Tratamento químico superficial e metalização de ABS, PVC e blendas de PVC/ABS

Abstract

ResumoVisando à substituição do ABS em peças cromadas, amostras de PVC e blendas de PVC/ABS, na razão mássica de 20/80, 40/60 e 60/40, foram submetidas ao pré-tratamento em solução sulfocrômica sob diferentes condições de concentração, tempo e temperatura e sendo em seguida cromadas. As modificações na superfície das peças após o condicionamento foram analisadas por microscopia eletrônica de varredura, microscopia de força atômica e rugosidade. A qualidade da deposição metálica foi avaliada por inspeção visual e teste de adesão. Os resultados mostraram que, aumentando a concentração de PVC nas peças necessitou-se de condições operacionais mais agressivas, tais como maiores temperaturas de banho, tempo de imersão e concentração de solução sulfocrômica para que ocorresse a adesão da camada metálica. De todas as condições testadas com a solução condicionante sulfocrômica no tratamento das peças de PVC e blendas PVC/ABS de 20/80 e 40/60, a concentração de 350 g/L de ácido crômico e 400 g/L de ácido sulfúrico, temperatura de 70°C e tempo de imersão de 15 minutos, ocasionou deposição do metal em toda a superfície das peças, as quais foram aprovadas nos testes de adesão e corrosão. Palavras-chave: cromagem, ABS, PVC, blendas PVC/ABS. AbstractTo replace ABS in plated objects, samples of PVC and blends of PVC/ABS, in mass ratio of 20/80, 40/60 and 60/40, were subjected to step-conditioning (etching) in sulfochromic solution, under different conditions of concentration, time and temperature, being plated in sequence. Modifications of the surface of the samples after conditioning were analyzed by scanning electron microscopy, atomic force microscopy and roughness. The quality of metal deposition was evaluated by visual inspection and adhesion tests. Results show that increasing the amount of PVC in the blend required more aggressive operational conditions to promote metallic adhesion; higher temperature, immersion time and sulfochromic solution concentration. From all tested conditions with the sulfochromic solution for the treatment of PVC, and 20/80 and 40/60 PVC/ABS blend samples, the concentration of 350 g L -1 of chromic acid and 400 g L -1 of sulfuric acid at 70 o C and immersion time of 15 minutes, resulted in the deposition of metal layers in all evaluated specimens. These were approved in adhesion and corrosion tests. Keywords: plating, ABS, PVC, PVC/ABS blends. IntroduçãoA galvanoplastia em polímeros é um tipo de tratamento de superfície muito utilizado, e ao contrário do que ocorre com os metais, nos quais a camada metálica depositada tem uma utilidade anticorrosiva, em polímeros, possui finalidade estética e decorativa. Para uma adequada adesão desta camada, a superfície da peça precisa ser modificada por processos químicos e/ou físicos que ocasionam alterações na morfologia e estrutura da superfície do polímero por meio de formação de microcavidades com aumento na rugosidade e aspereza, que proporcionam maior interação metal-polímero e favorecem a adesão da camada metálica [1] . O processo mais empregado pelas...

Reprocessing of chromed ABS parts with chemical pickling and new chrome plating

“…It can be seen from the DSC curves (Figure ) that the glass transition temperature ( T g ) values of the pickled ABS samples were very close to those of the virgin ABS sample, ranging from 104 to 105 °C, and also as described in the studies by Kurek et al . of 105 °C, which evaluated the chemical conditioning of the surface of pieces in ABS for adhesion of metallic layers.…”

“…The ABS samples subjected to two pickling were chromed three times and, before each chrome plating step, were immersed in sulfochromic solution in the pre‐treatment stage (bath conditioning) of the galvanic process. The sulfochromic solution removes part of the ABS components, mainly of the butadiene, causing the formation of pores, besides causing oxidation of the surface . This surface modification was further intensified with acid pickling under more severe operating conditions (immersion time in nitric acid and number of larger pickling), as observed in the micrographies of samples AM2_50, AM2_70, AM2_130, and AM2_190.…”

“…The application of chromium polymers has stood out significantly in the automotive industry, household appliances, civil construction, among others, mainly due to the appearance and functionality of the pieces being similar to those of metallic pieces . Chroming is defined as a process in which a part is covered by metal layers in order to improve the aesthetic finish in the case of polymeric parts, and in metal parts has the function of increasing its resistance to corrosion, friction, and mechanical stresses, thus providing greater durability and also adding value to the piece …”

“…There are several studies reported in the literature regarding the recycling of ABS parts without metallic surface finish and also involving process improvements and application of cleaner technologies in polymer chrome, aiming at minimizing waste generation, costs, and environmental impact . However, studies on the recycling of chrome and pickled ABS parts are scarce.…”

Evaluation of the etching and chrome plating on the ABS, PVC, and PVC/ABS blends surface

“…Plated plastic is used to address a variety of needs, from decorative finishes such as chrome‐plated automotive trim used in interior and exterior applications, to functional requirements such as controlling electromagnetic emissions from electronic devices . Unlike metals, in which the deposited metal layer has an anticorrosive utility, polymers, for example, have aesthetic and decorative purposes and, for adequate adhesion of this layer the polymer surface must be modified by chemical and/or physical processes, such as etching in chemical solutions, – vacuum metallization, plasma, photocatalysis, ion beam bombardment, etc.…”