Dynamic mechanical analysis of adhesion between poly(vinyl chloride) and nitrile rubber

The degree of adhesion between poly(vinyl chloride) and nitrile rubber sheets depends on the contact time and temperature. Good adhesion is attributed to the compatibility of the two polymers which allows interdiffusion of the chains across the interface. The dynamic mechanical properties of the composites are found to vary according to the moulding conditions. The changes in the storage modulus and the loss tangent values of the composites with contact time and temperature are explained on the basis of the extent of adhesion and the molecular dynamics of the chains at the interface.     

High-pressure CO2-enhanced polymer interdiffusion and dissolution studied with in situ ATR-FTIR spectroscopic imaging

A novel application of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic imaging to study polymer interdiffusion and dissolution under high-pressure or supercritical carbon dioxide environments has been demonstrated. Miscible systems of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) of different molecular weights have been chosen for this investigation. These systems were subjected to a controlled pressure of CO₂ and the interfacial area of contact between the two polymers was studied by ATR-FTIR imaging in situ. Using this spectroscopic imaging approach, the phenomenon of polymer interdiffusion enhanced by CO₂ dissolved in both polymers was investigated as a function of time. The evolution of spatially resolved images as a function of time was studied with FTIR imaging and the corresponding concentration profiles for both polymers were obtained. The chemical specificity of FTIR imaging also allowed us to measure the amount of CO₂ dissolved in each domain of the polymer system. Effects of PEG molecular weight and pressure of CO₂ on the mechanism and the rate of polymer interdiffusion was investigated. This approach has not only shown the ability to visualise the process of interdiffusion but also demonstrated the ability of high-pressure CO₂ to ‘tune’ the rate of interdiffusion, this information is important for a better understanding of CO₂-induced mixing of polymeric materials.     

Interdiffusion in microlayered polymer composites of polycarbonate and a copolyester

The interdiffusion of two miscible polymers, polycarbonate (PC) and a copolyester (KODAR), was studied at temperatures from 200 to 230°C. The two polymers were coextruded as microlayer composites with up to 3713 alternating layers. The microlayer structure provided a large area of intimate contact between the two polymers with minimal mixing. Initially, two glass transition temperatures were observed by DSC that were intermediate between the glass transition temperatures of the pure components. Upon annealing, the glass transition temperatures shifted closer together, reflecting the extent to which inter-diffusion had occurred. After no more than 2 h of annealing, a single glass transition temperature was observed. A model was formulated based on Fick's law of diffusion that related the mutual diffusion coefficient, D, to the change in the glass transition temperatures. The model also incorporated an “equivalent” residence time to account for diffusion that occurred during the coextrusion process. It was not necessary to consider the concentration dependence of D to satisfactorily describe the data with this model. For the temperature range from 200 to 230°C, the value of D varied from 4.0 × 10^?16 to 1.6 × 10^?15 m²/s. The activation energy of interdiffusion was determined to be 95 kJ/mol. © 1994 John Wiley & Sons, Inc.     

Comparison of interdiffusion at polystyrene–poly(vinyl methyl ether) and polystyrene–poly(isobutyl vinyl ether) interfaces

The effect of polymer–polymer compatibility on interdiffusion at polymer interfaces with dissimilar mobilities was investigated by attenuated total internal reflectance infrared spectroscopy. The polymer pair consisting of polystyrene and poly(vinyl methyl ether) was used to study interdiffusion at the interface of compatible polymers. The polymer pair consisting of polystyrene and poly(isobutyl vinyl ether) was used to study interdiffusion at the interface of incompatible polymers. Results indicate that the extent of interdiffusion is controlled by the polymer–polymer compatibility parameter, irrespectively of the differences in the mobility of the polymers.     

Polymer-polymer interdiffusion during coextrusion

Polymer-polymer interdiffusion during coextrusion is considered theoretically from the point of view of interdiffusion between two melt streams flowing side by side in a film or sheet coextrusion die. It has been found that three factors, namely, molecular weight, the interaction parameter, and polydispersity have a profound influence on the interfacial layer thickness and adhesive bond strength of coextruded films and sheets. It is pointed out that when interdiffusion between two chemically dissimilar polymers takes place In stratified two-phase flow, the chain orientation in the flow channel greatly influences the rate of interdiffusion, and consequently the interfacial layer thickness and adhesive bond strength. Orientation factors for macromolecular chains in a steady shear flow field are expressed in terms of shear stress at the interface and the plateau modulus of each of the respective polymers being coextruded. As an illustration, we have used information on the self-diffusion coefficients for poly(vinylidene fluoride) and poly(methyl methacrylate) in the molten state, to estimate the interfacial layer thickness and adhesive bond strength of coextruded two-layer sheets, as affected by processing variables.     

Structure and Dynamics in the Interfacial Zone Between Partly Compatible Polymers

The interface between two partly miscible polymers is characterized by a finite interfacial region of width w comparable to the polymer size. The composition variation and in particular the time development of this restricted zone have recently been studied experimentally using a new depth-profiling approach based on nuclear reaction analysis. The results show w to vary quantitatively in a way consistent with mean-field models, while its time development appears to follow a power law w ∝ t^α, with the mean value of the exponent α = 0.34 ± 0.06 being significantly lower than its free interdiffusion value of 0.5.     

Interdiffusion during film formation of ionically cross-linked acrylics investigated with Förster resonance energy transfer (FRET)

Polymer interdiffusion is crucial to obtain continuous films from aqueous polymer dispersions. Here, interdiffusion in films from dispersions of acrylates which were ionically cross-linked prior to film formation was studied by Förster resonance energy transfer analysis. Dispersions of copolymers of n-butyl acrylate, methacrylic acid, and zinc dimethacrylate (ZnDMA) were investigated. ZnDMA was used as a co-monomer to ionically cross link the polymers during the synthesis. Ionic cross-linking does not prevent interdiffusion even at high gel contents. Interdiffusion data were compared with results of tensile tests on final films. Films of ionically cross-linked polymers fracture at both higher stress and strain than films of covalently cross-linked polymers. Further interdiffusion studies addressed effects of temperature and humidity. Both increased temperature and humidity accelerate interdiffusion of ionically cross-linked polymers. Thus, using ZnDMA allows for preparing dispersions which can form continuous films. Also, no volatile organic compounds are released during the film formation. © 2020 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48972.     

Reflection methods for the study of polymer interfaces

The direct study of polymer Interfaces is very difficult. Small angle scattering methods have been most successfully applied to block copolymer Interfaces where the morphology is well known. Other techniques such as electron microscopy, Rutherford back scattering, and forward recoil spectroscopy generally only give resolution of the order of 10 nm. Here we describe two techniques which have only recently been applied to polymer interfaces, neutron reflection, and spectro-scopic ellipsometry. Both reflection techniques examine planar samples and give compositional information in the depth direction. Neutron reflection gives a resolution of 0.5 nm and spectroscopic ellipsometry may give better than 5 nm. We will describe experiments using neutron reflection which measure the inter-facial thickness between two immiscible polymers and experiments using both techniques which measure the interdiffusion of miscible polymers. Other applications and limitations of the techniques will also be discussed.     

Neutron Reflectometry Characterization of Interface Width between Sol-Gel Titanium Dioxide and Silicon Dioxide Thin Films

Neutron reflectometry (NR) was used to directly measure the interface width between a titanium dioxide and a silicon dioxide film deposited by sol-gel processing. In a bilayer heated to 450°C, NR measurements showed that the interface width is 0.8 nm. This width is the same as the roughness of a sol-gel silicon dioxide surface after the same heat treatment, suggesting no interdiffusion or mixing at the bilayer interface.     

Deformation-induced bonding of polymer films below the glass transition temperature

Bonding between polymers through interdiffusion of macromolecules is a well-known mechanism of polymer adhesion. A new polymer bonding mechanism in the solid state, taking place at ambient temperatures well below the glass transition value (T_g), has been recently reported; in this mechanism, bulk plastic compression of polymer films held in contact led to adhesion over timescales of the order of a fraction of a second. In this study, we prepared various blends of plasticized polymer films with desirable ductility from amorphous and semicrystalline powders of hydroxypropyl methylcellulose and polyvinyl alcohol derivatives; then, we observed the bonding of these polymers at ambient temperatures, up to 80 K below T_g, purely through mechanical deformation. The deformation-induced bonding of the polymer films studied in this work led to interfacial fracture toughnesses in the range of 1.0–21.0 J/m² when bulk plastic strains between 3% and 30% were imposed across the films. Scanning electron microscopy observation of the debonded interfaces also confirmed that bonding was caused by deformation-induced macromolecular mobilization and interpenetration. These results expand the range of applicability of sub-T_g, solid-state, deformation-induced bonding processes.     

Oxygen-plasma-treated polypropylene interfaces with air,water, and epoxy resins: Part I. Air and water

Oxygen plasma treatment of polypropylene (PP) surfaces led to introduction of oxygencontaining functionalities, with consequent improvement of surface wettability. A combination of X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectroscopy (SSIMS), and contact angle measurements (water-in-air and air-in-water) allowed us to characterize the behavior of the treated surface in contact with air (low-energy surface) and water (high-energy surface). The treated surface showed the tendency to rearrange itself to minimize its interfacial energy. When contacted with air (low-energy surface), polar groups were buried away from the polymer/air interface, while in contact with water (high-energy surface) polar groups remained at the polymer/water interface. When contacted with air, the polymer surface layer rearranged by macromolecular motions within itself, since interdiffusion with the bulk polymer seems forbidden. These motions are thermally activated and it was possible to obtain an apparent activation energy (58.1 kJ/mol) close to those reported for other vinyl polymers.     

Solid-phase nanoreactor based on calix[4]resorcinarene: Gel diffusion kinetics of ion exchange

A nanoreactor effect is found that consists in a considerable (two orders of magnitude) increase in the rate of ion exchange in sulfonated calixarene-containing polymers. The kinetics of ion exchange in network calixarene-containing polymers with sulfonic acid and phenolic ionogenic groups is studied. It is shown that the interaction of these polymers with aqueous solutions of LiCl, NaCl, AgNO₃, LiOH, NaOH, and (CH₃)₄NOH is controlled by ion diffusion in the polymeric phase. An analytical dependence of the conversion on an interdiffusion coefficient and the time of ion exchange in bifunctional cation exchangers is derived using the spherical-layer model.     

Studies of polymeric systems for damping of vibrations in the sonic range

Closed-cell foams based on rigid polyurethanes blended with more viscoelastic polymers possess good vibration-damping properties. The damping characteristics of the various polymers differ, indicating that the chemical nature has an influence on the acoustical performance of the blend. Damping is also temperature dependent. By selection of polymers, foam effective for damping at various service temperatures and over various frequency ranges can be made. The damping characteristics of polymers can be changed by adding fillers. Such methods may be employed to achieve a broader damping peak at the desired service temperature. The damping of vibration of an aluminum strip could be increased by one to two orders of magnitude between 20°C to 60°C when the strip was coated with the experimental materials in comparison with commercial open-cell, elastic foams of comparable density. A dynamic resilience of only 9% was achieved.     

Evaluation of surface energy of solid polymers using different models

In the present work, contact angles formed by drops of diethylene glycol, ethylene glycol, formamide, diiodomethane, water, and mercury on a film of polypropylene (PP), on plates of polystyrene (PS), and on plates of a liquid crystalline polymer (LCP) were measured at 20°C. Then the surface energies of those polymers were evaluated using the following three different methods: harmonic mean equation and geometric mean equation, using the values of the different pairs of contact angles obtained here; and Neumann's equation, using the different values of contact angles obtained here. It was shown that the values of surface energy generated by these three methods depend on the choice of liquids used for contact angle measurements, except when a pair of any liquid with diiodomethane was used. Most likely, this is due to the difference of polarity between diiodomethane and the other liquids at the temperature of 20°C. The critical surface tensions of those polymers were also evaluated at room temperature according to the methods of Zisman and Saito using the values of contact angles obtained here. The values of critical surface tension for each polymer obtained according to the method of Zisman and Saito corroborated the results of surface energy found using the geometric mean and Neumann's equations. The values of surface energy of polystyrene obtained at 20°C were also used to evaluate the surface tension of the same material at higher temperatures and compared to the experimental values obtained with a pendant drop apparatus. The calculated values of surface tension corroborated the experimental ones only if the pair of liquids used to evaluate the surface energy of the polymers at room temperature contained diiodomethane. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1831–1845, 2000     

On the efficiency of internal lubricants for polymers under different sliding conditions

When polymers are used as bearing materials or are processed over tooling under dry sliding conditions, the formation of a transfer layer at the interface controls friction and wear properties. The film formation may be enhanced by the addition of internal lubricants. This article reviews some effects of internal lubricants, such as graphite, polytetrafluoroethylene, and internal silicone oil, on the friction and wear of bulk polymers such as polyimide, polyester, and polyamide. Known lubricating mechanisms are complemented by an interpretation of tribophysical reactions in the sliding interface. Test results are obtained during small and large‐scale laboratory testing under high‐load and high‐temperature conditions and are further related to the effect of contact conditions. The study reveals that some lubricants are not effective under the entire range of sliding temperatures and/or normal loads. For internally lubricated polymers, the efficiency of internal lubricants strongly depends on the contact geometry. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

A new kinetic model for interdiffusion at semicrystalline polymer interfaces

A kinetic model has been developed to describe the behavior of semicrystalline polymer interfaces. In these systems, the competition between interdiffusion and crystallization drives the overall transport. The crystallization rate is based on the Avrami equation, in which the Avrami exponent and the crystallization rate constant as a function of temperature and blend composition are determined by in situ optical microscopy and differential scanning calorimetry. The mutual diffusion coefficient is obtained by using the fast mode theory. The predicted density profiles as a function of position are used to extract the interfacial widths, which are affected by molecular weight, equilibrium degree of crystallinity, and temperature. At low temperatures, the crystallization rate is fast, and the crystals present near the interface hinder the interdiffusion, causing the interfacial width to be small. At high temperatures, the crystallization is much slower, and interdiffusion dominates crystallization. The model predictions are compared with interfacial behavior observed by transmission electron microscopy and small angle X-ray scattering in a system composed of polyethylene and isotactic polypropylene and the agreement with the experiments is satisfactory.     

Fluorescence study of polymer chain interpenetration and of the rate of phase separation in incompatible polymer blends

The application of fluorescence techniques has been demonstrated for the study of four polymer problems: (a) If two different polymers are labeled with donor and acceptor fluorophores, respectively, which exhibit nonradiative energy transfer, the emission spectrum of their blends will depend on whether the two polymeric species are miscible or segregated into separate phases. Thus, the emission spectrum may be used as a measure of polymer compatibility. (b) Since rapid freeze-drying preserves the extent of chain interpenetration which existed in solution, the energy transfer between labeled polymers may be used to study the extent of such interpenetration on solution concentration. (c) Phase separation when heating blends of poly(methyl methacrylate) and poly(benzyl methacrylate) may be followed by the change in the emission spectrum of the latter. (d) The interdiffusion of separated poly(ethyl methacrylate) molecules labeled with donor and acceptor fluorophores may be monitored by the increase in the nonradiative energy transfer.     

Autohäsion von Elastomeren

Autohesion is a particular form of adhesion. It occurs when two surfaces of the same elastomer are pressed together. The increase of the autohesive strength, with the increase of contact time, is caused by interdiffusion of mobile macromolecule chain ends across the boundary face. After a certain time of contact, the contact zone disappears and a homogeneous system is obtained. The autohesive strength is then equal to the bulk strength of uncrosslinked elastomers. The autohesion of polybutadiene, butadiene-acrylonitrile copolymers, ethylenpropylen copolymers and polychloroprene was studied. The influences of microstructure, polar side groups, cristallinity, contact time, test rate and the influence of solvents on autohesion were investigated in detail.     

Water‐soluble aldehyde‐bearing polymers of 2‐deoxy‐2‐methacrylamido‐D‐glucose for bone tissue engineering

In this study the methods of synthesis of hydrophilic aldehyde‐bearing polymers and copolymers based on 2‐deoxy‐2‐methacrylamido‐D ‐glucose have been developed. Polymers with controllable aldehyde group content were synthesized via free‐radical polymerization and subsequent polymeranalogous modification. The water‐soluble polymers obtained were investigated in view of their capacity to be adsorbed on two commercial mineral supports used in bone tissue engineering. Besides, cytotoxicity of synthesized polymers was tested. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Comparison of surface energies using various approaches and their suitability

The surface chemistry and surface energies of materials are important to performance of many products and processes—sometimes in as yet unrecognized ways. This article has been written for the researchers who wish to calculate solid surface energy (SE) from contact angle data. In this article, we describe various methods of calculations and their assumptions. The theoretical and experimental approaches for understanding the solid surface free energy using various methods are discussed in this article. Researchers concerned with many fields such as printing, dyeing, coating, adhesion, pharmaceuticals, composite materials, textiles, polymers, and ceramics should have interest in this topic. SE calculated by various methods for polyethylene surface treated in air plasma is discussed. Using contact angle data, the values of surface roughness using Wenzels equation, have been obtained and correlated to surface roughness calculated from AFM data. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008