Critical analysis of the graphical determination of Hansen's solubility parameters for lightly crosslinked polymers

Abstract

SYNOPSISThe most widely accepted method for determining Hansen's three-dimensional solubility parameters (3DSP) for crosslinked polymers entails graphically estimating the center of a spherical region in SDSP-coordinate space whose boundaries are defined in terms of the extent of swelling by solvents whose 3DSP values are known. In this article, the results of immersion tests performed a t 25OC with 53 solvents on each of four commercial polymeric glove materials are used to critically evaluate this method. Analyses reveal a number of serious shortcomings with respect to the reliability of 3DSP estimates obtained. In the context of modeling solubility or other measures of solvent-polymer compatability, it is recommended that alternative methods be sought for determining 3DSPs for crosslinked polymers.

Parameters controlling the swelling of butyl rubber by solvents

“…The Hansen affinity between butyl rubber and each solvent was calculated using eq. (3) and the values of the three HSPs obtained by Zellers et al 16 According to the criterion favored by Hansen in his method for the determination of polymer HSPs, 16 only solvents producing a swelling superior to 10% in butyl rubber (including benzonitrile with a swelling ratio of 9.9%) were considered. For each of these 32 solvents, Table I displays the volume swelling S v meas-ured on butyl rubber as well as the butyl rubbersolvent Hansen affinity A, the solvent molar volume V M , and saturation vapor pressure P vs at 25 C. The volume swelling values range from 9.9% for benzonitrile to 391% for perchloroethylene.…”

“…It must be mentioned that, even for such a large swelling ratio, Zellers et al reported that all butyl rubber samples were recovered intact after immersion. 16 Looking for a general law for butyl rubber swelling…”

“…For example, leached-out carbon black, which may be added in protective glove formulations, was associated by the authors with an amber tint appearing in certain solvents during swelling experiments. 16 Zellers et al reported differences generally smaller than 3% but sometimes larger than 10% between pre-exposure and postdrying weights. As the swelling ratio calculation should only take into account the weight of absorbed solvent, the weight of the additives that have leached out during the swelling process needs to be subtracted from the sample weight.…”

“…This article presents a detailed analysis of the influence of various potential relevant parameters on the swelling of butyl rubber based on measurements carried out by Zellers et al with a list of 53 solvents. 16,18 The detail of the experimental procedures is described in his articles. The tested butyl rubber samples were cut out of protective gloves (Model B-161, North, Charleston, SC).…”

“…First of all, the selection of the criterion differentiating ''good'' from ''bad'' solvents, i.e., solvents in which the polymer is soluble or not, does seem to have in certain cases a strong influence on the values obtained for the polymer partial solubility parameters. 7,16 In addition, Zellers et al 16 also described how the absence of theoretically justified and experimentally observed linear relationship between the affinity and the mutual solubility of solvents with a given polymer throws doubt on the reliability of the Hansen HSP determination method for polymers. Finally, he reports that the calculated HSP values are highly dependant on the presence or the absence of a few critical solvents, the list of these critical solvents varying for each polymer.…”