Search Results (1,080)

Stabilizing thermoplastic polymers against thermal degradation is an important aspect that must be addressed during material development and becomes critical in the case of bio-polymers, which often reveal reduced thermal stability and a narrow processing temperature window. Herein, we propose a new methodology to analyze and compare the thermal stability of thermoplastic materials, exampled by several types of bio-polyesters, such as aliphatic PBS and PBSA, aliphatic-aromatic PBAT and PBST, and amorphous PHBV, and evaluate the impact of thermal stabilizer on their processability and thermal stability. The proposed method relies on multi-step torque rheometry experiments that involve controlled cycling of the tested material under varied thermal conditions, shear forces, and processing times to acquire and evaluate the changes in flow behavior of the sample after its processing. By monitoring polymer melt behavior and comparing the changes before and after repetitive processing steps, we can gain valuable insights into the material performance and stabilizing efficiency of additives. The thermal stability of polymers and the efficiency of thermal stabilizers can be assessed by means of the relative change in temperature-normalized torque, $∆\tau \left(\%\right)$, measured after different processing steps. Significantly, we demonstrate that the obtained $∆\tau \left(\%\right)$ values correlate with changes in the molar mass of neat polymers as a result of their processing. The proposed approach enables a semi-quantitative evaluation of the thermal stability of various polymers and the study of the efficiency of thermal stabilizers and their performance, providing a robust strategy for optimizing compound formulations, particularly regarding the optimal fractions required. Full article

A novel fluorinated diamine monomer, 4,4′-((bicyclo[2.2.1]hept- 5-ene-2,3-diylbis (methylene)) bis(oxy))bis(3- (trifluoromethyl) aniline) (NFDA), featuring a tailored alicyclic norbornane core, flexible ether linkages, and pendant trifluoromethyl groups, was successfully synthesized. This monomer was polymerized with six commercial dianhydrides to produce a series of poly(amic acid) precursors, which were subsequently converted into high-performance polyimide (PI) films via a thermal imidization process. The strategic integration of the alicyclic, ether, and fluorinated motifs within the polymer backbone resulted in materials with an exceptional combination of properties. These PI films display outstanding solubility in a wide range of organic solvents, including low-boiling options like chloroform and tetrahydrofuran, highlighting their superior solution processability. The films are amorphous and exhibit remarkable hydrophobicity, evidenced by high water contact angles (up to 109.4°) and minimal water absorption (as low as 0.26%). Furthermore, they possess excellent optical transparency, with a maximum transmittance of 86.7% in the visible region. The materials also maintain robust thermal stability, with 5% mass loss temperatures exceeding 416 °C, and offer a desirable balance of mechanical strength and flexibility. This unique set of attributes, stemming from a rational molecular design, positions these polyimides as highly promising candidates for next-generation flexible electronics and advanced photovoltaics. Full article

Active packages have become a significant center of attention, and especially those based on biodegradable materials, due to their ability to enhance food preservation and extend shelf life. A suitable base for obtaining such types of packages has turned out to be polymers with natural origin, such as hydroxylpropyl methylcellulose (HPMC) and zein. Therefore, the present study is focused on developing films using the casting method based on pure HPMC and blends between HPMC and zein. Three types of polymer matrices were developed: pure HPMC film, HPMC 3:1 zein, and HPMC 1:1 zein. Further, all of them were loaded with curcumin to improve their biological activity, and mainly their antioxidant activity. In order to investigate the potential of these films, some of their most vital properties in terms of potential application as packaging material are established, such as mechanical properties (strain at break, Young’s modulus), barrier properties (water vapor transmission rate), and morphology. A significant change in the Young’s modulus was present after the addition of zein; it went from 276.98 ± 28.48 MPa for pure HPMC to 52.17 ± 10.19 MPa in a 1:1 ratio between the polymers. Meanwhile, strain at break showed a slight drop from 86.74 ± 8.64% to 72.44 ± 9.62%. Barrier properties were also influenced by the formation of composite film and the addition of polyphenol, lowering the water vapor transmission rate from 913.07 ± 74.01 g/m².24 h for pure HPMC to 873.05 ± 9.07 g/m².24 h for 1:1 ratio film and further to 826.35 ± 33.67 g/m².24 h after the addition of rutin to the latter. Additional characterization of radical scavenging ability towards DPPH free radicals showed a similar A-shaped trend to the values of Young’s modulus, due to the presence of hydrogen bonds, which affect both properties of the film structures. Thermal behavior and phase state investigation of the films obtained by differential scanning calorimetry prior to and after polyphenol addition was carried out, indicating full phase transition of rutin from crystalline to amorphous state. Full article

A spring–dashpot model, consisting of a spring branch and two Maxwell (named long- and short-term) branches, was used to simulate stress drop during the relaxation stages of multi-relaxation (MR) tests. This work shows that the stress drop at relaxation in a deformation range around the peak stress could be closely simulated without changing the parameter values for the short-term branch. This possibility was confirmed using three ethylene/1-hexene copolymers and one ethylene homo-polymer, among which the main differences are mass density and short-chain branch (SCB) content. The work examined the influence of SCB content and mass density on the stiffness of the two Maxwell branches, and the results showed that, unlike the long-term branch counterpart, stiffness of the short-term branch is not a monotonic function of the SCB content or the mass density. This led to a discussion on the possible relationship between the stiffness of the two Maxwell branches and the deformation resistance of the amorphous phase at different locations of the microstructure, i.e., in the interlamellar region and as part of the network structure. The paper concludes that a combination of the MR test and the spring–dashpot model could provide information that is related to the stiffness in different parts of PE’s amorphous phase, though further work is needed to verify this conclusion. Full article

Fused filament fabrication (FFF, often called FDM) is widely used in polymer additive manufacturing; however, it suffers from mechanical anisotropy and weak bonding in the Z direction. This work examines how the infill pattern influences the tensile response of PLA parts at fixed printing conditions. Dog-bone specimens (PLA, four patterns: grid, honeycomb, rectilinear, adaptive cubic) were printed and tested in tension (n = 3 per pattern). Grid yielded the highest ultimate tensile strength, whereas honeycomb produced the largest Young’s modulus; rectilinear was intermediate and adaptive cubic was trailed in both metrics. X-ray diffraction of printed PLA showed a broad halo at 16–20° (2θ) with weak α-form reflections, consistent with largely amorphous microstructure after FFF. Together, the results indicate that, at constant material and nominal infill, pattern selection alone can shift the strength–stiffness balance, with grid favoring strength and honeycomb favoring stiffness. Full article

The present article relates to the description of phenomenological relations of amorphous material behavior within the framework of viscoelasticity and elastic-viscoplasticity theory, as well as to the creation of its digital analog. Ultra-high-molecular-weight polyethylene (UHMWPE) is considered in the study. The model is based on the results of a series of experimental studies. Free compression of cylindrical specimens in a wide range of temperatures [−40; +80] °C and strain rates [0.1; 4] mm/min was performed. Cylindrical specimens were also used to determine the thermal expansion coefficient of the material. Dynamic mechanical analysis (DMA) was performed on rectangular specimens using a three-point bending configuration. Maxwell and Anand models were used to describe the material behavior. In the framework of the study, the temperature dependence of a number of parameters was established. This influenced the mathematical formulation of the Anand model, which was adapted by introducing the temperature dependence of the activation energy, the initial deformation resistance, and the strain rate sensitivity coefficient. Testing of the material models was carried out in the process of analyzing the deformation of a spherical bridge bearing with a multi-cycle periodic load. The load corresponded to the movement of a train on a bridge structure, without taking into account vibrations. It is shown that the viscoelastic model does not describe the behavior of the material accurately enough for a quantitative analysis of the stress–strain state of the structure. It is necessary to move on to more complex models of material behavior to minimize the discrepancy between the digital analog and the real structure; it has been established that taking into account plastic deformation while describing UHMWPE would allow this to be performed. Full article

Conventional dental materials with organised crystal structures exhibit limitations in corrosion resistance, bioactivity, and drug delivery capability. In contrast, amorphous nanomaterials offer potential advantages in overcoming these limitations due to their unique structural properties. They are characterised by a non-crystalline, disordered atomic structure and are similar to a solidified liquid at the nanoscale. Among the amorphous nanomaterials used in dentistry, there are five major categories: calcium-, silicon-, magnesium-, zirconia-, and polymer-based systems. This study reviewed these amorphous nanomaterials by investigating their synthesis, properties, applications, limitations, and future directions in dentistry. These amorphous nanomaterials are synthesised primarily through low-temperature methods, including sol–gel processes, rapid precipitation, and electrochemical etching, which prevent atomic arrangements into crystalline structures. The resulting disordered atomic configuration confers exceptional properties, including enhanced solubility, superior drug-loading capacity, high surface reactivity, and controlled biodegradability. These characteristics enable diverse dental applications. Calcium-based amorphous nanomaterials, particularly amorphous calcium phosphate, demonstrate the ability to remineralise tooth enamel. Silicon-based amorphous nanomaterials function as carriers that can release antibacterial agents in response to stimuli. Magnesium-based amorphous nanomaterials are antibacterial and support natural bone regeneration. Zirconia-based amorphous nanomaterials strengthen the mechanical properties of restorative materials. Polymer-based amorphous nanomaterials enable controlled release of medications over extended periods. Despite the advances in these amorphous nanomaterials, there are limitations regarding material stability over time, precise control of degradation rates in the oral environment, and the development of reliable large-scale manufacturing processes. Researchers are creating smart materials that respond to specific oral conditions and developing hybrid systems that combine the strengths of different nanomaterials. In summary, amorphous nanomaterials hold great promise for advancing dental treatments through their unique properties and versatile applications. Clinically, these materials could improve the durability, bioactivity, and targeted drug delivery in dental restorations and therapies, leading to better patient outcomes. Full article

Composite materials based on polymethylmethacrylate (PMMA) and carbon nanoparticles are used in aviation, construction, medical and other fields of activity. Carbon nanotubes and carbon nano-dots are mainly used as carbon nanoparticles. Both carbon nanotube and carbon nano-dots are difficult to obtain materials with considerable cost. Amorphous carbon nanoparticles, on the contrary, are easy to obtain and have a low cost. The purpose of this work is to study the physico-chemical and biological characteristics of polymethylmethacrylate modified with amorphous carbon nanoparticles. Laser ablation was used to obtain the nanoparticles. Dynamic light scattering, measurement of the electrokinetic potential, TEM, AFM, and Raman microscopy are used to characterize nanoparticles. FTIR, MIM, AFM, UV-visual diagnostics, ROS tests, and biopolymer regeneration tests were used to analyze the combined sensors. The bacteriostatic effect was evaluated using turbodimetry, and the antibacterial effect was evaluated using precision cytofluorometry. Mammalian cells were examined using fluorescence microscopy. Carbon nanoparticles (CNPs) have been obtained and characterized. A protocol has been developed for the introduction of CNPs into photolithographic resin. Printed samples of complex geometry. It is shown that the printed samples are amenable to polishing, have pro-oxidant properties, and are able to prevent damage to biopolymers. Printed samples inhibit the development of bacteria and cause loss of viability. At the same time, the printed samples do not affect the development of mammalian cells. The obtained resins based on PMMA with CNPs can potentially serve as the basis for the creation of non-toxic materials in biomedicine and pharmacology. Full article

Lycopene is a potent antioxidant carotenoid with significant health-promoting properties. However, its practical application is limited by poor water solubility. This study aimed to enhance lycopene dispersibility through the development of solid dispersions obtained by hot-melt extrusion (HME). Polymeric carriers composed of polyvinylpyrrolidone K30 (PVP K30), phosphatidylcholine, and xylitol were designed to achieve optimal processing conditions and thermal stability. Nine formulations containing 10–30% lycopene were prepared and characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FT-IR), and dispersibility testing. TGA confirmed the thermal stability of lycopene at the extrusion temperature (150 °C). DSC and XRPD analyses indicated partial amorphization of lycopene in the extrudates, while FT-IR spectra revealed molecular interactions between lycopene and carrier components, particularly hydroxyl and carbonyl groups. Among the tested systems, the formulation containing PVP K30 and xylitol without phosphatidylcholine exhibited the highest dispersibility (1.0484 mg/mL after 3 h). Dispersibility decreased with increasing lycopene content. These findings demonstrate that HME is an effective technique for producing partially amorphous lycopene dispersions with improved dispersibility, and that polymer–polyol systems are particularly promising carriers for enhancing lycopene bioavailability. Full article

A series of poly(5-n-butyl-2-norbornene) oils with controlled molecular weights was synthesized via metathesis polymerization, fully hydrogenated, and characterized in terms of viscosity and tribological performance. In contrast to established lubricant base stocks—such as poly(α-olefins) and multiply alkylated cyclopentanes—these novel norbornene-based polymers remain underexplored, despite their promising anti-wear activity. Based on differential scanning calorimetry (DSC) data, all the synthesized products are amorphous compounds whose thermograms show a single glass transition temperature. The effect of molecular weight and temperature on the viscosity of poly(5-n-butyl-2-norbornene) oils was quantified over an extended temperature range, including extra-cold conditions down to −80 °C. The pour points of the oils were determined and can be as low as −66 °C, indicating excellent low-temperature fluidity. The tribological performance of the synthesized oils was evaluated using the four-ball test, with friction coefficient and wear scar diameter measured to assess anti-wear and antifriction properties. The tribological results were benchmarked against commercially available polyalphaolefin (PAO) oils (PAO-4, PAO-20, and PAO-80). Metathesis and hydrogenated poly(5-n-butyl-2-norbornene) oils outperform conventional PAOs by up to 67% in wear protection and 30% in friction reduction. These findings establish alicyclic molecular strain as a viable design parameter for next-generation lubricating oils, thereby expanding the toolbox for material development beyond conventional chemical functionalization. Full article

Diabetes mellitus is a serious public health problem, mainly due to the difficulty in healing chronic wounds, which present an inflammatory response for long periods of time and are more vulnerable to infections. Hydrogels are a promising therapeutic solution due to their biocompatibility, biodegradability, and ability to allow controlled release of therapeutic agents. The addition of bioactive glasses doped with therapeutic ions to hydrogels can also provide specific biological responses to the system and thus improve tissue regeneration. In this study, a hydrogel based on carboxymethylcellulose and polyethylene glycol with different degrees of crosslinking and enriched with 10% by weight of CeO₂-doped Bioglass 45S5 was developed. Structural, morphological, mechanical, and biological characterizations were performed on bioactive glass, hydrogels, and hydrogels enriched with bioactive glass. Structural analyses confirmed the preservation of the typical amorphous structure of Bioglass 45S5, even after the incorporation of 5% molar CeO₂, as well as the effectiveness of the polymer matrix crosslinking process. Structural analyses demonstrated the preservation of the typical amorphous structure of Bioglass 45S5, even after the incorporation of 5 mol% CeO₂, as well as the effectiveness of the polymer matrix cross-linking process. The hydrogels exhibited distinct behaviours in terms of water absorption and degradation, showing that the sample with the lowest concentration of crosslinkers and bioactive glass allowed for a higher expansion rate and a higher degradation rate. The hydrogel with 10 wt% BG did not compromise cell viability and showed structural integrity after being subjected to cyclic flexible deformations, indicating its safety and suitability for use in tissue engineering. Full article

Industrial wastewater can be reused in other everyday processes to help combat water scarcity worldwide. One contaminant in industrial wastewater is hexavalent chromium, which is highly toxic and can cause kidney, liver, and respiratory problems, making its removal vital. In this study, PLA-based films containing modified zirconia nanoparticles were developed via a solution-mixing process for hexavalent chromium adsorption. Obtaining the films involved two stages: the first was the chemical modification of ZrO₂ nanoparticles with thiamine hydrochloride (vitamin B1) using fixed-frequency ultrasound at an output of 750 W and 50% amplitude for 60 min. The second stage involved preparing the films by mixing them in the solution using an ultrasonic bath. The nanoparticle concentrations were 0.25, 0.5, and 1 wt%. The results obtained from characterization using Fourier-transform infrared spectroscopy (FT-IR) revealed the characteristic bands of PLA and the characteristic peak of the Zr-O bond corresponding to the ZrO₂ nanoparticles. Thermogravimetric analysis (TGA) showed that the ZrO₂ nanoparticles provided thermal stability to the PLA polymer. X-ray diffraction (XRD) showed a broad peak of amorphous PLA at 16.8° and signals corresponding to the crystalline phase of ZrO₂. The morphology of a cross-section of the films was observed using scanning electron microscopy (SEM), revealing a rough surface with pores. Finally, hexavalent chromium adsorption tests were carried out, measuring the adsorption efficiency under the parameters of pH, concentration, and contact time. The PLAZrO₂ sample achieved an adsorption efficiency of 83% at pH 2. Full article

Polymeric materials have become important components in prefilled syringes, drug delivery systems, and advanced medical devices. Background/Objectives: Nitrogen dioxide gas is used for the terminal sterilization of drug delivery systems. For the implementation of sterilization methods, compatibility with materials must be demonstrated such that the materials maintain product requirements and specifications after sterilization and at the time of use (i.e., product shelf life). Methods: Commonly used polymers were selected based on their chemical structures to provide insight into the nature of reactions that occur at the temperature and NO₂ concentration levels used in the sterilization process. After exposure to the NO₂ process, materials were evaluated for chemical, mechanical, and biocompatibility properties. Results: In this paper, we demonstrated the compatibility of polymers comprising carbonyl, unsaturated ester, and ketone groups which have been used in medical devices sterilized with NO₂. No significant chemical or physical changes were observed upon the treatment of Amorphous Polyester, Polysulfone (PSU), Polycarbonate (PC), PolyEtherEtherKetone (PEEK), PolyArylEtherKetone (PAEK), and Polypropylene (PP) with NO₂ at a sterilization temperature of 20 °C. At this relatively low sterilization temperature, the reactions of NO₂ with the polymer do not typically occur because the activation energies of these reactions require much higher temperatures. Conclusions: Not all materials will be compatible with NO₂ sterilization, and even with the established data, many devices will need to have their polymers evaluated for compatibility before moving to NO₂ sterilization. These results will provide guidance to device designers selecting materials for new drug delivery devices and to regulators that review the safety and efficacy of these devices. Full article

Hot-melt extrusion produces a solid dispersion (SD) containing a poorly water-soluble drug (k) and matrix polymer surfactant (PS), thereby enhancing k’s solubility. When dissolving the SD, the PS is first dissolved, forming micelles. The amorphous form of the solid phase k remains and is further dissolved by micellar solubilization. The goal here is to rigorously derive, on the basis of thermodynamics, a new expression for the change in the standard Gibbs free energy (${∆G}_{\Sigma }^0$). This change serves as a measure for increasing the degree of spontaneity in the dissolution of amorphous k from an SD with a polymeric surfactant relative to the dissolution of the crystalline-form k in an aqueous solution without surfactants (reference state). In the micelle-pseudophase model, it was found that ${∆G}_{\Sigma }^0$ depends on the natural logarithm of the ratio of mole fraction k in the aqueous phase to mole fraction k in the micellar pseudophase. In a simpler model, ${∆G}_{\Sigma }^0$ can be expressed as ln of the solubility ratio of the crystalline and SD forms, assuming that the activity coefficient depends on the process of incorporating k into the micellar particles and that the total amount of surfactants is many times smaller than the water amount, which is acceptable for polymeric surfactants with low values of the critical micellar concentration. Full article

Polypropylene (PP) is widely used and currently very little recycled. A promising method for recycling the PP present in plastic waste involves its selective dissolution and subsequent separation from undissolved compounds. We address here the fundamentals of PP dissolution. Specifically, we present a model that describes the different phenomena involved in the dissolution of semicrystalline PP and validate the model with the experimental results on the decrystallization and dissolution kinetics of PP pellets. The model provides detailed time-resolved and position-resolved information on composition (i.e., crystalline PP, amorphous PP, and solvent) and solvent diffusivity (which depends on composition) across the dissolving polymer particle, in different solvents and temperatures. Such information is unavailable experimentally or difficult to obtain. The key fitted parameters that capture decrystallization and polymer chain disentanglement decrease with increasing temperature following an Arrhenius relationship, with activation energies higher than that for crystallization and comparable to that for melt viscosity. Both decrystallization and dissolution times increase with particle size. For smaller particles, decrystallization and dissolution occur nearly simultaneously, while for larger particles, their interior remains solvent-poor and crystalline for longer times. This work offers insights into the interplay of decrystallization and polymer chain disentanglement during the time-course of PP dissolution. Further, this work facilitates the design and optimization of a dissolution–precipitation recycling process that can unlock value from the million tons of PP annually that is currently being landfilled or incinerated following its use. Full article