Linear and branched hydrophilic additives of various molecular weights (MWs) were extruded with polypropylene (PP) to make blend films. The surface-modifying additives included polyethylene glycol (PEG), hydroxylterminated four-arm polyethylene oxide (PEO), and a commercial hydrophilic additive, Irgasurf HL560. Films were extruded by using a twin-screw microcompounder at 2008C, and the resulting film thickness was 100 lm. Attenuated total reflectance (ATR)-FTIR spectrometry and water contact angle measurements were performed on the film surfaces over time to investigate the additive migration behavior. Although ATR-FTIR detected concentration increases for all additives in the subsurface region, there was no significant improvement in surface hydrophilicity for the PEGs and four-arm PEOs in the same period of time as water contact angles were measured on the surfaces. Among the linear additives, low MW PEG (1 kDa) was found to migrate faster than the high MW varieties. The linear PEG and four-arm PEO with MW higher than 2 kDa did not exhibit significant migration to the surface within a month. Irgasurf was found to change the surface wettability effectively in a relatively short time. J. VINYL ADDIT. TECHNOL.

An electronically-controlled drug delivery system (eDDS) for the on-demand release of anti-inflammatory, anti-microbial and analgesic agents to aid in wound healing is currently under development. The loading of several drugs into conductive polymer films and their subsequent on-demand, controlled release upon application of an electrical potential to the polymer film has been demonstrated. The loading and release (active and passive) of Ibuprofen sodium salt - a negatively charged analgesic and anti-inflammatory agent - from polypyrrole films is described. Major challenges identified include precise control over drug loading and passive release from the conducting polymers in the absence of an applied potential.

Deep-groove fibers are of interest for the unique cross-section shape, which provides several deep grooves on the surface running axially along the entire fiber. The parallel surface grooves on so-called deep-groove fibers offer new applications in many areas, such as medical devices to allow guided cell growth along the grooves [1], liquid absorbent materials [2,3], liquid transport [4,5], chemical separation [6], and filtration [7]. Among these applications, spontaneous liquid transport was first examined when deep-groove fibers were introduced [8]. The deep grooves on the fiber surface have been considered the open capillary channels to convey energetically favorable liquids. For example, a hydrophilic surface is required for the transport of an aqueous solution. Conventional round polypropylene (PP) fiber has been widely used for fabrics and composites [9]; however, the hydrophobic nature of PP and the lack of polar surface functionality limit its application in liquid absorption applications, such as wound dressings.Abstract This paper presented photografting as a surface modification method to provide permanent wettability improvement to deep-groove polypropylene (PP) fibers. We also evaluated their wettability by testing the dynamic contact angle (DCA) on single fibers and characterized the wicking performance of fiber bundles when polyacrylamide (PAAm) and polyacrylic acid (PAA) were grafted onto the fibers. In this study, the increase in monomer concentration was found more effective than longer UV exposure time in creating higher graft density on deep-groove PP fibers. Acrylic acid (AA) monomers penetrated into the fiber and polymerized inside, but acrylamide (AAm) did not. Fiber dimension changed slightly upon grafting of PAAm, and enlarged significantly after grafting with PAA. DCA results show that the advancing water contact angle on single fibers decreased from 100 to 55° by grafting of PAAm and PAA, and spontaneous wicking of water was observed after surface modification. The wicking amount of the vertically placed fiber bundles showed a linear relationship to the square root of time at early wicking times.

This article describes the measurement of the diffusivity of a commercial hydrophilic additive (CHA), Irgasurf HL560, at concentrations of 5 and 10 wt% in polypropylene films at different temperatures. The model used was a standard 1-D diffusion model, in which the film weight was expressed as a function of time as the additive concentration at the film surface was kept at zero at all times. Experimentally, two cases were compared: (1) Washing additive off the film surface with limited contact with the solvent, while PP films were stored in air and tested at 25, 40, 55, and 70°C up to 20 days. (2) Immersing the film in solvent with continuous stirring at 25°C for 10 days, 44°C for 2 days, and 65°C for 10 h. Diffusivity measured by the surface-washing method was 10-14 to 10-12 cm2/s, and 10 -12 to 10-10 by the immersion method. TGA results showed no effect of solvent enhancement to additive diffusion at 25°C but slightly enhanced at 44 and 65°C. Results for both the surface-washing and immersion methods are shown for instructive purposes. It is clear that the diffusivity calculated from surface-washing is much lower than from continuous immersion, largely because the boundary condition of zero additive concentration of the film surfaces was invalid between washings as additive bloomed to the surfaces and accumulated there. The continuous immersion method more closely matched the zero boundary condition used in the model and thus gave more accurate diffusivity values than did the surface-washing method.