Effect of Cross-Linkers on the Processing of Lignin/Polyamide Precursors for Carbon Fibres

This work reports the use of cross-linkers in bio-based blends from hydroxypropyl-modified lignin (TcC) and a bio-based polyamide (PA1010) for possible use as carbon fibre precursors, which, while minimising their effects on melt processing into filaments, assist in cross-linking components during the subsequent thermal stabilisation stage. Cross-linkers included a highly sterically hindered aliphatic hydrocarbon (Perkadox 30, PdX), a mono-functional organic peroxide (Triganox 311, TnX), and two different hydroxyalkylamides (Primid((R)) XL-552 (PmD 552) and Primid((R)) QM-1260 (PmD 1260)). The characterisation of melt-compounded samples of TcC/PA1010 containing PdX and TnX indicated considerable cross-linking via FTIR, DSC, DMA and rheology measurements. While both Primids showed some evidence of cross-linking, it was less than with PdX and TnX. This was corroborated via melt spinning of the melt-compounded chips or pellet-coated TcC/PA1010, each with cross-linker via a continuous, sub-pilot scale, melt-spinning process, where both Primids showed better processability. With the latter technique, while filaments could be produced, they were very brittle. To overcome this, melt-spun TcC/PA1010 filaments were immersed in aqueous solutions of PmD 552 and PmD 1260 at 80 degrees C. The resultant filaments could be easily thermally stabilised and showed evidence of cross-linking, producing higher char residues than the control filaments in the TGA experiments.

Automated summary

This study investigates the use of cross-linkers in bio-based blends for carbon fibre precursors. Cross-linkers including highly sterically hindered aliphatic hydrocarbon, mono-functional organic peroxide, and two different hydroxyalkylamides were used. The results showed considerable cross-linking with PdX and TnX, and some evidence of cross-linking with the Primids. In the melt spinning process, the Primids showed better processability, but the resulting filaments were brittle. However, immersion in aqueous solutions of PmD 552 and PmD 1260 improved the thermal stabilisation and cross-linking of the filaments.