In recent years, with the continuous improvement of electric heating film radiant heating system technology and the practical application of numerous cases, the advantages of electric heating film underfloor heating systems — such as being environmentally friendly, comfortable, flexible in control, capable of peak shaving and valley filling in electricity use, and conducive to behavioral energy conservation — have been increasingly recognized by all sectors of society. However, the booming market inevitably brings mixed quality. Failure cases caused by electric heating film quality problems are not uncommon, including electrical safety and local overheating issues in electric heating film underfloor heating systems, heating performance failing to meet design requirements, and indoor temperatures decreasing year by year. Therefore, ensuring and improving the safety and performance of electric heating film products, as well as researching, developing, and manufacturing high-quality electric heating film products, is particularly important. The research and development of polymer electric heating film products has not only enriched the variety of electric heating film products but also enhanced and expanded their application fields.

Conductive Polymers: A Revolution in Electric Heating Film Materials

Product revolutions often begin with revolutions in the materials used to produce them, and the research and development of polymer electric heating film products in the electric heating film industry is no exception. The birth of the new material — conductive polymers — has provided the material foundation and guarantee for the research and development of polymer electric heating films.

Conductive polymers were born in the 1970s as a brand-new branch of polymer materials, belonging to the frontier discipline of new materials. Their inventors were awarded the Nobel Prize in Chemistry in 2000. The electrothermal conversion principle of conductive polymers can be briefly described as follows: while organic monomers polymerize to form polymers, through different molecular designs and organic synthesis processes, positive, negative, or amphoteric groups (known as polar groups) with different chemical structures, different numbers of groups, and different numbers of free electrons can be grafted or doped, thereby forming conductive polymers of different structures with different dielectric and electrothermal properties. When electricity is applied to a conductive polymer, the free electron groups bound within countless clusters of polar groups move directionally against the current direction in a narrow space, forming an electric current. At the same time, the electrons encounter resistance during movement, collide, and generate frictional impact heat, which is mainly transmitted outward in the form of far-infrared radiant heat.

It is precisely because conductive polymers possess the above superior heating properties during conduction that they become natural heating resistance materials (also known as electrothermal materials or heating materials). Since different heating resistance materials have different "dielectric properties, half-lives, electrothermal conversion efficiencies, and compatibility," they determine that their electric heating film products have different electrical safety performance, thermal stability, electrothermal conversion efficiency (including the proportion of radiant heat), anti-aging and anti-oxidation capabilities, service life, and so on. For conductive polymers applied in polymer electric heating films, molecular design allows for the adjustment of dielectric and electrothermal properties, acid and alkali corrosion resistance, material compatibility as needed, effective control of the far-infrared radiation wavelength range, and adjustment of the main peak wavelength and its proportion. As a result, polymer electric heating film products using conductive polymers as heating resistance materials feature a wide power density range, long service life, high electrothermal conversion efficiency, no electromagnetic radiation, a large proportion of far-infrared radiant heat, and strong comfort.

As is well known, the heating resistance material is the core of an electric heating film. The heating resistance material and product structure of the polymer electric heating film developed by Beijing Xinyuyang Technology Co., Ltd. (hereinafter referred to as "Xinyuyang") possess outstanding features and advantages. China's construction industry standard Low-Temperature Radiant Electric Heating Film (JG/T 286-2010) lists polymer electric heating films alongside metal-based electric heating films and inorganic non-metallic electric heating films (including carbon fiber electric heating films, ink electric heating films, etc.) as the three major product categories of electric heating films. Furthermore, after comprehensively evaluating the inspection reports of numerous submitted samples, the standard drafting committee designated Xinyuyang's polymer electric heating film as the sole product for technical indicator verification of this standard.

High-Performance Polymer Electric Heating Films

It goes without saying that the heating resistance material and product structure determine the quality and performance of electric heating film products. Only by combining excellent conductive polymer heating resistance materials with a reasonable product structure can efficient and high-quality polymer electric heating film products be developed and manufactured.

According to reports, the research and production of polymer electric heating films requires synthesizing conductive polymers and composite conductive polymers based on the application fields, dielectric properties, and functional requirements of the electric heating films. Specially treated metal wires are used as electrodes, which are knitted or woven together with glass fibers, chemical fibers, cotton threads, etc., into a substrate with metal electrodes, used respectively for electric heating films with different performance requirements. Then, through a "foolproof" coating process, the composite conductive polymer material is coated onto the substrate according to the power density requirements at different voltages, forming a bare electric heating film. Next, depending on usage requirements, the bare electric heating film is covered with different insulating materials. Finally, the film is cut, connected to terminal blocks, welded with lead wires, and the finished products are inspected and tested.

The polymer electric heating films produced through the above manufacturing process have the following three major characteristics:

1. Polymer electric heating films are electric heating films with a substrate. Most electric heating films have no substrate, with the heating material directly sandwiched between two layers of insulating film. Electric heating films with this structure have a small effective heating area and a high power density for the same power, making local overheating prone to occur. Once a substrate-free electric heating film overheats, the heating material may crack, causing increased resistance; electrodes may crack; insulation resistance may decrease, or even leakage may occur. Users may experience circuit breaker tripping, gradually decreasing room temperature, floor collapse, and other phenomena during use; in severe cases, fires, electric shocks, and other accidents may occur.

Compared with substrate-free electric heating films, the heating material of polymer electric heating films — the conductive polymer — is tightly integrated with the substrate and electrodes through a binder, overcoming the drawbacks of substrate-free electric heating films. Moreover, it has good flexibility, greatly improved anti-aging and anti-cracking capabilities, and a wide range of options for outer insulating materials. At the same time, the substrate material, density, and electrode spacing can be changed according to subsequent product development and design requirements to produce bare electric heating films with various functions, such as breathable electric heating films, high-temperature-resistant electric heating films, flexible electric heating films, and special-functional electric heating films, which can be applied to the development of electric heating products in various fields.

2. Polymer electric heating films use metal wires as electrodes. Inorganic non-metallic electric heating films typically use copper sheets as electrodes, with the electrodes in cross-sectional contact with the heating material. Copper sheet electrodes are difficult to continuously and tightly bond with the heating material and are vulnerable to bending, which is one of the main reasons why this type of electric heating film is prone to sparking after being energized. In contrast, the electrodes of polymer electric heating films consist of several groups of specially treated ultra-fine metal wires. Not only do they form an integral whole with other fibers during the substrate weaving process, but after the conductive polymer is coated, they are completely wrapped by the heating material. This not only ensures tight bonding with the heating material, stable electrical performance, and good flexibility, but also greatly enhances the anti-oxidation and anti-aging capabilities of the electrodes.

3. Polymer electric heating films are electric heating films with arbitrarily adjustable power density. Power density refers to the electric power per unit effective heating area (unit: W/m²). Since the conductivity of the conductive polymer, the substrate with implanted electrodes, the automated coating process, and the selection of outer insulating materials all offer flexibility, the power density of polymer electric heating films can be arbitrarily designed. Coupled with the ease of processing into flexible and functional electric heating films, polymer electric heating films have a wider range of uses compared with other types of electric heating films.

Widely Applied Polymer Electric Heating Films

The numerous characteristics of polymer electric heating films have earned them a renowned reputation in the electric heating film industry. Their "three arbitrary" features — arbitrary width and shape, arbitrary operating voltage, and arbitrary power density — as well as the advantage of being endowed with special functionality, give polymer electric heating films greater room for subsequent product development and broader application fields.

In traditional building heating applications, Xinyuyang installed the first domestic electric heating film underfloor heating project at Yuanmingyuan Garden in Haidian District, Beijing in 2002, pioneering the use of electric heating films for underfloor heating in China. To date, Xinyuyang's polymer electric heating film heating systems — including "electric underfloor heating, electric wall heating, electric ceiling heating, and radiant electric heating panels" — have been widely applied in residential and public buildings, agricultural greenhouses, and rural coal-to-electricity conversion projects. To ensure the safety of its electric heating film underfloor heating systems, Xinyuyang has also successively developed patented technologies such as overheat protection devices, leakage current shielding films, and electric heating films, making it one of the few electric heating film manufacturers in China with multiple invention patents.

In fields already put into use, such as snow melting and deicing for satellite receiving antennas, road and roof snow melting, physiotherapy and health care, agriculture and animal husbandry, and heat tracing for industrial equipment and pipelines, Xinyuyang's polymer electric heating films have also achieved good usage results and impressive market returns. In newly developed application fields such as snow melting and deicing for wind turbine blades, aerospace industry applications, equipment camouflage, far-infrared therapy equipment, and other areas, Xinyuyang is also actively exploring the application path of polymer electric heating films.

While the promotion and application of polymer electric heating films have achieved good market and social benefits, they have also received recognition and praise from numerous industry professionals: Xinyuyang's polymer electric heating film is the only leading brand in the electric heating film industry selected by China Construction News; it is a consecutively recommended brand for two terms by the Radiant Heating and Cooling Committee of the China Construction Metal Structure Association; the "Xinyuyang Polymer Electric Heating Film Underfloor Heating System" was selected as a "Beijing 2012 Low-Carbon Technology Product Recommendation" (Jing Fa Gai [2012] No. 780) jointly issued by six commissions and bureaus including the Beijing Municipal Development and Reform Commission and the Beijing Municipal Science and Technology Commission; it has obtained the Beijing Independent Innovation Product Certificate and been included in the government procurement list... As a manufacturer of polymer electric heating film products, Xinyuyang has also been widely recognized by all sectors of society: it is a national-level high-tech enterprise that passed re-evaluation twice in 2009 and 2012; it is one of the "Top Ten Technological Innovation Enterprises" jointly awarded by six ministries including the Ministry of Science and Technology; as an outstanding contribution unit in the drafting of the Low-Temperature Radiant Electric Heating Film standard, it is a national electric heating film production demonstration base.