Makroporöse Styrol-Divinylbenzol-Copolymere und ihre Verwendung in der Chromatographie und zur Darstellung von Ionenaustauschern

Universal calibration of gel permeation chromatography and determination of molecular shape in solution

Flow patterns have been observed during the injection molding of rheologically characterized low-density polyethylene and polystyrene melts under various molding conditions. Some studies of high-density polyethylene were also carried out. Various mold designs were included in the study and the flow patterns investigated under both isothermal and cold cavity wall conditions. In addition to investigating injection molding of single polymer melts, flow patterns in the sandwich molding of polyethylene and polystyrene were studied.

Flow visualization for injection molding of polyethylene and polystyrene melts

Three different emulsion polymerization techniques, the batch (B), monomer addition (M Add), and emulsion addition (E Add) procedures were studied. Rates of polymerization indicated that the B reacted more rapidly than either the M Add or E Add. This was related to the lower monomer concentration present in the M Add and E Add systems. This is described as monomer starvation. MW and MW distributions were compared for these polymers. The B polymer had a significantly higher MW than either the M Add or E Add polymer. This could also be related to monomer starvation in the latter systems. However, the MW distribution of these polymers gave comparable values of Mw/Mn = 3.1. This indicates a similar molecular growth phenomena which appears to result from polymerization occurring near the particle surface for the addition systems. Particle size distribution measurements showed the B latex to have the narrowest distribution while the E Add latex had the widest. Also, the M Add had a particle diameter distribution which was approximated by a normal distribution. This is explained by use of the monomer starvation concept. Additional polymerizations were carried out called “hybrids” which were variations of the polymerizations discussed above. Significant differences result from the various techniques of emulsion polymerization. These differences manifest themselves not only in average particle size and MW, but also in particle size distribution. No significant differences were obtained in MW distributions.

Particle size and molecular weight distributions of various polystyrene emulsions

An extrapolation method for eliminating overload effects from gel permeation chromatograms

Gel permeation chromatography (GPC) has been applied to a wide variety of polymers within the pawl year, including those with molecular weights above 106 and those with molecular weights of 200–300. A wide variety of solvents has been used at temperatures varying from 25 to 130°C. While many polymers can be characterized with a single column, improved resolution can be obtained by using a series of columns, containing different gels with different permeability limitations, to analyze both the low end and the high end of a broad distribution curve. Plate counts of all columns must be high in order to obtain good results. The GPC technique has been extended to waxes, lubricating oil additives, and asphalts as well as to a wide variety of rubbers. Caution must be exercised in testing certain types of rubber, as gel formation within the column may lead to plugging.

Application of gel permeation chromatography to high and low molecular weight polymers

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Application of gel permeation chromatography to high and low molecular weight polymers