPa for Young's modulus.     

Drawing of self‐reinforced cellulose films

Self‐reinforced cellulose films were prepared by incomplete dissolution of commercial microcrystalline cellulose in LiCl/DMAc solvent and subsequent coagulation of regenerated cellulose in the presence of undissolved microcrystalline cellulose. By drawing in wet conditions and subsequent drying, preferred orientation was introduced into the self‐reinforced cellulose films, resulting in significantly improved tensile strength of up to 430 MPa and modulus of elasticity of up to 33 GPa. A linear relationship was observed between applied draw, and the orientation of cellulose in the films, and the measured elastic modulus and tensile strength, respectively. The optically transparent drawn films significantly surpass the strength and modulus of elasticity of current all‐bio‐based planar materials and may therefore present a bio‐degradable alternative to nonbio‐based materials with similar performance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2703–2708, 2007     

Mechanical properties of films of poly(vinyl alcohol) derived from vinyl trifluoroacetate

In order to study the influence of the stereoreguralities of polymer chains on the mechanical properties of films of poly(vinyl alcohol) (PVA)_(VTFA) derived from vinyl trifluoroacetate, the strength of the film was measured. In the case of undrawn PVA_(VTFA) films, Young's modulus and strength at break were the smallest at the annealing temperature of about 100°C. It is considered to be due to the melt of small microcrystals and the increase in mobility of chains in amorphous parts. Young's moduli of undrawn PVA_(VTFA) films were in the range of 1.50–3.75 GPs and the values were higher than that (0.17–0.36 GPa) of undrawn film of commercial PVA with the low concentration of syndiotacticity and the high concentration of head-to-head bounds. In the case of drawn, annealed PVA_(VTFA) films, the maximum Young's modulus was about 20 GPa.     

Preparation of polybenzimidazole/functionalized carbon nanotube nanocomposite films for use as protective coatings

Functionalized multi‐walled carbon nanotubes (MWCNTs) via microwave‐induced polymerization modification route, and polybenzimidazole (PBI) nanocomposite films containing 0.1‐5 wt% functionalized MWCNTs were successfully synthesized. The functionalized MWCNTs were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X‐ray photoelectron spectroscopy (XPS). The results verify that the polymer was successfully grafted to the MWCNTs with a polymer layer that was several nanometers thick. The TGA results showed that the quantity of the attached polymer reached approximately 9.4 wt%. The mechanical properties of the nanocomposite films were measured by tensile test and dynamic mechanical analysis (DMA). The tensile test results indicated that the Young's modulus increased by about 43.9% at 2 wt% CNT loading, and further modulus growth was observed at higher filler loading. The DMA studies indicated that the nanocomposite films had a higher storage modulus than pure PBI film in the temperature range of 30‐300°C, and the storage modulus was maintained above 0.82 GPa. Simulation results confirmed that the PBI nanocomposite films had desirable mechanical properties for use as a protective coating. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.     

Structure and properties of novel regenerated cellulose films prepared from cornhusk cellulose in room temperature ionic liquids

Cornhusk cellulose was regenerated using the ionic liquids viz., 1‐allyl‐3‐methylimidazolium chloride (AmimCl) and 1‐ethyl‐3‐methylimidazolium acetate (EmimAc). The cast cellulose films were characterized by FTIR, WAXD and SEM techniques. Their mechanical properties were also studied. These studies indicated that AmimCl and EmimAc are good solvents for the regeneration of cornhusk cellulose. The regenerated cornhusk cellulose (RCC) was found to be cellulose (II) with dense structure. The films cast from AmimCl exhibited good mechanical properties; the tensile modulus and strength were as high as 6 GPa and 120 MPa respectively, whereas these values for those films cast using EmimAc were found to be 4.1 GPa and 47 MPa respectively. Further, it was observed that after regeneration, the solvents could be effectively recycled. Thus a novel nonpolluting process of forming RCC films from agricultural waste was developed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of uv-curable acrylated urethane prepolymers,I. Effects of reactive diluents and relative humidity on physical properties

A UV-curable acrylated urethane prepolymer was synthesized from tolylene-2,4-diisocyanate (TDI), a polyether polyol (Arcol 1131) and endcapped with 2-hydroxyethyl methacrylate (HEMA) by addition reaction in the presence of dibutyltin dilaurate as catalyst. UV curing was performed with either diethylene glycol diacrylate or thiodiethylene glycol diacrylate as reactive diluent. The effects of reactive diluent types, their concentrations and the humidity of environment on mechanical properties of cured films were investigated. Changes in the tensile strength, elongation and Young's modulus values of the cured films upon addition of reactive diluents with different concentrations were related to the effect of the diluent on the crosslinking density of cured films. The increase of relative humidity from 50 to 95% caused a decrease of tensile strength and Young's modulus values of cured films. It is proposed that the decrease of these physical properties in high relative humidity is due to the formation of hydrogen bonding in polymer chains caused by water molecules.     

Shape memory CTBN/epoxy resin/cyanate ester ternary resin and their carbon fiber reinforced composites

Carboxylated-terminated liquid acrylonitrile rubber (CTBN) and epoxy resin (JEF-0211) were coreacted with cyanate ester (CE) to form CTBN/EP/CE ternary resin systems. Further, the ternary resin system was applied as prepreg for carbon fiber composites with vacuum bag degassing molding process. CTBN/EP/CE ternary shape memory polymer (SMP) exhibited relatively high tensile strength, Young's modulus, impact strength, and excellent shape memory properties. Compared with CTBN/EP/CE ternary SMP, CTBN/EP/CE carbon fiber composites showed much higher mechanical properties, such as their tensile strength and Young's modulus were high to 570 MPa and 36.7 GPa, respectively. Furthermore, CTBN/EP/CE carbon fiber composites exhibited good shape memory properties, their shape fixity ratio and shape recovery ratio were more than 95% after 30 times repeating shape memory tests. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48756.