LADY'S FINGER FIBRES FOR POSSIBLE USE AS A REINFORCEMENT IN COMPOSITE MATERIALS Md. Moniruzzaman*, Mohd. Maniruzzaman*, M..A. Gafur**, C. Santulli*** * Department of Applied Chemistry and Chemical Technology Islamic University, Kushtia, Bangladesh **Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhaka, Bangladesh ***Department of Electrical Engineering, Università di Roma – La Sapienza, Rome, Italy

SUMMARY Lady's finger (okra: Abelmoschus esculentus) fibres Chemical treatments and micro-structural effect Raw and treated fibres tensile strength Okra fibres-bakelite composites: tensile and flexural strength Conclusions

OKRA FIBRES Raw okra fibresOkra (Abelmoschus esculentus)

CHEMICAL TREATMENTS One of the problems in using okra fibres is their difficult extraction. There are two aspects which concur to the definition of this issue, first the separation of the technical fibre, and second the “washing out” of non-structural matter, such as wax, pectin, etc. It is to be demonstrated whether the fibre withstand a secondary treatment after bleaching or if just a primary treatment would be preferable. From the initial results, it appears that any treatment is able to ease the separation of the technical fibre, also because okra fibres tend to be only loosely connected after retting.

EFFECT ON THE MICROSTRUCTURE

CONSIDERATIONS ON MICROSTRUCTURE (PRE- AND POST-TREATMENT) SEM micrographs of fibres showed a non negligible presence of voids along the fibre length in raw okra fibres. After treatment, the resulting technical fibres have much less scattered diameters. However, the results showed that the presence of internal voids was in some cases increased, because of non selective nature of treatment, which degraded lignocellulosic structure as well as "cleaning" the fibres. This is particularly true for sodium sulphate treatment and bleaching + alkalisation respectively, whilst the most conservative treatment, leading to lower internal void percentage, appeared to be acetylation.

TENSILE PROPERTIES OF OKRA FIBRES (RAW AND TREATED) A primary bleaching leads to improved properties of the fibres in most cases, except for the sodium sulphate treatment, where the fibres appear to have been substantially damaged.

TENSILE STRENGTH Only the introduction of 5% wt. of raw fibres leads to a substantial improvement. A smaller improvement is observed with the same amount of bleached fibres.

FLEXURAL STRENGTH The trend shown for tensile strength of raw okra fibre composites can here be confirmed. Once again, introducing more than 5% wt. fibres does not lead to improvement in properties. Also, fibre bleaching leads to further decrease in composite properties.

CONCLUSIONS This preliminary attempt of introducing okra fibres in a polymer matrix showed some possible scope only for very low volume (few percents) of reinforcement. Higher volume of reinforcement would result in a difficult resin impregnation, as an effect of the variable geometry of the technical fibre. This issue could be solved by appropriate chemical treatment: however, an appreciable improvement has been only shown by fibre bleaching, whilst in other cases the reduced void content, whenever obtained, did not lead to enhanced mechanical properties. This implies that a sounder analysis and comparison of the possibilities of chemical treatment on these fibres would be needed, possibly implying different chemicals concentration.