Improved apparatus for trapped radical and other studies down to 1.5 K.
This note describes a Dewar system and associated apparatus for trapped free radical and other studies at temperatures down to 1.5 K. Cylindrical and rectangular microwave cavities can be used.
AN OPTICAL CELL FOR USE WITH LIQUID HELIUM
A low temperature cell is described that permits spectral absorption and emission measurements, as well as high energy irradiation of materials held at liquid helium temperatures. The liquid helium capacity of one liter is sufficient for up to 24 hours of continuous operation. Any substance whether it be solid, liquid, or gas at room temperatures can be studied. The all‐metal cell is entirely portable and can be employed with a number of instruments without modification. A sylphon bellows arrangement permits vertical displacement within the cell of the samples under study.
Enhancement of surface properties on Low Density Polyethylene packaging films using various fluorination routes
Nowadays, packaging market deployment requires an important attention. Influence of treatment with molecular (F2) or atomic (Fradical dot) fluorine on properties of Low Density Polyethylene (LDPE) films was investigated. The films were treated using direct fluorination conditions with F2 or a specific reagent XeF2, which releases atomic fluorine Fradical dot. Changes of LDPE chemical composition were investigated by FTIR and solid state NMR. Surface morphology was studied by several microscopy techniques (SEM and AFM). Finally to further characterize film properties after treatments, surface energy measurements and electron paramagnetic resonance (EPR) analyses were also carried out. An upper fluorinated layer, which contains mainly high amount of single bondCF2single bond, was formed during the direct fluorination conditions (F2). For the process performed with XeF2, specific groups single bondCHFsingle bond were detected not only on the polymer surface but also in the bulk. The final CHF/CF2 ratio depended on the fluorination route. Treatment with Fradical dot (originated from XeF2 decomposition) resulted in single bondCHFsingle bond groups in bulk prevailing formation whereas F2 formed mainly single bondCF2single bond groups. Regardless to the reactive species, radicals (dangling bonds) appeared during the fluorination and reacted with oxygen during the exposition to air after the treatment. Such a process resulted in oxygenated polar groups formation and consequently in the surface energy increase.