Über die γ‐strahleninduzierte polymerisation an oberflächen von feststoffpulvern

Abstract

ZUSAMMENFASSUNG:Versuche mit feinkornigen Pulvern, bestehend aus Kieselgel, Kaolinitverbindungen und Calciumcarbonat, wurden durchgefuhrt, um zu prufen, o b mit Hilfe der 60Co-y-Vorbestrahlungsmethode die Oberflachenpfropfung rnit Methylmethacrylat (MMA) und Styrol gelingt. Es zeigte sich, daD nennenswerte Mengen Polymeres aufgepropft werden konnen. Der Pfropfungsgrad (PG) steigt mit zunehmender absorbierter Dosis an und strebt bei hoheren Dosen einem Sattigungswert (PG"' "") zu. Die gemessenen Werte von PGYx (in g Polymeres/m2 Pulveroberflache) sind fur alle Substanzen groDenordnungsmaDig gleich. Daraus wird geschlossen, daB die Polymerisation durch aktive Zentren ausgelost wird, die sich an der Oberflache der Pulverpartikeln befinden, und daD die an der Oberflache maximal erreichbare Konzentration an aktiven Zentren ungefahr gleich groD ist. Unterschiede in den PG$""-Werten der einzelnen Substanzen sind vermutlich darauf zuruckzufiihren, da13 die verschiedenen gepfropften Pulver einen unterschiedlich groRen Anteil an nicht kovalent gebundenen und trotzdem nicht extrahierbaren Polymeren enthalten, der sich in engen Poren befindet. Hinweise dafur ergab die durch AIBN thermisch ausgeloste Polymerisation von .MMA in Gegenwart von porenreichem Kieselgel, die zu P G F =~ x 10-4g Polymeres/m2 fiihrte. Mit der Vorbestrahlungsmethode wurde PGY" = 8 x 10-4g Polymeres/m2 erhalten. Es wird vermutet, daD das nach der Vorbestrahlungsmethode aufgepfropfte Polymere zumindest zum Teil nicht kovalent gebunden ist. Der Anteil des nicht kovalent gebundenen und nicht extrahierbaren Polymeren sollte eine Funktion der Anzahl und der GroBe der Poren und infolgedessen substanzabhangig sein. SUMMARY:Experiments with fine grained powders of silica gel, kaolinite and calciumcarbonate have been carried out, in order to prove whether the h°Co-y-preirradiation method is applicable for grafting methylmethacrylate (MMA) and styrene onto the surface of these powders. It is demonstrated that significant amounts of polymer may be grafted by this method. The degree of grafting (PG) increases with increasing absorbed dose and approaches a limiting value (PGmaX) at high doses. Measured values of PGY" (expressed in units of g polymer per m2 surface of powder) are the same within an order of magnitude for all substances. Therefore, it is concluded, that the polymerization is 23 B. Dinh-Ngoc, J. G. Rabe und W. Schnabel started by activecentersgenerated previously at the powder surface and that the maximum concentration of active centers attainable at the particle surface is about the same for all powders. Differences of PGt""-values obtained with the various substances are presumably due to the fact that the grafted powders contain a fraction of not covalently bonded and in spite of this not extractable polymer in narrow pores. Evidence for this was obtained by initiating the polymerization of MMA with AIBN at 50°C in the presence of a highly porous sample of silica gel. In this case P G F =~ x 10-4g polymer/m2 was obtained which compares with PGIa"=8 ...

Catalytic grafting: A new technique for polymer–fiber composites I. Polyethylene–asbestos composites

“…These such modified fillers were then used to conduct graft polymerization of acrylonitrile, acrylic acid, methyl methacrylate, and vinyl acetate.' Ball milling and ultrasonic irradiation of fillers in presence of monomers were also used for surface polyrneri~ation.~~'~ Gamma irradiation of mineral fillers was used by Dinh-Ngoc and Fukano 11,12 to initiate the polymerization of styrene and methyl methacrylate and to produce composite materials. Plasma treatment of the fillers and reinforcements is also known to activate the surface and to produce grafted fillers for subsequent mixing with thermoplastic resins.13 Similar objectives (surface treatment of the fillers) can be achieved by photo-initiated graft polymerization after peroxide, ', chlorosilanes, '' or quinone l6 treatment of the fillers.…”

Functional silane‐modified calcium carbonate

“…Graft polymerization of methyl methacrylate or styrene on the surface was accomplished by the method of y-ray preirradiati0n.l' Sulfur dioxide-modified calcium carbonate was also used for the graft polymerization of vinylic compounds. 12 In the course of the study on the graft polymerization of styrene on the silane-modified mineral fillers, gelation of the reaction mixture of the calcium carbonate was observed, just as in the clay system.13 Our interest in the difference in the reactivity of the agent towards the two filler surfaces urged us to undertake this work. This paper will show that the polymeric silane coupling agent, prepared through the condensation of the monomeric agent on the filler surfaces and extracted with styrene monomer, acts as a primary crosslinking agent rather than the silane-modified filler particles.…”

Encapsulation of calcium carbonate by styrene polymerization

“…Attempts have been made for more than 30 years to increase the compatibility between CaCO 3 particle surface and polymers to be filled with it. Besides those forementioned works where coupling agents were used for CaCO 3 surface treatments [8±10, 16], these attempts include the simple addition of a type of phosphate coupling agent while blending CaCO 3 with polymers [4], graft polymerization of vinyl monomers onto CaCO 3 by mechanochemical method [21], or by irradiation of g-rays [22].…”