Welding of plastics

Although it might be argued that the penetration of polymer molecules into the pores of an anodized metal surface is a form of interfacial diffusion, the present text will not consider such a process to represent an example of the diffusion theory. However, it has been reported [53] that interdiffusion does occur across polymer/metal interfaces when certain metals are evaporated or sput- 

In summary, the interdiffusion of polymer chains across a polymer/polymer interface requires the polymers (adhesive and substrate) to be mutually soluble and the macromolecules or chain segments to have sufficient mobility. These conditions are usually met in the autohesion of elastomers and in the solvent welding of compatible, amorphous plastics. In both these examples interdiffusion does appear to contribute significantly to the intrinsic adhesion. However, where the solubility parameters of the materials are not similar, or one polymer is highly crosslinked, crystalline or below its glass transition temperature, then interdiffusion is an unlikely mechanism of adhesion. In the case of polymer/metal interfaces it appears that interdiffusion can be induced and an interphase region created. But this effect enhances the interfacial adhesion by improving the adsorption of the polymeric material rather than by a classic diffusion mechanism. 

---

There are at present only a few commercial applications of ultrasound in the plastics industry. The best knovm is probably the welding of thermoplastics, a process which now lends itself readily to automation. In common with the welding of metals, the ultrasonic welding of plastics is primarily a hot stage. In the process ultrasound is applied to two layers of plastic, heat is generated at the interface causing the material... 

The second theory—winter-diffusion—would seem applicable to the particular case of the adhesion of like surfaces (known also as auto-adhesion ). Certainly it occurs in the welding of plastics, and in instances such as tyre manufacture when unvulcanized rubbers adhere spontaneously. On the other hand, it is unlikely that much inter-diffusion takes place when materials dissimilar chemically are brought together. It is well-known that many plastics are incompatible and if mixed will, over a period of time, tend to separate— forming eventually discrete layers. Behaviour of this kind is precisely the reverse of inter-diffusion. 

Zade, H.P., Heat Sealing and High-Frequency Welding of Plastics. Temple Press Limited, London, (1979), P. 79. 

FIGURE 2.79 Welding of plastics (a) hot-gas welding (b) ultrasonic contact welding. 

Chem. Descrip. y-Butyrolactone CAS 96-48-0 EINECS/ELINCS 202-509-5 Uses Solvent for PAN, PS, fluorinated hydrocarbons, cellulose triacetate, shellac, used in paint removers, petrol, processing, hectograph process, specialty Inks Intermediate for aliphatic and cyclic compds. reaction and diluent solvent for pesticides dyeing of acetate wetting agent for cellulose acetate films, fibers solvent welding of plastic films in adhesive applies. 

Coelho JP, Abreu MA, Pires MC (2000) High-speed laser welding of plastic films. Opt Lasers Eng 34 385-395... 

Ultrasound has long been used for a wide range of applications [5]. These include inter alia the welding of plastics [6], ultrasonic imaging in medicine [7], the dispersion of pigments and solids [8], cleaning both on an industrial scale [9] and in precision applications such as dentistry [10], and in catalyst manufacture [11]. Sonoelectrochemistry [3,12-15] is concerned with the coupling of power ultrasound to electrochemical systems in order to both achieve and develop new processes and applications. 

W. V. Titow, Solvent welding of plastics, in Adhesion-2, K. W. Allen, Ed., Applied Science Publishers, London, 1978. 

K. Sato, Y. Kurosaki, T. Saito, 1. Satoh, Laser welding of plastics transparent to near-infrared radiation, Proc. SPIE 2002, 4637, 528-536. 

Laser welding of plastic parts has been available for the last 30 years. However, only recently have the technology and cost allowed these joining techniques to be considered broadly. Laser welders produce small beams of photons or electrons. The beams are focused onto the work piece. Power density varies from a few to several thousand W/mm, but generally low-power lasers (less than 50 W/mm ) are used for plastic parts. 

Sensors Electromagnetic shielding Electrochromic screens or windows Lithography Conductive textiles Microwave welding of plastics Electrolytic capacitors... 

Wise, R.J. Ultrasonic welding of plastics by a Terfenol driven magnetostrictive transducer. Proc. 3rd Conf. on Welding and Adhesive Bonding of Plastic, Diisseldorf, Nov. 1992, pp. 10-12... 

This theory, put forth by Vo)mtskii, accounts for the autoadhesion of polymers by the interdiffusion of polymers across the interface and their mutual solubility. Direct radiometric and luminescence experiments have confirmed that the diffusion boundary may be as deep as 10 pm. Interdiffusion is also important in solvent welding of plastics where the solvent essentially plasticizes the surfaces and... 

Methylene chloride is employed in the manufacture of polycarbonate resin used for the production of thermoplastics. It is used as a solvent in the production of cellulose triacetate which serves as a base for photographic film. Other applications include its use in the solvent welding of plastic parts, and as a releasing agent to prevent the manufactured part from permanently bonding to the mold. 

To protect polymers while under severe conditions, such as high temperature, by an inert atmosphere (nitrogen, water vapor, carbon dioxide) welding of plastic materials is usually done by heated inert gases. 

Benatar A. Ultrasonic welding of plastics and polymeric composites. In Gallego-Juarez JA, Graff KF, editors. Power ultrasonics applications of high intensity ultrasound. Waltham, MA Elsevier 2015. 

Grewell D, Benatar A. Welding of plastics fundamentals and new developments. Int Polym Process 2007 22 43-60. 

Tappe, R, and Potente, H., New Findings in the Spin Welding of Plastics, ANTEC Conf Proc., Soc. Plastics Eng., 1989. 

Conductive polymers have been suggested for use in the welding of plastics. A strip of conducting polymer-coated material can be used to convert microwave radiation into thermal energy [94]. Similarly, composite structures can be manufactured using conducting... 

In the case of polymer joining, the assumption of no physical mixing is not reasonable. Welding of plastics, using heat or solvents, is a clear example of interpenetration occurring at the joint surface. 

---