Interferometric method for determining the distribution of graft concentration in radiation‐induced graft copolymer

Abstract

Microinterferometry was applied as a quantitative method for determining the transversal distribution of graft concentration instead of the usual determination of an overall graft concentration of the radiation‐induced polypropylene–styrene graft copolymer. Since polystyrene has a higher refractive index than polypropylene, the features of the interference fringe provide direct visualization of the distribution curve of graft concentration. The application of the method leads to clarify the effects of radiation dose rate, film thickness, monomer concentration, temperature, and grafting technique on the graft composition. A retardative effect on grafting appears in the vicinity of the surface, when the grafting is performed in lower radiation field and with thinner film. This is well explained by the variation in the grafting rate constant as a function of monomer concentration in the film. Furthermore, the post‐irradiation effect and accelerative effect of methanol were followed. They act effectively to form the surface, volumetric, and embedded grafts. The method has also proved useful in routine examination for a qualitative estimate of the graft copolymer.

Pre‐Irradiation Grafting of Styrene/Divinylbenzene onto Poly(tetrafluoroethylene‐co‐hexafluoropropylene) from Non‐Solvents

“…They demonstrated that the effect is related to a reduced termination rate and attributed this to a particularly pronounced TrommsdorffÀNorrish effect [3] [4] [34] [35] that is caused by an insolubilization of the grafted chains. The same observation was later explained in slightly different ways by Matsuo et al [36], Machi et al [37], Wilson [38], and Burchill et al [39], focusing on the degree of swelling of the base material, entanglement effects, and solubility parameters. Even before the work of Odian et al [33], Dobo¬ et al ascribed the same phenomenon to a suppression of the protective effect of styrene with respect to the radiation activation of the substrate [40].…”

Grafting of pre-irradiated poly(ethylene-alt-tetrafluoroethylene) films with styrene: influence of base polymer film properties and processing parameters

“…Ranogajec and co-workers reported that grafting levels 8 increased with ®lm thickness, although the effects were less pronounced at the higher temperatures. In contrast Matsuo and co-workers have reported 9 that the grafting levels of 200 mm or thicker ®lms at constant grafting times was inversely proportional to the ®lm thickness. However, the grafting levels decreased as the PP ®lm thickness decreased further.…”

“…However, the grafting levels decreased as the PP ®lm thickness decreased further. In one of the above cited investigations, only the ®lm thicknesses were reported, 9 in another two cases the ®lm manufacturer and crystallinity or density were reported in addition, 7,8 in the fourth case the molecular mass was also reported. 6 Film orientation was not characterized in any of these investigations.…”

Interferometric testing and description of polarization ray tracing in multi-layer thin films

“…The fringe deflection (C e ) is determined at three different incident angles (θ 0 = 0.0 • , θ 1 and θ 2 ) and substituted into equation (6). The solution of these equations is given by…”

“…The films' thickness and refractive index have been estimated by many authors using IR spectrophotometers and interferometric techniques [6][7][8][9][10][11][12][13][14].…”