The difference between polyurethane encapsulant and epoxy encapsulant

Condensed silica gel absorbs atmospheric moisture during the curing process and cannot be heated to speed up curing (adding too much heat during curing is not good). Usually small amounts of by-products are produced during the curing process. Additive curing silicone uses a platinum curing agent for fixing, and no by-products are produced during the curing process.

Once the hardener is added, they do it themselves, even in an airtight container, and they don't need to be open to the atmosphere to do so. Shenzhen Shangshang Technology **** is a Quantum Silicones, Inc. in the United StatesOffice & Head Office in Asia Pacific**.

QSI (Quantum) Group is the world's top professional potting and sealing silicone manufacturing company, headquartered in Richmond, Virginia, USA, and the factories are ISO9001:2000 certified. Our goal is to be the best in the industry....

Encapsulant, also known as electronic adhesive, is a broad term, which is mainly used for bonding, sealing, potting and coating protection of electronic components. Polyurethane encapsulants and epoxy encapsulants are often used, so what are the differences between the two?

The main component of polyurethane (PU) potting compound is polyisocyanates and polyether polyols in the presence of catalysts (triethylenediamine) cross-linked and cured to form polymers, polyurethane adhesive has good adhesion properties, insulation properties and good weather resistance, hardness can be changed by adjusting the content of diisocyanate and polyether polyols, it is mainly used in the packaging of various electronic and electrical equipment.

Compared with epoxy resin potting compound, the toxicity of the former is relatively large, and epoxy resin glue and polyurethane glue are the same, can be made into two-component glue, epoxy resin potting compound is generally composed of bisphenol A epoxy resin, curing agent (amine or anhydride), reinforcing additives and fillers, etc., its room temperature curing time is longer, can be heated and cured, the bonding strength is large after curing, and the hardness is generally relatively large, can be made into transparent potting glue, used to encapsulate electrical modules and diodes, etc.

For two-component potting compounds, the method of use is basically the same, and their general process is: batching-mixing-vacuuming-—— potting-curing. Of course, this process can use two-component potting equipment, which simplifies the whole operation process, and also saves operation time and reduces raw material waste.

The main components of polyurethane (PU) potting compound are multi-ben diisocyanate and polyether polyol in the presence of catalyst (triethylenediamine) cross-linked and cured to form polymer, polyurethane glue has good adhesion performance, insulation performance and good weather resistance, hardness can be changed by adjusting the content of diisocyanate and polyether polyol, which can be transported to the packaging of various electronic and electrical equipment. Compared to epoxy encapsulants, it is highly toxic.

Epoxy resin glue and polyurethane glue are the same, can be made into two-component glue, epoxy resin potting compound is generally composed of bisphenol A epoxy resin, curing agent (amine or anhydride), reinforcing additives and fillers, etc., room temperature curing time is longer, can be heated and cured, after curing the bonding strength is large, and the hardness is generally relatively large, can be made into transparent potting glue, used to encapsulate electrical modules and diodes, etc. For two-component potting compounds, the method of use is basically the same, batching-mixing-vacuuming-potting. Two-component potting equipment can be used, simplifying the entire operation process while also saving operating time and reducing raw material waste.

Epoxy resin potting compound is a commonly used material in life, maybe you often come into contact with it, but you don't know much about it, in order to let you further understand this material, we will introduce the concept and characteristics of epoxy resin potting compound in detail, let's take a look!

What is epoxy encapsulant.

Epoxy resin potting compound is generally composed of bisphenol A epoxy resin, curing agent (amine or anhydride), additives, fillers, etc., which has a long curing time at room temperature, can be heated and cured, and the bonding strength is large after curing, and the hardness is generally relatively large, which can be made into a transparent potting compound for encapsulating electrical modules and diodes.

After curing, there are no bubbles, the surface is smooth, shiny, and the hardness is high; The cured material has good acid and alkali resistance, good moisture-proof, waterproof, oil-proof and dustproof performance, and is resistant to damp heat and atmospheric aging, but it is not easy to repair after bonding.

Epoxy resin encapsulant features.

1. It has excellent fixed, potting, electrical, insulation, moisture-proof, shockproof, thermal conductivity, aging resistance and other properties.

2. Condensed liquid silicone rubber does not use polar compounds as raw materials, and no by-products are released during cross-linking, which can maintain the best electrical performance under harsh conditions.

3. The vulcanized silicone rubber has good weather resistance, heat resistance and cold resistance at a temperature of -57 250.

4. Non-toxic, tasteless, non-corrosive and non-swelling.

5. Widely used in sealing, electrical, potting, insulation, thermal conductivity, anti-fouling, waterproof, shockproof, coating, electronic appliances and comprehensive household appliances.

Epoxy resin encapsulant construction process.

There are two kinds of potting processes for epoxy resin, normal and vacuum, among which: epoxy resin and amine normal temperature curing potting materials are generally used for low-voltage electrical appliances, and normal potting is mostly used; Epoxy resin and acid anhydride are generally used for potting of high-voltage electronic devices, and the vacuum potting process is mostly used.

The construction process of epoxy resin potting compound is as follows: first, manual vacuum potting process; The second is the mechanical vacuum potting process, which is mixed with deaeration and then potting process and A and B are deaeration and then mixed potting process respectively. In contrast, mechanical vacuum potting, large equipment investment, and high maintenance costs, but it is significantly better than the manual vacuum potting process in terms of product consistency and reliability.

Precautions for the construction of epoxy resin potting compound.

1. After mixing, it will begin to solidify gradually, its viscosity will gradually rise, and some heat will be released. 2. The more glue mixed together, the faster the reaction, the faster the curing speed, and may be accompanied by a large amount of heat, please pay attention to control the amount of glue at one time, because due to the acceleration of the reaction, its usable time will also be shortened, and the mixed glue will be used up in a short time as much as possible.

3. All components should be sealed and stored. The mixed rubber should be used up at one time to avoid waste.

4. This product is not a dangerous product, but do not enter and eyes.

Epoxy encapsulant: This type of glue is mostly hard, and a small part is soft. Its biggest advantage is that it has good adhesion to hard materials, high hardness and good insulation performance. However, the disadvantage is that it cannot be opened after potting, and it cannot be repaired when the internal electronic components are damaged.

Polyurethane encapsulant: the adhesion is between epoxy and silicone, the temperature resistance is poor, the working temperature can only reach about 150, and the higher the temperature will age and lose its performance, and the stability performance is weaker than that of silicone potting compound.

1. Problems that should be considered when selecting epoxy resin encapsulant:

1. Requirements for performance after potting: use temperature, alternating cold and heat, internal stress of components, outdoor use or indoor use, stress condition, whether environmental protection is required, flame retardant and thermal conductivity, color requirements, etc., such as TH893;

2. Potting process: manual or automatic glue filling, room temperature or heating curing, the usable time of the mixed glue, the solidification time, the complete curing time, etc.;

3. Cost: The cost of potting materials varies greatly, we must look at the actual cost after potting, rather than simply looking at the selling price of materials.

Second, the requirements for material storage conditions are very strict

1.It has good performance and long application period, and is suitable for large-scale automatic production line operation.

2.Low viscosity, strong impregnation, can fill the elements and between the wires.

3.During the potting and curing process, the powder components such as fillers settle little and do not stratify.

4.The curing exothermic peak is low, and the curing shrinkage is small.

5.The cured material has excellent electrical and mechanical properties, good heat resistance, good adhesion to a variety of materials, and small water absorption and linear expansion coefficient.

6.In some cases, the potting material is also required to have the properties of flame retardancy, weather resistance, heat conductivity, high and low temperature alternating resistance, etc.

Potting is an important application area for epoxy resins. It has been widely used in the manufacturing of electronic devices and is an indispensable and important insulating material in the electronics industry. What it does is:

Strengthen the integrity of electronic devices and improve the resistance to external shocks and vibrations; Improving the insulation between internal components and lines is conducive to the miniaturization and lightweight of devices; Avoid direct exposure of components and circuits, and improve the waterproof and moisture-proof performance of the device. Epoxy potting compound has a wide range of applications, different technical requirements, and a wide variety of varieties. In terms of curing conditions, there are two types: room temperature curing and heating curing.

3. Precautions for use.

1. The products to be potted need to be kept dry and clean;

2. When using, please check agent A first, observe whether there is sedimentation, and stir agent A well; After stirring evenly, please fill the glue in time, and try to use up the mixed glue within the usable time;

4. Before using it in large quantities, please try it in small quantities to master the skills of using the product to avoid mistakes.

There are also silicone potting compounds.

What is a silicone encapsulant?

Silicone thermally conductive potting adhesive is a composite material prepared with silicone material as the matrix, which can be cured at room temperature or heat, and has the characteristics of faster curing at higher temperature. It is made of adding heat conductive material on the basis of ordinary potting silica gel or silica gel for bonding, and will not produce any by-products in the curing reaction, and can be applied to the surface of PC, PP, ABS, PVC and other materials and metals. It is suitable for thermal conductivity, insulation, waterproof and flame retardant of electronic accessories, and its flame retardancy should reach UL94-V0 level.

To comply with the requirements of the EU RoHS Directive. The main application field is the potting of electronic and electrical components and electrical components, and it is also used in similar occasions such as temperature sensor potting.

The most common silicone thermally conductive potting compound is composed of two components (A and B components), the most common of which is the addition molding thermal conductive potting compound, which can be deeply potted and there is no low-molecular material generation during the curing process, and the shrinkage rate is extremely low.

Silicone thermal conductive potting adhesive can obtain different thermal conductivity according to the addition of different thermal conductive powders, which can be achieved by ordinary ones and can be achieved by high thermal conductivity. Generally, manufacturers can make special deployments according to their needs.

After curing, the silicone thermal conductive potting compound is mostly soft, with poor adhesion, high and low temperature resistance, can be used at 200 degrees for a long time, and the heating and curing type has higher temperature resistance, good insulation performance, and can withstand voltage above 10000V, which is moderate and has good repairability. Because it has a good ability to resist high and low temperatures, it can withstand the cold and heat changes between -60 and 200 without cracking and maintaining elasticity, and it has a good thermal conductivity after filling and modification with thermal conductive materials, which can effectively improve the heat dissipation capacity and moisture-proof performance of electronic components after potting, and the electronic potting compound made of silicone material is soft after curing, which is convenient for the maintenance of electronic equipment.

The color of silicone encapsulants can generally be adjusted as needed. Transparent or non-transparent or colored. Silicone potting adhesive performs very well in terms of shock resistance, high and low temperature resistance, and anti-aging performance.

Hello, it is impossible for polyurethane to completely replace silicone! Polyurethane is relatively hard and can only reach about 150 degrees Celsius at operating temperatures, and at higher temperatures, it ages and loses its properties. The silica gel is relatively soft, the working temperature can reach more than 300 degrees, and the performance of silica gel is more stable than that of polyurethane.

Therefore, in the case of low hardness requirements and high temperature requirements, polyurethane cannot replace silicone! However, polyurethane is much cheaper than silicone, and polyurethane is often chosen instead of silicone in order to save costs.

Mine, are you still satisfied?

It is not possible for polyurethane to completely replace silicone.

Polyurethane is relatively hard, and the working temperature can only be closed to about 150 degrees, and the higher temperature will age and lose its performance.

Silicone is relatively soft, the working temperature can reach more than 300 degrees, and the performance of silicone is more stable than that of polyurethane.

Therefore, in the case of low hardness requirements and high temperature requirements, polyurethane cannot replace silicone! However, polyurethane is much cheaper than silicone, and polyurethane is often chosen instead of silicone in order to save the cost of side modification when the requirements for the workplace are not very strict.

1.The glue does not cure:

Possible causes: too little or too much curing agent; The glue is stored for a long time, and it is not stirred or evenly before use;

2.The glue that was supposed to be hard glue is soft after curing:

Possible causes: Incorrect glue ratio: such as not proportioning according to weight ratio or large deviation;

3.Some places the glue cures, some places the glue does not cure or does not cure completely:

Possible causes: uneven stirring;

4.After curing, the surface of the glue is very uneven or there are many bubbles:

Possible causes: curing too fast, heating and curing temperature too high, close to or beyond the operation time potting and dispensing;

5.After curing, the surface of the glue is oily

Possible causes: Water and humidity during the glue filling process.