The high frequency (27.12 MHz) weldability of a thermoplastic polyuret
hane elastomer coated fabric was investigated after determination of i
ts dielectric properties. It was shown that at 27.12 MHz, maximum heat
ing occurred at 50 degrees C. Subsequent tests were thus carried out a
t this temperature. Temperature needs to be measured continuously duri
ng the welding operation as the integrity of the weld depends on the c
ore temperature. Since conventional methods using probes or adhesive i
ndicator strips are disrupted by high frequency (HF) radiation, the in
tegrity of the weld obtained by HF was compared to that obtained by im
pulse welding at a given temperature under the same conditions of pres
sure with the same peeling performance and with the same temperature v
ariation after welding, measured by the i.r. thermometer. The highest
peeling forces were found when the welding temperature exceeded that o
f the melting point (180 degrees C) of the hard segments in the polyme
r. The interactions occurring during welding were found to depend on t
he temperature. At temperatures below 180 degrees C, the peeling resis
tance only derived from entanglements of flexible segments at the inte
rface between the two TPU-coated fabrics. At temperatures of 180 degre
es C and above, melting and mixing of hard segments produced total coh
esion of the two coated fabrics resulting in an enhanced peeling force
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