ISSN:
0021-8995
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Maschinenbau
,
Physik
Notizen:
Functionalization of molten linear low-density polyethylene (LLDPE) with 2-(dimethylamino)ethyl methacrylate (DMAEMA) was studied in an intermeshing co-rotating twin-screw extruder using a peroxide initiator. The influence of monomer concentration, initiator concentration, reaction temperature, the screw speed, and the mean reaction residence time on the grafting reaction was investigated in order to determine the reaction conditions necessary to obtain a controlled degree of grafting, DG, while minimizing homopolymerization and crosslinking. Relatively high grafting levels can be obtained without excessive polyethylene crosslinking by using high monomer concentrations, wm, with low initiator concentrations, wI. DG increased with increasing monomer concentration when wm exceeded a certain value. Processing temperatures between 130 and 160°C are optimal to achieve high grafting efficiency, GE. Too high a processing temperature resulted in both low DG and GE. An optimal reaction residence time of about 5 min was found for wm = 23 wt % and wI = 0.56 wt % to obtain relatively high DG and GE. The melt flow index of the reaction product, MFI, increased with increasing wm at constant wI. This suggests that the DMAEMA monomer has the ability to suppress crosslinking of the LLDPE chains. The ability of the DMAEMA monomer to compete for initiator and polymer radicals and reduce LLDPE crosslinking was further demonstrated by the study of sequential addition of monomer and initiator along the extruder. The competition among the three reactions (i.e., the desired grafting, homopolymerization, and crosslinking) is discussed.
Zusätzliches Material:
7 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/app.1990.070410537
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