Durability of corona discharge and low-pressure air plasma-treated ethylene–vinyl acetate copolymers (EVAs)

• Published in: International journal of adhesion and adhesives 2008, Vol.28 (1), p.38-46
• Main Authors: Martínez-García, Asunción, Sánchez-Reche, Ana, Gisbert-Soler, Santiago, Landete-Ruiz, María D., Torregrosa-Maciá, Rosa, Martín-Martínez, José Miguel
• Format: Article
• Language: English
• Subjects: Application fields; Applied sciences; B. Polyolefins; B. Surface treatment by excited gases; Coating, metallization, dyeing; D. Ageing; Exact sciences and technology; Machinery and processing; Plastics; Polymer industry, paints, wood; Technology of polymers
• ISSN: 0143-7496; 1879-0127
• DOI: 10.1016/j.ijadhadh.2007.03.001

EVA (ethylene–vinyl acetate copolymer) containing 20 wt% vinyl acetate (VA)—EVA20—was treated with corona discharge and low-pressure air plasma, and the durability of these treatments was monitored for 12 months. The corona discharge treatment was carried out at corona energy of 0.3 J/cm 2 and the air plasma treatment at 300 W and 10 mbar for 3 s. Water contact angle values of EVA20 markedly decreased after treatment, and then were constant (about 60°) by increasing the time after treatment. On the other hand, a few hours after treatment the oxygen concentration on the treated EVA20 decreased, and after 12 months the surface chemistry of the corona discharge-treated EVA20 did not vary. However, for the air plasma-treated EVA20, a decease in oxygen concentration was obtained, becoming similar to that of the as-received EVA20. Peel strength values of treated EVA20/polychloroprene adhesive+5 wt% isocyanate joints increased from 1.5 kN/m (as-received EVA20) to 3.0–4.0 kN/m in the corona discharge and 4.5 kN/m for the air plasma-treated EVA20. On the other hand, the locus of failure in the joint produced with the as-received EVA20 was interfacial whereas a mixed failure (interfacial+cohesive failure in the EVA20) was produced in the joints produced with the corona discharge and air plasma treated EVA20. The adhesive strength of the corona discharge-treated samples remained unchanged for 12 months after treatment, whereas they markedly decreased 35 days after air plasma treatment.