Summary — The flame retardancy of fully biodegradable, natural fiber reinforced thermoplastic
starch (TPS) composites was studied in this work. Thermoplastic starch of significantly reduced
flammability could be prepared by using a phosphorus containing polyol for plasticizing starch.
The thermal degradation of the obtained flame retarded TPS was compared to conventional glycerol-plasticized
TPS using not only TGA and DSC but also LP-FTIR (Laser pyrolysis FT-IR coupled
method) measurements, which allowed the identification of all the gaseous degradation products.
The flame retardant TPS matrix was reinforced with chopped flax fibers and woven linen-hemp
fabrics. Due to the embedding of biofibers significant increase in tensile and impact properties of
TPS could be achieved, however, the flammability characteristics of the biocomposites, measured
by LOI, UL-94 and cone calorimetric tests, become inferior to those of the unreinforced TPS matrix,
thus the flame retardant treatment of the reinforcing natural fibers was indispensable. The thermal
behaviour and flame retardancy of biofibers, investigated by TGA and cone calorimetry, showed
substantial improvement as a consequence of their phosphorous surface treatment. The prepared
fully biodegradable biocomposites, comprising of TPS matrix plasticized with P-polyol and
P-treated biofibers, exhibit increased mechanical performance accompanied with excellent flame
retardancy: pass V-0 rating in UL-94 test, reach LOI of 32 vol. %, and show with 45 % reduced
pkHRR during combustion than the unreinforced TPS reference.
Keywords: biocomposites, thermoplastic starch, natural fiber reinforcement, flame retardancy,
plasticizer, phosphorous polyol, ammonium phosphate, thermal degradation.