Thermoplastic welding

In high-frequency dielectric welding thermoplastic materials are joined by applying simultaneously pressure and alternating high-frequency fields, using electrodes of suitable design and shape. ... 

Ultrasonic welding is a frictional process that has been well established for heat welding thermoplastic parts. Like induction welding, it also has been adapted for curing structural adhesives such as epoxy. 

Flash - In welding thermoplastics, molten plastic that seeps out of the joint area during the welding process. In molding, surplus plastic attached to the molding along the parting line. Flash must usually be removed before parts are considered to be finished. 

An example of a 100% solid, non-flammable, heat-activated hot-melt adhesive recommended for structural bonding of aluminum, steel, copper, brass, titanium, fabric, and some plastics is 3M Company s Scotch -Weld Thermoplastic Adhesive Film 4060. Strength data are shown in Table 5.5. " Bonding using this clear, amber, unsupported film adhesive takes place rapidly. The speed of bonding is hmited only by the heat-up time required to reach the optimum bonding temperature of 149°C at a pressure sufficient to maintain contact between the surfaces to be bonded. The adhesive... 

The possibility of using microwaves to weld thermoplastics has existed since the development of the magnetron in the 1940s. In 1993, TWl built a research facility to explore... 

High-frequency welding n. A method of welding thermoplastic articles in which the surfaces to be joined are heated by contact with electrodes of a high-frequency electrical generator. 

These methods are generally capable of joining thermoplastics to themselves and other thermoplastics, and in certain cases they may also be used to weld thermoplastics to nonplastic substrates. 

The application of inherently conducting polymers (ICPs) to welding thermoplastics was reported by Kathirgamanathan [145] however, the use of ICPs as micro-wave absorbers for welding was suggested earlier by Epstein and MacDiarmid [ 146]. In a typical experiment, a small amount of ICP either as powder (20 mg) or tape (two strips with dimensions 20 mm X 2 mm x 40 pm) was placed onto the upper surface of the plastic (10 cm X 2 cm X 0.1 cm). The second piece was placed on the top and clamped. The clamp assembly was then placed in a household micro-wave oven with a total power of 500 W for 2-120 s. The results are summarized in Table 18. The method can be applied to any thermoplastic. 

Dennis Hurley, Welding Thermoplastics, Modem Plastics Encyclopedia, McGraw-Hill, New York, NY, 1974-75. 

Friction Welding. A method of welding thermoplastic materials in which the heat necessary to soften the components is provided by friction. 

In radio-frequency welding, thermoplastic parts to be welded are placed underpressure between two electrodes. Energy, usually 27 MHz, is applied to the electrodes, and the resulting alternating current induces a rapidly reversing (several million times per second) electric field around the parts. Polar molecules in an electric field tend to orient in the field direction, so that... 

Stainless steel heating elements can be used alone in welding thermoplastics. Stainless steel heating elements introduce foreign material into the joint but are used to minimize any potential for galvanic corrosion and to reduce fiber motion, which has a detrimental effect on joint strength. The heating element comprises the innermost portion of the weld stack (Fig. 14.36) used in... 

Heatsealing method of welding thermoplastic materials, principally used for sealing polyethylene film in the manufacture of bags. 

B. Baylis, Y.P. Huang, D. Watt, Welding Thermoplastic Elastomers to Polypropylene with a Diode Laser, ICALEO (2002). 

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