Optical properties of honey: FTIR spectroscopy and refractometry

115 samples of honey of various botanical types, geographical origin and harvest year (2019– 2021) were analysed using attenuated total reflection infrared spectroscopy of impaired total reflection, refractometry and biochemical analysis. Initial honey samples in liquid and crystallised states were investigated. Crystalline D-glucopyranose (glucose), D-fructopyranose (fructose), their 40% solutions and invert sugar were used as auxiliary substances. Biochemical analysis was used to determine the glucose content in honey samples. Based on the obtained data, a relationship between the results of biochemical analysis and refractometry (refractive index, the content of invert sugars, humidity) was established. We deduced equations that allow the content of glucose and fructose in honey to be evaluated by the refractive index. Studying honey by IR spectroscopy showed that all investigated samples, regardless of the botanical and geographical origins, can be classified into three groups dominated by: I – glucose, II – fructose and III – mixed, with a close content of two monosaccharides. This allowed the bands characteristic of α- and β-pyranose forms of glucose and fructose to be identified, as well as the nature of their changes depending on the ratio of both monosaccharides in honey as a result of their crystallisation to be assessed. It is noted that the ratio of monosaccharides determines not only the stability of the liquid crystal structure and crystallisation rate in honey but also their optical, biochemical and nutritional properties, which are important for the preferred use of honey in medical and pharmacopoeial practice, dietetics and cosmetology.

Physical Properties and Non-Isothermal Crystallisation Kinetics of Primary Mechanically Recycled Poly(l-lactic acid) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

The physical properties and non-isothermal melt- and cold-crystallisation kinetics of poly (l-lactic acid) (PLLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biobased polymers reprocessed by mechanical milling of moulded specimens and followed injection moulding with up to seven recycling cycles are investigated. Non-isothermal crystallisation kinetics are evaluated by the half-time of crystallisation and a procedure based on the mathematical treatment of DSC cumulative crystallisation curves at their inflection point (Kratochvil-Kelnar method). Thermomechanical recycling of PLLA raised structural changes that resulted in an increase in melt flow properties by up to six times, a decrease in the thermal stability by up to 80 °C, a reduction in the melt half-time crystallisation by up to about 40%, an increase in the melt crystallisation start temperature, and an increase in the maximum melt crystallisation rate (up to 2.7 times). Furthermore, reprocessing after the first recycling cycle caused the elimination of cold crystallisation when cooling at a slow rate. These structural changes also lowered the cold crystallisation temperature without impacting the maximum cold crystallisation rate. The structural changes of reprocessed PHBV had no significant effect on the non-isothermal crystallisation kinetics of this material. Additionally, the thermomechanical behaviour of reprocessed PHBV indicates that the technological waste of this biopolymer is suitable for recycling as a reusable additive to the virgin polymer matrix. In the case of reprocessed PLLA, on the other hand, a significant decrease in tensile and flexural strength (by 22% and 46%, respectively) was detected, which reflected changes within the biobased polymer structure. Apart from the elastic modulus, all the other thermomechanical properties of PLLA dropped down with an increasing level of recycling.

EFFECTS OF ADMIXTURES ON THE CRYSTALLISATION RATE OF GYPSUM A BATCH CRYSTALLISATION STUDY

This paper descripbes a study on the effects of admixtures on the crystallization rate of gypsum. Two different types of biodegradable admixtures commonly used as flotation agent in copper/zinc concentrate production, namely, sodium isopropyl xanthate (=SIPX) and isopropyl thionocarbamate were investigated in this study. A laboratory batch crystallizer was used in this study, and the experiments were run using seeded method. The rate of desupersaturation or the time required to reach the equilibrium concentration was compared for varying admixture oncentrations. It was discovered that the added seed crystals started growing imediately upon addition into the supersaturated solution, i.e. there was no induction time.Results of this batch crystallizationstudy suggest that addition of admixtures individually or in combination, significantly affects the crystallization kinetics and in particular, reduces the rate of crystallization of gypsum. Activation energies were determined using three different temperatures, and the values obtained mostly agreed with other published values, i.e. 60.00 ± 3.00, 57.39 ± 2.87, and 37.65 ±1.88 kj/mol, for pure gypsum, isopropyl yhionocarbamate, and SIPX, respectively.Keywords : activation energy; admixtures; CaSO4.2H2O; crystallization, gypsum; reaction rate

Polypropylene-based Nanostructured Materials

The effect of nanosized carbon additives on the properties and crystallisation of polypropylene was investigated. It was shown that the introduction of carbon nanoparticles affects the crystallisation rate and the properties of polypropylene.

Morphology, thermal properties and mechanical relaxations of metallocene syndiotactic polypropylenes

The complex polymorphic behaviour of four syndiotactic polypropylene (sPP) samples have been analysed by means of DSC and WAXD techniques. Two samples (sPP1, sPP2) were synthesised via metallocene polymerization by using the ansa-zirconocene Ph2C(Cp)(9-Flu)ZrCl2 as catalyst. Finally, two additional specimens with different molar masses (sPP1-Fr1, sPP1-Fr2) were prepared from the most syndiotactic sPP1 sample by temperature gradient extraction. The WAXD analysis shows that together with the orthorhombic form I, form II can coexist in a variable but small proportion depending on both the chain features and the processing conditions. The relative contribution of the disordered and the ordered types of form I is also dictated by molar mass, configurational microstructure as well as processing conditions. The observed changes in the thermal properties as measured by DSC and in the mechanic-dynamical relaxations of the samples, on slowing the crystallisation rate down, can be rationalised in terms of two concurrent processes, namely the perfection undergone by the crystals and the segregation of the amorphous phase.

Influence of Flame Retardant and Glass Fibre on Non-Isothermal Crystallisation Behaviour of Pa66

The authors studied the influence of melamine polyphosphate flame-retardant (MPP-FR) and glass fibre on the non-isothermal crystallisation behaviour of a polyamide (PA66) by differential scanning calorimetry (DSC). The glass fibre reinforced PA66 (PA66/GF) and its reinforced flame retarded equivalent (PA66/GF/FR) were prepared using a twin-screw extruder. The experimental results demonstrated that the MPP-FR increased the crystallisation rate and decreased the supercooling required for crystallising nucleation. The glass fibres increased the crystallisation rate and the amount of supercooling. Avrami analysis showed that the non-isothermal crystallisation of PA66 and its composites followed the Avrami equation. The activation energy for the transport of macromolecular segments to the growing surface was calculated by using the Kissinger method based upon DSC data, and the calculated activation energies were 243.5 kJ·mol−1, 201.1 kJ·mol−1 and 305.9 kJ·mol−1 for PA66, PA66/GF and PA66/GF/FR, respectively. The activity of nucleation for GF and MPP-FR were 0.87 and 0.79 respectively, calculated by Dobreva's method. The results indicate that the MPP-FR has more effective ability to promote heterogeneous nucleation than GF.