Infrared spectrophotometric studies on polyethylene. I. Structure

Abstract

A series of polyethylene resins made by making progressive changes in temperature, pressure, and catalyst content has been studied by infrared absorption spectroscopy. From the methyl content and the number‐averages molecular weight of each resin, it was found that as molecular weight increases degree of branching decreases. Also revealed was the fact that each of the three types of double bond groups present, i. e., RHCCH2, RHCCHR, and RRCCH2, decreases in concentration with increasing molecular weight. Using polarized radiation, high resolution grating spectra were obtained on polyethylene films which had been highly oriented by cold drawing 500%. The results show that the CH3 terminated branches are not predominantly oriented either parallel or perpendicular to the direction of stretch. It is the authors' view that the chain branches vary in length with a considerable fraction short enough to be essentially at right angles to the long chain axis while others are sufficiently long to be parallel to the long chain axis in stretched polyethylene. When a stretched polyethylene film is heat relaxed (110–115°C.), its spectra using polarized radiation reveal the presence of crystallites in which the long carbon‐to‐carbon chain axes are predominantly oriented at right angles to the direction of stretch.

The Effects of Alpha Particles on Low Density Polyethylene

“…All other longer side chains produced effects which were similar, but intermediate between the methyl and ethyl side chains. Their work supported the view of Rugg, et al 3 , that some of the branches in low density polyethylene are pendant ethyl groups and that the higher crystalline content of high density polyethylene is not a consequence of higher molecular weight, but rather of the lower degree of branching. These workers also determined that the carbon-carbon double bond groups present in low density polyethylene decrease in concentration with increasing molecular weight.…”

An effective method to identify the type and content of α‐olefin in polyolefine copolymer by Fourier Transform Infrared–Differential Scanning Calorimetry

“…Figure 1 shows the typical FTIR spectras of PE copolymers. FTIR is widely used as a rapid analytical tool to identify the type of short chain branching in polyethylenes 7, 8. Ethyl, butyl, and hexyl‐type SCB in PEs are readily distinguishable8 by the region of 1300–1400 cm −1 , 800–1000 cm −1 (the unsaturated groups), and 700–900 cm −1 (the branched chains absorption),16 respectively, as can be seen in Figure 2.…”

“…Therefore, the qualitative analysis of short chain branching (SCB) in polyethylene is necessary for the correlation of molecular structure with physical properties. A variety of techniques have been used to identify and quantify the type and composition distribution of comonomer in bulk PE, such as temperature rising elation fractionation,3, 4 nuclear magnetic resonance (NMR),5, 6 Fourier Transform Infared (FTIR),7, 8 and thermal analysis9–11 techniques. However, it is often difficult to identify the type and composition of PE blends by a single analytical instrument, as they have the similar molecular and chemical structures.…”

Structure and some physical properties of polyvinyl chloride polymerized at different temperatures

“…CROSS et al 15), RUGG et al 16), BRYANT et al 17) and SLOWINSKI et a1.18) have pointed out that the number of branching in polyethylene can be estimated by determining the methyl contents of the sample by infrared analysis. CROSS et al 15), RUGG et al 16), BRYANT et al 17) and SLOWINSKI et a1.18) have pointed out that the number of branching in polyethylene can be estimated by determining the methyl contents of the sample by infrared analysis.…”