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Core−shell latexes based on poly(butyl acrylate) and poly(methyl methacrylate) and latexes of poly(butyl acrylate) and polystyrene were synthesized at high and low temperatures. In both cases the shell content was 33% in weight. Transmission electron microscopy and advanced NMR techniques have been used to investigate the structure of the system, and particular emphasis was put on the characterization of the interface between the two components. This interface can sensitively be analyzed using 1H spin-diffusion techniques. Dynamic gradients at the interface are detected with varying filter strengths of the dipolar filter selecting mobile components and 2D wideline separation (WISE) NMR spectra in which structural and dynamic information are correlated. These experiments show distinct differences in the interface structure of systems synthesized at different temperatures and those with poly(methyl methacrylate) or polystyrene in the shell, respectively.

SYNOPSISFree radical grafting of glycidyl methacrylate (GMA) onto molten polypropylene (PP) was studied in a co-rotating twin screw extruder. Grafting yields of GMA obtained under various experimental conditions along the screw length allowed for a good appreciation of the effects of chemical parameters (the presence of styrene and the concentrations of peroxide and monomers) and those of processing parameters (feed rate, screw speed, and specific throughput). Similar to the results obtained in a batch mixer,' free radical grafting of GMA carried out in the extruder in the presence or absence of styrene proceeded rapidly, as it was virtually completed half-way down stream of the extruder. Additionally, the presence of styrene as a second monomer increased the GMA grafting yield greatly with reduced PP chain degradation. The ultimate GMA grafting yield increased with increasing concentration of peroxide, 1,3-bis(tert-butylperoxyisopropyl)benzene. This similarity between the batch mixer and the extruder is related to the fact that in both cases it is the concentration of the peroxide and its half lifetime that determine the grafting rate and the ultimate grafting yield. On the other hand, the GMA grafting yield decreased with increasing screw speed or feed rate. For a particular specific throughput (the ratio of throughput to screw speed), an increase in throughput with a concomitant increase in screw speed brought about a decrease in GMA grafting yield. It was concluded that the GMA grafting yield is affected primarily by the residence time in the zone in which free radicals are not depleted. The effect.s of screw speed, feed rate, and specific throughput manifest mainly through this local residence time distribution. Specific energy is not a good measure of the performance of the extruder with respect to the free radical grafting of GMA onto PP. 0 1995 John Wiley & Sons, Inc.

This paper concerns free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) in the molten state carried out in a batch mixer. This free-radical grafting proceeds very rapidly as it goes to completion within two to three minutes at 200°C. The grafting yield of GMA alone is low and it is greatly enhanced upon addition of styrene as a second monomer with a reduced chain degradation of PP. Homopolymer and copolymer of GMA formed during grafting were quantified. It is suggested that in the presence of styrene, the dominating grafting mechanism is that styrene reacts with the PP macroradicals to form more stable styryl macroradicals which then react with GMA to form GMA-grafted PP. The rate of this reaction is much greater than that between the PP macroradicals and GMA. Unlike grafting of mixtures of maleic anhydride and styrene, which is dictated primarily by formation of a charge transfer complex, free-radical grafting of GMA in the presence of styrene follows a random copolymerization process. ZUSAMMENFASSUNG:Geschmolzenes Polypropylen (PP) wurde in einem Batchmischer radikalisch mit Glycidylmethacrylat (GMA) gepfropft. Bei 200 "C verlauft die Pfropfung sehr rasch und ist nach 2 bis 3 Minuten abgeschlossen. Die Pfropfausbeute beim ausschliefllichen Einsatz von GMA ist niedrig und kann in Gegenwart von Styrol als Comonomerem erhoht werden, wobei auch der Kettenabbau des PP verringert wird. Die wahrend der Pfropfung gebildeten Mengen an homo-und copolymerem GMA wurden bestimmt. Es kann angenommen werden, daB in Gegenwart von Styrol dieses zunachst mit den PP-Makroradikalen reagiert und stabilere Styryl-Radikale bildet, die dann mit GMA gepfropft werden. Die Geschwindigkeit dieser Reaktion ist sehr vie1 groBer als die der Reaktion von GMA mit PP-Makroradikalen. Im Gegensatz zu der uber einen Charge-Transfer-Komplex ablaufenden Pfropfung von Mischungen aus Maleinsaureanydrid und Styrol folgt die Pfropfung von GMA in Gegenwart von Styrol einem statistischen Copolymerisationsprozefl. Grafting CH3