Gel permeation chromatography of polyethylene. II. Rapid evaluation of long-chain branching and molecular weight distribution

Abstract

SynopsisA comparison is made of two methods by which one may derive molecular weight distribution and degree of long-chain branching using only the measured solution viscosity of a branched polyethylene whole polymer and its GPC trace. These are (a) Drott and Mendelson method and (b) Ram and Miltz procedure. In each case, the purpose of the method is to devise a means by which one may establish a relationship between solution viscosity and molecular weight for use in conjunction with the GPC universal calibration relationship of Benoit et al. The effectiveness of these theoretical approaches is evaluated by comparison with the true D and degree of long-chain branching data obtained using our complete iterative analysis method. Such a detailed comparison using low, moderate, and highly branched resins leads to a conclusion that both the techniques provide very good MWD and branching data and, further, that they may be considered interchangeable for most resins. For highly branched resins, the Ram and Miltz method, which is slightly more sensitive to the presence of a high degree of long-chain branching, is preferred. In practice, the Drott and Mendelson method has the advetage of using less computer time and providing a direct measure of degree of long-chain branching, and thus is likely to be used most frequently.

Molecular weight distribution in low-density polyethylene polymerization; impact of scission mechanisms in the case of a tubular reactor

“…The MWD of ldPE shows a bimodality, as experimentally shown by Tackx and Tacx (1998) and Wild et al (1977). The conventional linear scission reproduces this bimodality, whereas topological scission yields a long tail, although topological scission model describes the scission mechanism of branched ldPE more correctly.…”

Molecular chain heterogeneity of a branched polyethylene resin using cross-fractionation techniques

“…In literatures, the molecular weight and molecular weight distribution (MWD) of SRM1476 have been reported, and its long-chain branching (LCB) effect has been also studied. For example, Wagner, Beer, Penlidis, Wild, et al estimated its branch structures and MWD [29][30][31][32][33][34][35][36]. Moreover, Beer et al investigated its high molecular weight tail and LCB effect [33,35].…”

Development of a gel permeation chromatography method for analysing cellulose nitrate in museums

“…Molecular weight distributions (MWD) of cellulose derivatives are commonly characterised with gel permeation chromatography (GPC), also known as SEC [9][10][11] that physically separates polymer molecules according to their size in solution [12]. Only a few studies have published relevant work addressing CN [13], which mostly derives from research in native cellulose [14,15], and uses polymer dissolution methods for highly nitrated cellulose (nitrogen > 12%) used in explosives (i.e.…”

“…dynamites and gun propellants) [9,11,16,17]. The primary challenge of CN and its preparation for GPC analysis relates to solubility issues: (1) the intrinsic nitrogen content that results from CN production influences its solubility (reduced nitrogen levels lead to lower solubilities) [13,16]; (2) the ageing of CN results in a reduction of nitrogen content, which causes a further decrease in solubility [12].…”