Evaluation of bast fibre retting systems on hemp

In this paper the effect of eight different retting methods on decorticated hemp skins were analyzed. The methods were taken from six publications that looked at the retting of different bast fibres such as ramie, flax and kenaf. The fibres were batch retted in a package dye-vat at 100oC under 2 bar of pressure. The rinsed fibres were opened twice using a Shirley cotton trash separator. The opened fibre was assessed for fibre width, fibre width variation, colour and handle. It was found that the fibre that had undergone chemical retting with 7% Sodium Hydroxide (NaOH) and 0.5% Sodium Sulphite (Na2SO3) had the best diameter (18.39 micron) and the best coefficient of variation of diameter (57.32%). The fibre that was processed with 7% Sodium Hydroxide (NaOH) and 0.5% Sodium Sulphite (Na2SO3) had the whitest colour (YI D1925 = 31.61). The method treated with 1% Sodium Hydroxide (NaOH) and 1% Sodium Sulphite (Na2SO3) had the softest handle and the method treated with 1% Sodium Hydroxide (NaOH) and pre-rinsed with 0.3% Hydrochloric Acid (HCl) showed the best conversion of decorticated skins into spin able fibre (33.9% of dry green skins). It was decided that method treated with 1% Sodium Hydroxide (NaOH) and pre-rinsed with 0.3% Hydrochloric Acid (HCl) had the best fineness of fibre micron, conversion to spin able fibre (33.9% of dry green skins), whitest colour (YI D1925 = 36.13) and softest handle for the cost of chemicals involved.