Güneri Akovali

Surface energy and mechanical properties of plasma-modified carbon fibers

The surfaces of carbon fibers were treated by allylcyanide and xylene/air/argon plasma polymers. The surfaces of untreated and treated fibers were examined by scanning electron microscopy. Electron micrographs of the surface of carbon fibers showed that the surface striations and surface roughness were changed increasingly on the fiber surface after plasma treatment. Surface energy determinations of the fibers were carried out from advancing contact angle measurements, together with tensile testing of the single fibers. A qualitative agreement between an increase in the strength of the plasma-coated fibers and an increase in the surface energy of the fibers was observed.

Some performance characteristics of plasma surface modified carbon black in the (SBR) matrix

Abstract Performance of carbon black reinforced elastomers strongly depend on the adhesion at the filler–matrix interface. Surface characteristics of carbon blacks can be changed by use of a number of different techniques each with certain advantages and disadvantages and as regards to these, plasma surface modification is a novel one. This study aims to check the limits of applicability of plasma surface modification of carbon black to be used in the tire manufacturing industry. For this purpose, RF range cold plasma has been utilized in styrene or butadiene atmospheres. Tensile strengths and percent elongations of vulcanizates are found to respond differently if modified fillers are used as compared with those prepared by the unmodified fillers. Glass transition temperatures of vulcanizates are found to correlate well with the results of mechanical properties. Findings are also supported by the SEM pictures.

Plasma polymerization of selected organic compounds

Plasma polymerization reactions and plasma polymers of xylene/air, xylene/argon, xylene/air/argon, toluene/air/argon, dioxane and allyl cyanide were compared with respect to discharge power (between 50 and 500 W), where all other plasma operational parameters were kept constant. In plasma polymerization, the glow characteristics are known to play an important role depending on the factor WF, where W is the discharge power and F is the monomer flow rate. In plasma polymerization reactions, it is known that decomposition of the monomer and/or polymer produced competes with polymer formation. Above a certain power level, polymer decomposition may become the predominant reaction, and hence polymer deposition rates decrease with increasing discharge power. The plasma polymer films were characterized by Fourier transform infra-red spectroscopy, elemental analysis and thermogravimetric analysis. Infra-red spectra of the plasma polymers obtained indicated that when the discharge power was increased, the absorption intensities of all the functional groups decreased. The deposition rates and chemical structures of the plasma polymers prepared appeared to depend strongly on the structure and characteristics of the monomer used and on the conditions of discharge and other operational parameters.

Use of silane coupling agents to improve epoxy-rubber interface

Abstract Scrap car tyre particles can be used as filler or toughening agent in rigid epoxy matrices if the resultant interface is adequate. The objective of this work was to investigate the effects of use of different silane coupling agents (SCAs) to improve the interface between the epoxy resin and recycled rubber particles. For this purpose, seven different SCA were used to modify surfaces of the rubber particles. After the preparation of epoxy–rubber specimens, tensile Charpy impact and plane-strain fracture toughness tests were conducted. Mechanical tests and fractographic studies revealed that some of the SCA can improve of the interface between the epoxy matrix and the rubber particles leading to increases in strength while slight decreases in toughness of the samples.

Frontiers in the science and technology of polymer recycling

Preface. 1. Introduction. 2. Fundamental Issues Pertinent to Polymer Recycling. 3. Reprocessing of Single Type Polymers. 4. Reprocessing of Mixture of Polymers. 5. Recovery of Chemicals and Energy. 6. The Way Forward. Index.

Mechanical Properties of Plasma Surface-Modified Calcium Carbonate–Polypropylene Composites

Calcium carbonate was surface-modified by plasma-polymerized acetylene and the effect of surface modification on the mechanical properties of calcium carbonate–polypropylene composites was investigated. Two different plasma polymerization conditions were selected and applied. Chemical structures of plasma-polymerized acetylene products were identified. Mechanical and thermal properties of the composites prepared were evaluated and the effects of surface modification on the extent of adhesion of filler to the matrix, as well as on polymer phase, were investigated with the help of scanning electron microscopy. Some of the composite samples prepared with surface-modified calcium carbonate are found to yield higher percentage elongations and are mechanically superior compared to those prepared with unmodified filler.

Time-related wettability characteristic of acrylic resin surfaces treated by glow discharge.

STATEMENT OF PROBLEM Adhesion and cohesion have important roles in denture retention, and attempts have been made to improve the wettability of the acrylic resin material by surface treatments. PURPOSE This study examined the initial and subsequent wettability of an acrylic resin denture base material treated under air or argon plasma atmosphere before and after exposure to air or distilled water. MATERIAL AND METHODS Acrylic resin specimens were treated with plasma under air or argon atmosphere and were either exposed to air or distilled water for up to 60 days. Wettability characteristics of the acrylic resin specimens were determined by contact-angle measurements after 2 hours and after 60 days. Surface composition of the specimens also was analyzed with x-ray photoelectron spectroscopic (XPS) measurements. RESULTS Statistically significant difference was found between control and each of the plasma treatment groups (P <.05). Although the storage condition and storage period caused statistically significant difference on contact angle values (P <.05), atmosphere type did not have any effect on the results (P >.05). XPS spectra of the plasma-treated specimens differed from control specimens only in the O1s region with a narrower and more intense peak that could be assigned to -COH groups. During 60 days of exposure, the O/C atomic ratios decreased within the first 2 weeks but settled to 0.40 and 0. 32 up to 60 days compared with 0.26 for untreated control specimens. CONCLUSION Glow discharge plasma altered the surfaces of the acrylic resin and increased thc wettability as shown both by XPS and contact-angle measurements, and plasma treatment seemed to offer a durable (at least up to 60 days) wettability.

Side-chain functionalization of polystyrene with maleic anhydride in the presence of lewis acids

Polystyrenes with different molecular weights were chemically modified with maleic anhydride by use of certain cationic catalysts of Lewis acid type (BF3·OEt2, AICI3, TiCL4, ZnCl2, FeCl3, and SnCl4) in chloroform. The effects of molecular weight of polystyrene, as well as type of Lewis acid used, on properties and structure of products were investigated. The interrelation between the molecular weight of polystyrene and content of carboxyl groups in the products was made. A direct relationship between the activity of catalyst used and the number of carboxyl groups was found. For characterization of side-chain functionalized polystyrene, fractional precipitation was applied which yielded carboxyl groups in all fractions. The carboxyl group concentrations were found to be the highest in the case of BF3·OEt2. Modified polystyrene samples containing COCHCHCOOH fragments in side chains are easily crosslinked at 140–150°C and by UV irradiation as proved by IR, DTA, and TGA analyses. Functionalized polymers obtained are characterized by their high thermostability, adhesion, and photosensitivity.

Study of sol–gel processing for fabrication of low density alumina microspheres

Abstract A sol–gel process for producing microspheres of low density alumina has been developed. A Dispal alumina sol and aluminum monohydrate were used as starting materials. Microspheres with spherical shape and controllable size have been produced by using a drop generation technique. The technique consists of producing a continuous stream of uniform droplets of alumina sol and then converting the drops into a rigid form by exposing them to an ammonium hydroxide gelation medium. By using this technique, alumina spheres with surface area 351 m2 g−1 and pore size 10.7 A° have been prepared.

Mechanical properties and surface energies of low density polyethylene-poly(vinyl chloride) blends

Abstract A series of blends of poly(vinyl chloride) (PVC) and low density polyethylene (LDPE) are prepared and examined. Plasma treatment is applied to one of the components (LDPE) in order to affect the degree of compatibility. For this purpose, different monomers, such as carbon tetrachloride and vinyl chloride, are used. Tensile test results for all the blend samples, with and without plasma-treated LDPE, are compared. The surface energy results of blends prepared from untreated and treated LDPE-PVC showed considerable differences, with appreciable increases for the latter, indicating an increase in the work of adhesion as a result of the plasma surface modifications applied. The tensile test results and the measured surface energies are found to show a similar parallel behaviour.