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Adhering plastic to a car or even in the home is relatively common, but presents the user with one challenge or another. In any case, a special plastic adhesive is required – and appropriate pre-treatment of the surfaces to be bonded. How exactly plastic bonding should work and how you can bond plastic to metal, for example, is explained in our plastic adhesive guide.
Table of Contents
- 1 What Is Plastic Glue?
- 2 Overview of the Most Common Plastics
- 3 Polyethylene (PE-HD, 02) and Polypropylen (PP, 05)
- 4 Polyamide (PA, 07) and Acrylonitrile Butadiene Styrene (ABS, 07)
- 5 Polyvinyl Chloride (PVC, 03)
- 6 Polystyrene (PS, 06)
- 7 Polymethyl Methacrylate (PMMA)
- 8 Instructions for Gluing the Plastic
- 9 Safety Instructions
- 10 Tips and Tricks for Bonding Plastics
What Is Plastic Glue?
If you want to glue broken plastic, there are several things you have to consider. Above all, the choice of the right adhesive is of great importance to achieve a durable bond.
Plastic adhesive or also plastic glue was developed especially for the requirements of plastic bonding. As a rule, it can even be used to bond materials that are very difficult to join, such as PP plastic. Even ABS plastic bonding should hardly be a problem. Nevertheless, you must pay attention to the correct bonding technique, because plastic is a somewhat special material. But what exactly is plastic?
Overview of the Most Common Plastics
In today’s world, the list of plastics seems to be endless. Nevertheless, besides relatively unknown types of plastics, there are some that should be known to everyone. The most common of them are presented below.
In order to be able to better recycle plastics after they have been sorted out, the Recycling Code was created by the Society of the Plastics Industry, SPI for short. This has greatly simplified the categorisation of the various types of plastic. The plastic abbreviations were standardised and recycling forms that are comprehensible to the end user were also used. As a result, every household can now take the appropriate steps for pre-sorting in everyday life. Apart from the “Grüner Punkt” system in Germany, there are special recycling centres to which sorted plastic parts can be taken. All this is intended to reduce the mountain of waste.
In the following, you will find a table of the seven most common types of plastic with their areas of application and recyclable material abbreviations.
|Polyethylene Terephthalat||PET, PETE||Especially food packaging and films, bottles and polyester fibres|
|Polyethylen High Density||PE-HD, HDPE||Pipes, waste containers, bottles, artificial wood|
|Polyvinyl Chloride||PVC||Pipes, window frames, floor coverings|
|Polyethylen Low Density||PE-LD, LDPE||Foils, tubes of all kinds, soap dispensers, buckets and plastic bags|
|Polypropylene||PP||Covers for DVDs, industrial fibres, interior linings for cars, bumpers, food packaging, among others|
|Polystyrene||PS||Suitcases, foam, CD cases, toys and flower pots|
|Various other types of plastics, for example polymethyl methacrylate (PMMA) or polycarbonate (PC)||O (for others)||This is a voluntary labelling, as these types of plastics are not listed in the German or European guidelines. The legal basis for these types of plastics is unclear. Fields of application vary depending on the type of plastic.|
Polyethylene (PE-HD, 02) and Polypropylen (PP, 05)
Polyethylene, or PE-HD for short, and polypropylene, or PP for short, are thermoplastics with very valuable properties for further processing. The following is a comparison of the two materials:
- Belongs to the Polyolefins
- Is partially crystalline and non-polar
- Ranks among the standard plastics and is used most frequently
- Is one of the most important Packaging materials
- Is divided into High Density, Linear Density and Low Density and has accordingly different characteristics
- Has a high chemical resistance, solid sliding behaviour and good electrical insulation
- Has a disadvantage: it does not have good mechanical properties, especially in direct comparison to other plastics; has a rather low stiffness, hardness and strength, but a high impact strength and ductility
- Expands very strongly under heat
- Has a very low gas and water vapour permeability, but allows flavours and oxygen to pass through very well
- Can only be bonded with appropriate pretreatment
- Has good electrical insulation properties
- Can be processed with all known original moulding processes, such as injection moulding, extrusion, casting and blow moulding
- Belongs to the polyolefins
- Is partially crystalline and non-polar
- Has similar characteristics to polyethylene, but has a higher hardness and heat resistance
- Is the most commonly used packaging material after polyethylene
- Also often used for plastic parts and claddings
- Has the lowest density among the standard plastics, but this can be changed by adding fillers
- The melting temperature is higher than for polyethylene
- Has a high resistance to solvents and greases at room temperature, but is less resistant to chemical attack than polyethylene
- Suitable in industrial processing, especially for injection moulding, hot forming, deep drawing, welding, blow moulding, extrusion and for machining processing crystalline and non-polar
- Suitable in industrial processing, especially for injection moulding, hot forming, deep drawing, welding, blow moulding, extrusion and machining
- Can only be bonded to a small extent and only with appropriate pretreatment
Applications of Polyethylene and Polypropylene
Polyethylene is primarily used in film production, as well as for cable sheathing and as a material for pipes and pump parts.
Polypropylene is used in many different areas of daily use, such as child seats and vehicle interiors, cable sheathing, fibers of home and sports textiles, parts for model making, surgical parts and many more.
Bonding Polyethylene and Polypropylene
As noted above, bonding of polyethylene and polypropylene is not beginner-friendly, as these are materials with low-energy surfaces. Bonding is particularly difficult with polyethylene, as this plastic has the lowest density of all plastic types. For this reason, prior surface treatment is essential.
The difficulty, especially with PP, is that its surface can hardly be attacked by chemical substances. These include greases and organic solvents. It is also resistant to alkalis and acids. In order to be able to bond polyethylene and polypropylene, a thorough and complex surface activation must precede. In industry, this is often done by pickling with sulphuric acid. Corona discharges are also a possibility for activating the surface of PP and PE-HD.
In the meantime, special plastic adhesives equipped with an activator are available in the trade for do-it-yourselfers. Pre-treatment with a primer is also a possibility for the home user to bond such low-energy surfaces. Especially when joining with a superglue like the Pattex Plastix superglue presented below, a primer must be used – we will tell you why the Pattex Plastix is very convenient in this respect for the user.
Also check out of tutorial on how to glue HDPE.
Recommendation: J-B Weld Plastic Glue
The J-B Weld Plastic Glue is supplied in a handy little syringe and is therefore easy to use. Its advantages are obvious:
This glue forms a long-lasting bond with polyethylene and polypropylene. You can even use it to bond plastic to your car; not even the vibrations of driving can harm the adhesive bond.
We could only see one drawback with the Pattex Plastix:
In our plastic adhesive guide we explicitly recommend the Pattex Plastix superglue.
- Quick-setting and multipurpose two-part urethane adhesive
- Gap filling system provides a strong and lasting bond
- Takes 15 minutes to set and 30 hours to cure
Polyamide (PA, 07) and Acrylonitrile Butadiene Styrene (ABS, 07)
Below are the properties of the two materials polyamide and acrylonitrile-butadiene-styrene:
- Polar, thermoplastic material with very low surface energy
- High resistance to solvents and chemicals
- Very difficult to bond due to both of the above properties; the surfaces to be bonded must be pretreated
Acrylonitrile Butadiene Styrene
- Thermoplastic hard plastic, which is colourless to yellow and has solid material properties such as high resistance to ageing, weathering and chemicals
- Has a good heat deflection temperature
- Is insoluble in fats, oils, alkalis, mineral oils, ethanol and diluted acids
- Difficult to bond; this is only possible after an appropriate surface pretreatment
Applications of Polyamide and Acrylonitrile Butadiene Styrene
Polyamides are used in a wide range of applications due to their excellent material properties. They are stiff and impact resistant while at the same time being highly durable and not only have a high abrasion resistance, but also a high wear resistance as well as optimum sliding properties. Because of these characteristics they are often used as construction materials. Care must be taken with acids and oxidizing chemicals, as these can attack polyamide. In addition to the use as a construction material, polyamide can be used in the following areas of application:
- Synthetic fibres in clothing, especially in rainwear and sportswear
- Synthetic fibres in sports equipment, for example in kites or parachutes
- Fibre in technical textiles and fabrics
- Breakproof everyday and household objects
- Machine parts
- Smaller components like cable ties, nuts and dowels
- Housing and insulation material in the field of electrical engineering
- In vehicle construction as engine components
In order to identify polyamide, you can make the burning test. To do this, take a small sample of the material and hold it up to an open flame. The result is a slight foaming as well as a tough drop formation and the formation of a blue flame with an orange-yellowish edge. The resulting smoke smells like burnt horn.
ABS is used in particular for housings of all colours, as it not only has a high impact resistance and optimum surface hardness, but also very good coating properties. This can be done with metals or also with polymers. Furthermore, ABS can be printed, chrome-plated or even painted.
ABS is mainly used:
- As household products and objects of daily life such as hard-shell cases, toys, telephones, motorcycle and bicycle helmets
- In the automotive industry
- In the sanitary industry as pipes
- In electrical engineering as housing
Bonding Polyamide and ABS
In order to bond polyamide or ABS plastic, not only a surface pretreatment is required, but also a special reactive adhesive. We recommend pre-treatment with a special primer to optimally increase the adhesion of the substrates as well as the final strength and load-bearing capacity. The primer is first applied very thinly to both surfaces to be bonded. These should of course have been cleaned beforehand – how exactly is explained in our chapter “Preparation work”. The primer must now take effect for a certain time; follow the manufacturer’s instructions.
As an adhesive we recommend, for example, solvent-based adhesives or a two-component plastic adhesive based on epoxy resin. For very heavy loads, a two-component methyl methacrylate adhesive or a 2K polyurethane adhesive is suitable.
Recommendation: Plastruct Plastic Weld
The Plastruct Plastic Weld weld from the bottle is an extremely effective and durable adhesive that can bond even difficult to join materials such as ABS plastic. At the same time, it offers the user many advantages:
We highly recommend this glue for ABS and Polyamide bonding. This glue is also very popular amongst model making with plastic models. We would recommend this plastic glue without reservation!
Polyvinyl Chloride (PVC, 03)
Polyvinyl chloride is probably known to most users under its abbreviation PVC. PVC is a thermoplastic polymer which is synthesized from the monomer vinyl chloride. PVC is one of the most important plastic polymers and is highly resistant to chemicals. It is also highly resistant to weathering and UV radiation. A relatively small amount of natural gas or crude oil is required for its production, compared to most other types of plastic. PVC is therefore flame retardant.
However, its extremely positive properties are only achieved by adding various additives such as lubricants, stabilizers or plasticizers.
PVC is considered controversial as it may contain potentially hazardous substances such as vinyl chloride. This is considered to be carcinogenic. Therefore, occupational health and safety is particularly important in PVC production. Whether the end product, PVC, also emits harmful substances is still a major point of contention between industry and environmental associations. However, this discussion is primarily about soft PVC.
Applications of Polyvinyl Chloride
PVC plastics are divided into two different categories:
- Soft PVC has an elastic behaviour because it contains plasticisers. It is mainly used as flexible sealing material, floor coverings and insulation material for cables and wires.
- Rigid PVC does not contain any plasticizers and is used in particular for the production of pipes, ducts, profiles, skylights, ventilation shafts and façade elements, but also in model making, for example as rigid foam sheets.
Another application of polyvinyl chloride will be familiar to music lovers: In the 1940s, vinyl replaced shellac as the material for records.
When bonding PVC, it is particularly important to pay attention to any plasticizers that may be present. With rigid PVC this is not a question, but soft PVC presents the user with great challenges. This is because the molecules of the plasticizers contained can migrate to the surface and dissolve the adhesive there. This means that a permanent bond is not possible. This is further favoured in the case of adhesive surfaces that are under particularly high tension or are exposed to high loads.
One way to bond PVC is the contact bonding method, in which both surfaces are coated thinly with a suitable adhesive and then, after a certain flash-off time, are joined together. Here, a two-component adhesive based on polyurethane has proven to be a good solution. To ensure better adhesion, you can add a crosslinker to the adhesive.
Another possibility is the use of a high-quality, one-component special adhesive such as Pattex Special Modellbau, which we present to you below.
Recommendation: Gorilla PVC Glue
The Gorilla PVC Glue does not only offer an unbeatable price-performance ratio; it also provides model builders in particular with everything they need for their hobby. But these are not the only advantages of this special glue:
However, the many advantages outweigh the few disadvantages by far, so that we can make an absolute recommendation for Gorilla PVC Glue.
Polystyrene (PS, 06)
Polystyrene or PS has become an integral part of our everyday life. It is a mass-produced plastic that is not only found in sockets and other housings, but also in CD cases and even in food packaging. It is semi-crystalline and amorphous, its colour is usually transparent, but when foamed it is white.
Polystyrene is generally easier to bond than some other types of plastic because it is not only polar but also solvent-soluble. Nevertheless, even with PS it is important to ensure that the correct plastic adhesive is used. Particularly with regard to the second substrate – i.e. the second material with which PS is to be bonded – caution is required, as a durable bond is not possible with every material.
Applications of Polystyrene
The basic material, i.e. cured polystyrene, is initially available in granulate form. This is then used to manufacture many different mass-produced articles. Polystyrene scores highly in the household sector in particular because it is easy to process and very inexpensive. It is used
- As household articles such as yoghurt pots, plastic bottles and blender housings due to its non-toxicity and suitability for food
- In electrical engineering for cable insulation as well as in coil formers, housings and switches due to its good insulation properties
- In model making
- In medicine as blister packs
- In the construction industry both as packaging material and as insulating material under the name Styropor
In order to bond polystyrene, an optimal surface condition must be given. In the case of PS, this consists in a very smooth and clean structure. In addition, it must be of sufficient size to ensure that the adhesive effect of the plastic adhesive is given.
The substrates can be cleaned of dust and grease with a damp sponge cloth or dust-free cloth and a little mild detergent. If you want to glue the polystyrene on metal or wood, you should roughen the latter slightly before gluing. This increases the adhesive effect of the plastic glue. Afterwards, the adhesive surface must of course be freed from dust again.
Now a distinction is made between small and large adhesive surfaces. Small surfaces can be wetted with adhesive mainly by using a tube or a small brush. For large areas, a spray adhesive can be used. Use a solvent-based adhesive and quickly join the two surfaces together. Especially with spray adhesive, a flat surface is very important, otherwise the adhesive will not bond properly.
If it is not possible to level the two surfaces completely, you can use a putty that acts as a levelling layer. In this way cracks and holes are filled with the putty. In this case, start with a generous bead of adhesive on the outer edges of the substrates and then fill the adhesive into the inner area. The putty should now cover at least forty percent of the area to be bonded.
An alternative is the assembly adhesive, which can be used especially indoors, or a special styrofoam adhesive, which we recommend in the following chapter.
Recommendation: Tamiya Extra Thin Polystyrene Glue
The Tamiya Polystyrene Glue is an adhesive for particularly stubborn gluing cases. Its advantages and disadvantages are as follows:
However, the two disadvantages we have discovered certainly apply to most types of glue. Therefore, we give an unqualified recommendation for the Pattex Styropor adhesive.
- Tamiya Extra-Thin Cementfor Polystyrene
- This cement is extremely useful when gluing plastic parts to a desired position when holding in place together.
- The thin cement flows smoothly between the gaps of the fitted parts by capillary action.
Polymethyl Methacrylate (PMMA)
PMMA is mainly known under the names plexiglass or also acrylic glass, whereby the term plexiglass is a patent. It is used precisely because of its optical properties.
Two different types of PMMA are known:
- High molecular PMMA, which is cast and belongs to the group of thermoelastic materials; they are processed both by machining and thermoforming
- Thermoplastic PMMA, which is also processed by machining, but also by welding, thermoforming, extrusion and injection moulding
PMMA has medium strength combined with high impact strength and stiffness. As a result, the material has optimum scratch resistance, which can be significantly increased by appropriate surface treatment. If necessary, the surface can also be easily polished if unsightly scratches have occurred.
The material scores particularly well in outdoor applications due to its resistance to UV light, ageing and weathering. Furthermore, it is highly insensitive to chemical influences. Caution is required with chemicals such as
These can attack the PMMA. Therefore, if possible do not clean it with alcohol or solvents.
PMMA can be identified by a simple test: Hold a small sample over an open fire. If it burns under a sweetish smell and yellowish flame and a crackling sound is produced, it is PMMA.
Polymethyl Methacrylate Applications
Due to its non-toxic properties, PMMA can be used not only as glazing for shower stalls or skylights, but also in the household and for food packaging. It has optimum processing properties and is therefore a very popular material for both small users and industry. It has excellent colouring properties and even has better light refraction than mineral glass.
In general, its fields of application are as follows:
- In the building sector, it is often used for all types of glazing, especially for flat roofs, industrial door glazing, industrial flooring, polymer concrete and sanitary components such as shower cabins and bathtubs
- Vehicle construction benefits from PMMA as a material for reflector and column coverings and as a light guide
- In plant engineering and construction, safety doors and protective hoods are built with
- The aerospace industry uses PMMA for headlight covers, hoods and glazing
- The food industry uses PMMA to build line pipe for various liquids and beverages such as milk and beer
- For the textile industry fibres are produced from it
- The medical industry uses PMMA as dressing splints and dental prostheses
- Among household goods, PMMA can score points as housings, containers, protective screens and luminaire covers
The possible applications of PMMA are therefore incredibly diverse. Nevertheless, this material should not be disposed of prematurely in order to buy a new product. Especially small users can use our tips to bond PMMA and thus repair it. In the following we will tell you how you can bond PMMA.
As already described, PMMA is sensitive to solvents. However, these can be used to change the surface properties of the material so that it can be bonded more easily. Be careful not to use a polar solvent such as acetone, as this could cause stress and ultimately cracking of the material. Therefore, use a non-polar cleaner such as isopropanol to clean the substrate. After cleaning, allow the isopropanol to air out for about ten minutes before applying the plastic adhesive.
If the substrate has a scratch-resistant coating, this is usually based on polysiloxanes. In this case you can use a two-component polyurethane adhesive. PU adhesives have optimum adhesive properties with high mechanical and weather-related load-bearing capacity. Furthermore, they do not yellow.
Use a glass primer first to optimize adhesion.
Styrene-free MMA adhesives are also suitable for bonding PMMA, since it is virtually liquefied Plexiglas. However, these adhesives should always be tested in advance on an inconspicuous spot, as in some cases stress cracks in the substrate may occur.
The selection of the suitable plastic adhesive is complicated by the optically high demands on the adhesive surface. This question is of great importance, especially with uncoloured and therefore transparent PMMA.
In an emergency, you can also repair or bond PMMA with superglue, but this can cause unsightly streaks. In case of doubt, it is better to use a plastic adhesive recommended by us, such as the Acrifix PMMA adhesive, which we present below.
Recommendation: Super Glue Plastic Fusion Glue
The two-component Plastic Fusion Glue Acrifix PMMA adhesive is not only suitable for PMMA but also for various other types of plastics. It is supplied in a practical 1oz syringe and can be easily applied even by untrained do-it-yourselfers. It offers many advantages:
The Superglue Plastic Fusion offers the user many advantages with very few disadvantages and therefore receives a crystal clear recommendation from us.
Instructions for Gluing the Plastic
Materials such as ceramics, glass or many metals offer a high surface energy and thus perfect adhesion properties for adhesives. In general it can be said that an adhesive always adheres well if the substrate, i.e. the surface to be bonded, has a higher tension than the adhesive itself.
Therefore, it is often difficult to bond plastics, because many types of plastics have a non-polar, i.e. low-energy, surface. To be able to judge whether your substrate is a low-energy or high-energy surface, you can carry out a small test using a drop of water. Simply dribble a small amount of water onto the surface. If a drop forms, it is a low-energy surface. If the water runs off, you have a high-energy surface.
A low-energy surface must always be pre-treated, otherwise the plastic adhesive cannot develop its adhesive properties. The following chapter will show you exactly how to do this.
If you want to glue broken plastic, you should make sure that the surfaces are properly prepared. The surfaces must first be cleaned of dust and then of grease and oil residues. You can use a lint-free cloth and a suitable cleaning agent for this purpose. We recommend water and solvents.
Use either a spray or immersion method for cleaning. Stubborn fats can also be cleaned by gentle pre-drying in an oven.
After this, the surface should be treated by sandblasting or sanding. This roughens the surface to be bonded and the plastic adhesive can adhere perfectly. A chemical pre-treatment by pickling or etching can also be carried out, resulting in a new surface structure. Thermal and laser pre-treatments are also possible, but are not always feasible for home users. These are usually processes such as the electric plasma process, which changes the surface either physically or chemically.
Coating the surfaces before bonding is also a variant. As a small user you can fall back on a suitable primer. This is a substance that reacts chemically and must therefore be applied exactly as instructed. Please follow the instructions of the respective manufacturer.
Once you have cleaned the surface, you must not touch it with your bare hands, as this could cause new skin grease to be deposited on it and impair the adhesive effect. The surface would therefore have to be cleaned again.
Sticking and Removing Residues
Now you cannot apply the plastic adhesive too generously and join the two surfaces together with high pressure. Fix them if necessary, but be aware of the brittleness of the material. In any case, take into account the possible flash-off time of the plastic adhesive before joining the parts together. After joining, observe the drying time recommended by the manufacturer. This may vary as it depends on the ambient temperature, humidity and of course the substrates and the plastic adhesive used. To be on the safe side, give the adhesive a little more time than indicated.
Remove excess plastic adhesive immediately after bonding, because after curing it is hardly possible to loosen it. It must then be laboriously scraped off with a scalpel, which could damage the surface.
When bonding plastics, you should pay attention to your safety, as potentially harmful vapours can escape during work.
A well-ventilated workplace should be standard, as should the wearing of a respiratory mask and long-sleeved clothing. Disposable gloves are also for your safety. Should the adhesive come into contact with your skin, wash it off immediately with warm soapy water. If it comes into contact with your eyes or mucous membranes, rinse them with lukewarm water for several minutes. Afterwards, consult a doctor immediately and show him the package insert so that he can get an idea of the substances that have entered your eyes or mucous membranes.
Tips and Tricks for Bonding Plastics
A newer development in plastic bonding is the use of double-sided acrylic foam adhesive tapes. These are perfect for low energy surfaces and have a high absorption of mechanical stress. Acrylic foam tapes are also suitable for bonding plastic parts and dampen both temperature differences and vibrations.
However, double-sided adhesive tape cannot always be used. If, for example, you want to stick cracks in the material, you should use a suitable plastic adhesive. In this case, drill the crack at the end so that it does not expand any further. Then you can glue it as described above.
When bonding plastics, the composition of the material and the correct surface preparation are therefore very important. We hope we have been able to give you an overview of the most important plastics and valuable tips on how to bond plastics.