to modify crystallinity in the final polyester fiber these can include neopentyl glycol and glycerin renewable components based on plants animals or biomass processes have a different radioactive c 14 signature than those produced from petroleum these renewable biobased materials have carbon that comes from contemporary non fossil biological sources a more detailed description of biobased materials is described in a paper by ramani narayan u201c biobased amp biodegradable polymer materials rationale drivers and technology exemplars u201d presented at american chemical society symposium san diego 2005 american chemical society publication 939 june 2006 the biobased content is defined as the amount of biobased carbon in the material or product as fraction weight mass or percent weight mass of the total organic carbon in the material or product astm d6866 2005 describes a test method for determining biobased content in one embodiment the high molecular weight polyester resin is crystalline and comprises a crystalline melting temperature tm between about 100 u00b0 c and 150 u00b0 c in yet another embodiment the polyester has a tm greater than about 150 u00b0 c in yet another embodiment the polyester resin has a tm of at least 190 u00b0 c in another embodiment the polyester compositions include modifying traditional thermoplastic aromatic polyester resins useful as fibers by the addition of an amount of a renewable aliphatic diacid to help control crystalline regions and tm the thermoplastic high molecular weight polyester resin may also be branched for example utilizing aliphatic alcohols that have more than two functional groups such as glycerin or aromatic acids having more than two functional groups such as trimellitic anhydride may be used to produce branched polyesters although the above diacid components are described it is.