Dariusz M. Bielinski

Mechanical and Tribological Properties of Thin Remote Microwave Plasma CVD a-Si:N:C Films from a Single-Source Precursor

Silicon carbonitride (a-Si:N:C) films produced by remote plasma chemical vapor deposition (RP-CVD) were investigated. Tetramethyldisilazane as a single-source precursor and (H2+N2) upstream gas mixture for plasma generation were used. The influence of the upstream gas composition on the structure, density, mechanical and tribological properties of the films deposited on p-type Si (001) wafers (both heated—Ts=300°C and unheated—Ts=30°C) are reported. The H2 RP-CVD process was found to result in the formation of outstanding low friction (μ≈0.04) and high hardness (H=27-31 GPa) a-Si:N:C films exhibiting promisingly high H/E values.

Influence of iodination on tribological properties of acrylonitrile—butadiene rubber

Surface modification of acrylonitrile-butadiene copolymer (NBR) vulcanizates by treatment with an iodine solution results in a significant decrease in the coefficient of friction. The effect of modification is attributed to formation of a thin surface layer, incorporating iodine species, which has a higher modulus than the bulk material. The surface layer also has an increased roughness which, combined with the increased local stiffness, causes the reduction in friction. These factors overcome an observed increase in the surface energy after modification, which would act to increase the friction. NBR subjected to iodination kept its bulk elasticity, which plays an important part in the mechanism of deformation of the elastomer under conditions of friction, and ensures that the modified NBR retains its properties in engineering applications. The durability of the surface modification is attributed to interactions between iodine and nitrile groups from the acrylonitrile monomer units.

Modification of Polymer Materials by Ion Bombardment: Case Studies

The paper discusses possibility of application of ion beam bombardment for modification of polymers. Changes to composition, structure and morphology of the surface layer produced by the treatment and their influence on engineering and functional properties of wide range of polymer materials are presented. Special attention has been devoted to modification of tribological properties. Ion bombardment results in significant reduction of friction, which can be explained by increase of hardness and wettability of polymer materials. Hard but thin enough skin does not result in cracking but improves their abrasion resistance. Contrary to conventional chemical treatment ion beam bombardment works even for polymers hardly susceptible to modification like silicone rubber or polyolefines.

Properties of chlorinated polyethylene waxes/poly(methyl methacrylate) blends: dependence of surface composition on wax chlorine content and blend composition

Abstract Chlorinated polyethylene wax/poly(methyl methacrylate) (CPE/PMMA) blends have been investigated using X-ray photoelectron spectroscopy, static secondary-ion mass spectroscopy and contact angle measurements, and the surface composition has been observed to depend on the chlorine content in the wax and on the blend composition. Dielectric thermal analysis and dynamic mechanical thermal analysis measurements have been used to probe the phase structure of the blends and identify the glass transition temperature. These systems exhibit a complex phase behaviour with a microheterogeneous morphology. The waxes can be divided into two groups, according to their chlorination level: Cl ≤ 48 wt% and Cl > 48 wt%. The extent of specific interactions in the systems, determined using nuclear magnetic resonance and Fourier-transform infra-red spectroscopies, explains the differences in behaviour. A degree of chlorination >48 wt% is shown to be necessary for the CPE wax to form a sufficient number of hydrogen bonds to maximize compatibility with PMMA.