Impulse welding

When the heating phase was analyzed, it was seen that if the part that absorbs the laser beam has a high absorption constant, this process phase can be readily described by a physico-mathematical model, by analogy to single-sided heat impulse welding. A comparison of calculated and measured melt layer thicknesses showed that, by introducing a correction factor, it is possible for this model to be successfully used for the case of a low absorption constant as well. 

Impulse welding is an advanced form of hot-bar welding in which both the heating and cooling regimes are controlled while the joint is stUl under pressure. 

Welding plastics - external heat source A BUXTON Hot plate, impulse welding, etc. 

Use of Vectra A950 liquid crystal polymer is described with reference to the production of barrier packaging for the containment of anaesthetic emulsions. The pouches were compression moulded and sealed by thermal impulse welding. Concentrations of lidocaine and prolocaine in the emulsion were studied for 14 weeks at two different temperatures, 40 degrees C and 60 degrees C, and at 100% relative humidity. Loss of substances from the emulsion was due mainly to adsorption onto the polar surface of the liquid crystalline polymer, it is reported. 21 refs. 

Impuls, StoB, Anregung, Antrieb electr StromstoB impulse welding ImpulsschweiBen impure... 

Uses. A review of its use as an oxidizer in rocket proplnts is given in Ref 6. A 50 50 mixt of N trifluoride F, with ammonia as fuel, yields a specific impulse of 295sec and a d impulse (specific impulse X d) of 340 (Ref 6). Mixts with methyl fluoride, 1,1 -difluoropropane, and 1,3-dlfluoropropane have been patented as monoptoplnts(Ref 9). AN trifluoride/H flame has been proposed as a cutting and welding torch (Ref 8)... 

The heat is applied to the outer surfaces of the materials being welded, and in order to make the weld it must travel through the material to the interfaces. For many applications thermal sealing has been superseded by impulse sealing but the former process is in use still for welding thick sheets of flexible thermoplastics. The production equipment employs a heated wedge placed between the sheets, over which they are moved continuously. 

The essential difference between machines for thermal sealing and for impulse sealing is that, whereas the former employ electrode bars that are maintained at a constant temperature, the latter employ sealing bars which are heated only during the clamping and welding cycle. 

The thickness can also be determined by simple, portable ultrasonic devices. The delay time of the echo of an ultrasonic impulse from the back side of the geomembrane is measured which is sent by an ultrasonic measuring head placed on top of the geomembrane. This method is mainly used for the measurement of the thickness of weld seams (see Sect. 10.2). 

Total freedom of maintenance cannot be realized without peripheral devices because of the necessity of water replenishment. Even so, plastic housings totally electrolyte-tight, welded-on plastic lids, as well as totally sealed terminals make a new generation of batteries with high insulation resistances that are totally dry on the outside. Good insulation resistance is a demand that must be met, especially for modern impulse-guided vehicles, for resistance deficiency could cause malfunctions with these systems. 

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