welding of plastics
DOUGLAS AIRCRAFT COMPANY, NASA CR-2218, JAN 1973, REPRINTED AUG 1974 2. L.J. HART-SMITH, DESIGN AND ANALYSIS OF ADHESIVE-BONDED JOINTS, PROC. 1ST AIR FORCE CONF. FIBROUS COMPOSITES IN FLIGHT VEHICLE DESIGN, AFFDL-TR-72- 130, AIR FORCE FLIGHT DYNAMICS LABORATORY, 1972, P 813-856 3. L.J. HART-SMITH, ADVANCES IN THE ANALYSIS AND DESIGN OF ADHESIVE- BONDED JOINTS IN COMPOSITE AEROSPACE STRUCTURES, 14TH NATIONAL SAMPE SYMP. AND EXHIBITION, SOCIETY FOR THE ADVANCEMENT OF MATERIAL AND PROCESS ENGINEER ING, APRIL 1974, P 722-737 4. L.J. HART-SMITH, BONDED-BOLTED COMPOSITE JOINTS, J. AIRCRAFT, VOL 22, 1985, P 993-1000 5. L.J. HART-SMITH, ADHESIVELY BONDED JOINTS FOR FIBROUS COMPOSITE STRUC TURES, JOINING FIBRE-REINFORCED PLASTICS, F.L. MATTHEWS, ED., ELSEVIER, 1987, P 271-311 6. H.J. KIM AND R.E. BOHLMANN, "THERMAL SHOCK TESTING OF WET TH ERMOPLASTIC LAMINATES," 37TH INT. SAMPE SYMP. EXHIBITION, MARCH 1992 7. D.L. BUCHANAN AND S.P. GARBO, "DESIGN OF HIGHLY LOADED COMPOSITE JOINTS AND ATTACHMENTS FOR WING STRUCTURES," REPORT NADC-81194- 80, NAVAL AIR DEVELOPMENT CENTER, AUGUST 1981 8. E.T. CAMPONESCHI, R.E. BOHLMANN, J. HALL, AND T.T. CARR, "EF FECT OF ASSEMBLY ANOMALIES ON THE STRAIN RESPONSE OF COMPOSITES IN THE SPHERE JOINT REGIO N OF THE DARPA MAN RATED DEMONSTRATION ARTICLE," CDNSWC-SME- 92/22, DEFENSE ADVANCED RESEARCH PROJECT AGENCY, ARLINGTON, VA, 4 MARCH 1992 Welding of Plastics Thomas H. North and Geetha Ramarathnam, University of Toronto Introduction POLYMERS AND POLYMERIC COMPOSITES are attractive because of their high strength-to-weight ratio, chemical inertness, and ability to be molded into complex shapes at relatively low cost. Polymers can be categorized as thermosets or thermoplastics. In the case of thermoset resins, a chemical reaction occurs during processing and curing, that is, as a result of irreversible cross-linking reactions in the mold. Both molded thermoset and vulcanized elastomer components cannot be reshaped by means of heating, because degradation occurs. It follows that thermoset and vulcanized robber components can only be joined using adhesive bonding or mechanical fastening methods. Thermoplastic resins, on the other hand, can be softened, as a result of the weakening of secondary van der Waals or hydrogen bonding forces between adjacent polymer chains. Therefore, thermoplastics can be remolded by the application of heat, and they can be fusion welded successfully. Thermoplastics can be broadly divided into amorphous and crystalline resins, based on morphology, or structure. These materials are more attractive than thermosets because they: • ARE CHEAPER • ARE RECYCLABLE • CAN BE JOINED USING FUSION WELDING • HAVE GREATER DAMAGE TOLERANCE • ARE EASY TO PROCESS • HAVE GREATER IMPACT-RESISTANCE PROPERTIES Table 1 lists the major thermoplastic resins. Filled thermoplastics are being increasingly used in semistructural applications. Fillers can reduce material cost, enhance mechanical properties, improve thermal properties, provide flame retardation, and so on. TABLE 1 MAJOR CATEGORIES OF THERMOPLASTICS AND COMPOSITES COMMODITY PLASTICS POLYETHYLENE POLYPROPYLENE POLYVINYL CHLORIDE POLYSTYRENE ENGINEERING PLASTICS ACETAL ACRYLONITRILE-BUTADIENE-STYRENE POLYMETHYL METHACRYLATE POLYTETRAFLUOROETHYLENE NYLON POLYETHYLENE TEREPHTHALATE POLYBUTYLENE TEREPHTHALATE POLYPHENYLENE OXIDE POLYCARBONATE ADVANCED ENGINEERING PLASTICS POLYETHERETHER KETONE POLYETHERIMIDE POLYETHER KETONE POLYPHENYLENE SULFIDE LIQUID-CRYSTAL POLYMER POLYSULFONE REINFORCED AND ADVANCED THERMOPLASTIC COMPOSITES THERMOPLASTIC RESINS FILLED WITH SHORT, LONG, OR CONTINUOUS FIBERS OF GLASS, CARBON, OR ARAMID Joining is generally the final step in any fabrication cycle. Some important review articles are represented by Ref 1, 2, 3, 4, 5, and 6. The effectiveness of the joining operation can have a large influence on the application of any polymer or composite material. A variety of polymer joining techniques are available. Figure 1 provides a classification of these different methods (Ref 4). FIG. 1 CLASSIFICATION OF DIFFERENT JOINING METHODS. SOURCE: REF 4 Polymers are low-energy substrates, with surface free energies of less than approximately 50 mJ/m 2 (0.003 ft · lbf/ft 2 ) (Ref 7). The creation of a successful joint depends on four factors: the chemical nature of the polymer, the surface free energy, the surface topography, and contamination of the polymer surface by dust, oil, and grease. These factors markedly affect the effectiveness of the adhesive and solvent bonding methods. Fusion welding, however, is much more tolerant of aspects such as surface contamination and material variations from sample to sample. Adhesives are thermoset-type polymers that are classified as structural, nonstructural, or elastomeric. Reference 7 provides additional details. Structural adhesives are generally used in load-bearing applications, in joints that have high strength-to-weight ratios. They are also used to improve resistance to both component fatigue and corrosion resistance. The principal disadvantages of adhesive bonding are that surface preparation is required prior to bonding, curing times can be long, the components cannot be disassembled following the joining operation, and health and/or safety hazards may be involved in their use. In spite of these problems, adhesive bonding is used extensively in numerous industries. Mechanical fastening and adhesive bonding can be used to join both similar and dissimilar materials. For example, mechanical fastening is commonly used when joining a plastic to a metal (Ref 8), producing either permanent joints or connections that can be opened and sealed again. The advantages of this approach are that no surface treatment is required and disassembly of the components for inspection and repair is straightforward. The main limitations of this approach are increased weight, the presence of large stress concentrations around the fastener holes, and subsequent in-service corrosion problems (Ref 8). The typical applications of mechanical fastening are in the aerospace, automotive, and construction industry. Polymeric materials that possess similar solubility parameters can be joined using solvent or fusion welding. Interdiffusion of polymer chains plays a major role in achieving intrinsic adhesion (Ref 9) and in promoting chain diffusion, either by applying a suitable solvent or by heating the polymer sample. As mentioned previously, only thermoplastics can be joined using the fusion-welding process. The glass transition temperature, T g , in amorphous polymers, and the melting temperature, T m , in crystalline polymers must be exceeded so that the polymer chains can acquire sufficient mobility to interdiffuse. A variety of methods exist for welding thermoplastics and thermoplastic composites (Fig. 2). Thermal energy can be delivered externally via conduction, convection, and/or radiation methods, or internally via molecular friction caused by mechanical motion at the joint interface. In the case of external heating, the heat source is removed prior to the application of pressure, and longer welding times are balanced by the greater tolerance to variations in material characteristics. Internal heating methods depend markedly on the material properties (Ref 10). Heating and pressure are applied simultaneously, and shorter welding times are generally involved during the joining process. FIG. 2 CLASSIFICATION OF DIFFERENT WELDING METHODS FOR THERMOPLASTICS Welding is accomplished in many stages. During the initial stage, the polymer-chain molecules become mobile and surface rearrangement occurs. This is followed by wetting and the diffusion of polymer chains across the interface. The final stage involves cooling and solidification. For linear random-coil chains, the mechanical energy required to separate the welded substrates, G, is given by the relation (Ref 11): G = W(T,T,P,M) (EQ 1) where W is the welding function to be determined, t is the time of contact, T is the temperature of welding, P is the pressure, and M is the molecular weight of the polymer. In solvent welding, the application of a solvent at the bond line induces sufficient mobility for the polymer chains to interdiffuse (Ref 12, 13). Because the solvent must strongly plasticize the polymer surface, this joining technique is primarily applied to glassy amorphous thermoplastics, such as polycarbonate, acrylic, and polystyrene resins. References 1. G. GEHARDSSON, THE WELDING OF PLASTICS, WELD. REV., FEB 1983, P 17-22 2. M.N. WATSON, R.M. RIVETT, AND K.I. JOHNSON, "PLASTICS AN INDUSTRIAL AND LITERATURE SURVEY OF JOINING TECHNIQUES," REPORT NO. 7846.01 /85/471.3, THE WELDING INSTITUTE, ABINGTON, UK, 1986 3. H. POTENTE AND P. MICHEL, THE STATE OF THE ART DEVELOPMENT TRENDS IN T HE WELDING OF PLASTICS, PROC. 5TH ANNUAL NORTH AMERICAN WELDING RESEARCH CONFERENCE, EWI AND AWS, 1989 4. V.K. STOKES, JOINING METHODS FOR PLASTICS AND PLASTIC COMPOS ITES: AN OVERVIEW, POLYM. ENG. SCI., VOL 29 (NO. 19), 1989, P 1310-1324 5. R.A. GRIMM, FUSION WELDING TECHNIQUES FOR PLASTICS, WELD. J., MARCH 1990, P 23-28 6. G. MENGES, THE JOINING OF PLASTICS AND THEIR COMPOSITES, PROC. LNT. CONF. ADVANCES IN JOINING NEWER STRUCTURAL MATERIALS, IIW (MONTREAL), P 33-63 7. A.J. KINLOCH, ADHESION AND ADHESIVES, CHAPMAN AND HALL, 1987, P 101 8. D. CHANT, JOINING TECHNOLOGY FOR THERMOPLASTIC COMPOSITE STR UCTURES IN AEROSPACE APPLICATIONS, PROC. INT. CONF. ADVANCES IN JOINING PLA STICS AND COMPOSITES, THE WELDING INSTITUTE, CAMBRIDGE, 1991 9. S.S. VOYUTSKII, AUTOHESION AND ADHESION OF HIGH POLYMERS, WI LEY INTERSCIENCE, 1963 10. A. BENATAR, MATERIAL CHARACTERISTICS FOR WELDING, PROC. 5TH ANNUAL NOR TH AMERICAN WELDING RESEARCH CONFERENCE, EWI AND AWS, 1989 11. R.P. WOOL, B L. YUAN, AND O.J. MCGAREL, POLYM. ENG. SCI., VOL 29 (NO. 19), 1989, P 1340- 1367 12. W.V. TITOW, CHAPTER 12, SOLVENT WELDING OF PLASTICS, APPLIED SCIENCE PUB LISHERS, LONDON, P 181-196 13. M. LICATA AND E. HAAG, SOLVENT WELDING WITH POLYCARBONATE, PROC. SPE 44TH ANTEC MEETING, SOCIETY OF PLASTICS ENGINEERS, 1986, P 1092-1094 Welding of Plastics Thomas H. North and Geetha Ramarathnam, University of Toronto Fusion-Welding Techniques The commonly available fusion-welding techniques will be described in terms of the basis of the joining method, the key joining parameters involved in the process operation, and the application areas of each joining method. Hot-Tool Welding Hot-tool welding occupies a central position among the different thermal fusion-welding techniques. This method can provide joint strength that is equal to that of the base material. The surfaces to be joined are brought to the melting or softening temperature by direct contact with a heated tool. Once the desired molten film thickness is produced, the heated tool is removed, the melted surfaces are brought together, and the joint is allowed to cool and consolidate under pressure. Typical welding times range from 10 s to 60 min, depending on the size of the component being joined. The surfaces of the heated tool are usually coated with polytetrafluoroethylene (PTFE) to prevent the polymers from sticking to the platen. However, the PTFE coating generally restricts the maximum tool surface temperature to 260 °C (500 °F). Some research on heated-tool welding has involved hot-plate temperatures in excess of 350 °C (660 °F) for very short heating times (4 to 6 s). This thermal cycle has been made possible through the use of high-temperature aluminum- bronze heating elements (Ref 1). The hot-tool welding process can be described by four phases (Fig. 3). During phase I, the surfaces of the material are brought in contact with the heated tool and are held under pressure. This pressure is maintained until a molten film appears. In phase II, the contact pressure between the heated tool and the substrate is reduced to increase the molten-film thickness. The rate of increase of melted-film thickness depends on the thermal conductivity of the polymer. Phase III is the change-over (removal of the hot tool) time, whereas phase IV is the joining and cooling under pressure. The amount of melted-polymer displacement from the weld zone is controllable. For example, computer-controlled machines will allow preselection of the pressure or displacement values that are applied during joining (Ref 15). In this connection, detailed mathematical analyses of the hot-tool welding process have already been carried out (Ref 15, 17). FIG. 3 PRESSURE-TIME AND DISPLACEMENT-TIME GRAPH SHOWING DIFFERENT PHASES OF HOT- TOOL WELDING PROCESS. P A , P E , AND P F ARE MATCHING, HEATING, AND JOINING PRESSURES, RESPECTIVELY. T E , T U , T F , AND T K REPRESENT HEATING, CHANGE-OVER, JOINING, AND COOLING TIMES, RESPECTIVELY. S F , REDUCTION IN LENGTH OF THE PART BEING JOINED; S A , DISPLACEMENT PATH PRODUCED DURING TIME T E . SOURCE: REF 16 The key joining parameters of hot-tool welding are: • THE HEATED-TOOL TEMPERATURE, WHICH DEPENDS ON THE POLYMER BEING WELDED • THE PRESSURE APPLIED AND THE DURATION OF PHASE I. (HOWEVER, HIGH PRESSURE DURING PHASE IV WILL PRODUCE TOO MUCH LATERAL FLOW AND POLYMER-CHAIN ORIENTATION IN THE COMPLETED JOINT, RESULTING IN ADVERSE MECHANICAL PROPERTY EFFECTS, AS DESCRIBED IN REF 15 AND 16) • THE THERMAL CONDUCTIVITY AND SPECIFIC HEAT OF THE POLYMER AND THE SIZE AND WALL THICKNESS OF THE PART BEING JOINED, WHICH ARE THE PARAMETERS THAT DETERMINE THE DURATION OF PHASE II • THE TOOL TRANSFER, OR CHANGE-OVER, TIME, WHICH MUST BE MINIMIZED SO THAT COOLING OF THE MOLTEN LAYER DOES NOT OCCUR (TO AVOID INHIBITING POLYMER- CHAIN INTERDIFFUSION) Applications. All thermoplastic materials can be joined using hot-tool welding. Components that have large, flat surface areas are commonly butt welded using this technique. It is also possible to join dissimilar materials through the use of two heated platens that are at different temperatures (Ref 14). The weldability factor, in this case, is the degree of compatibility. Hot-tool welding can be readily automated. Portable equipment is primarily used for on-site weld repairs. Small amounts of joint misalignment prior to joining have negligible effects on the weld quality. Hot-tool welding is used in a variety of industrial applications. The automotive sector, for example, uses it to weld polypropylene (PP) copolymer cases for batteries and to weld rear-light casings of acrylonitrile-butadiene-styrene (ABS) joints to polymethyl methacrylate (PMMA) or polycarbonate (PC) lenses. Hot-tool welding is also employed when welding thermoplastic tanks and when joining large-diameter polyethylene (PE) pipeline to transport gas, water, and sewage wastes. Hot-Gas Welding A stream of hot air or gas (nitrogen, air, carbon dioxide, hydrogen, or oxygen) is directed toward the filler and the joint area using a torch (Ref 18). A filler rod or tape (of a similar composition to the polymer being joined) is gently pushed into the gap between the substrates (Fig. 4). A variety of nozzles are available for different applications, and either automated or manual welding can be carried out. During welding, the gas temperature can range from 200 to 600 °C (390 to 1110 °F), depending on the polymer being joined. FIG. 4 SCHEMATIC OF HOT-GAS WELDING, SHOWING THE CORRECT POSITION OF TORCH AND FILLE R ROD FOR DIFFERENT THERMOPLASTICS. SOURCE: REF 19 The key joining parameters of the hot-gas welding process are: • GAS TEMPERATURE, WHICH DEPENDS ON THE TYPE OF POLYMER BEING JOINED, AND WHICH DETERMINES THE HEATING ELEMENT, NOZZLE DIMENSIONS, AND GAS/AIR FLOW RATES THAT ARE USED • WELDING SPEED AND DOWNWARD PRESSURE OF THE WELDING ROD (MANU AL JOINING OPERATIONS) Applications. The principal application areas involve the continuous welding of polyolefin tanks and containers, the welding of polyvinyl chloride (PVC), ABS, PE, and PP pipe sections, the sealing of packaging materials, and the field repair of PVC and other thermoplastic resins that are used in the construction and automotive industries. Hot-gas welding has a disadvantage in that the temperature of the hot gas/air is much higher than the melting point of the polymer being joined. Therefore, the process has poor energy efficiency, and degradation of the polymer substrate is possible unless care is taken. Polymers that oxidize at temperatures close to their melting points cannot be welded by this technique. Extrusion Welding Extrusion welding is similar to hot-gas welding. The weld area is heated using hot air, and plasticized filler material is extruded into V-shaped or lap seam joints under pressure by means of a welding shoe (Ref 20, 21). The preheating and welding-shoe assemblies are connected to the welding head, and the welding speed is kept constant by an automatic traversing unit that has adjustable motor speeds (Fig. 5). FIG. 5 SCHEMATIC OF VARIANTS OF EXTRUSION WELDING PROCESS. SOURCE: REF 20 The key joining parameters of this process are the: • FEED ANGLE AND TEMPERATURE OF THE HOT GAS • TEMPERATURE AND PRESSURE OF THE EXTRUDATE • RELATION BETWEEN THE EXTRUDATE DELIVERY RATE AND THE WELDING SPEED • HORIZONTAL AND VERTICAL FORCES APPLIED AT THE WELDING SHOE • WELD LENGTH AND TIME REQUIRED TO COMPLETETHE JOINT Applications. Extrusion welding is primarily used for producing long seams in thick-section polyolefin components. This joining technique is particularly useful when welding large container sections. Focused Infrared Welding This joining technique uses a quartz lamp and focuses the infrared (IR) radiation using highly polished, parabolic, elliptical reflectors. The focused IR method directs a precise, high-intensity reciprocating IR beam of a width that ranges from 1.5 to 3.0 mm (0.06 to 0.12 in.) onto the joint interface (Ref 22). A robotic fixture scans the IR beam back and forth over the two adherend surfaces, and when the joint line reaches the desired temperature, the heat source is removed and the substrates are forged together in a press. Sensors are mounted adjacent to the lamp fixture and are calibrated so that they selectively measure the adherend interface temperature only (Fig. 6). FIG. 6 SCHEMATIC OF FOCUSED IR LAMP AND OPTICAL SENSOR. SOURCE: REF 22 The welding of polyphenylene sulfide, using this IR technique, has been reported (Ref 23). Focused IR welding can be automated. Because this is a relatively new joining process, a detailed analysis of process operation has yet to be conducted. The key joining parameters of this welding process are the: • RADIATION DENSITY AND TIME OF IRRADIATION • RADIATION ABSORPTION, REFLECTION, AND TRANSMISSION PROPERTIE S OF THE POLYMER, WHICH DETERMINE THE RATE OF THE TEMPERATURE RISE IN THE IRRADIATED MATERIAL • FLOW TEMPERATURE AND THERMAL CONDUCTIVITY OF THE IRRADIATED POLYMER • RECIPROCATION RATE OF THE RADIATOR, WHICH DEPENDSON THE TYPE OF POLYMER BEING JOINED, AND ON THE PART SIZE • RETRACTION RATE OF THE RADIATIVE HEAT SOURCE AND CLOSING SPE ED OF THE PRESS (IN ORDER TO AVOID COOLING THE MELTED MATERIAL AT THE JO INT INTERFACE) Applications. This technique can be used to join both simple and complex joint configurations when a noncontacting method of heating is essential. In addition, reinforced-fiber disruption can be minimized when advanced thermoplastic composites are joined. Laser Welding Limited information is available on laser welding. Carbon dioxide (CO 2 ) lasers induce excitation of the vibrational modes and, hence, heating of the irradiated organic material (Ref 24, 25). At low power input levels, satisfactory weld penetration can be achieved. The technique also provides high welding speeds and produces very small heat-affected zones (HAZ). Typical joining conditions involve an energy input of 100 W using a wavelength of 10.6 m. The absorption of laser radiation depends on the relation: I(Z) = I 0 EXP (-αZ) (EQ 2) where z is the distance into the sample at which the laser intensity I (W/cm 2 ) is measured, I 0 is the laser intensity at the surface of the polymer sample (at z = 0), and α (1/cm) is the absorption coefficient. The laser power, P (watts) required for any given material to depth a (meters) can be derived using the relation (Ref 25): ( ) 0.484 p m m vWa C T H p ρ + ∆ = (EQ 3) where v is the welding speed (m/s), W is the weld width (m), ρ is the density of polymer (ks/m 3 ), C p is the heat capacity (J/kg · °C), T m is the melting temperature (°C), and ∆H m is the latent heat of melting (J/m 3 ). There is not much that has been published concerning the commercial application of this joining method. References cited in this section 1. G. GEHARDSSON, THE WELDING OF PLASTICS, WELD. REV., FEB 1983, P 17-22 14. K. GABLER AND H. POTENTE, WELDABILITY OF DISSIMILAR THERMOPLASTICS EXPERIMENTS IN HEATED TOOL WELDING, J. ADHES., VOL 11, 1980, P 145-163 15. H. POTENTE AND P. TAPPE, SCALE-UP LAWS IN HEATED TOOL BUTT WELDING OF HD PE AND PP, POLYM. ENG. SCI., VOL 29 (NO. 23), 1989, P 1642-1648 16. H. POTENTE AND J. NATROP, COMPUTER AIDED OPTIMIZATION OF THE PARAMETERS OF HEATED TOOL BUTT WELDING, POLYM. ENG. SCI., VOL 29 (NO. 23), 1989, P 1649-1654 17. A.J. POSLINSKI AND V.K. STOKES, ANALYSIS OF THE HOT-TOOL WELDING PROCESS, PROC. SPE 50TH ANTEC MEETING, 1992, SOCIETY OF PLASTICS ENGINEERS, P 1228-1233 18. H. GUMBLETON, HOT GAS WELDING OF THERMOPLASTICS AN INTRODUCTION, JOIN. MAT., VOL 5, 1989, P 215-218 19. "RECOMMENDED PRACTICES FOR JOINING PLASTIC PIPING," DOCUMENT XVI-322-78-E, IIW 20. P. MICHEL, "AN ANALYSIS OF THE EXTRUSION WELDING PROCESS," POLYM. ENG. SCI., VOL 29 (NO. 19), 1989, P 1376-1382 21. M. GEHDE AND G.W. EHRENSTEIN, STRUCTURAL AND MECHANICAL PROPERTIES OF OPTIMIZED EXTRUSION WELDS, POLYM. ENG. SCI., VOL 31 (NO. 7), 1991, P 495-501 22. H. SWARTZ AND J.L. SWARTZ, FOCUSSED INFRARED A NEW JOINING TECHNO LOGY FOR HIGH PERFORMANCE THERMOPLASTICS AND COMPOSITE PARTS, PROC. 5TH A NNUAL NORTH AMERICAN WELDING RESEARCH CONFERENCE, EWI AND AWS, 1989 23. H. POTENTE, P. MICHEL, AND M. HEIL, INFRARED RADIATION WELDI NG: A METHOD FOR WELDING HIGH TEMPERATURE RESISTANT THERMOPLASTICS, PROC. SPE 49TH ANTEC MEETING, SOCIETY OF PLASTICS ENGINEERS, 1991, P 2502-2504 [...]... 1992, SOCIETY OF PLASTICS ENGINEERS, P 888 31 M CAKMAK AND K KEUCHEL, U.S PATENT 4,998,663, MARCH 1991 32 K KEUCHEL AND M CAKMAK, SPIN WELDING OF POLYPROPYLENE: CHARACTERIZATION OF HEAT AFFECTED ZONE BY MICRO-BEAM WAXS TECHNIQUE, PROC SPE 49TH ANTEC MEETING, SOCIETY OF PLASTICS ENGINEERS, 1991, P 2477-2481 33 H RAJARAMAN AND M CAKMAK, THE EFFECT OF GLASS FIBER FILLERS ON THE WELDING BEHAVIOR OF POLY P-PHENYLENE... Welding of Plastics Thomas H North and Geetha Ramarathnam, University of Toronto Evaluation of Welds Because polymers are being used increasingly for semistructural and load-bearing applications, the testing of the welded joints is important The mechanical properties of welded plastics can be evaluated by performing standard destructive tests, such as tensile, peel, wedge, and four-point bending Of particular... WELDING RESEARCH CONFERENCE, EWI AND AWS, 1989 Welding of Plastics Thomas H North and Geetha Ramarathnam, University of Toronto References General Review Articles on Joining and Welding of Polymers: 1 G GEHARDSSON, THE WELDING OF PLASTICS, WELD REV., FEB 1983, P 17-22 2 M.N WATSON, R.M RIVETT, AND K.I JOHNSON, "PLASTICS AN INDUSTRIAL AND LITERATURE SURVEY OF JOINING TECHNIQUES," REPORT NO 7846.01/85/471.3,... VIBRATION WELDING OF THERMOPLASTICS, PART II, POLYM ENG SCI., VOL 28, 1988, P 727-739 29 H POTENTE AND H KAISER, PROCESS VARIANT OF VIBRATION WELDING WITH VARIABLE WELDING PRESSURE, PROC SPE 48TH ANTEC MEETING, SOCIETY OF PLASTICS ENGINEERS, 1990, P 1762-1765 30 H POTENTE AND M UEBBING, COMPUTER AIDED LAYOUT OF THE VIBRATION WELDING PROCESS, PROC SPE 50TH ANTEC MEETING, 1992, SOCIETY OF PLASTICS ENGINEERS,... 32 K KEUCHEL AND M CAKMAK, SPIN WELDING OF POLYPROPYLENE: CHARACTERIZATION OF HEAT AFFECTED ZONE BY MICRO-BEAM WAXS TECHNIQUE, PROC SPE 49TH ANTEC MEETING, SOCIETY OF PLASTICS ENGINEERS, 1991, P 2477-2481 33 H RAJARAMAN AND M CAKMAK, THE EFFECT OF GLASS FIBER FILLERS ON THE WELDING BEHAVIOR OF POLY P-PHENYLENE SULFIDE, PROC SPE 50TH ANTEC MEETING, SOCIETY OF PLASTICS ENGINEERS, 1992, P 896-899 Ultrasonic... MEETING, SOCIETY OF PLASTICS ENGINEERS, 1990, P 1829-1833 37 M.N TOLUNAY, P.R DAWSON, AND K.K WANG, HEATING AND BONDING MECHANISMS IN ULTRASONIC WELDING OF THERMOPLASTICS, POLYM ENG SCI., VOL 23, 1983, P 726-733 38 G HABERNICHT AND J RITTER, ENERGY CONVERSION IN THE ULTRASONIC WELDING OF THERMOPLASTICS, KUNSTST GER PLAST., VOL 78, 1988, P 49-66 39 A BENATAR AND T.G GUTOWSKI, ULTRASONIC WELDING OF PEEK GRAPHITE... MICHEL, THE STATE OF THE ART DEVELOPMENT TRENDS IN THE WELDING OF PLASTICS, PROC 5TH ANNUAL NORTH AMERICAN WELDING RESEARCH CONFERENCE, EWI AND AWS, 1989 4 V.K STOKES, JOINING METHODS FOR PLASTICS AND PLASTIC COMPOSITES: AN OVERVIEW, POLYM ENG SCI., VOL 29 (NO 19), 1989, P 1310-1324 5 R.A GRIMM, FUSION WELDING TECHNIQUES FOR PLASTICS, WELD J., MARCH 1990, P 23-28 6 G MENGES, THE JOINING OF PLASTICS AND... JOINING PLASTICS AND COMPOSITES, THE WELDING INSTITUTE, CAMBRIDGE, 1991 28 V.K STOKES, VIBRATION WELDING OF THERMOPLASTICS, PART II, POLYM ENG SCI., VOL 28, 1988, P 727-739 29 H POTENTE AND H KAISER, PROCESS VARIANT OF VIBRATION WELDING WITH VARIABLE WELDING PRESSURE, PROC SPE 48TH ANTEC MEETING, SOCIETY OF PLASTICS ENGINEERS, 1990, P 1762-1765 30 H POTENTE AND M UEBBING, COMPUTER AIDED LAYOUT OF THE... microstructural examination of bonded regions is important because it allows: • • • • • MEASUREMENT OF THE WELD ZONE AND HEAT-AFFECTED ZONE DIMENSIONS AND THEIR UNIFORMITY ALONG THE WELD LINE EVALUATION OF THE DEVELOPMENT OF CRYSTALLINITY, ESPECIALLY THE TRANSCRYSTALLINE REGION EVALUATION OF THE CHAIN ORIENTATION, ESPECIALLY PARALLEL TO THE BONDLINE REGION ESTIMATION OF THE FAILURE MODES OF MECHANICALLY TESTED... represents phase IV FIG 8 SCHEMATIC OF PENETRATION-TIME GRAPH SHOWING THE FOUR PHASES OF VIBRATION WELDING PROCESS SOURCE: REF 26 The key joining parameters of this process are the: • • AMPLITUDE, FREQUENCY, AND TIME OF VIBRATION APPLIED DURING WELDING PRESSURE APPLIED DURING THE JOINING OPERATION It has been reported that the use of a process-controlled pressure profile (high pressures during phase . 44TH ANTEC MEETING, SOCIETY OF PLASTICS ENGINEERS, 1986, P 1092-1094 Welding of Plastics Thomas H. North and Geetha Ramarathnam, University of Toronto Fusion-Welding. be softened, as a result of the weakening of secondary van der Waals or hydrogen bonding forces between adjacent polymer chains. Therefore, thermoplastics