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Bonding plastic in the home or to a car is quite common, but the process can have its difficulties. You may require a special plastic adhesive and to ensure your surface is pre-treated correctly to achieve the desired bond. That said plastic can be bonded and our how-to guide should help you along the way.
Table of Contents
- 1 What is Plastic Glue?
- 2 Overview of the Most Common Plastics
- 3 How to Glue Plastic
- 4 Bonding Plastic – Tips and Tricks
What is Plastic Glue?
You need to take a few things into consideration before you attempt to glue broken plastic. The most important element is that you select the correct adhesive to ensure you achieve the durable bond you require.
Plastic glue (or plastic adhesive) was formulated specifically for bonding plastic. You can even use it to bond materials such as PP plastic or ABS plastic which is thought of as hard to bond. Ensure you pay attention to the right bonding process as plastic is thought of as a special material.
|Name of Plastic||Abbreviation||Use for the Plastic||Number|
|Polyethylene Terephthalat||PET, PETE||This type of plastic is mainly used for making films and packaging, polyester fibers and bottles|
|Polyethylen High Density||PE-HD, HDPE||This form of plastic is used to make artificial wood, pipes, bottles and waste containers|
|Polyvinyl Chloride||PVC||This type of plastic is used to make floor coverings, pipes and window frames|
|Polyethylen Low Density||PE-LD, LDPE||This form of plastic is used to make plastic bags, buckets, a variety of different tubes, and soap dispensers|
|Polypropylene||PP||This type of plastic is used to make many things including food packaging, covers for DVDs, car’s interior lining and industrial fibers|
|Polystyrene||PS||This form of plastic is used to make flower pots, CD cases, toys, foam and suitcases|
|Various other types of plastics, for example polymethyl methacrylate (PMMA) or polycarbonate (PC)||O (for others)||This form of plastic is not listed in guidelines, it is unclear in terms of the legal outlines for these plastic types.|
Overview of the Most Common Plastics
There are so many different plastics available today. We will go into more detail on the different types of plastic. The Recycling Code was established by the Society of the Plastic Industry (SPI) to add in sorting out plastics to better recycle them. This code makes the categorizing of the different types of plastic easier. The abbreviation of the plastic has been standardized and a comprehensive recycling form established making everything easier to understand by the end-user.
The Recycling Code makes it so much easier for households to pre-sort and recycle on the day-to-day. You will be able to locate specialized recycling facilities that you can take your plastic to and in doing so reduce your waste. What follows are details about the seven most common forms of plastic including their recyclable material abbreviations and their area of application.
Polyethylene (PE-HD, 02) and Polypropylene (PP, 05)
Polypropylene (PP) and Polyethylene (PE-HD) are both forms of thermoplastics that have properties that are considered valuable for additional processing. Both plastics are polyolefins and are non-polar and crystalline.
Polypropylene is often used in industrial processing and it can be bonded once the necessary pretreatment has been done, that being said it can only be bonded to a small extent. Polypropylene has a higher heat resistance and hardness, and a higher melting temperature than that of polyethylene. It is the second most commonly used plastic (after polyethylene). What follows are the pros and cons of polypropylene:
Polyethylene is a harder an has a great level of heat resistance to that of polypropylene, and also has an even greater melting temperature. It is considered a standard plastic which is frequently used, however should you wish to bond it you will require pretreatment. What follows are pros and cons of polyethylene:
Applications of Polyethylene and Polypropylene
Polyethylene is used for cable sheathing, as well as film production, and also as a substance to make pump and pipe parts. Polypropylene is used in so many different ways of daily use, as parts for model making, cable sheathing, child seats, surgical parts, fibers of home and sports textiles, vehicle interiors, and many more.
Bonding Polyethylene and Polypropylene
As both polyethylene and polypropylene have low-energy surfaces, bonding of them is not easy for beginners to do. In particular, due to it having the lowest density out of any type of plastic, polyethylene has trouble bonding. It is then very important to first surface treat the plastic.
The issue is that in particular with PP chemical substances (including organic solvents and greases) have difficulty attacking the surface. It is resistant to acids and alkalis. You need to ensure a complex and thorough surface activation must occur. This is normally achieved by pickling with sulphuric acid and this is the method that is normally used in the industry. You can also activate the surfaces of both PE-HD and PP by using corona discharges.
For DIY-ers you can buy special plastic adhesives that include an activator. As a home-user to aid in bonding such low-energy surfaces you can use a primer to pre-treat. If you are using a superglue such as Pattex Plastix for joining you must use a primer.
Recommendation: J-B WELD Steel Reinforced Epoxy
This epoxy adhesive is reinforced with steel for a superior level of strength. This epoxy adhesive is versatile and can be used for a permanent bond over various materials.
Polyamide (PA, 07) and Acrylonitrile Butadiene Styrene (ABS, 07)
The next types of plastic we look at are polyamide (PA) and Acrylonitrile Butadiene Styrene (ABS), what follows are their respective properties.
- Very resistant to chemicals and solvents
- Low surface energy polar, thermoplastic material
- Due to the above-listed properties, the substance is quite hard to bond, to achieve any type of bonding the surface requires pretreatment
Acrylonitrile Butadiene Styrene
- The relevant surface pretreatment as to be used to ensure the substance will bond
- Hard thermoplastic plastic has solid material properties like a great resistance to chemicals, aging, and weathering. The plastic is colorless to yellow.
- Insoluble in diluted acids, fats, ethanol, oils, mineral oils, and alkalis
- The temperature of the heat deflection is great
Polyamide and Acrylonitrile Butadiene Styrene – Applications
Polyamides have amazing material properties making them ideal to use in an assortment of applications. They are impact resistant and stiff while also being highly durable, with optimum sliding properties, high abrasion resistance, and high wear resistance. They are frequently used as construction materials thanks to their properties. You need to be careful with oxidizing chemicals and acids as they can attack polyamide. Polyamides can be used for other purposes than construction materials which include:
- As engine components in vehicle construction
- Synthetic fibers in an assortment of clothing, particularly sportswear and rainwear
- As insulation and housing materials in the electrical engineering field
- Synthetic fibers in a variety of sports equipment, such as parachutes or kites
- Dowels, nuts, cable ties, and other such smaller components
- Fabric and technical textile fibers
- Parts of machines
- Breakproof household and everyday objects
You can use the burning test to identify polyamide. Hold a small piece of the material carefully over an open flame. You are looking for slight foaming, the formation of a blue flame with a yellowish-orangish edge, and a tough drop formation. The smoke will smell similar to a burnt horn.
ABS has high impact resistance and is used for housing of all colors while having an optimum surface hardness, and amazing coating properties, you will use polymers or metals to do this. What is great is ABS can be painted on, printed on, or chrome-plated. You can use ABS for the following things:
- Housing for electrical engineering
- As objects of daily life and household products, such as motorcycle and bicycle helmets, hard-shell cases, telephones, and toys
- Pipes in the sanitary industry
- Within the automotive industry
Bonding Polyamide and ABS
You will have to ensure surface pretreatment is done to bond polyamide or ABS plastics and you will have to use a special reactive adhesive. Use a special primer to increase the substrate’s adhesiveness and the final load-bearing and strength of the final capacity. Begin by applying the primer thinly to both surfaces that require bonding.
Naturally, ensure your surfaces have been adequately cleaned before applying the primer (how to clean is explained in detail in the chapter ‘Preparation work’). Allow the primer sufficient time to take effect, consult the manufacturer’s instructions to determine the time required. We recommend a two-component plastic adhesive based on an epoxy resin or a solvent-based adhesive. You should use methyl methacrylate adhesive if you have a heavy load, or perhaps a 2K polyurethane adhesives.
Recommendation: Plastruct Plastic Weld
This plastic weld sold in a bottle is a durable adhesive and is very effective that can bond an assortment of materials even difficult ones like ABS plastic.
We suggest you use this glue for Polyamide and ABS bonding. Model makers who work with plastic models are huge fans of this product. We strongly recommend this adhesive!
Polyvinyl Chloride (PVC, 03)
You will know this plastic as PVC, it is a thermoplastic polymer that is synthesized from the monomer vinyl chloride. PVC is very resistant to chemicals and is a very important plastic polymer. A hardy material resistant to both weathering and UV radiation. Only a small quantity of crude oil or natural gas is needed to produce PVC, unlike most other plastics, this makes PVC flame retardant. PVC has very positive properties which can only be achieved when you add additives such as plasticizers, lubricants, or stabilizers.
PVC may contain harmful substances such as vinyl chloride so it is considered quite controversial. This substance is thought to be carcinogenic. It is therefore very important that occupational health and safety are followed during the production of PVC. There is still major contention between environmental associations and industries whether or not the end product PVC emits any forms of harmful substances. However, this concern is mainly around soft PVC.
Applications of Polyvinyl Chloride
There are two categories of PVC plastic:
- RIGID PVC: this is utilized in the production of ducts, pipes, profiles, ventilation shafts, skylights, and façade elements. It does not have any plasticizers and can also be used in model making (such as rigid foam sheets)
- SOFT PVC: this is used as floor coverings, flexible sealing material, and insulation material for wires and cables. It contains plasticizers and has an elastic behavior.
Music lovers will know another use for PVC. In the 1940’s vinyl no longer was made with shellac and instead, PVC was used to make records.
Pay attention if there are any plasticizers that could be present when you are bonding PVC. Soft PVC is a challenge for the user, while rigid PVC is not a question at all. Should there be molecules of plasticizers they can move to the surface and begin to compromise the adhesive by dissolving it. This stops a permanent bond from forming. This is additionally favored in the situation where adhesive surfaces receive extreme tension or are exposed to loads that are high.
You can use the contact bonding method to bond PVC, this is done by coating both surfaces with a thin layer of a suitable adhesive, allowing the relevant period of flash-off time, and then joining them together. A good option is then using a two-component polyurethane-based adhesive. If you wish to increase the over-all adhesion you can simply add a crosslinker. You could also use the one-component adhesive Pattex Special Modelbau which is a high-quality adhesive, such as follows:
Recommendation: GORILLA PVC Glue
The Gorilla PVC Glue is the go-to for model builders and offers an incredible price-performance ratio, other advantages of the product include.
Polystyrene (PS, 06)
As mass-produced plastic polystyrene (PS) is used throughout everyday life. The plastic is used to make an assortment of household objects including CD cases, sockets, and food packaging. It has a clear color that when foamed becomes white and it is semi-crystalline.
Thanks to it being solvent-soluble and polar it makes polystyrene much easier to bond than other forms of plastic. Regardless the correct form of adhesive has to be used. In particular, the second substrate (the second material that you will be bonding the PS to) be careful as you will not be able to achieve a durable bond with all material.
Application of Polystyrene
The initial material of polystyrene is in a granulated form. The granules are then utilized to manufacturer an assortment of mass-produced items. Polystyrene is simple to process and is not expensive they score highly in the household sector. Polystyrene is used to make the following items:
- Used under the name Styropor in the construction industry as insulating materials and packaging materials
- In an assortment of household items such as blender housing, yogurt pots, and plastic bottles. It is also suitable for storing food thanks to it being non-toxic
- As blister packs
- In electrical engineering for housings and switches and coil formers thanks to it having amazing insulation properties
- Used for model making
You need to ensure the correct surface conditions are present to bond polystyrene. You require a clean and smooth structure in the case of PS the surface needs to also be of sufficient size to allow effective adhesion from the plastic adhesive.
Clean the substrate and ensure to remove any grease and dust using either a dust-free cloth or a damp sponge cloth with some mild detergent. If you wish to glue to wood or metal you will have to roughen up the surface a little before gluing. This will significantly increase how effective the plastic glue’s adhesion is. If you do choose to rough up the surface ensure you remove any dust again before using the adhesive.
If their area you are gluing is a small surface you can apply the adhesive using a small brush or directly from the tube. If however, the surface area is large re recommend you use spray adhesive. Apply an adhesive that is a solvent-based and quickly join together the two surfaces. You need to ensure a flat surface, particularly when working with a spray adhesive otherwise you will not be guaranteed a proper bond.
Should you be unable to level the two surfaces efficiently you can create a leveling layer using putty. The putty will be able to fill up any holes and cracks. Should you have to use putty when then applying the adhesive begin with a large bead of adhesive placed on the outer edge of the surfaces and working towards the inner area, fill in with adhesive. You should have then covered about 40 percent of the area which requires bonding, with putty. You can also try assembly adhesive which is a great option for items indoors, or a Styrofoam adhesive which we will go into more detail about shortly.
Recommendation: TAMIYA Extra Thin Polystyrene Glue
If you have a particularly difficult gluing case Tamiya is your go-to glue.
Polymethyl Methacrylate (PMMA)
PMMA or as you know it, acrylic glass or plexiglass The name plexiglass is very descriptive due to the substance’s optical properties but that particular name is a patent. There are two different PMMA types:
- HIGH MOLECULAR PMMA: processed by thermoforming and machining, it is cast and is part of the group of thermoplastic materials
- THERMOPLASTIC PMMA: machining is used to process it, but can also be done with injection molding, welding, extrusion, and thermoforming
PMMA has a high impact stiffness and strength combined with medium strength. The resulting material has superb scratch resistance and can be further increased by the relevant surface treatment. You can polish the surface to remove any scratches if required.
PMMA is a great material to use particularly in outdoor applications thanks to its resistance to weathering, aging, and UV lights. In addition, it is highly insensitive to any chemical influences but be careful with the following chemicals:
These particular chemicals will potentially attack the PMMA, so rather do not clean the material with solvents or alcohol. To identify PMMA you can use the following test; take a small sample and hold it over an open fire. Should the sample burn under a yellowish flame and a sweetish smell and produces a crackling sound, you can be assured it is PMMA.
Polymethyl Methacrylate Applications
Thanks to PMMA being non-toxic it can be used for glazing skylights and shower stalls, and also for food packaging and household packaging. Thanks to its amazing processing properties it is quite popular for both industries and small users. PMMA’s light refraction is even better than mineral glass and offers stunning coloring properties. PMMA is used in the following fields of application:
- It is used in the building sector for an assortment of glazing including industrial door glazing, flat roofs, industrial flooring, polymer concrete, and sanitary components like bathtubs and shower cabins
- PMMA is used to make dental prostheses and dressing splints in the medical industry
- PMMA is used in vehicle construction to make light guides, reflectors, and column coverings
- Fibers for the textile industry are made from PMMA
- In construction and plant engineering, it is used to build protective hoods and safety doors
- PMMA is used in the food industry to build pipe-lines for an assortment of beverages and liquids like beer and milk
- PMMA is used in the aerospace industry for glazing, hoods, and headlight covers
As you can see PMMA can be used in a number of diverse industries. Should PMMA be damaged don’t just throw it away or buy a new one, there are ways to repair it.
We already know that PMMA is very sensitive to solvents but this fact can be used in your favor to alter the surface properties of the material and make it easier to bond it. Do not use a solvent like acetone that is a polar solvent this can cause the material to be put under stress and ultimately crack. Rather clean the surface using a non-polar cleaner (such as isopropanol). All the isopropanol to air out once you have finished cleaning for at least 10 minutes before the plastic adhesive is applied.
A scratch-resistant coating based on polysiloxanes could cover the surface of the substrate. Should this be the case you can utilize polyurethane adhesive which is a two-component adhesive. PU adhesives do not yellow and have optimum adhesive properties with weather-related and high mechanical load-bearing capacity. First, utilize a primer to ensure optimum adhesion.
When bonding PMMA you can also look to styrene-free MMA adhesives as it is basically liquefied Plexiglass. Ensure you test these adhesives on an inconspicuous spot in advance, as sometimes the substrate may show stress cracks.
Due to the high demand for opticals on the adhesive surface selecting the correct plastic adhesive can be complicated. Which adhesive used is of great importance particularly with uncolored (transparent) PMMA. You can use superglue in an emergency to bond or repair PMMA but this can result in terrible streaks. Rather use one of the plastic adhesives that we recommend such as PMMA Acrifix adhesive.
Recommendation: SUPER GLUE Plastic Fusion Glue
Plastic Fusion Glue Acrifix PMMA is a two-component adhesive that can be used on a number of different plastics including PMMA. You can purchase it in a user-friendly 1 oz syringe and almost anyone can apply it with ease.
How to Glue Plastic
Materials offering high surface energy such as glass, many metals, or ceramics have ideal adhesive properties for adhesives. If the surface has a greater tension than the adhesive does then it can be said that the adhesion will adhere well.
Most plastics have a low-energy (non-polar) surface making it difficult to bond plastics. How do you know if your plastic is a high-energy or low-energy surface? With just one drop of water, you can perform a test to determine, just dribble a small amount of water onto the surface. If the water forms a drop then the surface is low-energy but if the water rolls off, the surface is high-energy. You need to pre-treat a low-energy surface otherwise the plastic adhesive will not bond, what follows is how to do this.
Always prepare your surface properly before gluing your broken plastic. Clean any oil residues, grease, and dust on the surface using the correct cleaning agent and a lint-free cloth. We suggest using solvents and water. Use an immersion method or spray to clean. If there are stubborn fats gently pre-drying in an oven will help.
Next, you should treat the surface by sanding or sandblasting. This will aid the bonding by roughening up the surface and will ensure the plastic adheres better. You can also do a pre-treatment that is chemical by etching or pickling creating a new surface structure. You can also try laser pre-treatments and thermal pre-treatments, but these options are not always available for home users. These are normal processes that will alter the surface either chemically or physically, such as the electric plasma process.
It is a variant in coating the surface before you bond. As a home user, you will lean towards a suitable primer. This type of substance needs to be applied as instructed as it reacts chemically. Do not touch the surface with your bare hands after you have cleaned it as you could potentially impair the effects of the adhesion with your skin grease. If you were to touch it, you would have to clean the surface again.
Residues, Sticking and Removing
You can not apply the adessive too generously and put the two surfaces together using high pressure. Take note of the fragility of the materials, but if necessary, you can fix them. Keep in mind the relevant flash-off time of your plastic adhesive. Once joined ensure sufficient dry time is given, consult the manufacturer’s instructions to determine the correct drying time. The stipulated drying time may vary due to factors such as humidity, ambient temperature, and naturally the plastic adhesive used and the substrates. To cover yourself always allow for a little longer drying time.
Once bonding is complete any excess plastic adhesive needs to be removed immediately, if it is allowed to cure you will not be able to loosen any excess adhesive. If you allow it to cure and only then try to remove it you would have to use a scalpel to scrape it off which could potentially damage the surface.
You will need to be aware of your safety when bonding plastic as it can give off harmful vapors during work. It is a given that you require a well-ventilated workspace to work in, in addition, you should wear long-sleeved clothes and a respiratory mask. We also suggest using disposable gloves. If any adhesive does come into contact with your skin use warm soapy water to wash it off immediately.
Should it come into contact with your mucous membranes or your eyes use lukewarm water to rinse them for several minutes. Next immediately consult a doctor, provide him with the packaging insert so that he knows which substances that have entered your mucous membranes or your eyes.
Bonding Plastic – Tips and Tricks
Double-sided acrylic foam adhesive tape is a new development in the bonding plastic. Should you have a high absorption of mechanical stress or low energy surfaces then the tape is ideal. It is perfect for dampening both vibrations and temperature differences and can be used to bond plastic parts.
Unfortunately, the double-sided adhesive tape cannot always be utilized, for example, you have cracks in your material you wish to stick rather use a suitable plastic adhesive. Should this be the case at the end of the crack drill to ensure it does not further expand, and follow with the relevant gluing as described above.
Necessary surface preparation and the material’s composition are very important when bonding plastic. Hopefully, we have equipped you with the relevant knowledge of plastic’s importance and useful tips on how to bond plastic successfully.
There are many different methods and considerations for bonding plastic. We hope that our complete guide above has helped you to find the perfect plastic adhesive for your project ahead!