Title of Invention

A PROCESS FOR PREPARATION OF ARAMID FIBRES HAVING IMPROVED ADHESION PROPERTY

Abstract

"A process for improving the surface adhesion property of kevlar aramid". This invention relates to a process for improving the surface adhesion property of kevlar aramid fibers comprising the steps of: growing the bacterial culture isolate (JP-1) in complex organic chemical medium wherein the organic complex is prepared by mixing 5kg of Tryptone, 15 kg of yeast extract and 30 gm KHPO, to this organic medium, 1 kg of chopped kevlar 29 or 49 fibres and 1 litre of distlled water as herein described are added, bacterial cells are grown at a temperature of 28 °C on rotary shaker for 2 to 5 days; separation of bacterial cells and aramid fibers to obtain filtrate or supernatant; treatment of kevlar aramid surface with the filtrate or supernatant thus obtained followed by incubation for 1 to 4 hours.

Full Text

A PROCESS FOR PREPARATION OF ARAMID FIBRES HAVING IMPROVED ADHESION PROPERTY This invention relates to a process for the improvement •of adhesion property of Kevlar aramid fibres by biotransformation. The kevlar aramid fibres are widely used as high modulus high strength fibres for making of Fibre reinforced polymer matrix composites in aircraft, helicopter, space systems and rocket motor castings. Poor surface adhesion property is one of the limiting factor for development of advanced aramid fiber reinforced structural composites. The fiber matrix interface strength is one of the most important parameter which govern off axis strength, toughness, impact strength, fatigue properties and enviornment stability of the aramid fiber reinforced composites. Extensive research efforts have been reported to improve composite interfacial properties though fiber surface treatments. Coupling agents and coatings like silicone based materials, polyurethane, and various sizing agents have boon used for improvement of adhesion property of aramid fibers. None of these agents have been effective in improving the interfacial bonding of the aramid fiber to resin. The oxidation of aramid fiber surface by thermal plasma treatment have shown some increase in off axis *^ • strength property but it causes losses in filament tensile strength. The increased surface fibrillation through oscillating particles cause physical damage to the fibers due to the high impact energy of the oscillating particles. Various chemical treatments viz. acid or alkali' treatment for partial hydrolysis of the aramid fiber surface have been used. These have the drawback of fast reaction rate which is difficult to control and the deep penetration of small acid or alkaly molecules causing excessive strength loss due to hydrolysis of inner fiber structures. Gold plasma in various gaseous environments result in increase surface functional group and limited improvement in adhesion property of aramid fibers. Stilll due to the poor adhesion of outer skin to inner core layers adhesion improvement remain poor this process needs costly equipments. Thus the existing physical and chemical treatment processes for improvement of adhesion property of aramid fibers have following limitations:- (i) limited adhesion improvement (ii) damage of aramid fiber structures resulting in strength loss. (iii) difficulty in process control and requirement of ' costly equipments * In recent years the biochemical reactions performed by micro organisms or catalyzed by their enzymes have been used for organic synthesis and other biotechnological processes. Such technology called microbial transformations or biotransformation is a process which involve conversion of one substance to another by a biological agency. Basically it is a chemical reaction catalyzed by the cellular enzymes. Though these enzymes are produced for processing of various nutrients for cellular growth, many enzymes can act on other substances which are structurally related to normal substrates and thus occasionally catalyze unusual reactions when come across such substances. Though synthetic polymeric materials as a class resist microbial attack, many of them are affected by various kinds of micro organism. Normally high molecular weight highly crystalline polymers are not easily affected by microorganisms but the low molecular weight or amorphous polymeric structures are affected preferentially by microbial enzymes. Minute surface changes in microbially affected nylon and polyethylenes have been reported in literature. Though due to fully aromatic nature, highly crystalline structures and high thermal and chemical resistance, aramid fibers are considered resistant to microbial attack some of the micro organisms have been found to cause limited to extensive degradation of aramid fibers. Object of Present Invention The present invention proposes a novel process for improvement of adhesion property of Kevlar and other aramid fibers hence increasing its suitability for development of advanced high performance fiber reinforced composites. Accordingly, a primary object of the present invention is to propose a novel process for the surface modification of kevlar aramid fibers to improve its adhesion property. Statement of Invention According to this invention there is provided a process for improving the surface adhesion improvement of kevlar aramid fibers comprising the steps of : growing the Bacterial Culture Isolate (JP-1) in complex organic medium in presence of aramid fibers in agaitating conditions; exposing kevlar aramid fibers to culture filtrate for exposing various time intervals raging from 1 hour to 4 hours; monitoring the kevlar fiber surface degradation by microscopic and u.v. visible spectrophotometry; measuring a fiber adhesion improvement by microbond technique. In accordance with the present invention a workpiece of kevlar 49 fiber or any other kevlar aramid fiber is exposed to the culture filtrate of bacterial isolate (JP--1) prepared by growing the cells in complex organic medium containing kevlar fibers; the exact level of fiber surface degradation, level of surface modification and adhesion improvement is determined. The exposurre period is kept between 1 to 4 hours, This kevlar aramid fiber biotransformation process for surface adhesion improvement has definite advantage over the other conventional methods in ease of operation and minimum damage to fiber structures hence strength loss. The invention is illustrated but not limited by the following example. EXAMPLE The bacterial isolate (JP-1) was grown in sterilized complex organic chemical medium containing 5g. Tryptone 15g of yeast extract, 30g of K HPO , Ig. of chopped Kevlar 29 or 49 fibers and 1 litre of distilled water. Cells were grown at 28 degree celcius 1 C on rotary shaker at 180 rpm for 2 to 5 days. The bactgerial cells and aramid fibers separated by centrifugation or filtration and supernatent or filtrate was used for kevlar aramid fiber surface treatment. One gram of kevlar 49 fibers were placed in 100ml of culture supernatent and incubated for 1 to 4 hours at 35 C. The treated fibers were washed by running tap water and dried at 120 C for 24 hours in oven. The adhesion -improvement of 30-50% with epoxy resin was obtained. I_CLAIM: 1. A process for improving the surface adhesion property of kevlar aramid fibers comprising the steps of growing the bacterial isolate (JP-1) in complex organic medium in presence of aramid fibers, separation of cells, treatment of kevlar aramid fibers to the cell free culture medium i ' '- . -' • containing active biotransforming agent. 2. A process as claimed in claim 1 wherein said cells are separated by centrifugation or filtration. 3. A process as claimed in claim 1 wherein the exposure period is for (abou,t 1 to 4 hours. 4. A process as claimed in claim 1 wherein the limited surface modification of kevlar aramid fibers is effected by biotransformation process by bacterially produced reactant. 5. A process for the preparation of kevlar aramid fibers having improved adhesion property substantially as herein described and illustrated in the example.

Documents:

475-del-1996-abstract.pdf

475-del-1996-claims.pdf

475-del-1996-correspondence-others.pdf

475-del-1996-correspondence-po.pdf

475-del-1996-description (complete).pdf

475-del-1996-form-1.pdf

475-del-1996-form-19.pdf

475-del-1996-form-2.pdf

475-del-1996-form-3.pdf

475-del-1996-gpa.pdf