When the liquid gradually evaporates from the material in the case of conventional paints and varnishes, these mixtures harden and acquire their physical and operational properties. But for some resins, such a process is impossible without additional intervention. Curing in this case is the result of a chemical reaction. During this time, the mixture polymerizes and acquires the final structure.
What hardeners are for
Epoxy resin hardeners act as a catalyst for the reaction and are fully involved in the process. They are combined with resin, as a result, it is possible to obtain product properties such as uniformity, hardness, durability and transparency. These characteristics are determined by how accurately the proportions were chosen when combining resin and hardener.
During self-mixing of ingredients, the correct dosage must be observed. Different substances act as hardeners, these can be anhydrides, carboxylic acids, diamines. Mixed with the aboveresin hardeners form thermosetting compounds that have the following characteristics:
- high adhesion;
- good water resistance;
- excellent dielectric properties;
- mechanical strength;
- small percentage of shrinkage.
Composition of different hardeners
Epoxy resin hardeners can be acid or amine. The former include dicarbic acids and anhydrides. The curing of the resin when using these mixtures occurs at elevated temperatures up to 200 ˚С. These hardeners are hot curing agents.
Epoxy resin hardeners are amine. This group includes various amines. This is the simplest and most common hardener option. Under the influence of these substances, the resin hardens at normal temperature. There is an advantage here, which is ease of use. There is no need to use special equipment. These hardeners are popular, but more effective results can be achieved with acidic compounds.
When hot cured, the resin acquires improved physical and chemical characteristics. Among the hardeners of epoxy resins, which belong to the acid group, anhydrides of dicarboxylic acids should be distinguished, namely:
- methyltetrahydrophthalic;
- maleic;
- methylenedic;
- phthalic;
- hexahydrophthalic.
These compounds have good dielectric properties, are resistant to temperature effects and contact withmoisture. They are often used for electrical insulation and as a bonding element for reinforced plastics. Among the substances of the amine group, one should highlight:
- triethylenetetramine (TETA);
- polyethylenepolyamine (PEPA);
- aminoacrylates;
- polyamines.
Use and proportions of some hardeners
In order to get to know the hardener better, you should know its characteristics. For example, diethylenetriamine, which is also denoted by the next abbreviation - DETA, is a liquid transparent, has no shade. Its shelf life is 2 years at a temperature ranging from - 5 to + 40 ˚С. The substance has an ammonia smell. The recommended curing mode is in a day at a temperature of + 25 ˚С. If this limit is increased to plus + 70 ˚С, then curing will occur after 5 hours. The material is exothermic, which means that the curing process will be accompanied by an increase in temperature. It cannot be used to fill volumetric parts.
Before you start, you may be wondering how much epoxy hardener you need. In the case of the described substance, the volume can range from 8 to 12%. This is true when combined with ED-20 resin. An analogue of PEPA is Telalit 0210. It is a viscous transparent hardener with a pungent odor. You can't leave it open. There are no foreign additives in it, so it is not so thermally stable. Before use, you need to carry out a test batch.
RC-19
If you are wondering which hardenerfor epoxy to use, you might want to consider RC-19, which has proven to work well in high humidity and low temperatures. Consumption is 500 g per kilogram of resin. The term of gelatinization is in half an hour. Suitable for casting large parts. Convenient for installation of self-leveling floors.
Epilox H 10-40
If you saw the label Epilox H 10-40, then you have a reactive hardener that can be used as an accelerator for amine hardeners. Works at a low temperature, which allows it to be used to create volumetric fills. The viscosity of this material is medium. The recommended dose is 50 parts per 100 parts resin.
DIY hardener
A do-it-yourself hardener for epoxy resin can even be prepared, but its quality will be questionable. Such a need arises quite often, because hardeners are sold complete with resin, but the first component is not always enough. It can be quite difficult to keep the exact dosage, so the hardener is used up faster.
It is quite difficult to find a hardener in the construction market or in a store. Before home craftsmen, the question of replacing or self-manufacturing a component quite often arises. At home, it is almost impossible to replace the hardener. Improvised means are not suitable at all, it is necessary to purchase the appropriate chemicals - hardeners, which are little known. Among them, it should be noted"Etal-45M". The method of application of such a substance may differ from the use of conventional polyethylenepolyamine. You will have to test the most suitable ratio of hardener and resin.
Self-cooking
However, several options for making a hardener at home already exist, but the effectiveness remains doubtful. One option is to add dry alcohol to the resin. Urotropin tablets should be crushed into powder and mixed with resin. In this case, it is necessary to use a ratio of 1 to 10. Some masters recommend leaving the prepared mixture for up to 10 hours. After it becomes viscous, you can use the substance for its intended purpose.
Features of application. How to breed correctly
If you follow the technology of mixing the hardener with the resin, you can achieve a positive final result. All components of the mixture are measured according to the instructions. To work, you need to prepare:
- wooden stick;
- mixing container;
- two syringes.
A stick will be needed for mixing. Before diluting epoxy with hardener, it is important to remind yourself that the reaction is irreversible. It is better to practice on test samples, use a small amount of material for this. This will allow you to determine the proportions and understand how much the resin will dry. It is heated above room temperature before mixing. The substance should become less viscous. If resincrystallized, it is returned to its original state, heated to a temperature of + 40 ˚С. In this case, you should constantly stir the mixture. Warming up is best done in a water bath.
It is important to avoid overheating the resin, because after boiling it will be covered with foam, becoming unusable. The resin should be drawn into the syringe and placed in a glass. You must calculate the dosage in advance. The required amount of hardener should be collected by adding it to the resin container. The composition is well mixed to a homogeneous consistency, while using electric tools is impossible.
After the clear epoxy and hardener are mixed, the mixture is ready to use. It is applied to the desired area, where the composition gradually hardens. The mass must be worked out quickly enough, because polymerization will begin within a few minutes after mixing. The structure of the substance will change, which will adversely affect the characteristics of the cured epoxy.
Some modern compositions
On sale today you can find modified hardeners that are devoid of some of the disadvantages of traditional mixtures, but their cost is somewhat higher. Finished products acquire high strength characteristics, the resin polymerizes more fully. These products act as plasticizers, and in some cases are able to plasticize and dilute the epoxy.
Among othersit is necessary to highlight the M-4 hardener, which is amine and has a high viscosity. Its color is red-brown. Mixing is carried out in a volume of 20 to 25% of the base material. The substance cures epoxy at a temperature of + 2 ˚С, as a result, it is possible to obtain a product with increased strength.
The product is a fast curing substance and is made on the basis of PEPA. In addition to cold curing, you can also do hot curing. The plasticizing and gelling time will be 30 minutes at room temperature. If the temperature is lower, the time may increase up to 50 minutes.
If you want to combine a clear epoxy resin with a hardener, you can consider 921, which comes in several varieties. The agent is low-viscosity, allows you to get unique epoxy compositions. They are UV and damage resistant.
