Plastic materials are used everywhere in many industries. The characteristic property of polymeric materials to acquire mechanical rigidity and strength after melting is widely used not only in the manufacture of various products, but also during repair work at home.
This connection of plastic materials, called welding, is the most technologically advanced. in a reasonable and economical way when repairing a variety of products. Welding plastic allows you to create high strength butt joints. Moreover, the process technology and equipment used for welding is not particularly difficult for use at home.
Basic welding methods
With all the wide variety of technological methods of the welding process, methods of welding plastics can divided into two main groups:
- cold welding is carried out using special chemicals that effectively facilitate the joining of plastic products, without melting surfaces;
- hot welding is a plastic joint SCI at the molecular level, when surfaces are brought to a semi-liquid state by heating.
The task of a welded joint of any type is to create a strong contact between the polymeric materials by means of a smooth transition of one substance to another. Plastic welding can be carried out with or without special additives.
Cold welding method
With the development of the chemical industry, cold welding for plastic has gained the greatest popularity not only among professionals, but and among ordinary people who carry out repair work of products at home. In principle, this name is more consistent with the scientific term, which designates the type of compound of polymeric materials. In general, this is a technology for bonding plastic parts using chemically active substances.
Currently, manufacturers produce the necessary components for welding three types:
- One-component composition in appearance resembles a simple clerical glue. The versatility of this composition allows you to weld almost any polymer material, with high quality. Most often, one-component adhesive is used for welding plastics at home.
- Two-component adhesive consists of epoxy resin and hardener, which are supplied to the consumer in separate containers. Mixing of the components is carried out in a certain proportion, just before the job.
- The core with the active reagent has an outer shell of hardener and an inner one, filled with epoxy resin. Having cut off the desired piece of the core, it must be carefully kneaded with your fingers until a homogeneous plastic mass is formed.
All work on the preparation of the adhesive composition must be carried out strictly according to the manufacturer’s instructions.
Cold welding technology
Before welding plastic, it is necessary to prepare the surfaces of the products to be joined. For this purpose, it is necessary to process the edges of the parts with abrasive material (sandpaper, file). This treatment allows you to create a surface roughness, which significantly increases the adhesion of the plastic material.
The welding technology is as follows:
- After pre-treatment, immediately before the work is done, degrease the surfaces to be joined products. To do this, you can use almost any alcohol-based solvent.
- Further, according to the instructions, an adhesive is applied to the edges of the parts to be joined.
- The surfaces are pressed tightly against each other. Moreover, the compression should be carried out until the composition completely hardens.
- After the components have completely dried, the plastic welding process is considered completed.
The main advantage of the cold joint is the ability to efficiently weld surfaces from dissimilar materials, with no additional equipment required. The disadvantage of the method is the low vibration stability of the seam, so the use of cold welding is limited in movable mechanisms.
Hot welding of plastic
The hot method of welding plastic materials is based on the molecular interaction of the molten surfaces to a viscous state. In this case, it is necessary to take into account the nature of the polymer reaction to the temperature effect. According to this principle, plastic materials are divided into thermoplastics and thermosets.
Thermoplastics do not change their performance and chemical properties, even with repeated transition to the molten state. And most importantly, returning after cooling to the original hardness, the materials do not lose their strength. Unlike thermoplastics, thermosets, returning to their original state, almost completely lose their plastic properties. Such a reaction of the material does not allow it to re-enter the viscous phase, completely losing strength. Most plastics are thermoplastics.
Methods of heated welding
Depending on the method of supplying thermal energy to the joining zone of polymeric materials, the following types of hot welding are available:
- hot gas stream;
- a special heated device;
- exposure to the edges of the products with a molten additive;
- using an ultrasonic stream;
- using infrared or laser radiation;
- by heating the joint at the friction;
- by exposure to an electric current of high stots.
The first three methods are effective when welding plastic with your own hands in the home. The rest are most often used directly at industrial enterprises in the manufacturing process.
Hot gas welding
The junction can be heated using a gas burner, using nitrogen or argon burning. But the safest and most cost-effective is welding plastic with a hairdryer, since the edges of the joined products are heated by hot air.
The manufacture and repair of plastic products is carried out by industrial or domestic hot air guns. Structurally, this equipment for plastic welding is designed in the same way. Industrial hair dryers have high power, which is automatically adjusted and equipped with a number of additional functions and various nozzles.
The welding of plastic with a hot air gun is carried out in several stages:
- The type of plastic is determined according to which the heating temperature is selected, as well as the nozzle suitable for operation.
- The edges of the joined products are cleaned and degreased.
- The workpieces are firmly fixed so that they do not shift during work.
- The joint is heated to a molten state, at which the materials merge .
- After creating the weld, the product should cool in natural conditions. It is not recommended to use additional cooling.
- Then the final cleaning of the seam is carried out.
Resistance welding with a heating device
The simplest type of plastic welding in home environment is the direct heating of the edges of the product with a hot tool. The technological process of welding by contact is considered the most simple and easily applicable in the domestic environment, as it does not require the use of sophisticated equipment.
Welding can be divided into two main stages:
- Flashing the edges of the parts to be joined.
- Compress the molten surfaces tightly and allow them to cool completely.
The time between these operations should be minimal so that the material does not have time to cool. Otherwise, the quality of the weld will be insufficient.
At home, for minor repairs, they often use a simple soldering iron equipped with special nozzles.
Use of welding additives
To increase the strength and quality of the seam, when connecting materials from plastic, special additives are widely used. Plastic rods or strips are used as such material.
Adding an additive to the weld composition greatly improves the welding process using hot air heating. The main condition for a good connection of plastics is to match the composition of the additive and the polymer material.
Also, a very effective option for the use of filler material is the use of a manual welding extruder. This thermomechanical device, resembling a gun, first heats the polymer material to a viscous state, and then automatically squeezes the additive onto the connected surfaces.
Welding of plastic products is widely used both in production halls and at home. The technology of the welding process is easy to master even for an inexperienced person, while remembering that safety measures are being taken when working.