Capillarity of flax/linseed (Linum usitatissimum L.) and fibre hemp (Cannabis sativa L.) straw fractions

In a study of the wetting properties of the fractions of unretted and frost-retted fibre straws a method to separate fibre, fine shive, and coarse shive from fibre plants is introduced and tested on bast fibre plants (Linum usitatissimum L. and Cannabis sativa L.) The method consists of optional drying of stalks, cutting of straws, milling the straws with a hammer mill, separating fibres from shives with a drum separator, separating coarse shives from fine shives with a screen and a stream of air and finally cleaning of the fine shive with sieve vibrator. The described method works best for frost-retted plants and for unretted, green flax. The capillarity properties of these fractions were studied by measuring the amount of absorbed water as a function of time. The required time for the best-absorbing fibres of unretted and frost-retted hemp and unretted flax to absorb their own masses of water is less than 10 min compared with 2 h for the poorest-absorbing frost-retted flax. Overretting by frost retting seems to have an opposite effect on flax/linseed and hemp fibre capillarity. Both unretted and frost-retted coarse skive fractions behave quite similarly. If good absorption is needed, (over)retted hemp fibre should be used. If poor fibre absorption is desirable, (over)retted flax/linseed seems to have this feature. (C) 2001 Elsevier Science B.V. All rights reserved.