Electrical insulation varnishes

Winding wires are often made of copper but can also be produced out of aluminium or special alloys. Winding wires can be round and rectangular in cross-section and are usually insulated to prevent the wire from short-circuiting. Sometimes it is not possible to obtain all the desired properties at the same time by having one layer of enamel, so quite often winding wires have several layers of wire enamels. For example, the first layer of insulation can provide good electrical and physical properties, while the second layer will increase mechanical strength and resistance to aggressive environments. Copper winding wires with round cross-section and enamel insulation are the most widely used type of the winding wires. Winding wires are often used in electrical appliances, electric motors, motors, air conditioners, refrigerators, generators, TV sets and many other industrial and household appliances.

The use of insulating varnishes for enamelling winding wires has some nuances, depending on the technology and equipment of the manufacturer, but the typical method of applying varnishes on copper wires includes:

1. Annealing. The heat treatment temperature, the purpose of which is to soften copper and increase its plasticity, depends on the properties, diameter, and cross section of the wires
2. Applying varnishes to the wires. At this stage, varnishes are applied to the wires, to create a coating
3. Enamel polymerization. The wires coated with the specified amount of varnish are sent to the furnace, where the solvent evaporates, and the enamel is cured. The temperature in the furnace can reach 700 C, but because the wires coated with the varnish spend a noticeably short time in the furnace, the enamel temperature usually does not exceed 300 C. It is worth noting that the furnace temperature, as well as the amount of time that the wires spend in the furnace may vary greatly depending on the technology and equipment of the wire manufacturer. This process is repeated until the desired enamel thickness is reached
4. Cooling of the wires. At this stage, the wires are cooled, often using fans. Sometimes, at this stage, grease is also applied to the wires
5. The wires are than assembled into coils

It is important to note that in the production of the wires, other enamelling methods are often used. Each manufacturer of winding coils has its own nuances in the production and equipment used. INTECH GmbH works closely with its customers and partners, which allows it to adapt each product to the customer's needs, regardless of the type and application, special requirements or the end use of the finished product. Our specialists will be glad to analyse, in detail, the available applications and varnishes used, to provide samples of more competitive varnishes for wire enamelling and to introduce a solution that is fully adapted to your needs and requirements.

Wire enamels differ in terms of temperature classes and their composition. Usually wire enamels are made of polyester, polyamide, polyvinyl formal, polyester, polyimide, and other polymers. Depending on the main component, wire enamels have different temperature classes, which can range from 105 C to 250 + C. Varnishes and enamels are also divided into single and double-layer coatings. Composite coatings use two types of insulation, for example modified polyester insulating varnish, THEIC EL 25 can be used as the only coating for wire enamelling, but it can also be used as a primer in the composite enamelling, where the top layer can be polyester amide or polyamide amide.

Below you can find a general description of the products we supply:

INTECH GmbH also supplies wire enamels for the rectangular and aluminium wires. Our technical specialists will be glad to access your company`s needs, analyse the currently used varnishes and offer competitive alternatives, also for the rectangular and aluminium wires.

INTECH GmbH also supplies “PV” product series that are based on Polyvinyl Formal. “PV” product series have good resistance to chemicals and excellent mechanical, thermal and electrical properties and hence they are frequently used in formulations containing other ingredients such as phenolic resins. Polyvinyl Formal is highly versatile, having various outstanding properties, which makes it suitable for a wide range of applications. Specifically, Polyvinyl Formal is widely used for both, rectangular and round conductors. Polyvinyl Formal is also a key component in PVA based wire enamels that have outstanding resistance to transformer oil. These enamels provide excellent toughness, flexibility, and abrasion resistance. This material is available in five “PV” specifications with different molecular weights and different viscosities to suit various end usages.

Product EL 14

Thermal Class: 130 C

EL 14 is a terephthalic polyester wire enamel, which belongs to plain polyester class 130, for general purpose. It has excellent flexibility and adhesion. Wires with EL 14 enamels, satisfy pinhole free requirement, even after elongation, rubbing and bending. EL 14 is used in the manufacturing of plain polyester wires or dual coating wires, for motors, electric devices, and tools. The product has a 130 general purpose polyester class, used for single coat, or as the base coat in dual coating systems, for wires with 0.04mm diameters or above. It is suitable for high speed machine or traditional multi-line machine, for vertical or horizontal ovens, for dies and felts application.

Base coat: EL 14/36

Topcoat: None

Product EL 25

Thermal Class: 155 C

EL 25 is THEIC modified polyester enamel, with excellent performance, which can meet the strict demand on pinhole resistance test after elongation, rubbing and bending. It has good adherence property and remarkable levelling property that cause excellent appearance performance. It is suitable for single coating of the wire or as base coating of composite wire enamelling. If overcoated with polyesterimide, such as EL 88, the wire can meet with the requirement of IEC standard, class 180.

It is suitable for 0.04mm above different diameter wires. It is suitable for high speed machine or traditional multi-line machine, for vertical or horizontal ovens, for dies and felts application.

Base coat: EL 25/36

Topcoat: None

Product EL 38

Thermal class: 220 C

EL 38 is a polyamideimide enamel, with good wire surface, excellent mechanical capability, high heat, and chemical resistance, suitable for 0.05mm and greater diameter wires. It is usually used as a topcoat, during the composite wire enameling. The base coat, to be used with EL 38 is modified polyester (PE), or polyesterimide (PEI) wire enamels. The wires with EL 38, have good performance and freon resistance and are widely used for thermal resistant applications, including transformers and compressors. It can also be used as single coating, thermal class 220. UL listed. EL 38 is suitable for vertical and horizontal enameling processes, can be applied by dies or felt methods of application.

Base coat: EL 88/40

Topcoat: EL 38/35

Product EL 58

Thermal class: 200 C

EL 58 is THEIC modified polyester, with excellent adherence, good mechanical performance, and high thermal resistance, excellent STP performance. Good levelling property causes excellent appearance performance. It is recommended to use EL 58, as a base coating for the composite wire enamelling. Topcoat can be either nylon or polyamide-imide. If the top coating thickness of polyamide-imide is above 30%, the thermal class can reach to 220. When overcoated with polyamide-imide, it can be used for compressor wires, for air conditioner, and refrigerator motor. UL listed.

It is suitable for 0.20mm up different diameter wires, for high speed machine or traditional multi-line machine, for vertical or horizontal ovens, for dies or felts application.

Base coat: EL 58/40

Topcoat: EL 38/35

Product EL 88

Thermal class: 200 C

EL 88 is THEIC modified polyesterimide wire enamel with medium viscosity. EL 88 is easy to apply and it is widely used to produce high thermal resistant enameled wires. It has excellent performance on thermal resistance with thermal class 200, if used as a single coating. It has good adherence capability, excellent performance in terms of flexibility, good thermal rating capability, and good adherence retention, after heat treatment.

It can be used as a ground coating in composite wire enameling, with top coating consisting of polyamideimide. These enameled wires have excellent performance during Freon resistance testing and have excellent results in Freon blister testing. EL 88 meets the strict requirements of compressor manufacturers in Japan and South Korea. EL 88 is UL listed and can also be used as a single coating.

Base coat: EL 88/40

Topcoat: EL 38/35