DOWNLOAD PDF WETTING KINETICS AND POLYPROPYLENE-ALUMINUM BOND STRENGTH

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1 Chapter 1 : Metal oxide adhesion - Wikipedia The research accomplishments for this three-year metal matrix composite research program centered upon three areas: infiltration kinetics, wettability studies and predictions of interfacial. Weak Strong Figure 2: Wetting of different fluids: A shows a fluid with very little wetting, while C shows a fluid with more wetting. A has a large contact angle, and C has a small contact angle. The contact angle is determined by the balance between adhesive and cohesive forces. As the tendency of a drop to spread out over a flat, solid surface increases, the contact angle decreases. Thus, the contact angle provides an inverse measure of wettability. For water, a wettable surface may also be termed hydrophilic and a nonwettable surface hydrophobic. This is sometimes referred to as the " Lotus effect ". Similarly, the terms omniphobic and omniphilic apply to both polar and apolar liquids. Traditionally, solid surfaces have been divided into highenergy solids and low-energy types. The relative energy of a solid has to do with the bulk nature of the solid itself. Most molecular liquids achieve complete wetting with high-energy surfaces. The other type of solids is weak molecular crystals e. Depending on the type of liquid chosen, low-energy surfaces can permit either complete or partial wetting. For example, a surface presenting photon-driven molecular motors was shown to undergo changes in water contact angle when switched between bistable conformations of differing surface energies. William Zisman produced several key findings: This critical surface tension is an important parameter because it is a characteristic of only the solid. Knowing the critical surface tension of a solid, it is possible to predict the wettability of the surface. Differences in wettability between surfaces that are similar in structure are due to differences in the packing of the atoms. For instance, if a surface has branched chains, it will have poorer packing than a surface with straight chains. Lower critical surface tension means a less wettable material surface. Ideal solid surfaces[ edit ] An ideal surface is flat, rigid, perfectly smooth, and chemically homogeneous, and has zero contact angle hysteresis. Zero hysteresis implies the advancing and receding contact angles are equal. In other words, only one thermodynamically stable contact angle exists. When a drop of liquid is placed on such a surface, the characteristic contact angle is formed as depicted in Fig. Furthermore, on an ideal surface, the drop will return to its original shape if it is disturbed. Minimization of energy, three phases[ edit ] Figure 3: In equilibrium, the net force per unit length acting along the boundary line between the three phases must be zero. The components of net force in the direction along each of the interfaces are given by: Page 1

2 Chapter 2 : Bond Performance Variables The kinetics of joint formation, exemplified by the rate of wetting, is also important and can be measured by rate of change of contact angle, a process for which an empirical equation has previously been suggested. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Kinetics of emulsion polymerization of hydrophilic vinyl monomers in the presence of polyvinylpyrrolidone and technological principles of their synthesis are determined. Reasonable technological parameters in the synthesis of copolymers are determined. Physicochemical properties of the synthesized copolymers surface tension, the size of latex particles, and ph are determined. Synthesized graft copolymers were used to create high-adhesion polymer-monomer compositions. These compositions have high reactivity at room temperature. It can be regulated by the nature of the polymer matrix and the introduction of comonomers and fillers due to the influence of physicochemical factors on the process of polymer formation. The rate of polymerization and the degree of monomer conversion largely depend on the nature of the polymer matrix. The highest polymerization rate and the maximum degree of conversion are observed when using a copolymer of polyvinylpyrrolidone and polymethylmethacrylate. Materials based on the developed compositions are characterized by a low residual monomer content and high operational properties, such as surface hardness, Vicat softening temperature, and adhesive bond strength to supports of different nature. Introduction The contemporary development of science and technology requires the creation of new polymer materials with a corresponding set of special properties: These include low-toxic adhesive polymer-monomer compositions of medical and general technical purposes. Among the methods for preparation of such materials with the necessary properties the most interesting are those based on the modification of known industrial polymers in polymerization processes. These methods make it possible to obtain polymer materials with the preferable set of technological and operational properties at rather low material and energy costs. The determining factor for most of the technologies based on the preparation of modified polymeric materials is modifier. Polymers with high surface activity, good solubility in water and many aqueous organic media, high ability to complex formation, and high sorption characteristics are used as modifiers [ 1, 2 ]. Polyvinylpyrrolidone PVP and its copolymers belong to such polymers. Due to their specific properties, additional opportunities for improving modern technologies [ 3, 4 ], obtaining of new functionalized materials [ 5 ], and expanding the branches of their use are opened. Monomer-polymer compositions are widely used in a variety of industries especially as a basis for preparing materials with enhanced adhesion properties. Among such materials, acrylates based adhesives occupy a special place [ 6 ]. First of all, the increased interest in acrylates-containing glues is caused by their high operational properties: In this regard, these materials are widely used in a variety of industries, namely, in medicine, dentistry, construction, engineering, automotive, and electrical and textile industries [ 8 ]. It should be noted that the use of meth acrylic adhesives is expanding in current conditions to solve many technological tasks [ 9 ]. The main components of meth acrylic adhesives are meth acrylic monomers or polymers, initiating systems, hardeners, stabilizers, and modifiers. Methylmethacrylate MMA is often used as the main monomer in the meth acrylic adhesives. It provides high adhesive strength and is a good solvent for a number of polymers. When combined with oils MMA makes it possible to glue untreated surfaces. MMA has several disadvantages, in particular, high volatility, pungent odor, and fire risk. It is used in admixture with high boiling monomers such as hydroxyalkyl methacrylate, glycidyl methacrylate, and methacrylates of higher alcohols: The aim of the work is the development of functionalized materials based on graft copolymers of polyvinylpyrrolidone for high-adhesion methyl methacrylate-copolymer compositions. The kinetics of the emulsion polymerization of the test compositions were studied by dilatometric method for measuring the volume change of the reaction mixture during polymerization. The adhesive compositions were synthesized by the polymerization of MMA or a mixture Page 2

3 thereof with other monomers in the presence of synthesized copolymers at room temperature. To determine the properties of the adhesive compositions, a number of studies were carried out. The conversion degree of the monomer was determined by the bromide-bromate method. The surface hardness and Vicat softening temperature of the samples were measured on the Heppler consistometer. Adhesion was determined according to ISO Results and Discussion 3. The emulsion polymerization of vinyl monomers is mostly carried out in the presence of emulsifiers that are surfactants of different nature [ 13 â 15 ]. The nature of the emulsifier and its concentration in the reaction medium greatly influence the mechanism and kinetics of the polymerization and therefore the technological features of the process and its productivity. This influence is caused by changes in the interphase characteristics of the polymerization system, adsorption phenomena at the phase boundary, and changes in the solubility of monomers in the dispersion medium with the active participation of the emulsifier. Emulsifiers have to meet a number of requirements [ 13, 14 ]: Due to its properties and structure PVP can serve as an emulsifier in the processes of emulsion polymerization and also be an effective polymer matrix, which actively participates directly in the polymerization processes. It should be noted that the influence of the emulsifier on the regularities of the emulsion polymerization of vinyl monomers primarily resulted in change in the interphase characteristics of the polymerization system and the solubility of the monomers in the reaction medium. On the basis of the conducted studies, it has been established that PVP macromolecules exhibit high surface activity on the interphase surface of water-vinyl monomer. PVP has different effects on the total true and colloidal solubility of vinyl monomers in aqueous solution. Due to the increase of the PVP concentration up to 0. Obviously it is a consequence of specific intermolecular interactions in the system that will affect the polymerization processes in these systems. High surface activity and solubilization ability of PVP prove its high efficiency as an emulsifier in the processes of emulsion polymerization of vinyl monomers KKM PVP, 0. The effect of the monomer nature MMA and styrene, concentration factors, temperature, and stirring rate on the kinetic regularities the of emulsion polymerization process of vinyl monomers in the presence of PVP was established. Emulsion polymerization of vinyl monomers in the presence of PVP is characterized by a different rate depending on the nature of the monomer Figure 1. Degree and rate of emulsion polymerization of vinyl monomers in the presence of PVP: Page 3

4 Chapter 3 : Intermetallics In Soldering Eric Bastow Indium Corporation Blogs Solder Soldering Voidin Wetting was treated as a surface phenomenon, in which a surface reaction monolayer was sufficient to cause wetting. Aluminum matrix composite processing using the liquid metal route is complicated by the oxide barrier formed on the liquid metal. At least sixty pull-out tests were performed for each mortar totaling results. To measure the humidity a sample of still wet mortar was scraped from the layer on the back of each ceramic tile and weighed, giving the moist mass value Figure 2. The mortar was weighed a second time, revealing its dry-mass value. Precision scales 1 mg accuracy were used and 1. The results clearly show that immersion caused an important reduction in bond strength for all the mortars and that the additional day drying period allowed some recovery. Before immersion all mortars showed average bond strengths higher than 1. After immersion the values ranged from 0. These values are lower than those specified by EN [ 28 ] despite a likely increase in the mechanical strength of the cement matrix due to increased hydration of blast furnace slag and clinker phases of the cement. This reduction is usually attributed to the hydrolysis and swelling of the polymer film 30 which is important when using low porosity tiles such as those employed in the experiments. The VAE polymer content did not exert important influences B vs C bond strength results under saturated condition, as previously confirmed by Felixberger After a twenty-five-day drying period 63 days old, the mortars showed significant recovery in bond strength, reaching values higher than 0. A less than complete recovery was probably linked to the low porosity tiles used in the experiments seeing that Jenni et al. During the experiments the moisture content of the mortars varied from 2. All mortars produced similar behavior in reducing moisture content, including faster kinetics, during the first five days, followed by a period with lower rates. The large same day dispersion, was most likely caused by the manner in which the substrates were piled for storage. During wetting Figure 5, the water intake was slower than normally measured on porous materials as mortars and fit an almost linear function. This behavior is caused by the polymeric film phase, which has a hydrophobic characteristic and reduces capillarity 9, After 10 days of immersion the highest moisture content measured was in mortar A. As 10 days is a rather long period of immersion this value is probably related to an abundance of pores which resulted from the increased volume of entrapped air caused by the high content of MHEC 29, Figures 6 and 7 plot the bond strength versus moisture content. Figure 6a, b show drying results and Figure 7, the wetting. In all cases the higher the moisture content was, the weaker the bond strength was too. The typical profile measured can be divided into three parts: Despite different formulations and different wetting and drying conditions all the evaluated mortars produced similar profiles, but further results are necessary to confirm this behavior. No result higher than 0. A correlation index higher than 0. Bond strength equal to 1 corresponds to the minimum measured moisture content. Therefore, in regions of frequent rainfall, the mortar might never become completely dry. Consequently, reductions in mortar bond strength should be expected. Based on all results, Figure 9 presents a generic profile of the influence of moisture content on bond strength behavior. During wetting, reductions are faster and it only takes a few hours to degenerate mortar properties. It takes several days for the saturated mortar to become dry and recover. The dispersion is in function of the mortar properties. As frequently occurring localized failures in tiling system grout allow water infiltration, an increase in moisture content during service life and consequent adhesive performance decrease should be expected. A survey of materials used in external wall finishes in Hong Kong. Service life prediction of exterior cladding components under standard conditions. Construction Management and Economics. Cement and Concrete Research. Deformability and water resistance of C1 and C2 according to EN Stresses in ceramic tiling due to expansion and shrinkage effects. The influence of grout thickness on the adherence of ceramic tiling systems. Changes in microstructures and physical properties of polymer-modified mortars during wet storage. Cement and Concrete Composites. Microstructure of polymer cement concrete. Delf University of Technology; Influence of vinyl-versatic vivilelter copolymer on the microstructural of cement pastes. Pore size distribution Page 4

5 of hydrated cement pastes modified with polymers. Development of polymer films by the coalescence of polymer particles in powdered and aqueous polymer-modified mortars. Evolution of the film formation on the ceramic tile adhesive. Mechanical characterization of a styrene-butadiene modified mortar. Materials Science and Engineering. The Influence of different polymer types and concentration in dry-set mortar. The influence of moisture content on the transversal deformation of polymer modified mortar. Construction and Building Materials. Long-term performance of redispersible powder in Mortar. Cementitious adhesives performance during service life. Weathering effects on external wall tiling system. External wall tiling in tropical city of Singapore. Centre for Advanced Construction Studies; NBR â anexo C: Effect of wetting and drying on the behavior of polymer-modified cement materials. Some aspects of cellulose ethers influence on water transport and porous structure of cement-based materials. September 01, ; Revised: Page 5

6 Chapter 4 : Wetting - Wikipedia The preliminary approach has been to study the infiltration kinetics of molten aluminum alloys into green silicon carbide compacts and relate the results to the interfacial bond strength. November 11th, Intermetallics are a necessary evil in the metal-to-metal bonding world, which definitely includes soldering. We will focus just on intermetallics for the moment as that is the most pertinent to the soldering world. Many people confuse or interchange "wetting" for intermetallic formation bonding. Wetting is just wetting. In order for an intermetallic to form, some amount of the surface metallization must dissolve into the molten solder. For this reason, Sn tin has long been a critical component of solder alloys. Molten Sn tin is an excellent solvent of many other metals. And, conveniently for us, those "many other metals" include elements like copper, gold, silver and, to a lesser degree, nickel. The rates at which these other metals dissolve into molten tin solder will differ. Gold dissolves readily into solder; whereas nickel does so slowly. So, because the rate of dissolution is different for each metal, the rate of intermetallic formation is also different. It is important to note that the gold layer is very thin and only applied to protect the nickel from oxidation. When they make the change they sometimes encounter a number of issues such as incomplete wetting, poor bond strength, etc. As mentioned in my opening line, intermetallics are a necessary evil. Because they tend to be the most brittle part of the solder joint. Some intermetallics are more brittle than others. This should be taken into consideration when choosing a solder alloy for a particular metallization. For example, intermetallics that form between Sn and Au are often extremely brittle. Being brittle, they can be subject to fracture, etc. This is a case where more is not always better. Yes, you need an intermetallic to get a "bond". Believe it or not, the solder may not adhere well to its own intermetallic layer. Intermetallics are generally crystalline and chemically-stable structures Well, we first need to look at the reaction products. There are two basic types of reaction products that form the intermetallic layer between Sn and Cu. They are Cu3Sn and Cu6Sn5. In the f irst case there are 3 Cu atoms to every Sn atom and in the second case 6 Cu atoms to every 5 Sn atoms. In both cases the Cu is being consumed faster than the Sn atoms. Intermetallic formation is not only limited to the solder process. Metal atoms can diffuse even in the solid state. And that movement can cause the metal atoms to interact, react, and form intermetallics or cause the existing intermetallic layer to thicken. Whole books could be written on the topic. So, I am far from doing justice to the topic of intermetallics. Page 6

7 Chapter 5 : Surface Energy and Wetting ate the bond strength from the experimental results of wetting and reaction, work of adhesion (WAD) [15, 16] and push-off tests [] have been used. E is the binding energy of the material T is the temperature of the system S is the surface entropy of the material The binding energy favors a smoother surface that minimizes the number of dangling bonds, while the surface entropy term favors a rougher surface with increasing dangling bonds as the temperature is increased. As the temperature increases, the equilibrium concentration of lattice vacancies grows. Solid adsorption of an oxygen molecule depends on the heterogeneity of the substrate. Crystalline solid adsorption is dependent on the exposed crystal faces, grain orientations, and inherent defects because these factors provide adsorption sites with different steric configurations. Adsorption is largely determined by the reduction of Gibbs free energy associated with the exposed substrate. A dipole moment increases the surface Gibbs free energy, but the greater polarizability of oxygen ions as compared to metals allows polarization to decrease the surface energy and thus increase the ability of metals to form oxides. Consequently, different exposed metal faces may adhere weakly to non-polar oxide faces, but be able to perfectly wet a polar face. Defects[ edit ] Surface defects are the localized fluctuations of surface electronic states and binding energies. Surface reactions, adsorption, and nucleation can be drastically affected by the presence of these defects. Oxide growth is dependent upon the flux diffusion of either coupled or independent anions and cations through the oxide layer. Although there are only two valence states, there are three types: The presence of mobile electrons within the crystal lattice significantly contributes to the conduction of electricity and the mobility of ions. When the impurity element increases the adherence of the oxide to the metal it is known as the reactive element effect or RE effect. Many mechanics theories exist on this topic. The majority of them attribute the increase in adhesion strength to the greater thermodynamic stability of the impurity element bonded with oxygen than the metal bonded to the oxygen. Dislocations[ edit ] Dislocations are thermodynamically unstable, kinetically trapped defects. Surface dislocations often create a screw dislocation when stress is applied. In certain cases, screw dislocations can negate the nucleation energy barrier for crystal growth. Commensurate adsorption is defined by having a crystal structure relationship between substrate-adsorbate layer that produces a coherent interface. The difference between the resulting commensurate interfaces can be described as an effect of misfit. The positive trend seen shows as bonding increases, the force and stress required to debond the material does as well. The strength of the bond between the oxide and metal for the same nominal contact area can range from Pa to GPa stresses. The cause of this huge range stems from multiple phenomena dealing with at least four different types of adhesion. The main types of bonding that form adhesion are electrostatic, dispersive van der Waals or London forces, chemical and diffusive bonding. As the adhesive forces increase, separation in crystalline materials can go from elastic debonding to elastic-plastic debonding. This is due to a larger number of bonds being formed or an increase in strength of the bonds between the two materials. Elastic-plastic debonding is when local stresses are high enough to move dislocations or make new ones. The rate at which gas molecules strike the surface is a large factor in the overall kinetics of oxide growth. If there molecule is absorbed there are three potential outcomes. The surface interaction can be strong enough to dissociate the gas molecule into separate atoms or constituents. The molecule may also react with surface atoms to change its chemical properties. The third possibility is solid surface catalysis, a binary chemical reaction with a previously adsorbed molecule on the surface. Dispersion[ edit ] Most often it is kinetically favorable for the growth of a single oxide monolayer to be completed before the growth of subsequent layers. Dispersion in general can be modeled by: Chapter 6 : blog.quintoapp.com: Materials Science Page 7

8 In the present study, wetting kinetics, interfacial reactions and the formation of intermetallic compounds (IMCs) during solidification of SnAgCu solder alloy on Cu substrate and the corresponding joint strength were studied as a function of reflow time. Chapter 7 : The Bond Strength Behavior of Polymer-modified Mortars During a Wetting and Drying Process "Wetting out" means the adhesive flows and covers a surface to maximize the contact area and the attractive forces between the adhesive and bonding surface. A lower surface energy material, such as water, will spontaneously wet out a higher energy surface, such as the un-waxed hood of a car. Chapter 8 : Infiltration Kinetics and Interfacial Bond Strength of Metal Matrix Composites On HSE plastics, such as ABS or polycarbonate, adhesives flow more easily, wetting out the surface to form a strong bond. In contrast, most adhesives and tapes have a tough time sticking to LSE plastics, such as polyethylene or polypropylene. Chapter 9 : Synthesis and Properties of Adhesive Polymer-Methylmethacrylate Materials Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. The degree of wetting (wettability) is determined by a force balance between adhesive and cohesive forces. Page 8