Investigation of Adhesion Between Metal and Plasma‐Modified Polyethylene

Abstract

The polyethylene (PE) coatings could be very promising for various branches of industry due to their chemical stability and impact resistance. Plasma modification of powder has recently attracted much interest because of new prospects to control the interfacial properties. Plasma modification also significantly enhanced the adhesion of the polymer to the substrate. Powders find wide application in various branches of industry like paintings, biotechnology, filling for composite materials etc., but the plasma modification of powder surface has not found such application as plasma modification of flat solid materials. This is due to problems connected with the three dimensional geometry, necessity of solid mixing (due to the aggregation phenomenon) and the large surface area of powders which should be treated. We investigated plasma modification of PE powder, its adhesion properties on steel surface and mechanism influencing this adhesion. PE powder was modified using various working gases and chemicals. It was found that adhesion properties were strongly influenced by concentration of oxygen containing groups and also by PE crosslinking after modification. The value of crosslinking depends on used working gas and chemicals. The ternary mixture of O2/H2O/methanol was found to be an appropriate working gas for plasma treatment of PE for adhesion purposes. The treated PE had good wettability, low crosslinking and very high adhesion to the steel substrate.

Plasma treatment of polymer powders – from laboratory research to industrial application

“…Suction wettability (capillary penetration with benzyl alcohol) and adhesion to steel of PE powder treated by various plasma gases (Air, O 2 , O 2 /H 2 O/methanol, argon). The adhesion value for Ar plasma is not given because the PE‐metal bond broke just fixation of the measuring apparatus (data adapted from Horakova et al)…”

“…Píchal et al [46,76] Hladík et al [77] Špatenka et al [119] Water n.a. Horakova et al [144] Špatenka et al [22,23] Benzyl alcohol n.a.…”

“…[127] Plasma-modified PE powder is often used as raw material for the production of parts using rotational molding technology. [2,20,24,25,41,77,[117][118][119]144,147,148] There are numerous studies dealing with improved adhesive bonding for powder coating applications on metal surfaces. [20,[22][23][24]46,76,77,94,105,113,118,119,126,144,145] Parts sintering enables direct painting and adhesive bonding without any additional surface pretreatment.…”

“…Horakova et al [144] LDPE Air, O 2 Špatenka et al [10,[22][23][24] Pavlatova et al [145] LDPE O 2 , Ar, N 2 Rieß et al [105,113] Funke et al [94] LDPE Acrylic acid…”

First-principles study of aluminum-polyethylene interfaces

“…Various methods were developed towards this goal, e.g., increasing the oxidation of polyethylene [16], [17] using copper clusters as "nano-nails" to anchor the deposited metals [18], and plasma modification of polymers [19], making the interfacial structure more complicated. Theoretically, the charge-injection barriers have not been well studied so far, because such concept can only be rigorously understood through a quantum mechanical description of the interface bonding.…”