Physical Properties Of Polymeric Materials Research Articles

Theoretically predicting the solubility of polydisperse polymers using Flory–Huggins theory

Polydispersity affects physical properties of polymeric materials, such as solubility in solvents. Most biobased, synthetic, recycled, mixed, copolymerized, and self-assembled polymers vary in size and chemical structure. Using solvent fractionation, this variety in molecular features can be reduced and a selection of the sizes and molecular features of the polymers can be made. The significant chemical and physical dispersity of these polymers, however, complicates theoretical solubility predictions. A theoretical description of the fractionation process can guide experiments and material design. During solvent fractioning of polymers, a part of the polydisperse distribution of the polymers dissolves. To describe this process, this paper presents a theoretical tool using Flory–Huggins theory combined with molecular mass distributions and distributions in the number of functional groups. This paper quantifies how chemical and physical polydispersity of polymers affects their solubility. Comparison of theoretical predictions with experimental measurements of lignin in a mixture of solvents shows that multiple molecular features can be described well using a single set of parameters, giving a tool to theoretically predict the selective solubility of polymers.

Physical Properties of Isotactic Polypropylene Blended with Less Crystalline Polypropylene

AbstractThe physical properties of polymeric materials, which are mixtures of various molecules, are determined by the sum of their contributions. Industrially important isotactic polypropylene (iPP), which is produced using heterogeneous Ziegler–Natta catalysts, shows broader distributions of molecular weight and stereoregularity because of the multisite nature, compared to molecular catalysts. However, systematic studies on the effects of these distributions on physical properties are lacking, especially for variations in stereoregularity. In this study, polypropylene (PP) additives with various molecular weights and stereoregularities (and their distributions) are added to an iPP matrix to clarify the effects of low‐concentration components on the overall physical properties. The results indicate the importance of incorporating the PP additives into the crystal structure of the iPP matrix.

Co-based metal-organic framework with phosphonate and triazole structures for enhancing fire retardancy of epoxy resin

A phosphonate and triazole containing binary carboxylic acid ligand was synthesized via azide-alkyne “click” reaction, which was further coordinated with cobalt nodes to form metal-organic framework (MOF) containing two important fire retardant elements, phosphorus and nitrogen (PN-MOF). With the loading of 6 wt% PN-MOF in epoxy resin (EP), the peak heat release rate, average heat release rate, total heat release, and total smoke production of EP/PN-MOF composites dramatically decreased by 44.6%, 52.9%, 44.0% and 36.2%, respectively. Meanwhile, the limiting oxygen index increased from 24.3% to 29.8%. Thanks to the excellent catalytic activity of PN-MOF in carbonation and oxidation, the release of toxic gasses from the composites was significantly reduced, particularly, the production of CO was decreased by 48% in comparison with neat EP. In addition, the glass transition temperature and modulus of EP/PN-MOF composites were increased, suggesting a strong interfacial interaction between PN-MOF and EP matrix. Overall, this research provides an efficient strategy for the preparation of MOF-type flame retardant to simultaneously enhance the flame retardancy and physical properties of polymeric materials.

Tunable cross‐linked copolymer networks for improvement of physical performance

AbstractThe ability to tune the physical properties of polymeric materials through the different compositions in copolymer networks is suitable for the strategy of materials accompanied by combined high mechanical strength and stretchability simultaneously. Here, we developed a practical and straightforward strategy of a copolymer network structure via controlling the compositions of the acrylic‐based urethane copolymers of diurethane acrylate (DUA) and diurethane cyclic acrylate (DUCA) with hydrogen‐bonds through photo‐polymerization. The copolymer networks led to the development of a physically cross‐linked structure between the amide groups of DUA and/or DUCA and the hydroxyl groups of pentaerythritol ethoxylate (PEEL) by hydrogen‐bonds. Based on the rheological analysis, the composition of the copolymer networks had a significant effect on the control of physical properties and development of cross‐linked structure and thus led to the tunable comprehensive properties including high elastic modulus, high chain mobility and high recovery performance with a higher proportion of DUCA in the copolymer networks. Consequently, the tunable copolymer networks based on the developed physically cross‐linked structure can improve the elastic properties, recovery performance, and healing ability simultaneously, providing significant progress in the fields of coating and adhesive.

Structural Ensemble of Molecular Chains in Isotactic Polypropylene under Cylindrical Confinement

Helical chain assembly has a great influence on the physical properties of polymeric materials. It has been known that the newly developed, anisotropic nanostructure of polymers in nanoconfinement ...

Precise structural analysis of polymer materials using synchrotron X-ray scattering and spectroscopic methods

Polymers can exist in many different conformations and exhibit a variety of unique and complicated hierarchical structures, which are dominated mainly by entropy and sometimes by kinetics rather than thermodynamics due to the intrinsic high viscosity, polydispersity, and so on. The physical properties of polymeric materials are determined not only by their primary structures but also by their higher order (hierarchical) structures. Hence, precise determination of the structures at all spatial scales is essential to control the physical properties of polymeric materials. This focus review details the use of various characterization techniques, including variable-temperature (VT) synchrotron (SR) X-ray scattering, VT SR X-ray diffraction, and infrared p-polarized multiple-angle incidence resolution spectrometry (pMAIRS), to determine the structure of fully liquid-crystalline ABA-type triblock copolymers, highly crystalline aromatic polyimides, and thin-film polyimides, respectively. The advantages of these methods are briefly reviewed, and the relationship between the macroscopic physical properties and the inherent microstructure is discussed. Physical properties of polymer materials are deeply related to not only the primary structure but also the higher ordered structure such as periodic structures and molecular orientation. If the target material consists of ordered and non-ordered region, the former structure can be selectively detected by X-ray scattering method, whereas structural information of both the regions is obtained by infrared absorption spectroscopy. Particularly for thin film materials, infrared pMAIRS (p-polarized multiple-angle incidence resolution spectroscopy) and GI-XRD (grazing incidence X-ray diffraction methods are very useful for precise structural analyses.

Generation of well relaxed all atom models of stereoregular polymers: a validation of hybrid particle-field molecular dynamics for polypropylene melts of different tacticities

ABSTRACT The tacticity of vinyl polymer chains strongly affects the physical properties of polymeric materials, as example the chain conformations and stiffness. In the present work we tested how the hybrid Particle-Field Molecular Dynamics (PF-MD) technique is capable to describe conformational differences of polymer chains as function of the tacticity. In particular, we focus on tacticity effect of atactic, isotactic, and syndiotactic polypropylene (PP) homopolymer melts. We found that PF-MD simulations exhibit dependence of Flory’s Characteristic Ratio from the fraction of racemo diads along the PP chains in qualitative agreement with Small Angle Neutron Scattering (SANS) experiments and theoretical previsions. Finally, we calculated and compared the packing length parameter on very high stereoregular syndiotactic PP systems with rheological measurements. A qualitative agreement between the calculated and experimental packing length is found.

The Influence of Relaxation Effects on the Physical Properties of Polymeric Materials

The nature of the physical properties of polymeric materials is considered. Data on relaxation processes in high-molecular-weight compounds are given. The dependence of mechanical losses on the structure of polymer systems is shown. The modification of polymers as manifested by a change in their relaxation properties is investigated.

Influence of Operating Conditions on Structure and Physical Properties of Polymeric Materials

The changes in structure and physical properties of polymeric materials that exploited in a long time with complex mechanical loads used in pipe systems for high-pressure cold water have been studied. A significant reduction in the mechanical properties of polymeric materials has been established. The most typical structural defects that occur in polymer materials during manufacture and in the exploitations, using electron microscopic studies identified.

The Mechanical Strength of a Mechanical Bond: Sonochemical Polymer Mechanochemistry of Poly(catenane) Copolymers

AbstractTopological molecular connections and structures, including physical entanglements in polymer networks, knots along polymer chains, and rotaxanes in sliding ring gels, have important consequences for the physical properties of polymeric materials. Often these topologies contribute through their ability to bear mechanical stress, but experimental measures of their relative mechanical strength are rare. Here, we use sonochemical polymer mechanochemistry to assess the relative mechanical strength of a multicatenane copolymer relative to copolymers of cyclic and linear analogs. The relative mechanical strengths are obtained by comparing the limiting molecular weights (Mlim) and contour lengths (Llim) of the polymers under pulsed ultrasound of their dilute solutions. The values of Mlim and Llim, and thus the inferred mechanical strengths of the polymers, are effectively identical. The mechanical bonds of the catenanes are therefore as strong, or stronger, mechanically as the covalent bonds along the polymer backbone.

The Mechanical Strength of a Mechanical Bond: Sonochemical Polymer Mechanochemistry of Poly(catenane) Copolymers.

Topological molecular connections and structures, including physical entanglements in polymer networks, knots along polymer chains, and rotaxanes in sliding ring gels, have important consequences for the physical properties of polymeric materials. Often these topologies contribute through their ability to bear mechanical stress, but experimental measures of their relative mechanical strength are rare. Here, we use sonochemical polymer mechanochemistry to assess the relative mechanical strength of a multicatenane copolymer relative to copolymers of cyclic and linear analogs. The relative mechanical strengths are obtained by comparing the limiting molecular weights (Mlim ) and contour lengths (Llim ) of the polymers under pulsed ultrasound of their dilute solutions. The values of Mlim and Llim , and thus the inferred mechanical strengths of the polymers, are effectively identical. The mechanical bonds of the catenanes are therefore as strong, or stronger, mechanically as the covalent bonds along the polymer backbone.

Predicting the Tensile Properties of UV Degraded Nylon66/Polyester Woven Fabric Using Regression and Artificial Neural Network Models

UV radiation is the major source of radiation in environmental conditions and affects many characteristics of exposed fabrics. Physical properties of polymeric material and fabric deteriorate when exposed to environmental conditions. The study of the changes in physical properties has been a major issue for researchers. Color absorption of degraded fabrics varies with exposure time. The main aim of this work was to predict the physical properties of UV degraded woven fabrics at different levels of exposure time. Samples of plain-woven fabrics were selected. The fabric consisted of nylon 66 as weft yarns and polyester as warp yarns. A UV light source was used to induce controlled degradation at different exposure times. The samples were dyed in identical conditions and the color values for all samples were measured using a spectrophotometer. The samples were then tested with tensile testing machine and stress-strain curves were obtained. Six parameters were considered in stress-strain curves. Exposure time caused the differences in the color values of the samples. This was used to evaluate the tensile behavior. Regression and artificial neural network methods were used to correlate each of the six parameters of tensile properties with color values. To validate the methods, experimental samples were tested with the tensile testing machine and the results were compared with the predicted values. The results show a good agreement between the experimental and predicted models.

Challenges in Multiscale Modeling of Polymer Dynamics

The mechanical and physical properties of polymeric materials originate from the interplay of phenomena at different spatial and temporal scales. As such, it is necessary to adopt multiscale techniques when modeling polymeric materials in order to account for all important mechanisms. Over the past two decades, a number of different multiscale computational techniques have been developed that can be divided into three categories: (i) coarse-graining methods for generic polymers; (ii) systematic coarse-graining methods and (iii) multiple-scale-bridging methods. In this work, we discuss and compare eleven different multiscale computational techniques falling under these categories and assess them critically according to their ability to provide a rigorous link between polymer chemistry and rheological material properties. For each technique, the fundamental ideas and equations are introduced, and the most important results or predictions are shown and discussed. On the one hand, this review provides a comprehensive tutorial on multiscale computational techniques, which will be of interest to readers newly entering this field; on the other, it presents a critical discussion of the future opportunities and key challenges in the multiscale modeling of polymeric materials and how these methods can help us to optimize and design new polymeric materials.

Investigation of Properties of Polymer/Textile Fiber Composites

Polymer-based composite structures have advantages over other materials. The most important advantage is the higher mechanical properties obtained from the composites when supported by fiber reinforcement. The mechanical and thermal properties of fiber-reinforced composite structures are affected by the amount of fibers in the structures, orientation of the fiber and fiber length. Silk and cotton fibers are used in many fields but especially in clothing and textiles. However, there is not enough research on their usage as reinforcement fibers in composite structures. Silk fibers as a textile material have better physical and mechanic properties than other animal fibers. It is very important that the improvement of the mechanical and physical properties of the composite structures allows them to be used in many areas. From economical, technological and environmental points of view, the improved the mechanical and physical properties of polymeric materials are receiving much attention in the recent studies. In this study, various lengths (1 mm–2.5 mm and 5 mm) of waste silk and waste cotton fibers were added to high-density polyethylene (HDPE) and polypropylene (PP) polymer in the mixing ratios of (polymer:fiber) 100%:0%, 97%:3%, and 94%:6% to produce composite structures. On the other hand, known lengths (1–2.5–5 mm) of waste silk and waste cotton fibers were added to recycled polyamide-6 (PA6) and polycarbonate (PC) polymers in mixing quantities of 100%-0%, 97%-3%. A twin-screw extruder was employed for the production of composites. Tensile strength, % elongation, yield strength, elasticity modulus, Izod impact strength, melt flow index (MFI), heat deflection temperature (HDT), and Vicat softening temperature properties were determined. In order to determine the materials' thermal transition and microstructure properties, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used. Results have shown that cotton and silk fibers behave differently than in the composite structure. Waste silk fiber composites give better mechanical properties than waste cotton fiber.

Properties of Recycled Polycarbonate/Waste Silk and Cotton Fiber Polymer Composites

Polymer-based composite structures have advantages over many other materials. The most important advantage is the higher mechanical properties obtained from the composites when supported by fiber reinforcement. The mechanical and thermal properties of fiber-reinforced composite structures are affected by the amount of fibers in the structures, orientation of the fibers and fiber length. Silk and cotton fibers are used in many fields but especially in clothing and textiles. However, there is not enough research on their usage as reinforcement fibers in composite structures. Silk fibers as a textile material have better physical and mechanical properties than other animal fibers. The improvement of the mechanical and physical properties of the composite structures allows them to be used in many areas. From economical, technological and environmental points of view, the improvement of mechanical and physical properties of polymeric materials are receiving much attention in recent studies. In this study, different application areas were chosen to evaluate the waste silk and waste cotton rather than classic textile applications. Waste silk and cotton and recycled polycarbonate polymer were mixed and as a result composite structures were obtained. Silk and cotton waste fiber dimensions were in between 1 mm, 2.5 mm and 5 mm. The recycled PC/silk and cotton wastes were mixed in the rates of 97%/3%. Mixtures were prepared by twin-screw extruder. Tensile strength, % elongation, yield strength, elasticity modulus, Izod impact strength, melt flow index (MFI), heat deflection temperature (HDT) and Vicat softening temperature properties were determined. To determine the materials' thermal transition and microstructure properties, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used.

Synthesis of Poly(lactic acid) with Branched and Network Structures Containing Thermally Degradable Junctions

Polyperoxide, as a new kind of thermally degradable polymer, is synthesized by the radical alternating copolymerization of a 1,3-diene monomer with oxygen. The introduction of polyperoxide units into any other polymer is useful for the fragmentation of polymers and a change in the physical properties of polymeric materials. In the present study, we demonstrate the synthesis and fragmentation of poly(l-lactic acid) (PLLA) modified with thermally degradable branching and cross-linking points, which consist of a repeating polyperoxide structure as the degradable junctions. We prepared several PLLA with a dienyl group at the α- and/or ω-chain ends by the anionic and metal-catalyzed polymerizations of l-lactide. Radical alternating copolymerization of the mono- and difunctional PLLA with oxygen was carried out to obtain branched polymers and gels. These branched and cross-linked PLLA materials readily degraded upon heating to yield linear PLLA chains.

Thermal degradation of polyethylene film materials due to successive recycling

Mechanical recycling of plastic film involves subjecting plastic materials to a series of heat cycles that can potentially degrade the material, causing brittleness and increased melt viscosity. Plastic film recycling in the UK is in its infancy, in need of an increased understanding of how the physical properties of polymeric materials change before and during the process. Reliable data are required to estimate the behaviour of such film products when recycled. Measurements were made as to the changes in physical properties of four different varieties of polyethylene (PE) film products when subjected to a series of successive simulated heat cycles and evaluated after each step. Results showed that although changes in tensile properties were fairly small, changes in processing properties such as melt-flow index for highly branched or low-density PE are substantial and could be a concern during recycling operations.

The influence of biological factors on properties of some traditional and new polymers used for fermented food packaging

Packaging makes food more attractive and convenient in use. It also secures greater safety of the food against biological and chemical changes. Packaged foodstuff can enjoy longer shelf life. On the other hand, the food may become contaminated with components or degradation products of plastic packaging materials. Some chemical and physical properties of polymeric materials may change due to temperature changes, low pH, mechanical stress, and the presence of oxygen. Chemical changes of polymers are the source of food contamination. In certain situations, decomposition products from additives and monomers may migrate into the foodstuffs. Physical changes may occur as decreased structural, mechanical and barrier properties of the materials commonly used in food packaging. As a result, external microbiological and chemical contaminants may migrate through the packaging into the food. Till now, little information has been collected on the influence of biological factors on packaging properties. The paper discusses the effects of biological factors (lactic acid bacteria) on mechanical and morphological properties of plastics commonly used for fermented food such as cottage cheese. The preliminary investigations of bacterial biofilm forming on the polymer surface are also reported.

Analysis of the nonisothermal crystallization kinetics in three linear aromatic polyester systems

Melt or cold crystallization kinetics has a strong bearing on morphology and the extent of crystallization, which significantly affects the physical properties of polymeric materials. Nonisothermal crystallization kinetics are often analyzed by the classical Johnson–Mehl–Avrami–Kolmogorov (JMAK) model or one of its variants, even though they are based on an isothermal assumption. As a result, during the nonisothermal (e.g. constant heating or cooling rate) crystallization of polymeric material, different sets of model parameters are required to describe crystallization at different rates, thereby increasing the total number of model parameters. In addition, due to the uncorrelated nature of these model parameters with the cooling or heating rate, accurate modeling at any intermediate condition is not possible. In the present work, these two limitations of the conventional approach have been eliminated by exhibiting the existence of a functional relationship between cooling or heating rate and effective activation energy during nonisothermal melt or cold crystallization in three linear aromatic polyesters. Furthermore, it has been shown that when the JMAK model is used in conjunction with this functional relationship, it is possible to precisely predict the experimental nonisothermal melt or cold crystallization kinetics at any linear cooling or heating rate with a single set of model parameters.

Pré-tratamento físico: um procedimento importante para o aumento na resolução espectral em estudos de microestrutura de polímeros por RMN13C em solução

Em um material polimérico as variações nas propriedades físicas podem ser avaliadas pelo conhecimento da sua microestrutura. Os estudos de microestrutura em materiais poliméricos são geralmente realizados por ressonância magnética nuclear (RMN) em solução empregando o núcleo de carbono-13. Neste tipo de estudo a resolução espectral é muito importante e esta depende do preparo da amostra. Foi observado que um pré-tratamento físico permite obter uma melhor resolução espectral e, por conseqüência, informações mais detalhadas sobre os encadeamentos nas cadeias poliméricas podem ser obtidos. Isto facilita a determinação das estereoseqüências.