Effect of compatibilizers on lignin/bio-polyamide blend carbon precursor filament properties and their potential for thermostabilisation and carbonisation

Biobased blends from hydroxypropyl modified lignin (TcC) and a biobased polyamide (PA1010) were produced by continuous sub-pilot scale melt spinning process. A reactive compatibilization was employed with the help of two different compatibilizers (ethylene-acrylic ester-maleic anhydride (MA) and ethylene-methyl acrylate-glycidyl methacrylate (GMA)) to enhance the compatibility between the TcC and PA1010. The enhanced compatibility between the TcC and PA1010 achieved by reaction between hydroxyl groups with maleic anhydride groups in the MA compatibilizer or epoxy groups in the GMA compatibilizer via nucleophilic substitution, was confirmed by chemical (Fourier infrared measurements), physical (glass transition, melting and crystallization behaviour), rheological, morphological and tensile properties of the filaments from compatibilized blends. MA compatibilizer required a higher concentration (2 phr) than GMA (1 phr) to achieve an optimal performance because of the difference in the reactive group's concentration within the each compatibilizer. The MA compatibilizer though was more effective than GMA. The precursor blended filaments were successfully carbonized in a lab scale experiment to yield coherent carbon fibres with tensile stress values of 192 +/- 77 and 159 +/- 95 MPa; and moduli of 16.2 and 13.9 GPa respectively for uncompatibilised and 2% MA compatibilized blends. That the compatibilized carbon fibre properties are slightly inferior may be attributed to the need to accurately control and optimise applied stress during the thermostabilisation and carbonization stages. Notwithstanding, these differences, the results indicate the potential benefit of using compatibilized TcC/PA1010 blend filaments as carbon fibre precursors.

Automated summary

Reactive compatibilization using MA and GMA can enhance the compatibility between TcC and PA1010, with MA being more effective but leading to slightly inferior properties of the carbon fibers. Accurate control of stress during thermostabilization and carbonization stages is crucial for optimizing the properties of the compatibilized carbon fibers.