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Acrylonitrile-Butadiene-Styrene Copolymer Alloy
Chapter 74
Polycarbonate/Acrylonitrile-Butadiene-Styrene Copolymer Alloy General Discussion of Joining Techniques Bayer: Bayblend Parts molded of Bayblend FR resins may be joined to other parts molded of Bayblend resins, or other plastics or metal parts by any of the variety of techniques. The elasticity of Bayblend FR resins permits the application of snap fits. This method of assembly is a fast, easy, and economical way to assemble two or more parts. Bonding or welding may be used for permanent joints. Bolts, screws, or ultrasonic inserts work well for detachable assemblies. Table 74.1: Methods of Joining Parts Molded of Bayblend FR Polycarbonate/Acrylonitrile-Butadiene-Styrene Copolymer. -
Hinges Self-tapping screws Machine screws Molded-in threads Heat insertion Heat welding Electromagnetic bonding Spin welding
-
Adhesive bonding Snap fits Ultrasonic welding Ultrasonic insertion Ultrasonic and heat staking Ultrasonic spot welding Vibration welding Solvent bonding
Reference: Bayblend FR Resins For Business Machines And Electronics, supplier marketing literature (55-D808(5)J 313-10/88) - Mobay Corporation, 1988.
Ultrasonic Welding Dow Chemical: Pulse 1370 This study was designed to identify which resins could be effectively ultrasonically welded to themselves and other resins, and to identify the maximum bond integrity. Besides looking at the weld strength of various thermoplastic resins, this study explores the effects of gamma radiation and ethylene oxide (EtO) sterilization on the strength of these welds. A wide variety of resins used in the healthcare industry were evaluated including: ABS, polycarbonate (PC), polycarbonate/ ABS blends (PC/ABS), styrene acrylonitrile (SAN), thermoplastic polyurethanes (TPU), rigid TPU’s (RTPU), high impact polystyrene (HIPS), and general purpose polystyrene (GPPS). The strength of customized “I” beam test pieces was tested in the tensile mode to determine the original strength of each resin in the solid, nonbonded test piece configuration. Data from this base line testing was used to determine the percent of original strength that was maintained after welding. Only amorphous resins were used in this study. The most commonly used energy director for amorphus resins, a 90° butt joint, was used as the welding architecture. Every attempt was made to make this a “real world” study. The aim during the welding process was to create a strong weld, while maintaining the aesthetics of the part. One of the most important factors in determining whether or not a good weld had been achieved was the amount of flash, or overrun noticed along both sides of the joint. Another characteristic of a good weld was a complete wetting of the cross sectional weld area. The problem here, however, was that only clear polymers used as the top piece, allowed the whole weld to be seen.
© Plastics Design Library
PC/ABS
458 Almost all resins involved in the study could be welded together with some degree of success (except for thermoplastic urethanes which didn’t bond to the polystyrenes). Overall, it apppeared that resin compatibility and the ability to transfer vibrational energy through a part and not similar glass transition temperatures, were the overriding characteristics that lead to the best welds. Although not shown in this study, it should be noted that the ability of a resin to be welded is also a function of the architecture of the ultrasonic weld. Some resins which welded well in the architecture used for this study may not weld well with other architectures. The PC/ABS resin tested fairly well with itself, SAN, ABS, clear RTPU, and the PC. Since neither PC or ABS bonded very well with the polystyrenes, it wasn’t surprising that the PC/ABS blend didn’t bond very well either. With the urethanes it appeared that the PC phase was the dominating polymer since no bonds or weak bonds were the norm. If ABS dominated the weld surface one would have expected better results based on the bonds achieved between the ABS resins and the urethanes. The EtO or gamma sterilization didn’t weaken the bonds, outside of the standard deviation, of the polymers tested. Reference: Kingsbury, R.T., Ultrasonic Weldability of a Broad Range of Medical Plastics, ANTEC 1991, conference proceedings - Society of Plastics Engineers, 1991.
Vibration Welding GE Plastics: PC/ABS Table 74.2: Achievable Strengths of Vibration Welds of PC/ABS alloy to itself and other thermoplastics. Material Family Tensile Strength2, MPa (ksi) Elongation @ Break2, % Specimen Thickness, mm (in.) Mating Material 1 Material Family Tensile Strength2, MPa (ksi) Elongation @ Break2, % Specimen Thickness, mm (in.) Process Parameters Process Type Weld Frequency Welded Joint Properties Weld Factor (weld strength/ weaker virgin material strength) Elongation @ Break2, % (nominal)
PC/ABS
3.2 (0.125) ABS
44 (6.4) 1.8 3.2 (0.125)
60 (8.7) 4.5 3.2 (0.125) PC 68 (9.9) 6 3.2 (0.125)
6.3 (0.25) PC/ABS
60 (8.7) 4.5 6.3 (0.25)
vibration welding 120 Hz 0.85
0.7
0.85
1.8
1.8
2.3
1 1
ABS - acrylonitrile-butadiene-stryrene copolymer; PC - polycarbonate; PC/ABS - polycarbonate/ ABS alloy 2 strain rate of 10-2s-1 Reference: Stokes, V.K., Toward a Weld-Strength Data Base for Vibration Welding of Thermoplastics, ANTEC 1995, conference proceedings Society of Plastics Engineers, 1995.
PC/ABS
© Plastics Design Library
459
Adhesive and Solvent Bonding PC/ABS Table 74.3: Compatibility of generic adhesive groups with polycarbonate/ ABS alloys (PC/ABS). Characteristic Evaluated strength impact resistance gap filling cure time ease of application
Material Evaluated
Compatibility Ratings for Generic Adhesive Groupsa
Proloy PC/ABS Proloy PC/ABS
Acrylics 1 2
Urethanes 4 1
Cyanoacrylates b 3 5
Epoxies 3 4
Silicones 5 4
Proloy PC/ABS Proloy PC/ABS Proloy PC/ABS
2 2 3
1 5 4
5 1 1
3 3 3
1 3 2
Compatibility rating guide: 1 - excellent, 2 - very good, 3 - good, 4 - fair, 5 - poor. These ratings are generalizations and will differ for specific brands. Chemical compatibiliity should be evaluated prior to adhesive selection to prevent stress cracking. b Stess cracking is a concern with cyanoacrylates. Careful evaluation of chemical compatibility with the substrate is recommended. a
Reference: Techniques: Adhesive Bonding, Solvent Bonding, and Joint Design, supplier technical report (#SR-401A) - Borg-Warner Chemicals, Inc., 1986.
© Plastics Design Library
PC/ABS
Polycarbonate/Acrylonitrile-Butadiene-Styrene Copolymer Alloy General Discussion of Joining Techniques Bayer: Bayblend Parts molded of Bayblend FR resins may be joined to other parts molded of Bayblend resins, or other plastics or metal parts by any of the variety of techniques. The elasticity of Bayblend FR resins permits the application of snap fits. This method of assembly is a fast, easy, and economical way to assemble two or more parts. Bonding or welding may be used for permanent joints. Bolts, screws, or ultrasonic inserts work well for detachable assemblies. Table 74.1: Methods of Joining Parts Molded of Bayblend FR Polycarbonate/Acrylonitrile-Butadiene-Styrene Copolymer. -
Hinges Self-tapping screws Machine screws Molded-in threads Heat insertion Heat welding Electromagnetic bonding Spin welding
-
Adhesive bonding Snap fits Ultrasonic welding Ultrasonic insertion Ultrasonic and heat staking Ultrasonic spot welding Vibration welding Solvent bonding
Reference: Bayblend FR Resins For Business Machines And Electronics, supplier marketing literature (55-D808(5)J 313-10/88) - Mobay Corporation, 1988.
Ultrasonic Welding Dow Chemical: Pulse 1370 This study was designed to identify which resins could be effectively ultrasonically welded to themselves and other resins, and to identify the maximum bond integrity. Besides looking at the weld strength of various thermoplastic resins, this study explores the effects of gamma radiation and ethylene oxide (EtO) sterilization on the strength of these welds. A wide variety of resins used in the healthcare industry were evaluated including: ABS, polycarbonate (PC), polycarbonate/ ABS blends (PC/ABS), styrene acrylonitrile (SAN), thermoplastic polyurethanes (TPU), rigid TPU’s (RTPU), high impact polystyrene (HIPS), and general purpose polystyrene (GPPS). The strength of customized “I” beam test pieces was tested in the tensile mode to determine the original strength of each resin in the solid, nonbonded test piece configuration. Data from this base line testing was used to determine the percent of original strength that was maintained after welding. Only amorphous resins were used in this study. The most commonly used energy director for amorphus resins, a 90° butt joint, was used as the welding architecture. Every attempt was made to make this a “real world” study. The aim during the welding process was to create a strong weld, while maintaining the aesthetics of the part. One of the most important factors in determining whether or not a good weld had been achieved was the amount of flash, or overrun noticed along both sides of the joint. Another characteristic of a good weld was a complete wetting of the cross sectional weld area. The problem here, however, was that only clear polymers used as the top piece, allowed the whole weld to be seen.
© Plastics Design Library
PC/ABS
458 Almost all resins involved in the study could be welded together with some degree of success (except for thermoplastic urethanes which didn’t bond to the polystyrenes). Overall, it apppeared that resin compatibility and the ability to transfer vibrational energy through a part and not similar glass transition temperatures, were the overriding characteristics that lead to the best welds. Although not shown in this study, it should be noted that the ability of a resin to be welded is also a function of the architecture of the ultrasonic weld. Some resins which welded well in the architecture used for this study may not weld well with other architectures. The PC/ABS resin tested fairly well with itself, SAN, ABS, clear RTPU, and the PC. Since neither PC or ABS bonded very well with the polystyrenes, it wasn’t surprising that the PC/ABS blend didn’t bond very well either. With the urethanes it appeared that the PC phase was the dominating polymer since no bonds or weak bonds were the norm. If ABS dominated the weld surface one would have expected better results based on the bonds achieved between the ABS resins and the urethanes. The EtO or gamma sterilization didn’t weaken the bonds, outside of the standard deviation, of the polymers tested. Reference: Kingsbury, R.T., Ultrasonic Weldability of a Broad Range of Medical Plastics, ANTEC 1991, conference proceedings - Society of Plastics Engineers, 1991.
Vibration Welding GE Plastics: PC/ABS Table 74.2: Achievable Strengths of Vibration Welds of PC/ABS alloy to itself and other thermoplastics. Material Family Tensile Strength2, MPa (ksi) Elongation @ Break2, % Specimen Thickness, mm (in.) Mating Material 1 Material Family Tensile Strength2, MPa (ksi) Elongation @ Break2, % Specimen Thickness, mm (in.) Process Parameters Process Type Weld Frequency Welded Joint Properties Weld Factor (weld strength/ weaker virgin material strength) Elongation @ Break2, % (nominal)
PC/ABS
3.2 (0.125) ABS
44 (6.4) 1.8 3.2 (0.125)
60 (8.7) 4.5 3.2 (0.125) PC 68 (9.9) 6 3.2 (0.125)
6.3 (0.25) PC/ABS
60 (8.7) 4.5 6.3 (0.25)
vibration welding 120 Hz 0.85
0.7
0.85
1.8
1.8
2.3
1 1
ABS - acrylonitrile-butadiene-stryrene copolymer; PC - polycarbonate; PC/ABS - polycarbonate/ ABS alloy 2 strain rate of 10-2s-1 Reference: Stokes, V.K., Toward a Weld-Strength Data Base for Vibration Welding of Thermoplastics, ANTEC 1995, conference proceedings Society of Plastics Engineers, 1995.
PC/ABS
© Plastics Design Library
459
Adhesive and Solvent Bonding PC/ABS Table 74.3: Compatibility of generic adhesive groups with polycarbonate/ ABS alloys (PC/ABS). Characteristic Evaluated strength impact resistance gap filling cure time ease of application
Material Evaluated
Compatibility Ratings for Generic Adhesive Groupsa
Proloy PC/ABS Proloy PC/ABS
Acrylics 1 2
Urethanes 4 1
Cyanoacrylates b 3 5
Epoxies 3 4
Silicones 5 4
Proloy PC/ABS Proloy PC/ABS Proloy PC/ABS
2 2 3
1 5 4
5 1 1
3 3 3
1 3 2
Compatibility rating guide: 1 - excellent, 2 - very good, 3 - good, 4 - fair, 5 - poor. These ratings are generalizations and will differ for specific brands. Chemical compatibiliity should be evaluated prior to adhesive selection to prevent stress cracking. b Stess cracking is a concern with cyanoacrylates. Careful evaluation of chemical compatibility with the substrate is recommended. a
Reference: Techniques: Adhesive Bonding, Solvent Bonding, and Joint Design, supplier technical report (#SR-401A) - Borg-Warner Chemicals, Inc., 1986.
© Plastics Design Library
PC/ABS