Chemical modification of near-surface charge trapping in polymers

Abstract

The surfaces of three polyolefin films, low-density polyethylene, high-density polyethylene, and polypropylene, were chemically modified by etching with permanganic acid, and low-density polyethylene by etching with chromic acid and by staining with chlorosulphonic acid. Polytetrafluoroethylene (Teflon) was treated with a sodium naphthalene complex in glycol ether. The surfaces were examined with a scanning electron microscope, and chemical groups identified by attenuated total reflectance infrared measurements. The surfaces were then corona charged, and the charge stability and trap distributions determined by the methods of thermally stimulated charge decay and thermally stimulated current, respectively. Scanning electron micrographs revealed a nodular surface structure in polyolefins etched with permanganic acid, a rough surface without nodules in low-density polyethylene etched with chromic acid, isolated corroded surface spots in low-density polyethylene stained with chlorosulphonic acid, and a web-like surface in etched Teflon. Permanganic acid removed amorphous and defective regions of the polymer surfaces, exposing more crystalline regions and crystalline-amorphous boundaries, both of which provided trapping sites, producing better charge storers than the virgin equivalents. Lifetimes, and hence usable temperatures in device application, were increased for both negative and positive charge. The other acids reduced the lifetimes in low-density polyethylene. Etching made Teflon as good a positive charge storer as the virgin negatively charged material, a result important to practical applications. While attenuated total reflectance measurements showed the presence of various chemical groups, charge stability seemed to depend more on surface morphology than on which active groups were added to the polymers by the etchants and staining agent.

Sonochemically-Assisted Modification of Polyethylene Surfaces

“…The absorbance ratio I 720 /I 730 can therefore be used as a measure of the relative amounts of crystallinity. The values of this ratio obtained in the present work were 1.25 prior to treatment, 1.27 after 5 h oxidation with aqueous K 2 S 2 O 8 , and 1.36 after 24 h. These values are similar to those reported by Haridoss and Perlman during the acid etching of polyethylene films, 43 where the values of R increased from 1.09 for the untreated polyethylene to 1.45 for chromic acid oxidized samples. While the changes in the present work are lower, they also suggest that the ultrasonically promoted oxidation occurs in the same regions of the polymer.…”

“…These values are similar to those reported by Haridoss and Perlman during the acid etching of polyethylene films, where the values of R increased from 1.09 for the untreated polyethylene to 1.45 for chromic acid oxidized samples. While the changes in the present work are lower, they also suggest that the ultrasonically promoted oxidation occurs in the same regions of the polymer.…”

Facile Method for Obtaining Gold-Coated Polyester Surfaces with Antimicrobial Properties

“…The functional groups on a polymer film surface are very important in tailoring the properties for targeted biomedical applications [1,2]. The surface characteristics depend on the balance of hydrophobic-hydrophilic of the polymeric material, which induces properties such as adsorption, adhesion, permeability, wettability, and other important parameters for various applications [3][4][5][6].…”

Solid-state radical grafting reaction of glycidyl methacrylate and poly(4-methyl-1-pentene) in supercritical carbon dioxide: Surface morphology and adhesion

“…Applications of polymer-based materials are often extended in situations in which their surface properties play a protagonist role, such as, adhesion, electrical resistance, wettability, permeability, dyes, adsorption of pigments, and so forth [1,2]. Poly(4-methyl-1-pentene) (PMP) is a polyolefin that has a greater potential of applications, such as, electrical properties as insulator, chemical resistance, and gas permeability [3], because of its excellent transparency and high melting point, compared with other polyolefins.…”