Effect of HNT on mechanical and thermal properties of poly(lactic acid)/polypropylene carbonate blends

In this work, the influence of halloysite nanotubes (HNTs) on the mechanical and thermal properties of the poly(lactic acid)/polypropylene carbonate (PLA/PPC 70/30) blend was studied. The HNT was incorporated into the PLA/PPC blend by melt mixing. It was found that addition of 2-6 wt % HNT successfully improved the tensile and flexural strength as well as the flexural and Young’s moduli of PLA/PPC blend, due to the reinforcing effect. Although the elongation at break decreases with increasing HNT content, its value is much higher than that of pure PLA. Moreover, the addition of HNT didnot affect the miscibility of PLA and PPC, since two glass transition temperatures were observed in the DSC thermograms. However, a higher content of HNT may improve the compatibility between PLA and PPC as evidenced by the lower difference between the glass transition temperature of PPC and PLA and reduced crystallinity resulting in higher tensile strength of nanocomposites.Keywords: PLA, PPC, HNT, mechanical properties, thermal properties.

Effect of Biodegradable Hydrophilic and Hydrophobic Emulsifiers on the Oleogels Containing Sunflower Wax and Sunflower Oil

The use of an appropriate oleogelator in the structuring of vegetable oil is a crucial point of consideration. Sunflower wax (SFW) is used as an oleogelator and displays an excellent potential to bind vegetable oils. The current study aimed to look for the effects of hydrophobic (SPAN-80) and hydrophilic (TWEEN-80) emulsifiers on the oleogels prepared using SFW and sunflower oil (SO). The biodegradability and all formulations showed globular crystals on their surface that varied in size and number. Wax ester, being the most abundant component of SFW, was found to produce fibrous and needle-like entanglements capable of binding more than 99% of SO. The formulations containing 3 mg of liquid emulsifiers in 20 g of oleogels showed better mechanical properties such as spreadability and lower firmness than the other tested concentrations. Although the FTIR spectra of all the formulations were similar, which indicated not much variation in the molecular interactions, XRD diffractograms confirmed the presence of β′ form of fat crystals. Further, the mentioned formulations also showed larger average crystallite sizes, which was supported by slow gelation kinetics. A characteristic melting point (Tm~60 °C) of triglyceride was visualized through DSC thermograms. However, a higher melting point in the case of few formulations suggests the possibility of even a stable β polymorph. The formed oleogels indicated the significant contribution of diffusion for curcumin release. Altogether, the use of SFW and SO oleogels with modified properties using biodegradable emulsifiers can be beneficial in replacing saturated fats and fat-derived products.

Preparation and non-isothermal cure kinetics study of epoxy resin nanocomposites with amine and epoxy functionalized magnetic nanoparticles

Amine-functionalized magnetic nanoparticles NiFe2O4@SiO2@Amine (AMNP), and epoxy functionalized magnetic nanoparticles, CuFe2O4@SiO2@Epoxy (EMNP) were synthesized in three steps. Homogeneous stable dispersion of AMNP and EMNP, at concentrations of 1, 5, 10, 15, 20 wt% in epoxy resin were prepared using stoichiometric amounts of 4,4’-diaminodiphenylsulfone (DDS) as a curing. The optimum ratio of AMNP and EMNP were found to be 5%, and these were investigated by the total enthalpy of the curing reaction using differential scanning calorimetry (DSC) thermograms at 10°C/min. The cure kinetics of epoxy resin-functional magnetic nanoparticles-DDS composites were studied using non-isothermal DSC thermograms at different heating rates (5, 10, 15, 20°C/min). The kinetic parameters of the curing process, such as activation energy ( Ea), pre-exponential factor ( A), and rate constant ( k) were determined using several non-isothermal kinetic methods: Kissinger-Akahira-Sunose (KAS), Kissinger, Straink, Flynn-Wall-Ozawa (OFW), and Bosewell. The kinetic curing values obtained with different kinetic methods are well-matched. The Ea values were calculated in the range of 59.80 to 65.94, 57.69 to 63.92, and 45.38 to 52.45 kJ.mol−1 for the DGEBA/DDS, DGEBA/DDS/AMNP, and DGEBA/DDS/EMNP systems respectively. Also, The A values, using the Kissinger method, were calculated to be in the range of 7.0 × 105, 4.0 × 105, and 0.2 × 105 S−1 for the DGEBA/DDS, DGEBA/DDS/AMNP, and DGEBA/DDS/EMNP systems respectively. The glass transition temperatures of cured resins were determined with DSC, and the surface morphology of the nanocomposites and also the dispersion of the nanoparticles were investigated using scanning electron microscopy (SEM).

DIFFERENTIAL SCANNING CALORIMETRY OF LIQUID VEGETABLE

The thermophysical properties of vegetable oils were studied by differential scanning calorimetry method was used to study the fatty acid composition of vegetable oils liquid at room temperature, such as amaranth (Amaránthus), corn (Zea mays), flax (Línum usitatíssimum), sunflower (Helianthus), rape (Brusss napor), milk thistle (Sílybum mariánum), saffron milk cap (Camelina sativa) and pumpkin (Cucurbita pepo). The temperatures of the endothermic peak maxima and their area on the DSC thermograms of these oils were established as characteristic thermal effects. The interconnection between thermal effects and fatty acid composition are revealed. On the melting curves of liquid vegetable oils, up to 5 endothermic peaks of different intensities were selected in the ranges -80÷-55 °C, -40÷-15 °C, -25÷-8 °C, -19÷+6 °C and -10÷+4 °C. The coordinates of the maxima of these peaks (Ti) and their area (Si) significantly correlate with the content (Wi,%) in the oils, primarily oleic, linoleic and linolenic acids, the total proportion of which in oils is from 75 to 92%. Using the DSC thermograms of rapeseed oil as an example, it is shown that the program separation of DSC peaks allows a multiple increase in the number of analytical signals, an increase in the reliability of identification of the fat phase, and identification of the main fractions of triglycerides. DSC as a method for identifying vegetable oils using modern thermal analysis instruments is simple to sample, has good reproducibility and can be an independent method for identifying and controlling the quality of vegetable oils.

Green Synthesis Characterization and Thermotropic Behaviour of O-Linked Glycopyranosides of Phenolic Esters

Focusing on green chemistry protocols, a series of carbohydrate derivatives (5a–l) have been synthesized by Fischer glycosylation of α-D-glucose, D-xylose, and α-maltose with several nonpolar phenolic ester aglycones (3a–d) derived from menthol by employing solid-supported Si-H+ as the catalyst. In order to study the extent of mesomorphism in target molecules, the thermotropic behaviour has been studied by using the thermoanalytic DSC/TGA technique and polarized optical microscope. Phase transitions in the DSC thermograms of 5a–l with two endothermic melting point peaks and various exothermic crystalline transitions exhibits the existence of mesophases. However, optical photomicrographs revealed that the new glycopyranosides formed smectic A phases. Moreover, all the compounds (3a–d and 5a–l) were confirmed by FTIR and 1H NMR.

Melting and Recrystallization of Copper Nanoparticles Prepared by Microwave-Assisted Reduction in the Presence of Triethylenetetramine

The small sized copper nanoparticles (Cu-NPs), prepared in the presence of triethylene tetramine (TETA) and assisted with microwave irradiation, have an extremely low melting temperature. Melting of the small sizezd Cu-NPs can be triggered by the heat generated from the e-beam irradiation during SEM and TEM image construction. The dispersed Cu atoms around the agglomerated big Cu particles can undergo recrystallization immediately due to the strong driving force of the huge temperature difference to normal melting temperature (Tm = 1085 °C). Some of the Cu-NPs with bigger sizes also recrystallize and agglomerate into dense, big particles. According to X-ray diffraction patterns, these particles can agglomerate into compact, ordered Cu crystals in less than five minutes at 60 °C. The melting and recrystallization related endothermic and exothermic phase transitions of Cu-NPs can be found from differential scanning calorimeter (DSC) thermograms and optical microscopic pictures.

New wide-stability four-ring azo/ester/Schiff base liquid crystals: synthesis, mesomorphic, photophysical, and DFT approaches

DSC thermograms of some prepared compounds: (a) recorded from second heating and (b) from cooling at a rate of ±10 °C min−1.