Mechanical properties of polymers. They are classified as bulk properties, or intensive properties according to thermodynamics. Because of its properties like high compressive strength, fast curing, high specific strength, and resistance to chemical attacks polymer concrete has found application in very specialized domains. New to this edition is coverage of polymer nanocomposites, and molecular interpretations Apr 18, 2022 · Polymers -- Mechanical properties, Composite materials, Composites, Polymères -- Propriétés mécaniques, composite material, Polymers and polymerization Publisher New York : Marcel Dekker Collection internetarchivebooks; printdisabled Contributor Internet Archive Language English The mechanical properties of a polymer are strongly dependent upon the Van der Waals interactions of the polymer chains, and the ability of the chains to elongate and align in the direction of the applied force. See full list on onlinelibrary. To get deep insights into the modifying effects of various nanofillers on mechanical and physical properties of polymer nanocomposites, the three basic aspects of processing, characterization and properties are critically reviewed in this paper. The number of chapters have increased from 52 to 63 to include novel polymeric structures, specifically rotaxanes and related materials, self-assembly materials, foldamer supramolecular structures, tribology, mechanical Apr 1, 2024 · The incorporation of the glass fiber into the polymer matrix and its exposure to irradiation improved the thermal stability, and dynamic-mechanical and physico-mechanical properties. Mar 30, 2021 · The mechanical characteristics of a polymer scaffold depend closely on the molecular weight and the crystalline properties of the polymer that also affect the degradation rate and mechanism . 2 gives some representative mechanical properties of common polymers at 25°C. In this paper, the methods for dynamic loading of polymers will be briefly reviewed. About this book. 3. Motions in small molecules dissolved in a solid polymer matrix can also be studied by mechanical measurements. In specific terms, building efficient interconnected In the second edition of Physical Properties of Polymers Handbook, each chapter has been extensively updated and revised. The mechanical properties of solid polymers. Elastic modulus is very much lower than for metals or ceramics Beyond the yield point sample deforms plastically. H. The brittle polymer (red curve) elastically deforms and fractures before deforming plastically. The mechanical behavior of polymer melts is rather complex because they are viscoelastic materials, and, consequently, their properties are time-dependent. Polymer properties depend of their structure and they are divided into classes according to their physical bases. Importantly, studies have shown that MOFs can be used to influence polymer structure, and polymers can be used to modulate Apr 9, 2020 · The mechanical properties of the polymer are strongly affected by the temperature. They are often transparent. INTRODUCTION. Semi-crystalline Properties. 4 and 28. 15 is from Z. Location Boca Raton. The number of chapters have increased from 52 to 63 to include novel polymeric structures, specifically rotaxanes and related materials, self-assembly materials, foldamer supramolecular structures, tribology, mechanical Apr 22, 2021 · Considering this trend, there is a need for exploration of the interrelated thermal and mechanical properties of these commercially produced polymer-based materials for flexible heat spreading The mechanical properties of thermoplastic elastomers (TPEs) consisting of 6-arm star block polymers with glassy, crystalline, or composite crystalline-glassy physical cross-linking (hard) domains were investigated and compared to the analogous linear triblock or pentablock polymers. British Journal of Applied Physics. Amongst these, poly methyl methacrylate (PMMA) is a polymer that is most commonly used in dental laboratories (to make orthodontic retainers and dentures and for repair), dental clinics (for relining dentures and temporary crowns), and industry (such as fabrication of Nov 16, 2020 · In order to improve their mechanical properties, natural polymers are crosslinked, grafted with monomers, or blended with synthetic polymers . The regime of linear elasticity is arguably the most Oct 1, 2019 · The molecular-weight distributions (MWDs) of polymers have a striking impact over their properties, from processability and mechanical strength to nearly all aspects of morphological phase Jul 30, 2019 · The mechanical properties of these polymers follow a similar trend to the thermal behaviour and are clearly dependent on the stereochemical makeup of the polymer’s backbone. M. In this paper, an overview of the study of mechanical properties of polymers will be presented. • Polymers are viscoelastic —some properties of both viscous liquids and elastics • The results Jul 20, 2023 · The effects of different silicon sources on the mechanical properties of silica aerogels are summarized. Print ISBN:9781444319507 |Online ISBN:9781119967125 |DOI:10. 1, Callister 7e. The high strain rate Jan 1, 2020 · The mechanical properties of polymers are different to those of metals or ceramics and are reliant on the polymer type used, molecular structure, molecular weight (MW), and degree of crystallinity, etc. The chapter discusses the role of some of the structural and external factors on the mechanical properties of polymers, including molecular Jan 25, 2016 · The mechanical properties of polymers are becoming increasingly important as they are used in structural applications, both on their own and as matrix materials for composites. Many physical and chemical properties describe how a polymer behaves as a continuous macroscopic material. 2 Institute of Polymer Processing, Montanuniversitaet Leoben, Otto Gloeckel-Straße 2, 8700, Leoben, Austria. A range of Texture Analysers varying Dec 10, 2021 · High‐performance polymers have proliferated in modern society across a variety of industries because of their low density, good chemical stability, and superior mechanical properties. Book. Mechanical properties such as tensile, flexural and impact strength, flexural modulus, elongation at break, and hardness of the irradiated composites were Mechanical test methods varied widely, and studies of the degradation of mechanical properties were performed under a variety of conditions, mostly in vitro rather than in vivo. The wide range in properties reflects variations involved in physical testing. By Robert F. Tobushi are summarized. Other phenomena, such as the propensity of polymers to form crazes can impact the mechanical properties. The course will start with an overview of Jan 1, 2013 · Table 4. The chapter discusses the role of some of the structural and external factors on the mechanical properties of polymers, including molecular This course will focus on the mechanical properties and behaviors of polymeric materials. 15, Callister 7e. May 22, 2021 · 1. Toughness. Sep 20, 2023 · 21/9/2023 7. Results: Depending on the density of the porous ceramic the flexural strength of PICNs ranged from 131 to 160MPa, the hardness values ranged between 1. MECH 221 lecture 20/2. Tensile testing The mechanical properties of polymers are a measure of the deformation resistance under an applied force. Semi-crystalline Jun 21, 2018 · Hierarchically packed network structure, (small-length-scale 2D network structure of graphene nanosheets)-in-(large-length-scale 3D network structure of homogeneously dispersed graphene nanosheets), is observed, which plays an important role in governing the mechanical properties of polymer nanocomposites. Dec 1, 2011 · In this paper, the mechanical properties of vapor grown carbon nanofiber (VGCNF)/polymer composites are reviewed. A typical plot of stress versus strain is shown in Fig. Introduction. In general, the polymer with large side group or containing aromatic structure on the main chain exhibits higher mechanical properties as compared with polyethylene. Sweeney, First published:17 October 2012. Landel , Lawrence E. As shown in Fig. Jan 1, 1990 · Branched polymers can be dissolved and they flow but they exhibit melt rheology which is quite different from that of linear polymers. 1GPa. stress is proportional to strain. Local main chain motions are particularly sensitive to antiplasticization. Polymers can be both thermal and electrical insulators. Search for more papers by this author. May 25, 2023 · Polymer composites play a critical role in today’s society, and their excellent mechanical properties and multifunctionality contribute significantly to achieving global carbon neutrality goals Jan 12, 2024 · As porous polymer materials with continuous epoxy skeletons and pores, epoxy monoliths exhibit unique mechanical properties and fracture behavior different from the bulk thermoset of epoxy resins. It is a broad subject that provides tools to engineers and scientist interested in understanding the behavior of polymer components and how their performance can be predicted and optimized. The results show that when the nanoparticle size larger than the tube diameter of PVAc A. Polymers can be processed in various ways to produce thin fibers or Nov 13, 2022 · The tacticity of a polymer chain can have a major influence on its properties. For many applications, the mechanical properties of a polymer are a key engineering requirement for their use, where strength and impact resistance of the polymer are common criteria. Jun 12, 2020 · Compared to carbon nanotubes (CNTs), graphene possesses high strength due to wrinkled surface texture caused by a high density of surface defects which benefits more contact with the polymer material than a rolled-up CNT. Every polymer has its own characteristics, but most polymers have the following general properties: Polymers can be very resistant to chemicals. The most commonly specified mechanical properties of polymers include stiffness and breaking stress, quantified in the table of properties and applications as flexural modulus and tensile strength. Several aspects of the mechanical properties of polymers are discussed. The mechanical properties of plasma polymers are evaluated as a function of selected parameters. Pool Your Strengths. Ward,J. 1-14 These studies have demonstrated that MD techniques can be effectively used to predict both structure and properties of polymer-based material systems. The paper starts with the structural and intrinsic mechanical properties of VGCNFs. A wide range of polymers are commonly used for various applications in clinical dentistry [1,2,3,4,5,6,7,8]. e. Mechanical Properties of Polymers. 5N (roughly equivalent to the requirements of ASTM C150 for Type I Portland cement) was used as binder. 1. GCN-based models provide reliable prediction performances for the glass transition temperature (Tg), melting temperature (Tm), density (ρ), and elastic modulus (E) with substantial dependence on the dataset, which is the best for Tg (R2 ∼ 0. Tensile stress (TS) is the stress at fracture. Edition 2nd Edition. The emerging area of responsive biointerfaces that are capable of mimicking natural surfaces are based on synthetic polymers, where the function and structure In this paper, an overview of the study of mechanical properties of polymers will be presented. This publication is licensed for personal use by The American Chemical Society. 10GPa and the elastic modulus between 16. eBook Published 16 May 2014. 5 and CD-8. Copyright © 2013 John Wiley & Sons, Ltd. Jan 1, 2020 · To study the influence of complex geometry on the mechanical properties of printed ceramics, four different truss systems were printed using DLP of preceramic polymer resin. Another important property is toughness, which is the energy absorbed by a polymer before failure—often as the result of a sudden impact. The slope of the curves is a thermal This volume was produced at the invitation of Derek Brewis who asked me to edit a text which concentrated on the mechanical properties of polymers. ii) Chain branching. The effect of free volume on side chain motions is small. The properties of polymers are also much more sensitive to temperature than those of other materials. The synthetic route and characteristics of polymeric materials are presented. In the present review, we have discussed and compared the various properties of CNTs (1-D) and graphene (2-D) obtained in experimental results. Two of the truss designs were Kelvin cell arrangements which deform by bending of beams, one design was an octet cell arrangement which deforms by stretching of beams, and Oct 1, 2013 · PA and PU/PA latexes were used as polymer modifiers. A short survey is given of the various types of molecular motions giving rise to mechanical loss peaks. 3 The mechanical properties of many polymers are dependent on their Apr 1, 2021 · 2. Introduction to Mechanical Properties: General Considerations. Elongation. D. Schematic stress–strain curve for a plastic polymer showing how yield and Polymers are viscoelastic materials, having the properties of solids and viscous liquids, which are time- and temperature-dependent. From the plot, it is clear that with increase in the temperature, the elastic modulus and tensile strength are decreased, but the ductility is enhanced. Providing an updated and comprehensive account of the properties of solid polymers, the book covers all aspects of mechanical behaviour. Two of the truss designs were Kelvin cell arrangements which deform by bending of beams, one design was an octet cell arrangement which deforms by stretching of beams, and Optical and scanning electron microscopy (SEM) was employed to observe the indented areas. SEM observations of the indentation The mechanical response of polymers is far more time dependent than that of crystalline materials. Viscoelastic effects (Chapter 15) are much more important in polymers than in metals or ceramics. The mechanical behavior is closely tied to the manner in which the polymer chains move relative to one another under load. They offer many advantages over conventional composites including balanced strength and stiffness, enhanced bending and membrane mechanical properties, balanced thermal distortion Feb 12, 2021 · Incorporating the mechanical bond into polymer architectures allows access to polymers with high-mobility elements, leading to unique material properties. Its behavior begins in the linear elastic Physical, Thermal, and Mechanical Properties of Polymers. Introduction to mechanical properties of polymer • The mechanical properties are highly dependent on temperature and time-scale of any deformation. 1002/9781119967125. An important factor in the accurate prediction of properties of material systems via MD is the selection of the atomic potential. wiley. The course will utilize fundamental solid and fluid mechanics to understand the response of bulk polymers (solid and liquid, above and below Tg). Additionally, the accurate prediction of elastic modulus has been a long-standing difficulty owing to the Jun 22, 2023 · Physical Properties of Polymer. These properties in turn depends on the fabrication method and testing procedure utilized for reporting the values of particular property [11]. 1, the volumetric behavior (volume-temperature dependence) of a polymer is different in different physical states (glassy, rubbery, melt), and it is a function of temperature and pressure. Nielsen. Published 1966. The deformation of polymeric materials is a complex phenomenon that is influenced by many factors including the type of stress, strain rate, type of polymer, characteristics of polymers such as MW, chemical composition, degree of Oct 8, 2020 · 1. Jun 14, 2022 · Abstract. Dec 11, 2022 · Polyurethane elastomer is a kind of polymer material made from polyisocyanate and macromolecular polyol, which has good chemical and mechanical properties and is widely used in many fields, such as the automobile industry, the printing industry, the leather industry, and so on [1,2,3]. (Fig. These include linear and non-linear viscoelastic behaviour, anisotropy, rubber-like elasticity, breaking and cold drawing. The degradation of a polymer under environmental conditions is called biodegradation and involves changes in the structural, chemical and mechanical properties of the polymer to the final stage where compounds such as water, carbon dioxide, minerals and intermediates (such as biomass and humic materials) remain. Abstract. Properties of polymers, as in the case of any chemical compound, are highly dependent on the structure of the polymer chains and the molecular weight resulting from the number of units covalently bonded. Similarly, the cellulose nanofibers were synthesized from agro wastes like May 15, 2019 · This video will help you to measure and define strength, toughness, hardness, brittleness, stiffness, and flexibility of polymeric material from stress-strai In the second edition of Physical Properties of Polymers Handbook, each chapter has been extensively updated and revised. TS may be less or greater than the yield strength. (1) Characteristics of shape memory alloy heat engine, (2) Thermomechanical properties . This paper focuses on the filament extrusion method and presents a comparison of two modes: multi-material single mixing nozzle and multi-material multiple nozzles, thereby linking technology with the mechanical properties. Dec 5, 2023 · Using the multiscale model, we further analyze the individual effects of the polymer matrix and particle filling on the mechanical properties of the polymer composites. Thermoplastic polyurethane (TPU) is a polymer material that has high ductility, good biocompatibility and excellent abrasion resistance. This is why there's a big graph on your right. For many applications, desirable properties are known; however, achieving them has been challenging. Jan 17, 2019 · Understanding the effect of pressure on behavior of polymers is therefore of paramount importance. , John Wiley and thermoplastic polymer, both elastic and plastic (or viscous) deformation occurs. The mechanical properties of a series of polymer nanocomposites (PNCs) of polyvinylacetate (PVAc) and carbon dots (CDs) with average diameters of 2. The deformation process depends on both time and the rate at which the load is applied. 9 Abstract. Polymer mechanics is the study of how the mechanical behavior of polymers depends on external load environments. Melting Point and Boiling Point – Polymers have a high melting point and boiling point. Apr 4, 2024 · The physical properties of polymers are intimately related to the structural evolution in the crystallization process and also the structural changes in the samples subjected to an external field. Polymers are usually described as viscoelastic materials, which emphasizes their intermediate position between viscous liquids and elastic solids. The mechanical properties of polymers such as impact behavior, tensile test, bending test, and thermal properties like mold stress-relief distortion, generic thermal indices Feb 14, 2020 · The glass transition temperature (T g) of conjugated polymers governs chain dynamics and mechanical properties. Mechanical properties 1. Modulus. These properties open a pathway to manufacturing functional TPU parts for applications in various fields such as aerospace engineering, medical devices and sports equipment. Aromatic polyesters are characterized by polymer chains that do not have an aliphatic repeat unit such as ethylene glycol, 1,4-butane diol, or 1,4 Aug 1, 2021 · Characterization of the nanocomposites were performed using Scanning Electron Microscopy (SEM), and thermal properties were studied by TGA and DMTA revealed the thermo-mechanical degradation by the incorporation of fumed silica on both the polymers, PLA and PCL [113]. The techniques of characterization of mechanical properties of plasma polymers are summarized. This Review outlines the structure May 15, 2014 · Mechanical Properties of Polymers and Composites | Robert F. Mechanical Properties of Real Polymers. Furthermore, most polymers exhibit a distinct nonlinear behavior, which is particularly pronounced at the conditions of processing. Rheological Methods. tensile strength, flexure force, brittleness, compressibility) to name but a few. g. Repeated Some resin polymers available for three-dimensional (3D) printing are slightly elastic, which may be advantageous when used for full crown coverage of the primary teeth. Concrete methods and examples are introduced for these studies, making the book a useful and practical guide for young professional researchers Jan 1, 2022 · A balance of mechanical integrity, stiffness, flexibility, and materials performance is one of the most important tasks to be undertaken while designing the conjugated polymer (CP)-based optoelectronic devices. Moreover, the reaction mechanism of the three stages is also described. The impact of deformation rate and temperature on the mechanical response of polymers will be covered in detail. Jun 30, 2023 · Thermoplastic polyester films and fibers differ in their physical properties from extrusion-cast or injection-molded polyesters, owing to the orientation process involved in their manufacture. For example, synthetic polymer poly (vinyl alcohol) is used as a blending agent to increase the mechanical strength and flexibility of natural polymers [ 17 ]. Physical strength and durability depend on this property of polymers. Amorphous polymers are usually less rigid, weaker and more easily deformed. 3 Centre for Polymer and Material Technologies, Department of Materials, Textiles and Chemical Engineering, Ghent University, Technologiepark 130, 9052, Zwijnaarde, Belgium. In this study, two sets of data analyses are performed based on the designed composites. There are already many excellent books on the mechanical properties of polymers, and a somewhat lesser number of volumes dealing with methods of carrying out mechanical tests on polymers. Compared to annealed stainless steel, unreinforced biodegradable polymers were initially up to 36% as strong in tension and 54% in bending, but only about 3% as stiff Mar 1, 2019 · Abstract. This study was performed to evaluate the mechanical properties of two types of 3D-printed resin crowns in terms of strength and surface characteristics. Dec 29, 2013 · Polymer concrete was introduced in the late 1950s and became well known in the 1970s for its use in repair, thin overlays and floors, and precast components. Materials Science, Physics. Strength, toughness, and ductility are all mechanical Oct 17, 2012 · An introduction to the principal features of the chemical composition of polymer and physical structure. Generally, polymers are light in weight with varying degrees of strength. Various parameters can affect the mechanical properties of polymers, including molecular weight, processing condition, extent and distribution of crystallinity, composition of polymer, and application temperature. A discussion of future and current demands for the analysis of mechanical properties of plasma polymers is done. (aligned, crosslinked & networked polymer)-- plastic response (semi-crystalline polymers) Stress-strain curves adapted from Fig. Atactic polymers, for example, being more disordered, cannot crystallize. The deformation behavior of such materials in different length scales (molecular, mesoscopic, and macroscopic levels) can be optimized Aug 25, 2021 · A Texture Analyser gives a reliable way to test the mechanical properties of items by applying a choice of compression, tension, extrusion, adhesion, bending or cutting tests to measure a product’s physical properties (e. Tobolsky adhesion Appl ASTM behavior biaxial block polymers Chem coefficient compliance Composite Mater compression constant copolymer crack crazing creep cross-linking crystalline polymers damping peak decrease deformation degree of crystallinity density dewetting ductile dyn/cm² dynamic mechanical effect elastic elastomers elongation May 11, 2021 · In this paper, the applications of thermoplastic, thermoset polymers, and a brief description of the functions of each subsystem are reviewed. The green plot that a rigid plastics such as polystyrene, poly (methyl methacrylate or polycarbonate) can withstand a good deal of. The main subjects achieved are as follows. To facilitate quick tissue regeneration, the scaffold should have the right mechanical features and degradation rate with the bioactive surface. Sweeney. Hybrid composites have unique features that can be used to meet specified design requirements in a more cost-effective way than nonhybrid composites. Ward, J. One of the major breakthroughs in polymer chemistry occurred in the early 1950s when the German chemist Karl Ziegler discovered a group of catalysts that could efficiently polymerize ethylene. 2. Polymer nanocomposites have been investigated for about three decades. Then, five types of polymers that are commonly used to enhance the mechanical properties of silica aerogels are listed, and the current research progress is introduced. The details of the syntheses and physical properties of them can be found in the previous work [14]. Landel, L. 7. First Published 1993. Jastrzebski, The Nature and Properties of Engineering Materials, 3rd ed. Chapter5 Mechanical Properties of Polymers 聚合物的力学性能. Cement that satisfies the requirements of BS EN197-1:2000 for CEM I Portland cement of strength class 52. Oct 22, 2018 · Achieving polymer nanocomposites with high electrical and mechanical properties requires meticulous design of three segments: construction of strong and conductive nanofiller networks, appropriate polymer matrix, and good interfaces between the two components, as illustrated in Fig. Strength. Mechanical Properties of Polymers and Composites. Jul 30, 2019 · The mechanical properties of these polymers follow a similar trend to the thermal behaviour and are clearly dependent on the stereochemical makeup of the polymer’s backbone. Feb 22, 2013 · Properties of polymers, as in the case of any chemical compound, are highly dependent on the structure of the polymer chains and the molecular weight resulting from the number of units covalently bonded. Ian, I. Simultaneously these materials have been Oct 12, 2014 · Presentation Transcript. This includes finite elastic behavior, linear viscoelasticity and mechanical relaxations, mechanical anisotropy, non-linear viscoelasicity, yield behavior and fracture. stress, but Mechanical Behavior of Polymers. V. com Mechanical Properties of Solid Polymers: Third Edition. 15. Kantesh Balani, Kantesh Balani. If you've been reading much of The Macrogalleria you'll notice that we talk a lot about polymers as being "strong" and "tough" or maybe even "ductile". Jan 2, 2020 · The stark differences between the nature of MOFs and polymers has motivated efforts to hybridize crystalline MOFs and flexible polymers to produce composites that retain the desired properties of these disparate materials. polymers and polymer-based nanocomposites via MD techniques. The effects of covalent and Factors that influence the mechanical properties of polymers Molecular weight • σ TS often increase with Mw • Longer chains are entangled or anchored better %crystallinity: % of material that is crystalline • σ TS and E increase with %crystallinity • Annealing increases with %crsystallinity Predeformation by drawing Mar 15, 2017 · The mechanical properties of shape memory alloys, shape memory polymers and their composites studied by Prof. The blue curve is a plastic polymer and is similar to curves for many metals. Inset figures along elastomer curve (green) adapted from Fig. Polymers exhibit a wide range of stress-strain behaviors as shown in the figure below. Addition and condensation polymers are discussed, together with cross-linking, chain branching, molecular weight distribution and stereoregularity. Vivek Verma, Vivek Verma. An ideal linear elastic solid obeys Hooke’s law, i. Below T g, the storage moduli of conjugated polymers are on the order of one GPa Jan 1, 2017 · Abstract. 1, 2 These concerns persist for polymeric nanostructures, where mechanical properties are critical to feature stability. In terms of physical structure important issues are rotational isomerism within single chains Sep 16, 2021 · The mechanical response properties of materials, including therefore those of polymers, encompass a wide variety of very important physical behaviours exhibited under the effect of external stress loads (for example how much the material under consideration can be stretched or bent). It has long been known that these mechanical properties are dependent on strain rate, temperature, and pressure. In the solid state the mechanical properties of linear and t Laboratoire de Physicochimie Structurale et Macromoleculaire, Ecole Superieure de Physique et de Chimie Industrielles de Paris, 10 rue Vauquelin, F Increased crystallinity is associated with an increase in rigidity, tensile strength and opacity (due to light scattering). Author (s): I. Polymer networks are extensively utilized across numerous applications ranging from commodity superabsorbent polymers and coatings to high-performance microelectronics and biomaterials. We present machine learning models for the prediction of thermal and mechanical properties of polymers based on the graph convolutional network (GCN). Then the major factors (filler dispersion and distribution, filler aspect ratio, adhesion and interface between filler and polymer matrix) affecting Jan 21, 2020 · Multi-material 3D printing and process parameters optimization using multiple extruders are the significant challenges of fused deposition modeling (FDM). 05 and 2. Pub. E . Mechanical Properties of Real Polymers We've been talking abstractly for a long time, now, so it would probably be a good idea to talk about which polymers show which kinds of mechanical behavior, that is, which polymers are strong, which are tough, and so forth. 5 and 8. Tensile Strength – The strength of a polymer to elongate without breaking is its tensile strength. Three factors that influence the degree of crystallinity are: i) Chain length. The first set is to examine the effect of polymer matrix. 5 nm (denoted as CD-2. 5, respectively) or carbon black (N330) were investigated. Jan 1, 2020 · The crystallinity of the polymer regulates many properties such as piezoelectric performances (for polymers such as polyvinylidene fluoride), mechanical strength, and thermal stability. vg xa ny sw uj ni rm wd tv uj