This work reports a quantitative correlation based on the general epitaxial crystallization model between the lattice dimensions and nucleating efficiency of additive materials in isotactic polypropylene. The strong correlation is used to build an empirical model, which can predict the possible nucleation efficiency of a material with known crystalline lattice dimensions in isotactic polypropylene. The efficiency of the nucleation is characterized by differential scanning calorimetry (DSC). The crystalline lattice dimensions were collected from existing databases. The matching dimensions in different directions are handled as independent parameters and the prediction model is built up by nonlinear regression analysis on the correlation between the dimensional parameters and the nucleation efficiency. The results clearly indicate that a strong correlation exists between the dimensional matching and nucleating efficiency of the additives, and the prediction of efficiency can also be done with good accuracy. The prediction's reliability was tested using earlier data on β-nucleated iPP, and good agreement was observed between the measured and predicted efficiencies. In addition, the validation results gave a good explanation of the non-selective dual nucleation effect of β-nucleating agents. Accordingly, this type of modeling can be very useful in the development of nucleating agents for crystalline polymers.

This work aims to model the effect of water content on the stiffness of polyamide-6. Our empirical model developed earlier was used to model stiffness. The tensile modulus is calculated from parameters of the crystalline structure obtained by calorimetry. The model was fitted to modulus data estimated after conditioning standard specimens in desiccators at different but constant relative humidities to change the water content over the widest range. The mechanical properties were studied by standard tensile tests, and the parameters of the crystalline structure were studied by calorimetry. The calculated modulus values are in good agreement with the experimentally measured data, indicating that the prediction of the modulus is accurate. The effect of water content was also described accurately, and one of the iterative parameters of our model showed a strong correlation with the water content of the sample. We assumed that this parameter weighs the intermolecular interactions of the polymer. According to the results of this study, the stiffness of any polyamide-6 grade can be calculated at any water content if experimental data are recorded at a single water content, which makes it possible to model the tensile modulus of a polyamide-6 specimen under realistic outdoor conditions.

Epoxy composites, such as wind turbine blades from the renewable energy sector, pose significant end-of-life management challenges due to their crosslinked structure and complex composition. To prevent the landfill of the waste material, we present a potential hydrothermal treatment method enabling clean fiber recovery and selective matrix decomposition, supporting the circular economy. The effects of temperature, pressure, and average water residence time on matrix decomposition and product distribution of a bisphenol A-based epoxy resin were evaluated using a Box-Behnken experimental design in a semi-continuous flow-through system. The process yielded only four major organic-phase products, indicating high selectivity, in less than 10 min. The method was then applied to a decommissioned wind turbine blade. Decomposition was carried out at 330-360 degrees C and 25 MPa with an average water residence time of 3 min and a total processing time of 30 min. Scanning electron microscopy confirmed clean fiber surfaces, further supported by thermogravimetric analysis showing > 99% purity. The results demonstrate a water-based, selective and scalable decomposition method suitable for real composite waste from the green energy sector, offering an alternative to conventional end-of-life treatments.

This work introduces a probabilistic numerical simulation method to describe or predict the spherulitic morphology of semicrystalline polymer formed during non-isothermal crystallization process. The numerical simulation is based on the general crystallization theory, which consists of random nucleation and subsequent growth of supermolecular formations. The model is capable for prediction of morphology from the conversion curve of crystallization recorded by calorimetry during crystallization at a constant cooling rate. Samples made of polypropylene nucleated by different nucleating agents were used as a model material for testing the simulation approach. The results indicated that valuable structural information can be predicted from the conversion curve, like nucleus density, average spherulite size and size distribution as well. In addition, the simulation method also capable to predict the mechanism of nucleation during the crystallization process, namely, whether the number of nuclei is constant or continuously changing. The results also indicated that nucleus density increases significantly as a consequence of heterogeneous nucleation, which indicates that the simulation results in realistic and reliable structural data both in nucleated and non-nucleated samples.

Utilizing the electrospinning technique to entrap enzymes within nanofibers (providing nanofibrous enzyme catalysts, NEC) offers promising avenues for the scientific and industrial sectors as well. While numerous instances of poly(vinyl alcohol) (PVA)-based nanofibrous biocatalysts have been documented, a comprehensive investigation to characterize the effect of PVA on catalytic activity is notably lacking. This study systematically investigates the effect of PVA properties, such as molecular weight (24-205 kDa), degree of hydrolysis (DoH, 88% and 98%), and polymer concentration (6-16 wt%), on the structure of PVA nanofibers and on the biocatalytic properties of a lipase from Burkholderia cepacia (BcL) entrapped into PVA nanofibers, ensuring 100% yield of immobilization. The PVA-enzyme interactions were studied using viscometry, scanning electron microscopy, Raman mapping, differential scanning calorimetry, and computational docking simulations. Stereoselective hydrolysis and transesterification were used to evaluate enzyme activity. Results showed that the molecular weight and DoH of PVA have a significant effect on the biocatalytic activity of nanofibrous enzyme catalysts. Remarkably, activity yields (mostly exceeded 100%, with maximal yields achieved using fully hydrolyzed PVA) with a molecular weight of 61 kDa provided a 10-fold increase in the specific enzymatic activity of BcL immobilized in nanofibers (90.6 U x g-1) compared to its native form (9.0 U x g-1).

This study focuses on the prediction of the tensile modulus of polyethylene based on a previously developed empirical model. Just as in earlier works, the stiffness is estimated from the data evaluated from single calorimetric curves. During the work, three types of polyethylene (LDPE, MDPE and HDPE) were used. Calorimetry was employed to measure the degree of crystallinity and melting characteristics of the polymers investigated in this study, while the mechanical properties were evaluated through tensile tests conducted on standard-shaped specimens. The specimens intended for the tests were produced by injection molding and later annealed at various temperatures. The stiffness of the perfectly crystalline polymer was determined based on the propagation velocity of longitudinal sound waves in the material. The predicted and experimentally determined modulus values demonstrated a reasonably good agreement. These results verify the effectiveness of our prediction method in accurately estimating the tensile modulus of PE.

This work aims to adopt a simple modulus prediction method for the crystalline poly(ethylene-terephthalate) (PET), which has strong cold-crystallization ability. Based on a single melting curve generated by calorimetry, crystallinity and average melting temperature can easily be evaluated and consequently, tensile modulus can be predicted. Nonetheless, in the case of polymers with cold crystallization behavior, such as PET, the melting process is affected by cold crystallization, impeding the simple calculation of the aforementioned important parameters. In this paper, the techniques to eradicate cold crystallization during calorimetry are presented. Accordingly, the results of a tensile modulus prediction model are presented and discussed. The crystallization and melting characteristics of PET were measured by differential scanning calorimetry (DSC). The mechanical properties of the specimens were estimated by standardized tensile tests. The specimens, which were used for mechanical tests were fabricated using conventional injection molding. The samples were annealed at different temperatures in order to obtain different crystalline structures. The results clearly indicate that the prediction technique is capable to describe the tensile modulus of PET accurately in the case of very diverse crystalline structures.

This research delves into the hydrothermal decomposition of PET [poly(ethylene terephthalate)] between 523 and 573 K temperature at 10 MPa pressure. PET was placed in a packed column, and a constant water flow was maintained with an average residence time of water between 403 and 430 s as it travelled from the reactor to the end of the system. Terephthalic acid (TPA) recovery ranged from 87 % to 94 %, increasing with the temperature. The time of full conversion of the 0.5 g PET by 1 g/min water flow rate reduced from 2500 to 1200 sec, with increasing temperature. To prevent premature precipitation of TPA during cooling, an alkaline quench stream was employed. Terephthalic acid isolation involved acidification-driven precipitation and subsequent filtration at atmospheric pressure. The solid dry TPA product underwent NMR analysis, showing structural conformity and DSC/TGA measurement, which presented a purity of 99.5 w/w%. The fractional end-of-pipe sampling showed accelerating reaction rates at each temperature, which supports the autocatalytic nature of hydrothermal disintegration of the PET. Using the determined residence time distribution in the system, from the end-of-pipe data a crude Fourier transform-based backward calculation was carried out to map the variation of the TPA concentration in the high-temperature and -pressure reactor.

Thermal processing of Zr-loaded ion-exchangers is a facile route to synthetize (ZrO2, ZrC)@C composites. In the present paper, furnace and RF-thermal plasma processing of ZrOCl2 loaded thiourea-functionalized styrene-divinylbenzene copolymer was investigated and led to composites containing ZrO2 and ZrC. Different ZrO2@C composites were formed between 1000 and 1400 °C in 2 h, whereas the composite containing ZrC was created at 1400 °C in 8 h. The ratio of ZrO2/ZrC, the prevailing ZrO2 modifications, and the crystallite sizes strongly depend on the synthesis conditions. The ZrC-containing composites formed only at 1400 °C in 8 h and by the plasma treatment of the ZrO2@C sample prepared in the furnace, resulting in 8 and 16% ZrC content, with 44 and 41 nm ZrC crystallite sizes, respectively. The ZrO2-containing composites (tetragonal, monoclinic, and cubic modifications with 65–88 nm ZrO2 crystallite sizes and 15–43 m2/g BET surface areas) formed in a tube furnace between 1000 and 1400 °C in 2 h. All ZrO2@C composites had both amorphous carbon and graphite, and their ratio is temperature dependent. The carbonaceous compounds were characterized by Raman spectroscopy with analysis of the G and D band intensities. XPS studies showed the surface oxidation of ZrC.

This work presents a robustness study of a previously developed empirical model that links Young's modulus to two key parameters of crystalline structure; crystallinity and lamellae thickness. The reliability of this modulus prediction model was tested by using different calorimeters and different polypropylene grades as well. Small samples were fabricated from injection-molded bars from different locations of the specimens in order to check the effect of structural inhomogeneity originated by the dynamic processing conditions. In addition, the standard deviation and consequently the accuracy of the prediction was tested by repeated calorimetric measurements. The crystalline structure and melting characteristics were measured by differential scanning calorimetry (DSC). The tensile properties of studied specimens were evaluated by standardized tensile tests. Although, the accuracy and reliability of the prediction model is dependent on the instrument used for thermal analysis, reasonably good agreement was found between the predicted and measured values in most cases. However, we may note that only well-calibrated calorimeters are suitable for reliable prediction of the modulus.

We have introduced a novel solvent-based method to roughen polymer sur-faces and characterized treated polypropylene (PP). The method consists of three main steps: solvent treatment, drying, and peeling. We investigated the effects of process parameters such as time of immersion in the solvent, solvent temperature, and drying temperature on the surface morphology created. The structure formed on the surface is mainly influenced by solvent temperature and drying temperature. We also characterized the wetting behavior of the sur-faces. The patterned surfaces exhibit superhydrophobic characteristics with a high water contact angle (CA) (> 155 degrees) and low water contact hysteresis (< 5 degrees). Adding an effective nucleating agent to PP makes it possible to generate out-standing CAs (> 160 degrees) and tailor spherulite sizes. The method is simple and scalable, therefore this superhydrophobic material is easy to mass-produce.

Raman studies on carbon-containing phases in nanosized-ZrO2/C and nanosized-(ZrC,ZrO2)/C composites. / A. Martiz, A. Farkas, Z. Karoly, F. P. Franguelli, S. K. Samaniego, A. Menyhard, L. Kotai. / Nano Studies. – 2021–2022. – # 21/22. – pp. 177-186. – Eng. Raman spectroscopic studies were performed to identify the nature of the carbon-containing phases in nano-(ZrC,ZrO2)/C composites. The nano-ZrO2/C composites were prepared in a tube furnace by heat-treatment of zirconium-loaded sulfonated styrene-divinylbenzene resins between 1000 and 1400 °C. The plasma processing of a nano-ZrO2/C sample in inert or reducing atmosphere resulted in nano-(ZrC,ZrO2)/C composites. The Raman spectra of the nano-ZrO2/C samples show that the ratio of the amorphous carbon / graphitic components decreases, whereas the fraction of distorted graphite structures increases with increasing reaction temperature and time. This can be attributed to the formation of new graphene edges by the condensation of the polyene content in the amorphous carbon. The ratio of the amorphous carbon practically does not change if the plasma treatment was performed under inert (Ar+He) atmosphere. In contrast, under reducing (Ar+H2) atmosphere, the amorphous carbon almost completely crystallizes into graphite. The ratio of the defective / regular graphite structures and the change of the thickness or separation of the graphene (monolayer carbon) sheets are higher under inert than reducing plasma conditions. We found no catalytic effect of ZrC on the graphite crystallization under inert plasma conditions, but in the presence of H2, ZrC may catalyze the graphitization process. Fig. 3, Tab. 4, Ref. 40.

S and N double-doped high surface area biomass-derived carbons were obtained from marine biomass-derived ι-carrageenan. Adding carbon nanoparticles (CNPs), namely graphene oxide (GO) or carbon nanotubes (CNTs), in the early stage of the synthesis leads to a modified porous texture and surface chemistry. The porous textures were characterized by N2 (−196.15 °C) and CO2 (0 °C) isotherms. The best GO- and CNT-added carbons had an apparent surface area of 1780 m2/g and 1170 m2/g, respectively, compared to 1070 m2/g for the CNP-free matrix. Analysis of the Raman spectra revealed that CNT was more efficient in introducing new defects than GO. Based on XPS, the carbon samples contain 2–4.5 at% nitrogen and 1.1 at% sulfur. The Dubinin–Radushkevich (DR) and Henry models were used to assess the strength of the interactions between various gases and the surface. The N2/H2 and CO2/CH4 selectivities were estimated with ideal adsorbed solution theory (IAST). While the CNPs, particularly GO, had a remarkable influence on the porous texture and affected the surface chemistry, their influence on the separation selectivity of these gases was more modest.

This study investigates the formic acid-mediated hydrothermal carbonisation (HTC) of microalgae biomass to enhance green hydrogen production. The effects of combined severity factor (CSF) and feedstock-to-suspension ratio (FSR) are examined on HTC gas formation, hydrochar yield and quality, and composition of the liquid phase. The hydrothermal conversion of Chlorella vulgaris was investigated in a CSF and FSR range of-2.529 and 2.943; and 5.0 wt.% - 25.0 wt.%. Artificial neural networks (ANNs) were developed based on experimental data to model and analyse the HTC process. The results show that green hydrogen formation can be increased up to 3.04 mol kg-1 by applying CSF 2.433 and 12.5 wt.% FSR reaction conditions. The developed ANN model (BR -2-11-9-11) describes the hydrothermal process with high testing and training performance (MSEz = 1.71E-06 & 1.40E-06) and accuracy (R2 = 0.9974 & R2 = 0.9781). The enhanced H2 yield indicates an effective alternative green hydrogen production scenario at low temperatures using high-moisture-containing biomass feedstocks.

Nucleation efficiency and the special supermolecular structure formed in the presence of novel nucleating agents, N,N′-dicyclohexylsuberoylamide and N,N′-dicyclohexylsebacoylamide are presented in this work. The nucleation effect is studied in isotactic polypropylene (iPP). The melting and crystallization processes as well as the polymorphic composition are studied using calorimetric and thermo-optical techniques, while the solubility of the nucleating agents is studied by rheology. The properties of the iPP products nucleated by the novel compounds are characterized by conventional tensile and impact tests and the optical properties are measured by standardized haze measurements. The results indicated clearly that the studied nucleating agents are partially soluble in the iPP melt and possess dual nucleating ability. The formation of β-phase is evidenced by the calorimetric and thermo-optical measurements. The morphology of the nucleated samples shows similarity to iPP nucleated by well-known soluble “organogelators”; however, the nucleating agents introduced in this work are the first “organogelators” with β-nucleating efficiency.

We have developed a simple method to prepare nano-(ZrC 0.93 , ZrO 2- polymorphs)@carbon composites with graphite/amorphous carbon content and adjustable Zr/C ratio based on using a multistep tube furnace and plasma-assisted heat treatment of zirconium-loaded sulfonated styrene–divinylbenzene (STY-DVB) copolymers. Pre-pyrolysis of zirconium-loaded sulfonated STY-DVB ion exchangers with 2 and 8 mass % DVB at temperatures between 1000 and 1400 °C for 2 h produced nano-ZrO 2 @C intermediates with particle sizes of ~ 30–60 nm with no ZrC formation. Plasma processing of nano-ZrO 2 @C resulted in nano-(ZrC 0.93 , ZrO 2 )@C composites with 11% (under a He atmosphere) (C/Zr = 73) or 13% (under a H 2 atmosphere) (C/Zr = 58) ZrC 0.93 content. Three polymorphs of the zirconium dioxide (tetragonal, monoclinic and cubic, between 18 and 27 nm) were found in the products. The amounts of tetragonal and monoclinic ones are comparable to that of ZrC 0.93 . The average particle size of ZrC 0.93 prepared in this way was found to be 21–23 nm. The BET surface area of the nano-(ZrC 0.93 , ZrO 2 )@C(graphite) composites prepared in He and H 2 was over 250 and 300 m 2 /g, respectively. We developed a reproducible and easy method to prepare nano-(ZrC, ZrO 2 )@C products by setting the DVB content, sulfonation degree, Zr loading and the thermal treatment conditions, which have an influence on the ZrC and graphite/amorphous carbon content of nano-ZrO 2 @C intermediates. The zirconium-loaded sulfonated styrene–divinylbenzene (STY-DVB) copolymers (2 and 8 mass% DVB) or their thermal decomposition was characterized with vibrational spectroscopy, thermal analysis and DSC or powder XRD, BET, XPS and HRTEM methods, respectively.

Crystallization of heterogeneously nucleated isotactic polypropylene microdroplets in an immiscible polystyrene matrix allows the estimation of intrinsic nucleating efficiency of nucleating agents promoting the formation of different polymorphs.

We have developed an easy route to prepare (nano-ZrO2,nano-ZrCx)@C composites with varying ZrO2/ZrCx content. The process consists of preparing a zirconium-loaded, iminodiacetate-functionalized styrene-divinylbenzene (STY-DVB) copolymer, and its subsequent carbonization in a tube furnace and/or a thermal plasma reactor. Depending on the zirconium salt used (zirconyl chloride, zirconyl nitrate or zirconium (IV) sulfate) in the Zr loading, the Zr-loaded resins resulted in ZrO2@C pre-pyrolizates with C to Zr molar ratios of 5.8, 6.8 and 6.60. This carbon surplus is sufficient for the partial or even complete reduction of ZrO2 into ZrC0.58 at 1400 °C. The reaction products also contain 5 to 55 mass% residual free carbon. The plasma processing of the ZrO2@C composite formed at 1000 °C in a tube furnace led to ZrC0.94@C composites. The transformation of amorphous carbon content during the plasma treatment strongly depended on the atmosphere (He or H2) in the reactor and the anion type of the Zr salt. In the presence of He, amorphous carbon could be completely transformed into graphite. In the presence of H2, amorphous carbon and graphite were found at roughly the same ratio. No ZrO2 could be detected in the plasma-treated samples, whilst different ZrO2 polymorphs were found in the samples prepared in the tube furnace, depending on the synthesis conditions.

Application of nucleating agents is a common way to manipulate the structure and properties of crystalline polymers. Our goal was to synthesize N,N'-dicyclohexyl terephthalic dihydrazide (DCTDH) and study it from the viewpoint of applicability as a nucleating agent for isotactic polypropylene (iPP). We used differential scanning calorimetry to investigate the efficiency of DCTDH in samples containing the nucleating agent in a wide concentration range. We used polarized light microscopy to study the crystalline morphology developed in the presence of this nucleating agent. To characterize the mechanical properties of the nucleated samples, we performed tensile and impact tests on injection molded specimens. DCTDH proved to be a non-soluble α-nucleating agent in iPP, with a saturation concentration around 300 ppm. The nucleating agent has a significant effect on the crystalline structure of iPP, microspherulitic structure forms in its presence. Owing to the different structure, a considerable change in the mechanical properties is observable: with increasing nucleating agent content the tensile modulus increases, while impact resistance has a maximum value around 300 ppm nucleating agent content.

Application of nucleating agents is the most versatile and industrially applied way to manipulate the crystalline structure of isotactic polypropylene (iPP). Various materials possess a nucleating effect, but from the viewpoint of dispersibility, the partially soluble ones are the most advantageous. Our objective was to synthesize new N,N′-dicyclohexyldicarboxamide homologues and study their applicability as nucleating agents in iPP. Carbon-13 nuclear magnetic resonance (13C NMR) and infrared spectroscopy were used to prove that the synthesis reactions were successful. Thermal stability of the compounds was investigated with simultaneous thermal analysis. Nucleating efficiency and solubility were characterized by polarized light microscopy and differential scanning calorimetry. Polarized light microscopy was also applied to study the effect of novel additives on the morphology of iPP. The properties, important from the viewpoint of applicability, were also investigated. Tensile tests were performed to characterize the main mechanical properties, and standard haze measurements were performed to characterize optical properties. It can be concluded that the investigated compounds are partially soluble nucleating agents and influence the crystalline structure of iPP. Most of the studied compounds have a moderate nucleating efficiency, but a very interesting dendritic structure develops in their presence. Two of them proved to be non-selective β-nucleating agents, which result in a remarkable improvement of impact resistance and higher opacity.