Functionalized silica gels were applied as heterogeneous organocatalysts in PET glycolysis, and were recycled by filtration while preserving high monomer yields over five cycles.

The modulus of semicrystalline polymers mainly depends on two parameters of the crystalline structure, the crystallinity and the lamellae thickness. These parameters can be obtained from a single calorimetric melting curve, which makes it possible to predict the modulus from a calorimetric measurement. Our equation gives the relation between these two parameters and the elastic modulus. However, in polymers like polylactic acid (PLA), the cold crystallization influences the melting curve and hiders the simple evaluation. This work presents a novel method to eliminate the cold crystallization during the calorimetric measurements and determine the iterative constants needed for the modulus prediction. The crystalline structure of PLA was characterized by differential scanning calorimeter (DSC) and wide-angle X-ray scattering (WAXS) measurements. Tensile properties were determined by standardized tensile tests on injection molded specimens, which were annealed at different temperatures and times to achieve significantly different crystalline structures for the model's development.

The present work introduces a novel method to estimate the morphology of semicrystalline polymers, namely the average spherulite size, size distribution, and nucleus density based on experimental crystallization conversion curves recorded by differential scanning calorimetry (DSC). A fast and accurate probabilistic numerical simulation method describing random nuclei formation and subsequent growth is introduced to handle the crystallization process of polymers. The developed method was used in a curve-fitting procedure with experimental crystallization curves to obtain structural parameters of neat and nucleated isotactic polypropylene. The simulated morphology was used with success to predict haze of injection-molded samples, proving the reliability and applicability of our new approach. The method presented here can be a useful technique to construct the spherulitic morphology based on crystallization conversion curves and predict properties dependent on the spherulite size, size distribution, and nucleus density, even when microscopic measurement cannot be carried out.

The control of infectious bronchitis (IB) is essential in intensive broiler production and is pursued through strict biosecurity and mass vaccination. Despite effective and routinely adopted, hatchery spray vaccination has been hypothesized to affect chicks’ body temperature and wellbeing. Recently, gel administration has been proposed as an alternative and proved feasible in experimental settings. In this study, IBV spray and gel vaccination methods were compared in field conditions. One hundred birds from the same hatch were enrolled in the study and vaccinated, half by spray and half by gel, with 793B and Mass vaccines. After vaccination, rectal temperature was measured and vaccine intake assessed. The two groups were housed for 35 days in separate pens and swabs and blood samples were collected at multiple time points for genotype-specific molecular analyses and serology, respectively. The temperature was significantly lower in spray-vaccinated chicks 10 min and an hour after administration. A similar trend in 793B titres was observed in both groups, while the Mass vaccine was detected later but persisted longer in gel-vaccinated chicks. No differences were observed in mean antibody titres. Compared to spray, gel administration appears equally effective and less impactful on body temperature, thus supporting its application for IBV vaccination.

This work demonstrates the most widely used characterization methods and techniques of the supermolecular and lamellar structure of semicrystalline polymers. Polarized optical microscopy (POM) equipped with a hot-stage (thermo-optical microscopy, TOM), brightfield microscopy (BF), darkfield microscopy (DF), digital image processing techniques, optical profilometry (OP), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used as investigation techniques. The same iPP grade was used with different sample preparation techniques to compare these methods. The advantages and drawbacks of the sample preparation and investigation methods were discussed. The results show how the introduced techniques could reveal different kinds of information, and it is also shown how the experimental techniques should be matched to the goals of a structural study.

Nanofluids obtained from halloysite and de-ionized water (DI) were prepared by using surfactants and changing pH for heat-transfer applications. The halloysite nanotubes (HNTs) nanofluids were studied for several volume fractions (0.5, 1.0, and 1.5 vol%) and temperatures (20, 30, 40, 50, and 60 °C). The properties of HNTs were studied with a scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDX), Fourier-transform infrared (FT-IR) spectroscopy, X-ray powder diffraction (XRD), Raman spectroscopy and thermogravimetry/differential thermal analysis (TG/DTA). The stability of the nanofluids was proven by zeta potentials measurements and visual observation. With surfactants, the HNT nanofluids had the highest thermal conductivity increment of 18.30% for 1.5 vol% concentration in comparison with the base fluid. The thermal conductivity enhancement of nanofluids containing surfactant was slightly higher than nanofluids with pH = 12. The prepared nanofluids were Newtonian. The viscosity enhancements of the nanofluid were 11% and 12.8% at 30 °C for 0.5% volume concentration with surfactants and at pH = 12, respectively. Empirical correlations of viscosity and thermal conductivity for these nanofluids were proposed for practical applications.

This article reports a new model approach for the description of light scattering in semicrystalline polymers, to describe more precisely the influence of supermolecular structure on the optical properties. This is the first study in which light scattering of polymer films has been modeled using exact Mie scattering theory of radially anisotropic spheres. As a model material a well-known polymer, isotactic polypropylene (iPP) was used. Samples were prepared with different sample thicknesses and crystalline structures in order to identify the key parameters of light scattering in polycrystalline polymeric systems. Validation haze measurements were carried out with a spectrophotometer equipped with a 150 mm snap-in integrating sphere. It was found that the optical properties of the polycrystalline sample can be described using multiple light scattering on these scattering centers. Good agreement was found between the simulated and experimentally measured haze values which proves the reliability and applicability of our new approach.

This work demonstrates and models the self-organization of mixed polymorps in polymers containing simultaneously growing phases with different growth rates. The model was verified and demonstrated in isotactic polypropylene nucleated by a non-selective nucleating agent. The crystallization and melting processes were studied by calorimetry (DSC) and polarized light microscopy (PLM). The morphology of the samples was investigated using PLM and scanning electron microscopy (SEM). The fundamental rules of the formation of two polymorphic modifications developing simultaneously on the same nucleating particle are introduced. A simple equation is suggested to predict the morphological geometry on the lateral surface of the nucleating agent. The results indicated good agreement between the predicted and observed geometry. The proposed model explains the self-organization of micro-sized reinforcements of α-modification in the matrix of β-iPP. Although the proposed equation was tested for this particular case it is a general equation for all structures in which different polymorphs are growing simultaneously with different growth rates.

Over many years, great efforts have been made to develop new fluids for heat transfer applications. In this paper, the thermal conductivity (TC) and viscosity of SiO 2 –P25 TiO 2 (SiO 2 –P25) hybrid nanofluids were investigated for different nanoparticle volume concentrations (0.5, 1.0 and 1.5 vol%) at five various temperatures (20, 30, 40, 50 and 60 °C). The mixture ratio (SiO 2 :P25) in all prepared hybrid nanofluids was 1:1. Besides, pure SiO 2 , P25 nanofluids were prepared with the same concentrations for comparison with the hybrid nanofluids. The base fluid used for the preparation of nanofluids was a mixture of deionized water and ethylene glycol at a ratio of 5:1. Before preparing the nanofluids, the nanoparticles were analyzed with energy-dispersive X-ray analysis, scanning electron microscope, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The zeta potentials of the prepared nanofluids except SiO 2 nanofluids were above 30 mV. These nanofluids were visually observed for stability in many days. The TC enhancement of the hybrid nanofluid was higher than the pure nanofluid. In particular, with 1.0 vol% concentration, the maximum enhancement of SiO 2 , P25 and SiO 2 –P25 nanofluids were 7.5%, 9.9% and 10.5%, respectively. The rheology of the nanofluids was Newtonian. The viscosity increment of SiO 2 , P25 and hybrid nanofluids were 19%, 32% and 24% with 0.5 vol% concentration. A new correlation was developed for the TC and dynamic viscosity of SiO 2 –P25 hybrid nanofluid.

The solvolysis of poly(ethylene-terephthalate) (PET) is one of the most researched areas in chemical recycling. In this study PET aminolysis with isophorondiamine has been done - in opposition to recent trends - without excess reagent and the raw reaction product was further used without purification. The aminolysis product was thoroughly characterized with nuclear magnetic resonance (NMR) spectroscopy. Isophoronediamine was used as a solvent to prepare amine cross-linker solutions for epoxy resins. The effect of the concentration on the cross-linking reaction and thermomechanical properties were investigated. The curing reaction was found to be significantly accelerated by the presence of the aminolysis product. Both the ethylene-glycol and the terephthal-amide-diamines have a catalytic effect on the reaction. The glass transition temperature decreased with increasing concentrations of the cross-linker solutions due to the decreasing cross-link density. Thus, raw aminolysis products can be utilized for epoxy curing and are advantageous in modifying slower curing cycloaliphatic cross linker systems.

We investigate the growth of spherulites in the wake of a solidification front in a thin film of liquid menthol. We observed that the two enantiomeric forms of menthol ((-)-menthol and (+)-menthol)) form ring-banded spherulites, in which needle-like crystals self-assemble into high- and low-density crystal regions. Interestingly, the racemic mixture produces nonbanded spherulites consisting of closely packed plate-like crystals. In the ring-banded spherulitic growth, we could clearly identify the curvature effect of the solidification front on the pattern formation on a millimeter spatial scale. We developed a numerical model based on the Cahn-Hilliard equation, which qualitatively describes the main features observed in experiments, namely, the formation of periodic ring-banded structures and the curvature effect of the propagating solidification front.

This work introduces an easy calculation method, which results in the elastic modulus of semicrystalline polymers from data obtained from a single melting curve recorded by calorimetry. It is well known that the mechanical properties of semicrystalline polymers depend on the crystalline structure; however, the number of direct correlations between crystalline structure and mechanical properties is limited. The melting and crystallization of the polymers studied in this work were measured using calorimetry; the mechanical properties were estimated by tensile tests on the standard shape specimens. Good agreement was found between the calculated and measured modulus values, indicating that the correlation is reliable. In addition, the method was tested for polypropylene and polyamide-6 which proves clearly that the correlation reported here is generally valid for semicrystalline polymers.

Crystallization kinetics of simultaneously developing polymorphic modifications was investigated in isotactic polypropylene (iPP) under non-isothermal conditions. iPP was nucleated by a trisamide derivative (TATA), which is a non-selective β-nucleating agent, in order to obtain mixed polymorphic structure. The crystallization process was followed using differential scanning calorimetry under constant cooling rates and a stepwise experimental technique is presented, which can separate the development of α- and β-modifications. Ozawa method was applied to evaluate the crystallization kinetics of the two modifications separately. The results indicate clearly that the kinetics of the modification is different. Accordingly, any methods, which evaluate the crystallization process of samples containing mixed polymorphic structure without separation the modifications, are incorrect, and this is the reason why these complicated processes are difficult to linearize using the conventional kinetic evaluation techniques.