Investigation of the dyeability of post-consumer recycled acrylonitrile-butadiene-styrene (PCR-ABS) by using antistatic agent and plasma treatment

Abstract

The polymers, which became widespread especially in the 20th and 21th centuries, are preferred for their usefulness as they provide lightness and inexpensiveness. However, about 99% of the plastics including the single-use ones are derived from the petroleum. As the consequence of that situation, sustainability has brought to the agenda and became the focus of the industry. The waste management of plastics is carried out by recycling, landfill and incineration. Although recycling is the most sustainable disposal management method, recycled polymers have reduced properties in most cases. The challenges for incorporating recycled content into the products are the load-bearing and inflammable parts, food contact applications and visual parts. Acrylonitrile-butadiene-styrene (ABS) is a commonly used terpolymer in which each monomer provide different favourable properties to the structure. In addition to its decreased mechanical properties, ABS becomes more hydrophobic after the recycling processes and it may possess poor adhesion due to the chemical alterations caused by thermal degradation, the impurities coming from the mixed scraps and the impaired surface. As for the visual applications, local paint failures may restrict the recycled polymers to become prevalent. In this study, to overcome the adhesion problems, antistatic agent with an increased amount was used. As the antistatic agent forms a water-based film on the surface, hydrophilicity is provided to the surface. However, the mechanical and thermal properties may be decreased after compounding with antistatic agent. Additionally, plasma treatment was applied to the post-consumer recycled acrylonitrile-butadiene-styrene (PCR-ABS) to roughen the surface and create chemically active polar groups. As it is a surface treatment, the plasma does not affect the bulk properties of the polymer. Furthermore, to investigate the synergistic effect of the plasma treatment and antistatic agent, plasma treatment was applied to selected antistatic filled formulations. After preparing the samples by either compounding with antistatic agent or applying plasma treatment and lastly conducting both processes as the third phase, the surface measurements before the wet painting and the paint tests after the wet painting were carried out. Also, as an additional aspect of the study, the mechanical and thermal properties of the samples with and without antistatic agent were investigated. According to the results, a considerable hydrophilicity was obtained with antistatic agent and plasma treatment. The water contact angle was decreased from 94° to 85° and down to 60° with plasma treatment and maximum amount of additive, respectively. Besides, an increase in the surface roughness was observed with plasma treatment. After the paint tests, the sample comprising 2,5% antistatic agent showed humidity and salt spray resistance with a 100% adhesion. Besides, changes in mechanical and thermal properties revealed the plasticising effect of the antistatic agent. With the antistatic agent amount greater than 2,5%, a considerable reduction in most of the properties was observed. The elastic modulus and flexural strength were decreased 21% and 26%, respectively with the maximum additive content while the MFI was increased more than 3-folds. Lastly, when the interactions and chemical behaviours of the paint was investigated, it was seen that the characteristics of the paint was more likely to be hydrophobic than hydrophilic. As the hydrophobic interactions might be the preferred mechanism for the paint rather than the chemical bondings, the compound comprising 2,5% antistatic agent was found as the successful formulation to render the PCR-ABS to be dyeable. Also, considering the fact that PCR-ABS is cheaper than its virgin counterparts, the cost is reduced by incorporating PCR-ABS. However; as the antistatic agent is more expensive than PCR-ABS, having price almost 5 times higher than ABS, cost optimisation was realised and it was found that cost reduction was achieved with the scenario of PCR-ABS with 2,5% antistatic agent. However, for the formulas comprising higher content of antistatic agent, cost-up was obtained.