Melting Temperature Of Polymer Research Articles

The Effect of Stereocomplexation and Crystallinity on the Degradation of Polylactide Nanoparticles.

Polymeric nanoparticles (PNPs) are frequently researched and used in drug delivery. The degradation of PNPs is highly dependent on various properties, such as polymer chemical structure, size, crystallinity, and melting temperature. Hence, a precise understanding of PNP degradation behavior is essential for optimizing the system. This study focused on enzymatic hydrolysis as a degradation mechanism by investigation of the degradation of PNP with various crystallinities. The aliphatic polyester polylactide ([C3H4O2]n, PLA) was used as two chiral forms, poly l-lactide (PlLA) and poly d-lactide (PdLA), and formed a unique crystalline stereocomplex (SC). PNPs were prepared via a nanoprecipitation method. In order to further control the crystallinity and melting temperatures of the SC, the polymer poly(3-ethylglycolide) [C6H8O4]n (PEtGly) was synthesized. Our investigation shows that the PNP degradation can be controlled by various chemical structures, crystallinity and stereocomplexation. The influence of proteinase K on PNP degradation was also discussed in this research. AFM did not reveal any changes within the first 24 h but indicated accelerated degradation after 7 days when higher EtGly content was present, implying that lower crystallinity renders the particles more susceptible to hydrolysis. QCM-D exhibited reduced enzyme adsorption and a slower degradation rate in SC-PNPs with lower EtGly contents and higher crystallinities. A more in-depth analysis of the degradation process unveiled that QCM-D detected rapid degradation from the outset, whereas AFM exhibited delayed changes of degradation. The knowledge gained in this work is useful for the design and creation of advanced PNPs with enhanced structures and properties.

Polycaprolactone/ atorvastatin nanocomposite - A supplier for 3D printing and drug delivery systems

Atorvastatin (ATV) exhibits pleiotropic effects on bone tissue and cardiovascular diseases, among others. Improving ATV's effectiveness requires enhancing its bioavailability, possibly through prolonged drug release. This study produced polycaprolactone/ATV nanocomposites through Hot Melting Extrusion (HME) at 69 °C. HME altered the crystallinity of both ATV and PCL. The resulting filament can be employed in 3D printing near the polymer's melting temperature, preventing ATV thermal degradation. ATV release is extended for both the filament and the produced scaffold (2mgATV/g scaffold). Results indicate this filament's potential as a valuable resource for 3D printing personalized products aimed at ATV release.

Fate of Magnetic Nanoparticles during Stimulated Healing of Thermoplastic Elastomers.

We have investigated the heating mechanism in industrially relevant, multi-block copolymers filled with Fe nanoparticles and subjected to an oscillatory magnetic field that enables polymer healing in a contactless manner. While this procedure aims to extend the lifetime of a wide range of thermoplastic polymers, repeated or prolonged stimulus healing is likely to modify their structure, mechanics, and ability to heat, which must therefore be characterized in depth. In particular, our work sheds light on the physical origin of the secondary heating mechanism detected in soft systems subjected to magnetic hyperthermia and triggered by copolymer chain dissociation. In spite of earlier observations, the origin of this additional heating remained unclear. By using both static and dynamic X-ray scattering methods (small-angle X-ray scattering and X-ray photon correlation spectroscopy, respectively), we demonstrate that beyond magnetic hysteresis losses, the enormous drop of viscosity at the polymer melting temperature enables motion of nanoparticles that generates additional heat through friction. Additionally, we show that applying induction heating for a few minutes is found to magnetize the nanoparticles, which causes them to align in dipolar chains and leads to nonmonotonic translational dynamics. By extrapolating these observations to rotational dynamics and the corresponding amount of heat generated through friction, we not only clarify the origin of the secondary heating mechanism but also rationalize the presence of a possible temperature maximum observed during induction heating.

Further Step in the Transition from Conventional Plasticizers to Versatile Bioplasticizers Obtained by the Valorization of Levulinic Acid and Glycerol.

In the last two decades, the use of phthalates has been restricted worldwide due to their well-known toxicity. Nonetheless, phthalates are still widely used for their versatility, high plasticization effect, low cost, and lack of valuable alternatives. This study presents the fully bio-based and versatile glycerol trilevulinate plasticizer (GT) that was obtained by the valorization of glycerol and levulinic acid. The mild-conditions and solvent-free esterification used to synthesize GT was optimized by investigating the product by Fourier transform infrared and NMR spectroscopy. An increasing content of GT, from 10 to 40 parts by weight per hundred parts of resin (phr), was tested with poly(vinyl chloride), poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(lactic acid), and poly(caprolactone), which typically present complicated processability and/or mechanical properties. GT produced a significant plasticization effect on both amorphous and semicrystalline polymers, reducing their glass-transition temperature and stiffness, as observed by differential scanning calorimetry measurements and tensile tests. Remarkably, GT also decreased both the melting temperature and crystallinity degree of semicrystalline polymers. Furthermore, GT underwent enzyme-mediated hydrolysis to its initial constituents, envisioning a promising prospective for environmental safety and upcycling. Furthermore, 50% inhibitory concentration (IC50) tests, using mouse embryo fibroblasts, proved that GT is an unharmful alternative plasticizer, which makes it potentially applicable in the biomedical field.

A Novel In-Line Polymer Melt Viscosity Sensing System of Integrated Soft Sensor and Machine Learning

Real-time monitoring of melt viscosity is one of the many challenges faced in the polymer extrusion process. Viscosity is one of the important metric reflecting material properties during plastic process. However, viscosity is an indicator that can be evaluated by calculating the evaluation value through temperature, pressure, screw rotation speed, etc., but cannot be directly measured by physical sensors. Melt viscosity should be calculated at the exact melt temperature. Temperature sensors cannot accurately measure the temperature of the melt in the barrel. Soft sensing technique is the best solution for estimating material properties. It just needs some physical sensors and physical formulas. The proposed viscosity soft sensor consists of physical sensors, a temperature estimator, and a simulation analysis software for calculating material properties. Four physically temperature signals, one physically pressure signal, and the simulation properties data are used as the dataset for the temperature estimator. An ensemble machine learning model of temperature estimators consisting of Random Forests (RF) and Convolutional Neural Networks (CNN). Melt viscosity, shear stress and shear rate are calculated by physical formulas. Experimental results show that the proposed temperature estimator predicts that the temperature will reduce the MAE from 6.08 to 2.86. Compared with the current work, the prediction error rate of the soft sensor is also reduced from 4% to 1.1%. The proposed soft sensor can be used to better predict polymer melt temperature. Finally, according to the predicting results, the material property scatter chart of viscosity can be precisely plotted under the specific melt temperature. In the past, the melt viscosity could only be measured offline. The proposed method can be added as a plug-in to the existing process to achieve real-time viscosity monitoring.

Characterizing the temperature and strain rate dependent tensile strength of amorphous polymer by a theoretical model

AbstractThe temperature and strain rate dependent (TSRD) tensile strength of polymer closely concerns the service safety in wide temperature range and dynamic load. In this study, based on the decoupled modeling method, a theoretical model of TSRD tensile strength of amorphous polymer was established. The model quantifies the relationship between the TSRD tensile strength, Young's modulus, heat capacity, glass transition temperature and melting temperature of amorphous polymer. The model predictions demonstrated an excellent consistency with the experimental data. Furthermore, the influencing factors analysis regarding the TSRD tensile strength were conducted. This study contributes a theoretical method to conveniently predict the TSRD tensile strength of amorphous polymer, and would be helpful to the evaluation and application of polymer in extreme conditions.

Physicochemical fundamentals of processing solutions of thermoplastic poly(ether urethane)s to obtain fibrous-porous polymer composite materials

Objectives. To study the structure and properties of solutions of thermoplastic poly(ether urethane)s (PEUs) to inform their potential use in the production of fibrous-porous polymer composite materials with a given structure and set of performance properties depending on the field of practical application.Methods. The composition of PEUs was studied by attenuated total reflection infrared (ATR-IR) spectroscopy using a program for correcting the spectra on an IR Fourier spectrophotometer, as well by differential scanning calorimetry (DSC) using a heat flow calorimeter. The viscosity of PEU solutions was determined on a rotational viscometer.Results. The chemical composition of PEUs and the nature of the formation of hydrogen bonds were studied. An analysis of the spectra demonstrates the almost complete identity of the PEUs synthesized from the same 4,4'-diphenylmethane diisocyanate. In the studied PEUs of the Vitur and Desmopan® brands, as well as Sanpren, pronounced absorption bands characteristic of urethane groups involved in the formation of hydrogen bonds are visible in the region from 1702 to 1730 cm−1. The temperature transitions and thermal stability of the investigated PEUs were determined by DSC. The influence of the ratio of rigid and flexible blocks, as well as the nature of hydrogen bonds on the melting temperatures of polymers, was shown. Analysis of the DSC curves demonstrated all the studied PEUs to have high melting points ranging from 159 to 215°C. From the studied temperature dependences of the structural viscosity of thermoplastic PEUs solutions, all solutions were established to have a minimum viscosity anomaly; the value of the logarithm of viscosity depends on the chemical composition and structure of the initial PEUs. It is shown that the viscosity anomaly of PEU solutions can be reduced with increasing temperature.Conclusions. A comparison of the chemical composition, structure, thermal and rheological characteristics of thermoplastic PEUs with PEU solutions widely used for the production of fibrous-porous materials and coatings of Sanpren LQ-E-6 and Vitur R 0112 grades demonstrates their practicability as production materials and coatings having a predetermined structure and a set of properties depending on the requirements and operating conditions of finished products.

Nanoscale Melting of 3D Confined Azopolymers through Tunable Thermoplasmonics.

Phase transitions that are thermally induced by using light at the nanoscale play a vital role in material science. Enhanced optical heating sustained by resonant nanostructures can turn out to be insignificant when a higher thermal conductivity of a heatsink, regardless of the pumping intensity. In this Letter, we demonstrate an approach to control an operating temperature range due to excess heating of a structured heatsink. A design rationale has been performed by using a 2D array of TiN:Si voxels, consisting of stacked TiN and Si pillars. All the TiN nanoheaters responsible for enhanced light absorption at plasmon resonance are of equal size, and the height of the Si pillars varies to control heat localization. A height-dependent temperature rise of the Si pillars is found from Raman thermometry. Herein, for the first time, we have determined the melting temperature of azobenzene-functionalized polymers at the nanoscale using the tunable plasmonic metasurface.

Inside Cover: Efficient Polyester Hydrogenolytic Deconstruction via Tandem Catalysis (Angew. Chem. Int. Ed. 9/2022)

Commodity polyester plastics such as PET, PBT, and PEN are hydrogenolytically deconstructed to their starting monomeric carboxylic acids and light alkanes using a solventless tandem catalytic approach with two air- and moisture-stable catalysts, Hf(OTf)4 and Pd/C. These selective reactions operate near the polymer melting temperature under 1 atm H2 and are compatible with mixed plastics, as reported by Yosi Kratish and Tobin J. Marks in their Research Article (e202112576).

Degradation of Melt Electrowritten PCL Scaffolds Following Melt Processing and Plasma Surface Treatment.

Melt electrowriting (MEW) has been widely used to process polycaprolactone (PCL) into highly ordered microfiber scaffolds with controllable architecture and geometry. However, the integrity of PCL during specific processes involved in routine MEW scaffold development has not yet been thoroughly investigated. This study investigates the impact of MEW processing on PCL following exposure to high temperatures required for melt extrusion as well as atmospheric plasma, a widely used surface treatment for improving MEW scaffold hydrophilicity. The change in polymer molecular weight and melt temperature is characterized, in comparing unprocessed and processed samples, in addition to analysis of the mechanical and surface properties of the scaffolds. No significant difference in the molecular weight or mechanical properties of the PCL scaffolds is evident following 5 days of cyclic heating to 90°C. Exposure to plasma for up to 5min significantly increased hydrophilicity and surface adhesion force, characterized via contact angle and atomic force microscope, however, significant polymer degradation occurred evidenced by increased brittleness of the scaffolds. This study demonstrates the degradation of PCL following fabrication via MEW and surface treatment to guide the optimization of scaffold development for subsequent applications in tissue engineering and biofabrication.

Synthesis and Characterization of Lignin-graft-poly(ethylene brassylate): a Biomass-Based Polyester with High Mechanical Properties

Lignin is an important biopolymer that can be used as a raw material to produce functional polymers due to its abundance, low price, sustainability, and high concentration of aromaticity. However, lignin modification is not well understood or characterized, limiting its potential as a new sustainable raw material. The biopolymer lignin can be integrated with aliphatic polyesters to produce new biomass-based biodegradable polymers. Among various aliphatic polyesters, poly(ethylene brassylate) (PEB) is a relatively unexplored polymer with many advantages. PEB is low in cost and made from castor oil, making it a sustainable resource. In this work, we have synthesized a new lignin-containing copolymer, lignin-graft-PEB. The biopolymer lignin was chemically modified by sebacic acid to introduce a carboxylic acid functionality. Lignin’s abundant hydroxyl groups were used for its modification. Another precursor of the copolymer, PEB, was prepared by ring-opening polymerization of ethylene brassylate in the presence of the catalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). The condensation copolymerization of the modified lignin and PEB occurred by reactions between the TBD terminus of the PEB and the carboxylic acid of the modified lignin. A decent melting temperature (78 °C) of the new polymer enables thermal processing. The mechanical properties of the new lignin-graft-PEB can be conveniently controlled by changing the mass ratio of lignin and PEB and the molecular weight of PEB. The highest modulus of lignin-graft-PEB is 471.99 MPa, which is 3-fold higher than that of homoPEB.

A Computer Model of Starve Fed Single Screw Extrusion of Wood Plastic Composites.

In this study, we present a computer model of starve fed single screw extrusion of wood plastic composites (WPC). Experimental studies have been performed on the extrusion of the polypropylene (PP) based composites with various wood fiber contents (WF). The melting mechanisms of the composites in the extruder have been observed, and melting models have been proposed for partially and fully filled sections of the screw. It was observed that in the partially filled section the material is melted by conduction, as in the case of extrusion of neat polymers. On the other hand, in the fully filled section, the Tadmor melting mechanism appears, which is different compared to the melting mechanism of neat polymers at starve fed extrusion, where dispersed melting is observed. Using the melting models, the global computer model of the process has been developed which makes it possible to predict the process flow, i.e., the polymer melt temperature and pressure, the polymer melting rate, and the degree of screw filling. To build the model, the specific forward/backward procedure was developed, which consists in determining “forward” the melting profile, and “backward” the pressure and screw filling profile. The temperature profile in the melting section is computed “forward”, while “backward” in the metering section. This procedure makes it possible to solve the crucial problem of modeling of the starve fed extrusion process, which is to find the location of the point where the screw is fully filled, and the pressure is developed. The model has been tested by pressure measurements in the extruder.

Hybrid Approaches for Selective Laser Sintering by Building on Dissimilar Materials.

We introduced a new approach in selective laser sintering for hybrid multicomponent systems by fabricating the sintered polyamide 12 (PA12) part directly onto a similar (PA12) or dissimilar (polyamide 6 (PA6) and tool steel 1.2709) joining partner. Thus, the need for adhesive substances or joining pressure was completely circumvented, leading to the possibility of pure hybrid lightweight bi-polymer or metal–polymer systems. By taking advantage of the heating capabilities of the sinter laser regarding the substrate surface, different exposure strategies circumvented the lack of overlapping melting temperatures of dissimilar polymers. Therefore, even sintering on non-PA12 polymers was made possible. Finally, the transfer on metallic substrates—made up by selective laser melting (SLM)—was successfully performed, closing the gap between two powder-based additive processes, selective laser sintering (SLS) and SLM.

Antimicrobial and Physical–Mechanical Properties of Polyhydroxybutyrate Edible Films Containing Essential Oil Mixtures

In this study, three different combinations of essential oils (EO) of cinnamon, melaleuca and citronella were incorporated in polyhydroxybutyrate (PHB) films by conventional solution-casting method for food packaging applications. Although melaleuca and citronella EO films have been not demonstrated antimicrobial activity, they presented low UV transmission and high thermal stability. Films containing citronella and cinnamon EO or melaleuca and cinnamon EO, in turn, were active against all tested microorganisms and showed greater flexibility than pure PHB films. Aspergillus niger was the most sensitive microorganism to EO-based polymer films. Overall, the addition of EOs improved the thermal stability of films and reduced the polymer melting temperature as the result of its plasticization, affecting the elastic modulus and elongation at break of films. Taken together, these results suggest that EO-loaded PHB films could be used in designing of biodegradable active packaging for food products.

Study on rheological properties of in-mold co-injection self-reinforced polymer melt

The injection molding filling process is a complicated non-steady-state, non-isothermal non-Newtonian fluid flow process and heat transfer process. With the development of polymer melt pressure, temperature, shear rate and other physical quantities during the mold filling process will affect the melt rheological properties. This research combines the injection molding visualization device and analysis method to collect real-time online parameters of the co-injection self-reinforced parts in the mold under different molding conditions. The distribution and change data provide an effective means for better characterizing the rheological properties of the polymer in the mold and the theoretical analysis of the mold filling rheology. This article starts with the basic equations of viscous fluid mechanics, draws on the establishment of the mathematical model of the filling process of the conventional injection molding, corrects and resets the basic assumptions and boundary conditions, and establishes a flow that can reflect the melt flow at the slender scale. The basic equation of scale effect is made in the process, and it is substituted into the simulation software for simulation analysis. The results show that there is no deviation in the overall structure of the model, but the parameters in the model should be variable factors that change with the change of the melt molding parameters. Therefore, we made a second correction to the variable parameters of the in-mold co-injection self-reinforced cross-scale viscosity model. Although there is a certain difference (12.62%) between the viscosity results obtained after the simulation and the measured values, it is compared with the conventional model deviation value of the model (101.25%) has been better improved, which can better achieve the purpose of simulation prediction.

Effect of Alkali Hydroxide on the Properties of PTFE Graphite Bonded Aluminium Titanium Composite Sheet

This study focused on the effect of some alkali hydroxide on the properties of a composite sheet prepared by power spray coating of clean aluminium-titanium sheets with PTFE/graphite emulsion. The blank sheets were washed with hot water and dried at 80 °C for 5-6 minutes before power spraying of colorless polytetrafluoroethylene PTFE/graphite emulsion in perfluoro kerosene followed by hot-rolling under a pressure of 150-200 KPa at the temperature 50 °C higher than the melting temperature of the PTFE polymer (Du Pont). The obtained sandwich was sintered at 550 °C for a few minutes. Alkali hydroxide was added to the polymer emulsion before spraying. Results showed that temperature and time enhanced the extent of adhesion of the two metals to form a homogeneous composite metal sheet. Alkali hydroxide inclusion deteriorates the stability of the prepared sheet. The alkali effect was because PTFE is inactive material, Incompatible with molten alkali metals and alkali hydroxide. The disability of the alkali hydroxide to be incompatible with the polymer material experienced changes in its intrinsic properties. Alkali halides have insignificant effect. Alkali halides just displayed a filling in material.

The use of the phosphor of phosphogypsum as a filler for fluorescent polymers

In modern Russia and the CIS countries, phosphogypsum waste is an urgent environmental problem. This product is obtained in the production of phosphoric acid and is a large tonnage of low-recyclable waste. According to open sources, it is processed 20 times less than it is produced. Attempts to use it in cement production, in construction, in agricultural purposes do not lead to a cardinal fracture and it is still accumulating. In this regard, the topic of processing and use of phosphogypsum is an urgent topic. In the modern world there is a demand for bright luminescent colors, paints, consumer goods. An analysis of the literature showed that phosphors can be made from various chemicals, including metal sulfides. The purpose of the work is to study the possibility of obtaining a phosphor from phosphogypsum and its use as a filler-pigment for polymer products. The phosphor was obtained from phosphogypsum by the reduction of phosphogypsum with an organic substance. This phosphor was studied in polyethylene, polypropylene, polystyrene and other polymer matrices. It is shown to be compatible with polyolefins, polystyrene, polyvinyl chloride, nitrocellulose matrices; not compatible with epoxy matrices. It is shown that at the melting temperature of polymers this phosphor does not decompose, does not lose its properties. As a result of the work, conclusions were drawn about the possibility of obtaining a cheap phosphor filler, which is compatible with many industrial polymers. This phosphor can be used in toys, in the manufacture of special luminescent paint and consumer goods..

Changes in structure of PA6 during electron irradiation

The impact of electron irradiation on the structure of the PA6 polymer is researched in this article. The electron beam irradiation of samples from PA6 was carried out on an industrial pulse accelerator ILU-10 under different modes. Beam energy and radiation dose varied. The structural changes of PA6 were studied by scanning electron microscopy, X-ray phase analysis, IR Fourier spectroscopy, and the thermal characteristics of the polymer were studied by differential scanning calorimetry. It was revealed that after electron beam treatment, the melting temperature of the PA6 polymer decreases from 214 °C to 217 °C. It was found that electron beam treatment leads to a change in the surface morphology, that is, the surface becomes rough, the depth of the roughness and the structure of spherulites increase.

The Investigation Plasticizing Mechanism on Poly (vinyl alcohol)/Water/Caprolactam System and the Preparation of Raw PVA Fibers by Melt Spinning

A novel plasticizer system water/caprolactam (W/CPL) was applied in thermal processing of poly (vinyl alcohol) (PVA), water as the primary plasticizer and caprolactam as coplasticizer. The plasticizing mechanism of PVA/W/CPL system was investigated and the raw PVA fibers was prepared by melt spinning. The result showed that the melting temperature of PVA polymers decreased and the window of thermal processing has broaden due to W/CPL plasticizer. In addition, the raw melt-spun PVA fibers with circular structure and uniform structure had great potential application prospects in cement-based reinforcement.

The impact of non-vacuum electron beam treatment on the structure and properties of ultra-high molecular weight polyethylene

The results of work on the impact of electron beam treatment on the structure, mechanical properties, microhardness, and thermal stability of ultra-high molecular polyethylene (PE-UHMW) are presented in this work. Electron beam processing was carried out on an industrial impulse accelerator ILU-10. The samples were irradiated with electrons with energies of 2.5 MeV, 3.5 MeV and 4.5 MeV, and the radiation dose varied from 2MGy to 9 MGy. It was determined by the method of differential scanning calorimetry that the melting temperature of the PE-UHMW polymer practically does not change for all samples, regardless of the radiation dose. After electron beam treatment, the morphology of the surfaces of the PE-UHMW polymer is significantly improved, spherulites are formed at the micro level, which indicate the displacement of polymer molecules under the influence of irradiation. It was revealed that during electron beam treatment oxidation occurs as a result of chemical reactions of the polyethylene chain with oxygen O2. Significant changes in the mechanical properties of the PE-UHMW polymer were not observed after electron beam treatment. However, a significant decrease in the elongation from 300 % to 10 % as a result of radiation aging was observed after electron beam treatment.The hardness of the PE-UHMW polymer varies slightly in the studied mode of electron beam processing.