Synthetic and analytical procedures for the preparation of surface-functionalized polyolefins are described within the general context of polymer surface functionalization. Chemistry leading to simple functionalization of both polyolefins in general and polyethylene in particular is described. Selected examples of further chemistry leading to graft copolymers attached to these surfaces are described. The effects of such graft chemistry leading to various sorts of chemically modified surfaces with different solvent-polymer interactions specific to the graft microstructure and to temperature are discussed.

Modification of polyethylene and polypropylene film and powder surfaces with oxygen and hydrogen peroxide is promoted by nonporphyrinic, nonfree radical based iron reagents such as Fe₃O(OCOCH₃)₆(C₆H₅N)_3.5 and FeCl₃ • 6H₂O/picolinic acid. These oxidation systems introduced small amounts of carbonyl groups onto the surface of these hydrocarbon polymers. The most visible manifestation of this reaction was increased polyolefin wettability toward water. IR spectroscopy, XPS spectroscopy, and chemical derivatization all were used to verify that the reaction had occurred and that a chemically derivatizable surface had been prepared. The overall process produced a fraction of the density of functional groups introduced by conventional etching chemistry.

A method has been developed to measure the surface acidity of solids using the contact angles of seven probe liquids. The geometric mean model was used to calculate the surface free energy. Then the value of the solid polarity, from the geometric mean, was compared with the polarity values calculated using the geometric mean dispersive component and the contact angles of two Lewis acids (liquefied phenol and glycerol) and two Lewis bases (formamide and aniline.) The deviation between these values was used to determine a value for the acidity, referred to as D. D was measured for a series of polymeric and metallic materials. Lap shear joints were fabricated and tested using these substrates and two adhesives, a urethane and an epoxy. The acidity of the substrate surfaces was found to affect the lap shear joint strength.

Several commercial polymers (polyethylene, polyimide, polytetrafluoroethylene, polyvinylchloride and polycarbonate) have been treated by low temperature glow discharge plasmas in various gases, namely NH3, O2, Ar, and CF4. These surface modifications were performed in "pure" microwave (2.45 GHz, "single-mode") or in combined microwave/radio frequency (2.45 GHz/13.56 MHz, "dual-frequency") plasma. Important systematic changes of the surface composition, wettability, and adhesion of thin metal films were observed for different substrate bias values, and for the different gases. The modified surface-chemical structure is correlated with contact angle hysteresis of water drops; this helps to identify which surface characteristics are connected with the wettability heterogeneity and with adhesive bonding properties, and how they are influenced by plasma-surface interactions.

A corona discharge treatment of low-density polyethylene film (LDPE) was carried out in preparation for flexographic printing. Such treatment of the PE film is necessary if maximum adhesion of ink is to be achieved. This project involved three different treating machines for which the current had to be manipulated in all the machines so that a standard treatment could be accomplished. Using a mathematical relation, current requirements for each machine were calculated and used to standardize treatment level of PE films. Standardization was achieved by controlling input current in all the three machines so as to attain a treatment level of 38 dynes/cm. This level of treatment showed the best results in adhesion of ink to the PE film during printing. The exercise also confirmed that printing must be carried out within 24 h of treatment since the level of treatment deteriorates with time.

Digital image processing techniques are applied toward the determination of polymer surface tension by pendant drop measurements. Experimental values for poly(dimethylsiloxane) as a function of molecular weight and temperature correspond well with previous measurements of poly(dimethylsiloxane) surface tension, testifying to the applicability of the new technique. Current thermodynamic treatments are found to provide excellent predictions of poly(dimethylsiloxane) surface tension for molecular weights of 3900 and 75,000 at temperatures ranging from 20 to 120°C. Theories developed by K. M. Hong and J. Noolandi (Macromolecules, 14, 1223, 1981) and Y. Rabin (J. Polym. Sci. Polym. Lett. Ed. 22, 335, 1984) yield predictions within 5% of t he experimental results for the materials and conditions studied.

The present investigation studys the effects of different electrodes such as copper, nickel, and stainless steel under low-pressure plasma on physicochemical and adhesion characteristics of high-density polyethylene (HDPE). To estimate the extent of surface modification, the surface energies of the polymer surfaces exposed to low-pressure plasmas have been determined by measuring contact angles using two standard test liquids of known surface energies. It is observed that the surface energy and its polar component increase with increasing exposure time, attain a maximum, and then decrease. The increase in surface energy and its polar component is relatively more important when the polymer is exposed under a stainless-steel electrode followed by a nickel and then a copper electrode. The dispersion component of surface energy remains almost unaffected. The surfaces have also been studied by optical microscopy and electron spectroscopy for chemical analysis (ESCA). It is observed that when the HDPE is exposed under these electrodes, single crystals of shish kebab structure form, and the extent of formation of crystals is higher under a stainless-steel electrode followed by nickel and then copper electrodes. Exposure of the polymer under low-pressure plasma has essentially incorporated oxygen functionalities on the polymer surface as detected by ESCA. Furthermore the ESCA studies strongly emphasize that higher incorporation of oxygen functionalities are obtained when the polymer is exposed to low-pressure plasma under a stainless-steel electrode followed by nickel and then copper electrodes. These oxygen functionalities have been transformed into various polar functional groups, which have been attributed to increases in the polar component of surface energy as well as the total surface energy of the polymer. Therefore, the maximum increase in surface energy results in stronger adhesion of the polymer when the polymer is exposed under a stainless-steel electrode rather than nickel and copper electrodes.

The surface modification of high density polyethylene (HDPE) and polypropylene (PP) has been carried out by exposure to a DC glow discharge in air at different power levels of 5.28, 11, and 13 W. The surface energies of polymers exposed to glow discharge were estimated by measuring the contact angles of two test liquids: de-ionized water and formamide, whose surface energy components are known. Both the polar and the dispersion components of the surface energy increased rapidly at short exposure times but the increase of the polar component was relatively more than that of the dispersion component. At low power levels of 5.28 and 11 W, the polar component of the surface energy reached a maximum plateau depending on the exposure time, but at a 13 W power level the polar component of the surface energy decreased from a maximum value to a saturation level. For PP, this saturation level could not be attained in this study. The maximum total surface energy measured in this study corresponds to the maximum polar component at 13 W for an exposure time of 120 s. The contact angle of the adhesive, Araldite AY 105 mixed with hardener HY 840 in a weight ratio of 2 : 1, was minimum at this maximum surface energy attained with HDPE and PP by exposure to a glow discharge in air. The measured lap shear strengths of HDPE or PP-Araldite-mild steel joints show a maximum corresponding to the maximum surface energy measured on the above-mentioned polymers.

The effect of ultraviolet (UV) radiation in the presence of ozone as a surface treatment for polycarbonate is examined in regards to changes in the wettability, adhesion, and surface mechanical properties. Standalone, 175-µm-thick films of a commercially available polycarbonate were exposed to UV radiation from sources of different power with various treatment times in the presence of supplemental ozone. Significant decreases in the water contact angle were observed after exposure to UV radiation in the presence of ozone. After several variations in the experimental setup, it was determined that the change in water contact angle is a function of the UV irradiance and the work of adhesion follows a master curve versus UV irradiance. Nanoindentation experiments revealed that the modulus of the top 500 nm of the surface is increased following UV exposure, attributable to surface cross-linking. Adhesion tests to the surface (conducted by a pneumatic adhesion tensile test instrument) showed little change as a function of UV exposure. Analysis of adhesion test failure surfaces with X-ray Photoelectron Spectroscopy (XPS) showed the locus of bond failure lay within the bulk polycarbonate and the measured bond strength is limited by the bulk properties of the polycarbonate and/or the creation of a weak boundary layer within the polymer.

The van Oss–Chaudhury–Good theory (vOCGT) was checked for a small artificial set of the work of adhesion input data calculated for 9 solids and 7 liquids. Taking from the literature the data for Lifshitz–van der Waals (LW) component and acid and base (A and B) parameters for 7 liquids and the values of the component and the parameters for 9 solids (close to those in the literature), the work of adhesion was calculated and its value was assumed to be free of error. Next, new values of the work of adhesion were obtained by adding a random error of normal distribution belonging to 11 distributions of a mean value equal to the errorless work of adhesion value and standard deviations from 0.1 to 60% of the mean value. The LW components and A and B parameters for these solids were back-calculated for each solid and the error level by solving 20 3-equation systems. These 9 solids were grouped in 3 sets of 3 solids in each, and for each of the solid sets the over determined system of equations (of matrix 7 × 3) for these 7 liquids was solved. The root mean square errors (RMSEs) of the LW component and A and B parameters were linear functions of RMSE of the vector (matrix) of the work of adhesion in both solution methods of a set of equations. It was found that a solution of the 3-equation set of the vOCGT was always exact for all liquid triplets. Erroneous LW components and acid and base parameters are obtained because quite a different set of equations (caused by an existing error in the data) is solved than in the case of error-free data. There is a linear transformation from the input error in the work of adhesion vector (matrix) space into the output error in the solution vector (matrix) space, and the inverse (or pseudoinverse) of the matrix A is the transformation matrix. In the case of a 3-equation set there is a linear relationship between the total RMSE of the solution and the condition number of the matrix A. The higher the input error in the work of adhesion data the higher is the influence of the condition number on the error in the solution. The RMSE value of the solution of an over determined system of equations was about 10-times lower than the mean value of RMSE calculated for the same liquids used as separate triplets.

The occurrence of negative square roots of the Lifshitz–van der Waals (LW) component and acid and base (A and B) parameters calculated from the van Oss–Chaudhury–Good theory was checked for a small artificial set of the work of adhesion input data calculated for 9 solids and 7 liquids. Taking from the literature the data for the LW component and A and B parameters for 7 liquids and the values of such component and parameters for 9 solids (close to those in the literature), the work of adhesion was calculated and its value was assumed to be error-free (un-biased). Next, new values of the work of adhesion were obtained by adding a random error having normal distribution belonging to 8 distributions of a mean value equal to the error-free work of adhesion value and standard deviations of 1, 5, 7, 10, 20, 25, 30 and 40% of the mean value. The LW components and A and B parameters for the nine solids were back-calculated for each solid and the error (bias) level by solving the overdetermined system of equations (of matrix 7 × 3) for 7 liquids. These 9 solids were grouped in 3 sets of 3 solids in each. It was found that an experimental error caused the work of adhesion data for real systems to be biased. This bias caused the solution of the equation system also to be biased and both biases were linearly dependent. This paper confirms that the appearance of negative roots of A and B parameters is caused by a specific bias in the components of the work of adhesion matrix. If the work of adhesion matrix is negatively biased there is a greater possibility of obtaining a negative value of the square root of γ⁺, and the smaller the value of this parameter the greater is the possibility of obtaining a negative square root for it. Both the negative and positive biases in the work of adhesion matrix almost equally influence the bias in γ⁻. The smaller this parameter the greater is its bias and greater the possibility of obtaining its negative square root.

The van Oss–Chaudhury–Good theory (vOCGT) was checked for a large artificial set of work of adhesion input data calculated for 15 solids and 300 liquids. Numerical values of LW component and acid (A) and base (B) parameters were assigned to 15 solids. These 15 solids were grouped in 5 sets of 3 solids in each. Also numerical values of LW component and A and B parameters were assigned to 300 liquids (three sets of 100 liquids in each). Data for these solids and liquids were especially selected to represent real types of materials encountered in practice. For all 15 solids and 300 liquids the work of adhesion values were calculated and these values were assumed to be error-free. Next, new values of the work of adhesion were obtained by adding a random homoscedastic error (A vector of random variables is homoscedastic if it has the same finite variance.) of the normal distribution (Also called the Gaussian distribution — it is continuous probability distribution defined by two parameters: the mean and variance (standard deviation squared, σ²).), belonging to 8 distributions of a mean value equal to the error-free work of adhesion value and standard deviations of 0.5, 1, 2, 5, 7, 10, 15 and 20 mJ/m². The LW components and A and B parameters for these solids were back-calculated for each error level. Two different methods for the solution of a 3-equation set were used and they gave practically the same results irrespective of the error level and liquids and solids used. It was found that there existed a linear correlation between the RMSE (root mean square error) of the solution and the standard deviation of the work of adhesion data. This correlation was highly significant (with a correlation coefficient higher than 0.999) and was true separately for LW component, A and B parameters as well as for the total solution vector (i.e., combinedly for the LW component, A and B parameters). The RMSE values of the total solution vector (having as elements values of the LW component, A and B parameters) as well as separately for LW component and A and B parameters were correlated with the condition number of a given 3-equation set. A very good correlation was found only for the total solution, much worse for A or B parameters, and practically there was a lack of correlation for the LW component. Based on the correlation between the RMSE and the standard deviation of the work of adhesion it was possible to determine what should have been the maximal standard deviation of the work of adhesion if the calculated value of a given LW component or A or B parameter did not differ by more than 1 mJ/m² from an error-free (true) value.

For vacuum web coating for permeation barrier coatings in flexible packaging, the final functionality of the packaging media is extremely dependent on the whole chain of processing steps up to the final laminated packaging film. The most sensitive sector appears to be, on the one hand the hand-shake between substrate film pretreatment–substrate surface properties and the coating process with its characteristics on the other. The influence of different surface pretreatment processes (Corona activation, oxygen and ammonia plasma treatment) on active surface groups of BOPP (biaxial-orientated polypropylene) substrates is shown together with: (1) specifities of the thermal deposition (electron beam source); (2) the reactive deposition–microwave plasma process (plasma species, excitation characteristics, kinetic energies, obtained by in situ process monitoring); and (3) structural properties (chemical composition, adhesion and oxygen permeation) of the thin barrier films (Al₂O₃ and SiO_x), in correlation with the achieved functional properties of the barrier coated films.

This article will describe some of the recent progress in the area of plasma polymerization and plasma treatment. It is not intended to be an exhaustive overview of the field, but instead a summary of the highlights of research studies in this field selected by the authors according to the importance.

Comprehensive reviews on basic phenomena, theory, and reaction mechanisms of plasma-assisted processing and plasma polymerization will be covered in this review. Formation of diamond and amorphous carbon which has attracted considerable attention in the last few years will also be described.

Recent advances in plasma assisted deposition of composite metal/organic (polymeric or carbon) films will be discussed including deposition configurations and processes. Suggested applications particularly in optics and microelectronics will be emphasized.

Possible trends in future research and development of plasma deposition of organic films will also be outlined.

In the broad spectrum of contamination control, a major concern is the presence of organic contamination on various inorganic surfaces. In order to control surface contamination of materials, a rapid-detection method is required that does not adversely affect the surface. Wettability measurements provide a convenient and rapid method for probing the outermost surface of a material. The technique is highly surface specific, generally exceeding the sensitivity of electron spectroscopies and is sensitive to a fraction of a monolayer. The most widely used quantitative measure of wettability is the contact angle. When a drop of a liquid with a sufficiently small size is placed on a smooth, flat, homogeneous solid substrate, the drop takes the shape of a spherical cap. The shape of the drop approximates that of a spherical cap when the forces other than the surface tension become negligible. Each solid and liquid (and vapor phase) combination gives rise to a specific degree of wettability. The parameter defining the wettability is the observed contact-angle; the lower the contact angle, the higher the wettability. This angle is measured between a tangent to the liquid surface where it meets the solid substrate and the plane of the solid substrate. It is found that any test of surface cleanliness involving wettability by water cannot be used on metal surfaces that have an indeterminate oxide layer. It is tempting to assume that any clean metal oxide surface would be hydrophilic, but even this rule may have some exceptions.

The liquid state of matter plays a very important role in everyday life, and the liquid surface has a dominant role in many phenomena. In fact, about 70% of the surface of Earth is covered by water. The most fundamental characteristic of liquid surfaces is that they tend to contract to the smallest surface area to achieve the lowest free energy. Whereas gases have no definite shape or volume, completely filling a vessel of any size containing them, liquids have no definite shape but do have a definite volume, which means that a portion of the liquid takes the shape of that part of a vessel containing it and occupies a definite volume, with the free surface plane except for capillary effects where it is in contact with the vessel. This is evident in rain drops and soap films, in addition to many other systems that will be mentioned later. The cohesion forces present in liquids and solids and the condensation of vapors to liquid state indicate the presence of much larger intermolecular forces than the gravity forces. Furthermore, the dynamics of molecules at interfaces are important in a variety of areas, such as biochemistry, electrochemistry, and chromatography. The degree of sharpness of a liquid surface has been the subject of much discussion in the literature.

The surface energy parameters of polycaprolactone (PCL) were determined at 160 and 180°C from its interfacial tensions with probe polymers. The probe polymers were polystyrene (PS) and poly(methyl methacrylate) (PMMA). This method is based on the well-known relationship between blend interfacial tension and polymer surface energy parameters, and requires the use of at least two probe polymers, whose surface energy parameters at the temperature of interest have been independently determined. It also requires direct measurement of blend interfacial tension at the high temperatures of interest. The interfacial tensions were obtained from direct measurements by the imbedded fiber retraction method. The following results were obtained: (a) γ^P (polar component) values for PCL was within the range reported using other methods, (b) γ^D (dispersion component) values for PCL decreased with increasing temperature, consistent with expectations and (c) γ^D values for PCL were on the high end, but still within the rather broad range of reported values.