Biaxially oriented polypropylene film for metallizing applications

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The ethylene content and the distribution factor of the copolymer are determined with the aid of C.
sub.
13 NMR spectroscopy.
The measurements were carried out using a nuclear resonance spectrometer model HX-270 supplied by Bruker (Germany), which was equipped with a computer of the type Bruker Aspect 2000, supplied by Bruker.
The ethylene-propylene copolymer to be characterized is dissolved in a solvent mixture made from 65% by volume of hexachlorobenzene and 35% by volume of 1, 1-di-deuterotetrachloroethane, so that a 10% by weight solution resulted.
Octamethyltetrasiloxane (OMTS) was added as reference standard.
The 67.
9 MHZ C.
sub.
13 nuclear resonance spectrum was measured at 130.
degree.
C.
The evaluation of the spectra was carried out in accordance with the procedure described in J.
C.
Randall, Polymer Sequence Distribution (Academic Press, New York, 1977).
The distribution factor is defined as ##EQU1## in which C.
sub.
G denotes the total content of ethylene in the copolymer in % by weight and C.
sub.
i denotes the proportion of ethylene in % by weight, which is present as isolated ethylene component, i.
e.
, a single ethylene building block is located between two propylene building blocks in the manner illustrated as follows: ##STR1## The enthalpy of fusion .
DELTA.
H.
sub.
m is determined using the method of differential scanning calorimetry (DSC measurement).
A few milligrams (3 to 5 mg) of the raw material to be characterized are heated in a differential calorimeter at a heating rate of 20.
degree.
C.
/min.
The enthalpy of fusion .
DELTA.
H.
sub.
m of the raw material is obtained from the area below the corresponding fusion peak.
The base line on either side of the fusion peak is delineated by a linear tangent.
The idealized thermo-oxidation temperature T.
sub.
ox is determined in the following manner: 2 to 5 mg of the raw material to be investigated are heated in a differential calorimeter at a heating rate of 20 K/min.
Air is used as the purging gas, the outlet temperature being 295