Bacterial poly(hydroxy alkanoate) polymer and natural fiber composites

Abstract

A biocomposite is produced from natural fiber fabrics embedded in a matrix of biosynthetic polyhydroxy-alkanoate (PHA) polymers. The PHA is synthesized using aerobic microbial biosynthesis using mixed bacterial cultures and a feedstock containing anaerobic degradation products such as methane and volatile fatty acids derived from microbial biodegradation of organic waste materials, which may include waste biocomposites. Monomers may be added to the synthesized PHA polymer to control mechanical properties of the resulting biocomposite. The natural fibers and/or PHA may be pretreated using various techniques to improve the bond between the fibers and the PHA resin matrix and water absorption resistance of the fibers. The composite may be a laminate of treated and untreated fabric layers, or differently treated layers, to achieve good in-service performance as well as rapid and/or optimal biogas production when taken out of service and put in an anaerobic environment to degrade.

1 . A method for producing a biocomposite material, the method comprising:
 extracting biosynthesized PHA polymers from bacteria to obtain PHA granules;   pretreating the PHA granules with a first cyclic anhydride and a free radical initiator;   pretreating a natural fiber layer with a second cyclic anhydride in the presence of catalytic amounts of an acid to promote fiber crosslinking;   and   fabricating the biocomposite material from the pretreated PHA granules and the pretreated natural fiber layer.   
     
     
         2 . The method of  claim 1  wherein fabricating the biocomposite material comprises layering the pretreated natural fiber layer with differently pretreated natural fiber layers. 
     
     
         3 . The method of  claim 1  wherein the second cyclic anhydride is succinic anhydride. 
     
     
         4 . The method of  claim 1  wherein the first cyclic anhydride is maleic anhydride. 
     
     
         5 . The method of  claim 1  wherein the natural fiber layer is a woven natural fiber fabric. 
     
     
         6 . The method of  claim 1  wherein the natural fiber layer is a natural fiber mat. 
     
     
         7 . A method for producing a biocomposite material, the method comprising:
 extracting biosynthesized PHA polymers from bacteria to obtain PHA granules;   pretreating the PHA granules with a first cyclic anhydride and a free radical initiator;   pretreating a natural fiber layer with modified PHA polymers, wherein the modified PHA polymers are produced by treating PHA polymers with maleic anhydride;   and   fabricating the biocomposite material from the pretreated PHA granules and the pretreated natural fiber layer.