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Halogen-free flame retardant epoxy compositions

The offer pertains to halogen-free epoxy compositions with reduced flammability. The composition is destined to obtain the flame retardant halogen-free plates for manufacturing of printed circuit boards. Flame retardancy of the composition is achieved through the use of a polymeric compound containing phosphorus. An organophosphorus compound is build into the resin structure by means of a chemical reaction. The obtained composition gives a product of required non-flammability degree, good mechanical properties, high glass transition temperature and low water absorption.


A brief description of the process

The halogen-free flame-retardant epoxy composition is obtained in a multistage process. The first stage is a modification of a commercial epoxy resin with a polymeric organophosphorus compound. At this stage functional groups of the organophosphorus compound react with epoxy groups of the epoxy resin. The synthesis proceeds with an excess of epoxy groups in relation to functional groups of the organophosphorus compound in the presence of an appropriate catalyst, at temperature 100–130 °C in a inert gas atmosphere. After the assumed parameters of the synthesized resin are obtained, the resin is dissolved in an organic solvent. At the next stage to a solution of resin containing organically bound phosphorus is added a curing agent, dissolved in an organic solvent and a curing catalyst. In the next step prepregs are prepared by impregnating a glass fabric with the epoxy composition and precuring at temperature 150–170 °C. The obtained prepregs are pressed under pressure of 50 kG/cm2 at temperature 170–180 °C. The plates obtained using the offered composition meet a UL 94 rating of VO. Their glass transition temperature is about 170 °C (DMA) and water absorption 0.033 % (the acceptable value is 0.150 %).


Advantages of the technology offered

The technology offered allows to reduce the flammability of epoxy compositions in a pro-ecological way, without using harmful, halogen flame retardants. The organophosphorus compound applied is build into the structure of the epoxy system, thus allowing to avoid disadvantages related to the usage of additive flame retardants (worse mechanical and chemical properties, plasticization effect and lower glass transition temperature).


Equipment

Epoxy resins modification process:

  • reactor equipped with a stirrer with the possibility of heating up to 130 °C and the possibility of dissolving the resulting product in an organic solvent.

The process to obtain plates for production of printed circuits

  • industrial-available apparatus to produce epoxy laminates.


Advancement of proceedings

There have been carried out preliminary industrial tests to obtain halogen-free flame-retardant plates coated with copper film to produce printed circuit boards.


Patentability

Patent application No P-392 982 (2010) „Method to obtain epoxy resin with reduced flammability”.


Market competitiveness

The proposed solution is competitive in relation to currently used technologies to reduce epoxy materials flammability with halogen additives (mainly bromic ones), whose application is being restricted by the European Union legislation.


Type of expected cooperation

Finding a partner for industrial implementation of the proposed solution.


Information

Barbara Szczepaniak, Ph.D., Chem. Eng.

phone: + 48 22 568 20 55


Piotr Jankowski, Ph.D., Chem. Eng.

phone: + 48 22 568 24 63