Polyethylene IUPAC

Lithocholic acid, structure of, 1082 Locant, IUPAC naming and, 87 Lone-pair electrons, 9 Loratadine, structure of, 206 Lotaustralin. structure of. 766 Low -density polyethylene, synthesis of, 1210... 

Another polymer symposia was organised by IUPAC in 1947 in Liege. At this conference, the discussion included synthesis and technology of polymers like polyethylene, nylon, polyester. New characterisation methods such as x-ray scattering, x-rays, electron microscope, osmometry, nmr, IR, Raman spectroscopy, etc. were now available for characterisation of polymers. These methods become essential because of increasing complexity of new polymers. 

The number and weight average molecular weights were determined for two samples of linear polyethylenes distributed by the Macromolecular Division of IUPAC. The methods used were GPC, osmotic pressure, infrared analysis, melt viscosity and intrinsic viscosity. Data interpretations are discussed for each method. By comparing the results the average molecular weights were obtained for one sample, STN = 10,500 to 11,000 and Mw = 150,000 to 165,000 for another sample, MN = 13,600 to 18,500, and Mw = 40,000 to 48,000. 

Tn the previous papers of this series (1, 2, 3, 4) calibration and repro- ducibility of gel permeation chromatography (GPC) have been extensively examined. This paper describes the application of GPC to two selected samples of linear polyethylenes, one having a narrow molecular weight distribution (NMWD) and another a broad molecular weight distribution (BMWD). These samples were distributed by the Macro-molecular Division of IUPAC (5) for the molecular characterization of commercial polymers. The average molecular weights by GPC are compared with the data obtained from infrared spectroscopy, osmotic pressure, melt viscosity, and intrinsic viscosity. Problems associated with data interpretation are discussed. 

As the next example, attention is directed to a polymer in which the end groups are not significant, namely the polymer which is commonly named as polyethylene terephthalate, abbreviated PET (Figure 5). IUPAC... 

Data are for an unbranched polystyrene (PS i), a high density polyethylene without long side branches (HOPE i), and two low-density polyethylenes with long side branches (LDPE Hi and iUPAC A). Curves shifted to avoid overlap (from Laun [84]). 

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