The process of welding plastic work pieces together is called plastic welding, but that is not a very descriptive terms, as there are so many plastic welders, using a variety of techniques to accomplish this goal. As I am sure you are aware, plastic is a very pliable, varied material that can range from flexible, to solid, any thickness, and a huge variety of textures. So, when you want to attach two different pieces of plastic permanently, what is the best method, and what type of plastic welder is right for you?
In industrial applications, hot gas (or hot air) welding is a common, simple concept. Basically, a huge hot air gun (called the hot air welder) produces a jet of extremely hot air that softens both pieces to be joined, as well as a filler rod, and then they are rolled together. A great benefit of this plastic welding equipment is that is can be used continuously on moving sheets of plastic. This is common for manufacturing things such a chemical tanks, water tanks, heat exchangers and plumbing fittings.
A more versatile, but slower process is freehand welding. The concept is the same in that a jet of hot air (or inert gas) from the welder is used to soften the weld area and weld rod at the same time. As the rod softens, it is pushed into the joint and pressure is applied to fuse the parts. Although this is a slow process, it is used in smaller applications, and can be employed almost anywhere.
A very commonly used, faster method of plastic welding is called “speed welding”. In this method, the plastic welder is very similar to a soldering iron in appearance and wattage. A feed tube is fitted for the plastic weld rod. The tip heats the rod and the pieces to be welded and the welder presses the melted weld rod into position as the operator moves along the joint being welded. This is a very common method used by professional plastic fabricators and repairers all over the world for over 50 years.
All these methods of plastic welding have been for thin plastics. On material over 6mm thick, however, extrusion welding is the preferred method. The welding rod is drawn into a hand-held extruder, melted to a liquid, and then forced out against the parts, which have been softened with a jet of hot air to allow the bond to form.
A form of plastic welding equipment that is a little more direct is contact welding. This is a method where “pincher” tips are heated, and the plastic is joined where the pinchers squeeze the two pieces to be melted. Another, related form of welding is hot plate welding, in which two hot plates, molded to the shape of the weld geometry of the parts to the welded, actually contact the pieces, melts the plastic, and holds in place until the plastic cools, forming a solid joint.
Another form of industrial plastic welding that can be a continuous process is high frequency welding. Certain plastics with chemical dipoles, such as PVC, polyamides (PA) and acetates can be heated with high frequency electromagnetic waves. High frequency welding uses this property to soften the plastics for joining.
There are several more methods of industrial plastic welding including radio frequency welding, which has been around since the 1940s, most often used to weld PVC and polyurethane (PU) coated fabrics. There is injection welding, which is similar/identical to extrusion welding, except, using certain tips on the handheld welder, one can insert the tip into plastic defect holes of various sizes and patch them from the inside out. Friction welding is a method in which the two parts are rubbed together at a low frequency and high amplitude. The friction combined with clamping pressure between the two parts creates the heat which causes intertwining layers that result in a strong weld. Spin welding is another form of frictional welding in which one part is held stationary while the other is rotated at a high velocity and then pressed against the fixed part with significant force. Laser welding is a method in which a laser passes through the first part and is absorbed by the second, which gets hot and soft, as the two are pressed together causing a permanent weld. A method to join plastics without generating heat is solvent welding. This is where a solvent is applied which dissolves the polymer, and then evaporates, allowing the polymers to solidify, leaving a permanent weld.
Ultrasonic Plastic Welder
The final method of plastic welding I would like to tell you about in detail is ultrasonic welding. This method is very similar to radio frequency welding, except that this plastic welding equipment operates at a much higher frequency and much lower amplitude. This method can be used on almost all plastic materials, including dissimilar materials. This is the fastest heat sealing technology available. The materials solidify almost instantly when the ultrasonic acoustic vibrations are removed. You will find an ultrasonic plastic welder in many industries, including computer, automotive, aerospace, medical and packaging. There is no ventilation system required to remove heat or exhaust, and weld times are often less than a second. This machine is used when the assemblies to be built are too small, too complex, or too delicate for other welding methods.
Devcon Plastic Welder
The Devcon Plastic Welder™ is a chemical method of welding plastic that quickly creates a superior impact and peel resistance bond to most plastic surfaces as well as metals, ceramics and wood. It requires a minimal amount of surface preparation, and cures in an hour. The final bond is weatherproof, resistant to humidity, and will hold in wide variations of temperatures, making it good as an outdoor bonding method. It is a thick consistency with good gap filling capabilities.
Airless Plastic Welder
Airless Plastic Welder is a welder that employs the “speed welding” method as described above. It is a portable, easy to use method of bonding polyurethane, polypropylene, ABS, TPO, polyethylene, nylon and polycarbonate. It is commonly used for quick repairs of plastic automotive parts, such as bumper covers, plastic trim, etc.
Amazon.com Products
The most commonly sold plastic welding equipment found on Amazon.com is the Urethane Supply Co. Mini-Weld Model 6 Airless Plastic Welder, Model# 5600HT. For only $153.95 you can own this easy to use plastic welder that will allow you to repair bumpers, ATV body panels, canoes, kayaks, or any number of molded plastic items. This model includes eight types of welding rods. It operates at only 80 watts, meaning you could easily use it with a portable power inverter for on-the-trail repairs from your vehicle.
The customers who reviewed this product state that it exceeds their expectations, forms a permanent bond, and would recommend it to anyone doing plastic repairs, hobbyist or professional. One reviewer even stated that “even our youngest apprentice has had 100% success with this welder”.
The next most popular plastic welding equipment found on Amazon.com is the Portasol 011289210 Plastic Welding Kit for $148.40. This kit, too, is an airless model, relying on physical contact for welding. This is a cordless kit, meaning you are no longer dependent on a source of electricity. This would be a perfect kit for portable repairs on canoes, off-road vehicles, 4 wheelers, etc., while out on the trail. This tool uses butane as its energy source, meaning no worries about dead batteries, either.
The review of this product has rated it at 5 out of 5 stars, stating it works great.
The next most popular method of plastic welding found on Amazon.com is the chemical method in the form of ITW Plastic Welder Epoxy. At only $2.99 for 25mL, this is an extremely low cost option. This epoxy is thick for good gap-filling, water resistant and holds at a tensile strength of 3,500 psi. it dries cream colored and dries in only 15 seconds.
Summary
There are so many different methods of plastic welding. Most of the plastic welding equipment, however, is designed for industrial use. The most common methods for home or small business use would be solvent or airless welding, and the equipment can be purchase inexpensively at Amazon.com. Whether you are a professional or a hobbyist, I am sure you can see the benefits of being able to weld plastics.