Influence of Rubber Formulation on Surface Modifications Produced by RF Plasma

Abstract

The effectiveness of nitrogen, oxygen and air Radio Frequency (RF) plasma treatments on two styrene-butadiene vulcanized rubbers with a different formulation has been studied. The presence of an antiadherent surface layer containing low-molecular weight ingredients (sulfur-rich vulcanization agents and wax) from SW (Sulfur-Wax) rubber formulation requires an extended plasma treatment capable of removing this surface layer. When the percentage of antiadherent moieties is reduced in ZS (Zinc Stearate) rubber formulation, shorter plasma treatment times are enough to modify rubber surface and increase its polarity by the creation of C-O and C=O polar groups that enhance adhesion towards a polyurethane adhesive. Air and oxygen plasma treatments are more aggressive than nitrogen plasma and therefore they are more effective in removing the antiadherent layer of the outermost rubber surface layer prior to oxidation of the rubber surface.

Influence of Plasma Chamber Set‐Up on the Surface Modification of Non‐Vulcanized and Pure SBR Rubber Treated at Radio‐Frequencies Air Plasma

“…SBR polymer samples were exposed to low‐pressure air plasma leading mainly to chain scissions and formation of free radicals . As explained hereafter, it turns out that these radicals react mainly with plasma reactive species and oxygen of the atmosphere (after removal of the samples from the plasma chamber) to form an oxidized and hydrophilic layer.…”

“…Non‐thermal plasma treatments lead to oxidation, cleaning, ablation, crosslinking, chain scission, and/or roughening of the rubber surface, which generally modify adhesion properties . In particular, low‐pressure radio‐frequency (RF) air plasmas appear to be good candidates to generate a high level of surface oxidation, i.e., a high surface concentration of grafted oxygen . Studies from Martin‐Martinez's group, probably the most achieved works nowadays, evidence the role of low‐molecular weight additives in the rubber formulation, which are capable of migrating to the surface and dramatically affect interactions there.…”

Thermoplastic elastomers based on high‐density polyethylene, ethylene–propylene–diene terpolymer, and ground tire rubber dynamically vulcanized with dicumyl peroxide

“…The band located at 1464 cm −1 corresponded to the scissoring vibration of methylene and overlapped with the signal located at 1450 cm −1 , which corresponded to the asymmetric flexion of the methyl group. The broad signal at 1089 cm −1 was associated with the SiO stretching mode, and the intense signals at 966 and 912 cm −1 were characteristic of the CH flexion of the vinyl group of polybutadiene. Four sharp peaks dominated the spectrum of HDPE, including the methylene stretching vibrations located at 2920 and 2850 cm −1 and the methylene deformations located at 1464 and 719 cm −1 .…”

“…The strong peak located at 1540 cm −1 was assigned to the stretching of the COO − group of zinc stearate, which was a product of the reaction between zinc oxide and stearic acid. Zinc oxide and stearic acid are used as additives in the formulation of tires to protect the material from oxidation via air, UV radiation, and ozone . The band located at 1464 cm −1 corresponded to the scissoring vibration of methylene and overlapped with the signal located at 1450 cm −1 , which corresponded to the asymmetric flexion of the methyl group.…”

Improvement of the properties of plasma‐modified ground tire rubber‐filled cement paste

“…Plasma surface modification, which has advantages of simple operation, no pollution to environment, and power consumption, is widely used to improve the hydrophilicity of rubber powder 18–20. By the low‐temperature treatment, some physical and chemical changes, such as etching to produce crosslinked layer or polar group, occur on the surface of polymer material.…”