34
August/September
Figure 1. Analysis of a hydrocarbon wax. Columns: 2 x PLgel 5 µm MIXED-D (300 x 7.5 mm), eluent: trichlorobenzene + 0.0125% BHT, flow rate: 1.0 mL/min, injection volume: 100 µL, analysis temperature: 160 ºC, instrument: PL-GPC 220 fitted with a differential refractive index detector.
Figure 2. Analysis of several repeat injections of polypropylene. Columns: 3 x PLgel Olexis (300 x 7.5 mm), eluent: trichlorobenzene + 0.0125% BHT, flow rate: 1.0 mL/min, injection volume: 200 µL, analysis temperature: 160 ºC, instrument: PL-GPC 220 fitted with a differential refractive index detector.
Polyphenylene sulfide analysis
Figure 2. Analysis of several repeat injections of polypropylene. Columns: 3 x PLgel Olexis (300 x 7.5 mm), eluent: trichlorobenzene + 0.0125% BHT, flow rate: 1.0 mL/min, injection volume: 200 µL, analysis temperature: 160 ºC, instrument: PL-GPC 220 fitted with a differential refractive index detector.
is required throughout the entire analysis to ensure that the samples remain in solution throughout the experiment. A temperature of 160 ºC is required for the analysis of polyolefins.
The selection of GPC columns for the analysis of a polyolefin is dependent on the molecular weight range of the sample. Low molecular weight samples can be analysed using high efficiency, relatively low-pore-size columns. Higher molecular weight materials require media with large particle sizes to minimize shear effects, with a wide pore size distribution. Figure 1 illustrates the analysis of a polyolefin wax by GPC.
High molecular weight materials require analysis on high-pore-size GPC columns that minimize shear degradation. Figure 2 shows the analysis of several injections of a sample of high-density polypropylene by GPC.
These applications illustrate the diversity of polyolefin samples and indicate the flexibility of the PLgel series of columns in addressing the analysis of such samples.
Polyphenylene sulfide (PPS) is an engineering polymer with a rigid backbone of alternating aromatic rings linked by sulfur atoms. It is useful as a structural material due to its high resistance to both chemical and thermal attack and the material is very stiff, even at high temperatures. PPS is used in a number of applications, including as a filter fabric for coal boilers, in felts used in paper making, in electrical insulation applications and in the manufacture of specialty membranes. PPS is naturally insulating, although the addition of a dopant can be used to make the material semi-conducting.
PPS is particularly difficult to analyse by GPC. The high chemical and thermal resistance of the material means that it is only soluble in specialist solvents such as ortho-chloronaphthalene at elevated temperatures around 200 ºC, as shown in Figure 3.
Conclusions
Although the analysis of highly crystalline engineering polymers at high temperature presents particular challenges, it is evident from these examples that with careful choice of GPC instrument and columns it is possible to get good quality results from such materials.
References Modern Size-Exclusion Liquid Chromatography, W. W. Yau, J .J. Kirkland, and D. D. Bly, John 1979, Wiley and Sons, New York, ISBN 0-471-03387-1
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
