In situ near-infrared spectroscopic studies of the structural changes of polyethylene during melting

Abstract

Conformational changes occurring during the melting of various polyethylene (PE) materials, including high-density PE (HDPE), linear low-density PE (LLDPE) and low-density polyethylene (LDPE), were investigated using near-infrared spectroscopy. The assignment of PE to the 1650-1900 nm spectral region was suggested, on the basis of computational and experimental data for normal alkanes. The present results suggested that the 1690 and 1710 nm bands should be assigned to the CH 3 groups in branched chains and chain ends, respectively. The HDPE and LDPE crystal lattices have very few defects, in contrast to LLDPE, which has more crystal lattice defects. The chain ends and junctions of LDPE are excluded from the crystal lattice and exist in a thick amorphous layer, whereas LLDPE includes comonomers in its crystalline lattice.

Determination of optical properties of a corn starch biofilm

“…Figure shows the UV–vis–NIR spectrum. Both films present very similar values from 200 to 800 nm, but in the range 800 to 2500 nm, notable changes are due to the cyclic structure of the starch in comparison to the linear structure of the LDPE and its contributions by CH groups . In the range 1400 to 1600 nm, the contributions of CH 3 and OH groups are apparent, while in 1650 to 1850 nm the contributions of CH and CH 3 are observed.…”

“…At 2100 nm, the contribution of the O‐H from the alcohol on C6 of the ring of pyranose is observed. Finally, in the range 2300 to 2500 nm, the vibrations of CH 3 and CH 2 are observed …”

Pharmaceutical Application of Tablet Film Coating

“…In addition, it can be used to predict drug release rate in combination with multivariate analysis [ 16 ]. NIRS has a disadvantage that the assignment of bands for more complex organic materials is complicated due to the absorption overlap of overtones and combination tones [ 110 ]. Raman spectroscopy examining the vibrational transitions in molecules is also applicable for quantitative analysis of the coating process.…”

A Near‐Infrared Spectroscopy Study on Thermal Transitions of PMMA and PMMA/SiO2 Nanocomposites

“…In this sense near‐infrared spectroscopy (NIR) may be a simple alternative because transition moment of overtones and combination bands are quite lower allowing the sample of analysis to be thicker. There are several articles in which FT‐NIR is used to study thermal transitions in polymers …”

“…There are several articles in which FT-NIR is used to study thermal transitions in polymers. [8][9][10][11] On the other hand, variations in hydrogen bonding and other interactions manifest themselves as changes in the force constants of the X-H bonds. Generally, bands will shift in frequency and broaden due to the formation of those interactions.…”