Modification of polyolefin films surface with sodium hypochlorite

Abstract

Surface modification of high-density-polyethylene (HDPE) and linear-low-density polyethylene (LL-DPE) films is promoted by sodium hypochlorite solutions using two different processes (I and II). Such an oxidation system introduces limited amounts of carbonyl-carboxyl and hydroxyl groups onto the surface of hydrocarbon polymers. FTIR, XPS, and SEM were used to assess the efficiency of the oxidation. The hydrophilicity of the studied surfaces was investigated by the sessile drop technique and the Wilhelmy plate and a plausible oxidation mechanism is proposed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:

Influence of pretreatment on the surface characteristics of PLLA fibers and subsequent hydroxyapatite coating

“…ATR‐FTIR and XPS, two commonly used characterization methods for surface functional groups, have been used to identify carboxyl end groups and ester units on polymer surfaces 34, 36, 43. However, neither provided sufficient signal to differentiate the carboxyl end groups from the ester units abundant on PLLA fiber surfaces in our study (results were not shown here).…”

“…Similarly, when NaOCl solution is used, the etching process starts with nucleophilic attack of the OH − on the carbonyl carbon on the fiber surfaces. However, the newly generated hydroxyl end groups can be further oxidized into carboxylate end groups, owing to the presence of abundant hypochlorite (OCl − ) groups in the NaOCl solution 32–35, 40, 41. In the latter case, more carboxyl groups are generated on the PLLA surfaces and some of them are as shown for (III), which are connected to carbonyl of the ester instead of the carbon alpha to the ester.…”

“…Moreover, the hydroxyl and carboxyl end groups on the etched fiber surfaces could render the fiber with surface hydrophilicity 34. It was expected that the three end‐group species contribute to the degree of surface hydrophilicity of the etched fibers in the order of (III) > (II) > (I).…”

“…As etching by NaOCl results in less chain cleavage, fewer new hydroxyl and carboxylate end groups are formed. However, NaOCl etching can oxidize hydroxyl groups and thereby lead to more hydrophilic carboxyl groups on fiber surfaces 32–35, 40, 41. This process could explain the favorable HA coating thickness on fibers treated with NaOCl.…”

“…To increase the number of carboxyl groups on the fiber surfaces and improve the bonding between PLLA polymer and HA coating, dilute NaOH and NaOCl solutions were employed to pretreat the PLLA fibers. These two solutions are commonly used to treat polyester fiber surfaces by promoting surface hydrolysis and/or oxidation 30, 32–35. In this study, we systemically examined the effect of etching on the surface morphology and chemistry of PLLA fibers, and apatite formation on the etched fiber surfaces.…”