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Composites based on barium titanate and nickel zinc ferrite doped with cooper and samarium were prepared by a mixing method. The formation of barium titanate tetragonal crystal structure and nickel zinc ferrite cubic spinel structure was identified. Polygonal grains were formed in all three types of ceramics. Due to the very high conductivity of ferrite phase in the materials the ferroelectric hysteresis loops were roundish and not typical for classical ferroelectric material. The break down field was found to be similar for all compositions. Leakage current measurements have shown the existence of different types of conductivity mechanisms in each material. The impedance analysis suggested a bit stronger impact of grain boundaries on total conductivity of the composites and the mechanism of polaronic conduction of two types. The magnetization of the composites is lower than for the pure ferrite phase and corresponds to the weight fraction of the ferrite phase. The soft magnetic nature of these composites might be very useful for development of multifunctional devices which will be able to switch the magnetization with small external magnetic field. Humidity sensing properties of the prepared ceramics were also investigated.

In order to further improve the performance of 0.94[(Bi0.5Na0.5)TiO3]‐0.06BaTiO3/polyvinylidene fluoride (NBT‐BT/PVDF) flexible composite films prepared by the hot‐pressing method, the effect of surface modification of the NBT‐BT particles on the structure and properties of the films was investigated. Two coupling agents, namely, (3‐aminopropyl)triethoxysilane (APTES) and dodecyl triethoxysilane (DDTES) were added to enhance dispersion and interfacial adhesion of the active phase powder with the polymer matrix. The highest amount of the electroactive PVDF β‐phase was formed in APTES‐modified samples while in DDTES samples mainly γ‐phase was formed as shown by Fourier‐transform infrared spectroscopy analysis. Differential scanning calorimetry measurements indicated that the addition of filler particles reduced the total crystallinity degree of the PVDF. Dielectric permittivity values as well as dielectric losses decreased for silanized samples due to reduced tension at the interface between particles and polymer. Strong intermolecular interaction between the PVDF chains and the APTES‐modified particles led to enhanced breakdown strength of these samples. The highest level of agglomeration in the DDTES‐modified samples induced the deterioration of ferroelectric properties. The highest voltage output of ~15 V and 225 μW of power was obtained for the APTES‐modified harvester, evidencing their potential for energy harvesting applications. Highlights: Surface of NBT‐BT particles was successfully modified by the silanization method.NBT‐BT‐PVDF flexible lead‐free composite films were prepared by hot pressing.APTES coupling agent enabled the transformation of PVDF α‐phase into electro‐active β.APTES‐modified samples showed the highest breakdown strength.Notable properties for energy harvesting application found, up to 225 μW of generated power. [ABSTRACT FROM AUTHOR]

The scope of the present study was to prepare fully bio-based unsaturated polyester resins (UPRs) with comparable properties to the commercial formulations. The focus was set on the determination of the optimal prepolymer formulation using the same set of diacids (itaconic and succinic acid) and different diols (propylene glycol, isosorbide and neopentyl glycol) or its equimolar mixtures, keeping the fixed molar ratio of 1:1:2.1 in all feed compositions. Instead of commonly used styrene, bio-based dimethyl itaconate was used as a reactive diluent (RD). The rheology of the obtained resins was studied in detail. The effect of the used diol on structural (FTIR), thermal (DSC), thermomechanical (DMA), and mechanical (tensile) properties was explained. The properties of UPRs were found to be highly dependent on the diol used in the prepolymer formulation. The UPR with an equimolar ratio of propylene glycol and neopentyl glycol was shown to be the most promising candidate to compete with the commercial petroleum-based resins.

Novel soy alkyd-based nanocomposites (NCs) were prepared using TiO2 nanoparticles (NPs) surface modified with different gallates, and for the first time with imine obtained from 3,4-dihydroxybenzaldehyde and oleylamine (DHBAOA). Unmodified and surface modified anatase TiO2 NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy, while the amount of adsorbed ligands was calculated from thermogravimetric analysis (TGA) results. Surface modification of TiO2 NPs was confirmed by FTIR and UV-Vis spectra. The influence of the TiO2 surface modification on the dispersion of TiO2 NPs in alkyd resin, thermal, barrier and mechanical properties and chemical resistance of alkyd resin/TiO2 NC coatings was investigated. The obtained results revealed that glass transition temperature of all investigated NCs is lower than for pure resin, that the presence of TiO2 NPs surface modified with gallates had no significant influence on the thermooxidative stability of alkyd resin, while TiO2-DHBAOA NPs slightly improved alkyd resin thermooxidative stability. Also, the presence of surface modified TiO2 NPs improved barrier properties, increased stress and strain at break and hardness and chemical resistance and decreased modulus of elasticity and abrasion resistance of alkyd resin.

Influences of the vinyl modified nanosilica Aerosil® 380, i.e./i>, vinyl and methacryloyl silane coupling agent and linseed oil fatty acids (BD) reactive residues, on the mechanical properties of the unsaturated polyester resins (UPes) based nanocomposites, was studied. The polycondensation of maleic anhydride and products of poly(ethylene terephthalate) (PET) depolymerization with propylene glycol, with and without separation of ethylene glycol, yields UPe1 and UPe2 resin, respectively. The hydroxyl terminated PET depolymerization products (glycolyzates) and UPes were characterized by acid and hydroxyl values, Fourier Transform Infrared (FTIR) and nuclear magneti resonance (NMR) spectroscopies. Transmission electron microscopy (TEM) confirmed that silica nanoparticles formed domains of aggregates in the polymer matrix. An increase from 195 to 247% of stress at break (σb), and from 109 to 131% of impact strength (σi) of UPes based nanocomposites was obtained for 1 wt% addition of vinyl modified silica. Flexural strength (σf) increase from 106 to 156% for both UPes based nanocomposites with 1 wt% addition of BD modified silica. Cross-linking density (ν), storage modulus (G'), tanδ and Tg of the nanocomposite were determined from the dynamic mechanical testing and discussed in relation to the structure of silica modification.

Two series of polyurethane (PU) networks based on Boltorn® hyperbranched polyester (HBP) and hydroxyethoxy propyl terminated poly(dimethylsiloxane) (EO-PDMS) or hydroxy propyl terminated poly(dimethylsiloxane) (HPPDMS), were synthesized. The effect of the type of soft PDMS segment on the properties of PUs was investigated by Fourier transform infrared spectroscopy (FTIR), contact angle measurements, surface free energy determination, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). The surface characterization of PUs showed existence of slightly amphiphilic character and it revealed that PUs based on HP-PDMS have lower surface free energy, more hydrophobic surface and better waterproof performances than PUs based on EO-PDMS. PUs based on HPPDMS had higher crosslinking density than PUs based on EO-PDMS. DSC and DMTA results revealed that these newlysynthesized PUs exhibit the glass transition temperatures of the soft and hard segments. DMTA, SEM and AFM results confirmed existence of microphase separated morphology. The results obtained in this work indicate that PU networks based on HBP and PDMS have improved surface and thermomechanical properties.

A series of acrylate functionalized samples based on hyperbranched hydroxy-terminated polyesters with different molecular weights and different degrees of acrylation were synthesized. The obtained urethane acrylates were slightly yellow viscose liquids. Their composition was characterized by FTIR and 1H-NMR spectroscopy and their molecular weights were measured by GPC. All the synthesized samples were diluted with 25 wt.% 1,4-butanediol dimethacrylate (BDDM). The rheological properties of the uncured samples and the dynamic mechanical properties of the UV cured samples were examined. All the samples exhibit Newtonian behavior, which indicates the absence of physical entanglements in these polymers. The viscosity increases with increasing number of acrylic groups per molecule. The glass transition temperature of the UV cured samples increases with increasing the number of acrylic groups per molecule. The value of the storage modulus in the rubber-elastic plateau and the cross-link density increase with increasing number of acrylic groups per molecule. The formed networks are inhomogeneous and the residual unsaturation is the highest in the samples with the largest number of acrylic groups per molecule.