The controversy about emissions from plastics is not a new one. Emissions are particularly an issue in the field of electronics and electrics (E&E). Together with heavy metals and VOCs, halogenated flame retardants in polymer components are a controversial subject. Brominated flame retardants especially, although highly effective and versatile in their applications, can release corrosive gases in case of a fire. The recycling of plastics treated with this type of flame retardants is also no easy undertaking, as the requirements of the European Directive on Waste Electric and Electronic Equipment (WEEE1) must be met, which makes it mandatory to treat these types of polymers separately.

Against this background, Clariant has developed Exolit® OP, a series of non-halogenated flame retardants with superior properties. Already at relatively small amounts of less than 15 to 20%, Exolit OP is highly effective. Its addition has only minor impact on the material properties of the plastic. Other significant plastic advantages that are flame-retarded with Exolit OP are excellent mechanical and electrical properties, as well as laser markability and the ability to be dyed in almost all colors. The flame retardant has established itself in the field of fiberglass-reinforced polyamides (PA). Exolit OP also provides effective flame protection for the thermoplastics polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), which are often used in E&E. Various thermoplastic elastomers and epoxy resins are also successfully flame-retarded with Exolit OP.

How Exolit OP Works

Exolit OP is based on metal phosphinates and features high thermal stability up to 350 °C. In polyamides, the flame retardant deploys its effects in a combination of a gaseous and a solid phase mechanism, which reduces the smoke gas density and prevents the formation of corrosive gases. The formation of a thick, partially intumescent cover layer keeps the heat release rate low. Compounds that have been treated with Exolit OP can easily meet the standards of the V02 class according to UL 94, the leading standard for fire protection in E&E.

Polymers that are flame-retarded with Exolit OP also feature outstanding mechanical properties. Due to the low dosage of the flame retardant, e-modulus, tensile strength and impact strength remain at a sufficient level, unlike in compounds that have not been flame-retarded. The compounds can reach crucial electrical parameters, such as the Comparative Tracking Index (CTI) or the dielectric strength, without problems. The polymers also feature good overall insulation properties.

Ecological Aspects

Excellent effectiveness and physical properties are not all that is required from flame retardants today. Environmental compatibility is an additional important criterion for market success. Here Exolit OP also offers essential benefits. Emissions during the production process and in case of a fire, the release of VOCs, washing out behavior and the toxicity of the incineration products are only a few of the parameters that have been tested extensively for Exolit OP. The flame retardant receives good grades in all categories, especially in comparison with other flame retardants. Therefore, Exolit OP meets the standards of all widely recognized eco labels. The phosphinate-based products also show good resistance to migration and blooming.


Environmental compatibility and recyclability are two aspects that cannot be separated. Tests demonstrate the superiority of compounds treated with Exolit OP also in this field. After repeated granulation, the fire behavior of the test specimens continues to fulfill the standards of the V0 class according to UL 94. Test of the melting and color stability and the mechanical properties also show convincing results. All parameters remain at high levels, which indicates that production waste can be reused in the process. The product also meets the requirements of the European WEEE Directive and the European RoHs Directive.3

Application Fields

The superior properties Exolit OP listed above open a wide range of applications. Currently the product is being used in electrical outlets based on PA and PBT, basic materials for rigid and flexible printed circuit boards, solder masks, solder stop coatings, and other applications for printed circuit boards. A relatively new application for the flame retardants is anti-blocking systems, clamps and other installation components in the automotive and electronics industry. With Exolit OP now registered as a trademark worldwide, it can be used globally.


Flame retardant systems based on phosphinates are an excellent alternative to conventional products. Phosphinate-based non-halogenated flame retardants offer significant advantages because of their mechanical and electrical properties. The easy processing and versatile colorability of the compounds also contribute to putting these flame retardants at the forefront of modern flame retardant technology. In addition, the good ecological and toxicological rating, the recyclability and, last but not least, the balanced price-performance ratio, make Exolit OP a cutting-edge flame retardant for polymers in E&E and many other applications.