Migration and blooming of stabilizing antioxidants in polypropylene

Abstract

We have studied the migration of the hindered phenol, octadecyl‐3,5‐bis (1,1‐dimethylethyl)‐4‐hydroxybenzenepropanoate, and the phosphite co‐stabilizer tris 2,4‐bis(1,1‐dimethylethyl)phenylphosphite, out of films of polypropylene (nominal melt flow 3.5 g/10 min). Loss of additive from an initial 10% weight‐% level in the polymer was followed by FTIR bands in the appropriate regions. Temperatures of 298 K, 313 K and 333 K were used. An attempt was made to analyze migration data using Fick's law for diffusion by means of a least squares fit. Octadecyl‐3,5‐bis (1.1‐dim ethylethyl)‐4‐hydroxybenzenepropanoate diffused according to Fick's law with a temperature independent diffusion constant (D = 1.27 × 10−15 m2 S−1) to a steady state concentration of 7.2 % + −0.56 weight‐%. The phosphite did not diffuse at all at 298 K and 313 K, but diffused with D = 8.1 × 10−16 m2 S−1 to a steady level at 333 K. Our interpretation of the phosphite migration data assumes that most of the phosphite in the sample is immobilized. A subset of the total phosphite level is free to diffuse to the surface of the polymer.

Modification of the bacterial adhesion of Staphylococcus aureus by antioxidant blooming on polyurethane films

“…The ratios of these additives in the polymer bulk are very low (commonly less than 0.5%). However, as these additives are generally not soluble in the polymer matrix at the ambient temperature, they can diffuse through the polymer matrix after catheter processing, bloom onto the surface [1] and be present at very high concentration on the surface. As a consequence, the surface can be richer in additives than the bulk.…”

New bleeding model of additives in a polypropylene film under atmospheric pressure

“…There are many reports regarding the solubilities and the diffusions of additives in polymer films 1–12. To measure the diffusion coefficient and the solubility, the methods of using the permeation through a film, adsorption in a film, and release from a film have been devised 13–16.…”

Wall effects on flow of polymer/particulate/(carboxylic acid) in dies and rheometers

“…It has been found by many investigations that amphiphatic (polar, nonpolar) additives compounded into polyolefin thermoplastics migrate to the surfaces 1–6. Our own investigations7, 8 have found that various low molecular weight additives, including fatty carboxylic acids and amides as well as zinc stearate, induce slippage in polyethylene and polypropylene but not in polystyrene and polyamide‐12.…”