Metrohm 763 PVC Thermomat Manual - Manual (Page 73)

4 Operation
763 PVC Thermomat
66
4.6.2 Sample preparation
PVC or other plastics which decompose through the action of heat with
cleavage of hydrogen halides are prepared in accordance with DIN
53'381 as follows:
1 Powdery samples
• Polymers, dry blends and coating powders need no special
sample pretreatment.
2 Pastes
• Pastes are fused on a glass plate in a drying oven to a sheet
with a thickness of about 0.5 mm. After cooling, the sheet is
cut into pieces of edge length about 2 mm.
3 Solid samples
• Molding compounds in granular form, molded and finished
parts, semi-finished products as well as coatings separated
from the substrate are pulverized in accordance with DIN
53'733 and screened to separate the screening fraction be-
tween the analytical screens with wire mesh screen DIN 4188-
1.4 (wire mesh of stainless steel with 1.4 mm inside diameter
mesh size) and wire mesh screen DIN 4188-2 (wire mesh of
stainless steel with 2 mm inside diameter mesh size) for the
experiments.
4 Sheets
• Sheets are cut into pieces with an edge length of about 2
mm.
According to DIN 53'581, the samples are to be added directly into
the prewarmed reaction vessels inserted in the heating block. Never-
theless, comparative measurements have shown identical results for
sample addition to cold or hot reaction vessels.
4.6.3 Prepare instruments and accessories
Clean instruments and accessories
The cleanness of instruments and accessories is an absolute neces-
sity for achieving reliable, reproducible and correct analytical results.
Even minute contamination can catalytically accelerate the thermal de-
composition and lead to completely false results. Make sure that the
following checks and cleaning procedures are carried out before the
start of a determination:
1 Openings for reaction vessels
• Check whether the openings for the reaction vessels are
clean and empty. Blow out any dust in the openings with ni-
trogen.