Properties Of Polymer Products Research Articles

Optimal Printing and Post-Processing Modes of Polymer Products Manufactured Using SLA-Technology of Additive Мanufacturing

Innovative production technologies, such as additive synthesis, is inextricably linked with the development of methods for assessing the quality of manufactured products. At the initial stage of introducing of new production methods into various industries, the most studied and widely used control methods are usually used. In most cases these are standard destructive tests. As an alternative to standard tensile tests used to evaluate the elastic and strength properties of polymer products produced using SLA-technology, the dynamic indentation method is studed in this work. Using the samples of the high-temperature photopolymer resin High Temp RS-F2-HTAM-01, the possibility of optimizing 3D printing methods and post-processing modes based on dynamic indentation data is shown. It has been shown that non-pigmented photopolymers are most susceptible to embrittlement due to their ability to transmit UV radiation into the volume of the synthesized material. It was found that the embrittlement of a polymer material has a lesser effect on the result of measuring its dynamic hardness than on its tensile strength. It has been established that post-curing of polymer products at high temperatures (up to 160 °C) and UV radiation with a power of 39 W can increase their strength and elastic modulus by 170 % and 85 %, respectively, compared to the state before treatment. It has been proven that the sensitivity of the dynamic indentation method to changes in the physical and mechanical characteristics of products obtained using SLA-technology under various types and modes of their post-processing is comparable to the sensitivity of standard tensile tests.

Evaluating the Efficiency of the Tube Turbulent Apparatus Influence on Kinetics of Polymer Production Processes

Introduction. Because of high demand for polymer products, there are constantly modernized the technological aspects of their production, a huge share of which is based on the use of microheterogeneous catalytic systems. Physicochemical properties of polymer products can be improved through targeted hydrodynamic effect in turbulent flows. The study of physicochemical patterns of polymer product synthesis in the presence of modified catalytic systems is of great interest. Aim of the Article. The article is aimed at evaluating the efficiency of hydrodynamic influence in turbulent flows on the type of catalyst heterogeneity and the kinetics of polymer production processes. Materials and Methods. In the study of polymer synthesis processes, there is used a simulation approach to the system model description that is based on the idea of reproducing various scenarios of uninterrupted production and conducting the necessary empirical analysis. Parallel programming and cloud computing technologies are used in simulation modeling to increase computational speed. Results. A methodology for solving inverse problems has been developed to determine the influence of external factors on the kinetic activity and heterogeneity of active centers on the basis of known physicochemical information. The use of simulation modeling with the application of cloud computing technology makes it possible to unambiguously determine the type of kinetic heterogeneity in the conditions of averaging the reactive capacity of active centers. Discussion and Conclusion. Approbation of the new simulation approach to the solution of the inverse problem allowed evaluating the efficiency of the influence of the tube turbulent apparatus on the kinetics of producing polyisoprene in the presence of titanium catalyst and identifying the presence of two active centers: type ATi − lnM = 13.4, type BTi − lnM = 11.7, while the proportion of active centers type ATi is 0.91; type BTi – 0.09. Based on the data obtained, it becomes possible to formulate and solve inverse problems of identifying kinetic parameters for further model description of the system.

Using the method of calculating the total molar energy of cohesion to choose the most effective plasticizer

It is known that products made of polar, crystallized, and high-strength polymers (polyamides, polyesters, cellulose triacetate, polyvinyl chloride, etc.) lose their initial properties that reduce reliability and durability in the process of operation and even during long-term storage due to the increase in internal stresses in them caused by crystallization processes over time. To reduce the impact of such processes on the properties of polymer products, special substances are introduced into their composition, plasticizers, the selection of which is usually carried out empirically, which is not always successful. We proposed in this study to use the ratio of the calculated total molar volumetric energy of cohesion of the compound (the cumulative interaction of interatomic and intermolecular forces in the composition of the compound) to its molecular weight as the specific mass total energy of cohesion, which can be compared with a similar indicator for a plasticizing polymer. The use of such an approach makes it possible to purposefully, even before experimental verification, evaluate the suitability of using this or that compound, oligomer, or polymer as a plasticizer (or modifier), or develop a molecular structure of a new, necessary compound with the inclusion of certain groups in its composition for the purpose of further use as a plasticizer or modifier. In addition, there is an opportunity to monitor the influence of individual structural components of a new compound, oligomer or polymer, its molecular weight, side substituents and their nature on the value of the specific mass total energy of cohesion, as well as to reduce the time for performing research works in this direction and expenses for their implementation.

The Quality of Strengthening Impregnation of 3D-Printed Parts for Agricultural Machinery

It is noted that the level of mechanical properties of polymer products manufactured with the help of traditional technologies exceeds that of products made by 3D printing. The relevance of studying various methods of strengthening 3D printed products is shown, for example, the method of vacuum impregnation in epoxy compounds. (Research purpose) To determine the dependence between the quality of impregnation of 3D printed parts of agricultural machinery and the viscosity of the impregnating epoxy compound selected. (Materials and methods) The viscosity of the impregnating epoxy compound was changed by adding such diluents as acetone and DEG-1. The viscosity of the compound was measure by a rotational viscometer. The magneto drive pinion of the MTZ tractor starting engine and the auger pin support of the John Deere cutter bar were chosen as the objects for impregnation. The components were produced by a 3D-printer using FDM technology. After impregnation, the products were cut in certain sections to assess the existence of unfilled areas. The amount of resin hardened on the product surface was estimated. (Results and discussion) It has been found that acetone reduces viscosity 2 times more efficiently than DEG-1. Since acetone cost is lower, it was used for the subsequent experiments. For the impregnation of agricultural machinery parts, three levels of viscosity were chosen: the high level, corresponding to the 16 pascal-seconds initial viscosity of epoxy compound; the average level of 8.8 pascal-seconds, corresponding to the injection of 0.5 percent of acetone (by weight); the low level of 6.5 pascal-seconds, corresponding to the injection of 1.5 percent acetone (by weight). It was found that products impregnated with high and low viscosity compounds contained many pores in cross sections and a large amount of compound on the surface. (Conclusions) Based on the results of impregnation, the best composition proves to be that with the epoxy resin viscosity of 8.8 pascal-seconds corresponding to 0.5 percent of acetone (by weight). It is proved that the higher compound viscosity does not allow it to eff ectively penetrate into the product, at a lower viscosity, on the contrary, the compound leaks out of the product after impregnation.

Melt pre-shear induced orientation crystallization of PB and PB/HMwPB blend

Shear flow is important to understand the relationship between processing and properties of polymer products. In this work, the influences of shearing and high-molecular-weight polybutene-1 (HMwPB) on the evolution of oriented crystal's morphologies of isotactic polybutene-1 (PB) were investigated by shearing at a temperature slightly above the nominal melting temperature under different shear rate and shear duration. The shear thickening presented in primary normal stress revealed the presence of a gel-like network of shish-precursors, in which a birefringence region was observed in polarized optical microscopy (POM) images after crystallization in both PB and PB/HMwPB blend. Those shish-precursors enhanced the crystallization temperature and directly influenced the crystal structures of PB form II, and these crystal structures could be preserved from the form Ⅱ to form Ⅰ. The rheological, one-dimensional scattering, and DSC data reach a plateau with the shear duration, indicating that all the PB chains achieve their ultimate oriented state. The addition of a small amount of HMwPB caused the earlier formation of shish-precursors, the higher crystallization temperature of PB form Ⅱ, thicker lamellae, higher melting temperature, and degree of orientation of PB form Ⅰ. • Shear conditions for different crystal structures formation were given. • Shish-precursors formation and oriented crystal evolution were investigated using rheology methods combining optical microscopy and scattering technology. • The effect of HMwPB on shish-precursors formation and oriented crystal evolution was investigated.

Influence of the thickness of the cured layer of photopolymer resin during SLA-printing technology on the elastic and strength characteristics of polymeric products of additive production

The possibility of using dynamic indentation method for measurement the elastic and strength properties of polymer products obtained by additive synthesis using the SLA-technology is considered. The sensitivity of the method to changes in hardness, tensile strength, and elastic modulus of products obtained by different printing modes with a thickness of the cured layer of photopolymer resin of 100, 50, and 25 microns has been estimated. A comparison is made of two main methods for calculating the physical and mechanical characteristics of a material according to the data of its impact loading diagram: an adapted classical method of mechanics of contact interaction, considering the geometric parameters of the deformed region of the material, and a method based on the energy characteristics of shock interaction. It was found that the highest sensitivity of the dynamic indentation method to changes in the properties of the additive polymer, depending on the thickness of its hardened layer, is provided when using an energy computational model for evaluating the properties of the material. The results obtained are the basis for the methods of non-destructive testing of polymer products of additive manufacturing by the method of dynamic indentation. The implementation of these techniques in portable measuring equipment is an alternative to standard destructive tests and will allow obtaining reliable data on the properties of the controlled material without the need to manufacture special witness samples.

THE AUTOMATED RESEARCH OF THE IMPREGNATION PROCESS OF ELASTOMETERS

The problem of field fuel depots remains unsolved today. Incomplete sealing of drain devices and leaks lead to material losses and contamination of the soil, the restoration of which requires considerable time and money. The article presents the overview of existing problems of fuel filling and sealing systems of containers for storage and transportation of petroleum products, fuels and lubricants. (Research purpose) The research purpose is developing a methodology and algorithm for studying the swelling process of polymer materials used in the transportation and storage of fuels and lubricants to determine their durability and residual life. (Materials and methods) The article presents the main disadvantages of drain devices. The statistical analysis of the rejection of tank boilers owned by JSC «PGK» has been performed. The main malfunctions that are the cause of the cistern rejection is a valve malfunction and a residue in the drain device cup, which indicates that the valve is leaky due to a leak in the sealing device. (Results and discussion) A typical technological process for the production of polymer materials samples is presented. Authors have developed technical equipment, selected processing methods for the manufacture of polymer samples and technological equipment. Experimental studies of the effect of hydrocarbons on polymer materials were carried out using traditional methods. The article presents the express methodology and the automated experimental setup, the approbation of which allowed us to speed up the studying process. The article proves the possibility of practical application of the proposed methodology and installation, which gives identical results on the destabilization of the physical and mechanical properties of polymer products operated in a carbon-hydrogen environment. (Conclusions) The proposed express method and the developed scheme of the automated control system are simple to manufacture and are necessary for farms using fuel and lubricants storages of any design from various materials. The results of the data obtained make it possible to predict the operating time and residual resource of polymer materials used in containers for transportation and storage of lubricants in the field.

JUSTIFICATION OF METHODS OF POLYMERIC WASTE PROCESSING IN AGRICULTURAL PRODUCTION

The development of industry has led to the unlimited technological application of polymers, ranging from plastic bags, rubber, fabrics, paper and other materials. Displacing traditional materials, polymer products began to be used in agriculture. Polymers are used to make films for soil cover (mulching), anti-hail nets, shaft bushings, gears, body parts, tanks for storage and transportation of fertilizers and working fluids and many other parts. The operational properties of polymer products are becoming more and more perfect, but at the same time the methods of polymer waste management and their utilization are being developed and complicated. Over time, they can no longer be used for their intended purpose, so they are discarded and sent to landfills, while polymers are valuable structural materials and their reuse will not only be positive for the environment, but can also become a profitable branch of the agro-industrial complex. Pellet production is one of the methods of recycling polymer waste, which in the future can be used for the production of new parts, as well as added to the composition of composite materials based on organic or mineral fillers. This article examines the problem of recycling polymer waste by improving their processing technologies. The analysis of existing methods of utilization and processing of polymeric waste generated in agriculture is carried out. Determination of physical and mechanical properties of polymer waste, in particular thermoplastics. Taking into account the received information, conclusions are made and the analysis of methods of utilization and processing of polymeric waste in secondary raw materials is carried out.

Evaluation of melt quality during polymer extrusion

Polymer materials are widely spread and used in all industry sectors. The operating properties of polymer products make them practically indispensable in various industries. They have acquired widespread popularity and their production volumes are predicted to grow every year. The extrusion of polymers is one of the main methods for their processing. The melt uniformity is one of the main factors that influence the quality of the products and is determined by the level of mixing, i.e., by the redistribution of additives in a dispersion medium when these additives are introduced into the main polymer. The influence of working conditions, geometry of working bodies and other parameters on the melt temperature uniformity was determined. Nowadays, there are a lot of methods for determining the melt uniformity. They can be used indirectly in or after the extrusion process and can be short or long lasting, which in fact determines the acceptability of each of the methods. To determine the melt uniformity, statistical evaluation methods, which have been verified by many experiments and are well known, are often used. The analysis showed that the mixing index is most sensitive among the criteria described. 
 Although statistical criteria of evaluating the melt uniformity are widespread, it is better to use parameters that allow the state of the mixture to be analyzed directly in the work process for the extrusion of polymers, to identify those that depend on the mixing process. Methods and criteria for verifying the melt quality were analyzed and potential use of their temperature uniformity for measuring and evaluating the melt quality directly in the extrusion process, to eliminate the costly sampling process, was determined.

The role of expansion angle and speed on shish-kebab formation in expansion pipe extruder head explored by high temperature rapid stretch

Morphology and microstructures play a significant role on properties of polymer products. Self-reinforced shish-kebab formed inside the products by elongational flow induced orientation can improve the tensile strength and pressure rating properties, and the density of polymers consisting of shish-kebabs is fairly below those filled with glass fibers, basalt and talc. The threshold parameters to form shish-kebab structure in a novel annular expansion pipe extruder head were determined by high temperature rapid stretch (HTRS) in this study. Different morphologies of HDPE specimens made under the conditions in expansion head by HTRS were studied by SEM, 2D-WAXD and 2D-SAXS, specimen 7 with 15° and 6 mm/s base speed has the optimal shish-kebab structure and specimen 10 with 30° and 5 mm/s has the best orientation parameter and the best shish structure. The DSC results agree well with the morphology results shown in the SEM images. The specimen 7 displays the highest tensile strength, increases about 187% compared with the reference specimen. These outstanding properties were attribute to the perfect and compact shish-kebab structures inside it. The results of HTRS can prove a direction guide for extrusion processing.

Influence of Poisons Originating from Chemically Recycled Plastic Waste on the Performance of Ziegler–Natta Catalysts

AbstractChemically recycled monomer feed streams from postconsumer plastic packaging waste are expected to contain impurities that act as catalyst poisons. This work investigates the impact of such impurities on a commercial fourth‐generation Ziegler–Natta catalyst system. A recycled monomer feed stream in two different procedures by adding representative catalyst poisons (pyridine and n‐butanol) in various quantities to the reactor setup is simulated. Measuring catalyst activity and molecular weight distribution (MWD) and performing kinetic and MWD deconvolution modeling, the impact of the catalyst poisons on polymer product properties at the microstructural level is evaluated. The results demonstrate that, beyond a certain concentration (120 ppm), catalyst poisons have a substantial impact on the activity levels of the catalyst system tested. MWD deconvolution modeling shows an influence of the poisons on the composition of the resulting polymer product in the form of a shift toward lower or higher molecular weights (depending on the procedure). This microstructural analysis highlights the importance of purifying chemically recycled monomer feed streams.

Adaptable Parallel Acceleration Strategy for Dynamic Monte Carlo Simulations of Polymerization with Microscopic Resolution

Properties of polymer products are determined by their microscopic structures. Dynamic Monte Carlo (DMC) simulation is a powerful tool to capture detailed polymer microstructures. However, the heav...

Effect of Reprocessing Cycles on the Morphology and Mechanical Properties of a Poly(Propylene)/Poly(Hydroxybutyrate) Blend and its Nanocomposite

Abstract The use of polymer blends and composites based on fossil-based and bio-based polymers has become an important environmentally protective alternative for common use and disposable plastics applications such as packaging, bottles and trays. The disposal of these more degradable products, however, may also harm the environment and, therefore, recycling these systems becomes relevant. Recycling involves reprocessing which can significantly change the morphology and properties of polymeric products. Therefore, this study deals with the effects of reprocessing cycles on the properties and morphology of blends and nanocomposites based on fossil and bio-based polymers. The systems investigated were: a) neat polypropylene (PP), b) a polypropylene/poly(3-hydroxybutyrate) (PP/PHB) blend and c) PP/PHB/organoclay nanocomposite compatibilized with polypropylene-g-maleic anhydride (PP-g-MA) and erucamide. These materials were submitted to up to seven extrusion cycles in a single screw extruder operating at 60 rpm. Samples were taken after the first, third, fifth and seventh extrusion cycles and their tensile properties and morphology were determined. Scanning electron microscopy indicated that two phases were observed in the blend which showed spherical PHB domains. The addition of clay, PP-g-MA and erucamide improved the adhesion between the nanocomposites components. X-ray diffraction analysis showed that crystallinity tended to increase with the number of reprocessing cycles for all systems investigated up to the fifth cycle and then tended to decrease. A 10% crystallinity increase was observed for neat PP in the fifth cycle. In general, the tensile properties of all systems decreased with reprocessing and the highest losses were observed for the PP/PHB blend after seven processing cycles with 50% and 37% decreases in stress at break and elastic modulus, respectively. Impact strength of the PP matrix and of the PP/PHB blend tended to decrease with reprocessing, except for the nanocomposite which showed a slight increase especially after the seventh processing cycle in which an 18% increase in impact strength was observed.

Effective methods for evaluating the properties of polymer products

The application of the acoustic method and the Vickers microhardness test allow obtaining information on the effect of processing conditions on the morphological features and properties of products made of ultra-high molecular weight polyethylene.

In situ visualization of crystal nucleation and growth behaviors of linear and long chain branched polypropylene under shear and CO2 pressure

Crystallization and foaming behaviors of a semi-crystalline polymer in conditions comparable to those found in polymer processing, where the polymer melt experiences shear under elevated pressures, are key for modeling polymer processes and predicting the final structure and mechanical properties of polymer products. We investigate the crystallization behaviors of two different high-melt-strength polypropylene (PP) resins using a novel high-pressure visualization system that was developed to capture the crystallization process of a plastic specimen under high pressure and controlled shear. In situ visualization results under isothermal conditions demonstrate that both linear and long chain branched (LCB) PP exhibit crystal growth rates and nucleation densities that increase with higher applied shear stress but reach an optimum value with increasing CO2 pressure. By selectively choosing processing conditions, we can enhance the formation of observable critical size nuclei and the exclusion of CO2 from the crystal growth front. Therefore, overall crystallization kinetics can be easily controlled through the effect of induced-shear stress and the presence of pressurized CO2.

Fabrication of natural cellulose films with pattern by viscosity regulation of its solution

The structure and properties of polymer film are greatly affected by the patterns on its surface arising from solution convection. Therefore, it is necessary to explore more detail mechanism of pattern formation. Herein, we have successfully designed variable patterns on the surface of cellulose films via roller coating method. The cellulose with three degrees of polymerization was used as raw material, and a solution of N,N-dimethyl-acetamide/lithium chloride (DMAc-LiCl) was selected as the solvent system. The pattern variations were controlled by the solution viscosity, which was affected by the degree of polymerization of cellulose, concentration and temperature of solution. The formation process of the pattern on cellulose film was in situ tracked by video recording with the help of carbon black tracker. It was found that the solution moved from the edge of the cell pattern to the center at a relatively lower viscosity (η < 8.06 Pa s), and finally formed a polygon pattern with the convex center. With the increasing of the solution viscosity (η ≥ 8.06 Pa s), the direction of its convection was completely opposite and a circular or circular-like combination pattern with concave center appeared on the surface of the cellulose film. The higher the viscosity, the larger the concave area. Moreover, the film with polygon pattern demonstrated excellent mechanical properties, and also exhibited a potential anti-counterfeiting value. These results could provide guidance in perfecting the theory of polymer fluid, and regulating the structure and properties of polymer products.

A comprehensive model for the micro and meso-scale level olefin polymerization: framework and predictions

A fundamental understanding of the heterogeneous olefin polymerization process is critical for imparting desired properties to the final polymer product. In this work, we have developed a comprehensive model integrating the meso-scale level intraparticle resistances to mass and heat transfer as well as the micro-scale level kinetics. The model formulation is based on the combination of the polymer flow model with the intrinsic kinetic model derived using the method of moments approach. The model is employed to study the effect of varying the mass transfer and kinetic parameters on the monomer concentration and temperature profiles inside the growing polymer macro-particle and the subsequent implications on the catalyst activity, polymer molecular weights and the polydispersity index (PDI). The simulation results showed that the steeper monomer concentration gradients in the polymer macro-particle arose on decrease of the bulk diffusivity (Db) and increase of the number of active sites. The model also predicted the interdependence between the radial monomer concentration and temperature profiles. Further, with appropriate choice of $$D_{\text{b}}$$ , the number of active catalyst sites, initial catalyst active site concentration and kinetic rate constants, the model predicted the catalyst activity exceeding 100 kg/g cat.hr and PDI values higher than 2. We showed that the model is capable of predicting the experimental reported polymer product properties for Ziegler–Natta, hybrid Ziegler–Natta/metallocene and supported metallocene catalyst systems.

Creep behavior and mechanical properties of isotactic polypropylene composites via twice melt injection molding

Abstract Nowadays, the improvement of injection molding technology development research is in great demand due to the limitation of convenient injection molding for structural engineering applications. For injection-molded products, oriented structure is ubiquitous. To promote the formation of oriented structure, exert a positive impact on the final mechanical properties of polymer products, an advanced injection molding process is used to achieve multiple shear melt in this work. Based on our previous work about melt multi-injection molding technology, to investigate the influence about oriented structure of composites attracted by higher shear stress, iPP/MWCNTs and iPP/β-NA composites were studied. Compared to traditional injection-molded samples, the addition of MWCNTs impede the formation of oriented structure. For iPP/β-NA composites, the higher flow shear stress inside the mold wall increase the overall crystallinity but restrain the growth of β-crystal.

Polymorphic Crystal Transition and Lamellae Structural Evolution of Poly( p-dioxanone) Induced by Annealing and Stretching.

Semicrystalline polymers usually undergo multilevel microstructural evolutions under high-temperature annealing and stretching deformation; this is essential to tailor the physical properties of polymer products in industrial processing. Here, we choose poly( p-dioxanone) (PPDO), a typical biodegradable, biocompatible, and bioresorbable polymer, as a model semicrystalline polymer and investigated its polymorphic structural transition and crystalline lamellar evolution under high-temperature annealing and stretching. High-temperature annealing caused the α'-to-α phase transition of PPDO, accompanied by the improvement of crystallinity ( Xc) and thickening of crystalline lamellae. Tensile strength and Young's modulus of PPDO increased but the breaking strain decreased as the annealing temperature increased. Stretch-induced phase transition of PPDO depended strongly on the initial structure and stretching temperature ( Ts). The α-form PPDO transformed into its α' counterpart during stretching at low Ts. This phase transition was irreversible and did not retain the α form with the release of stress. However, no phase transition took place for the α-form PPDO stretched at high Ts (≥40 °C). Original lamellae of α-form PPDO changed into the fibrillar lamellae during stretching via the melt-recrystallization mechanism.

Systematic Investigation of the Photopolymerization of Imidazolium‐Based Ionic Liquid Styrene and Vinyl Monomers

ABSTRACTThe use of ionic liquids (ILs) as media in radical polymerizations has demonstrated the ability of these unique solvents to improve both reaction kinetics and polymer product properties. However, the bulk of these studies have examined the polymerization behavior of common organic monomers (e.g., methyl methacrylate, styrene) dissolved in conventional ILs. There is increasing interest in polymerized ILs (poly(ILs)), which are ionomers produced from the direct polymerization of styrene‐, vinyl‐, and acrylate‐functionalized ILs. Here, the photopolymerization kinetics of IL monomers are investigated for systems in which styrene or vinyl functionalities are pendant from the imidazolium cation. Styrene‐functionalized IL monomers typically polymerized rapidly (full conversion ≤1 min) in both neat compositions or when diluted with a nonpolymerizable IL, [C2mim][Tf2N]. However, monomer conversion in vinyl‐functionalized IL monomers is much more dependent on the nature of the nonpolymerizable group. ATR‐FTIR analysis and molecular simulations of these monomers and monomer mixtures identified the presence of multiple intermolecular interactions (e.g., π–π stacking, IL aggregation) that contribute to the polymerization behaviors of these systems. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2364–2375