Rejuvenating secondary fibers - A new concept and results

One of the major problems with recycling is the gradual loss in fiber strength properties in successive recycling. While some of the strength properties like burst, tensile etc., can be increased by use of modified starches and other chemicals, the tear factor is difficult to improve, as it is dependent of the intrinsic fiber strength, d.p. cellulose chains etc. These being basic characteristic of fibers, are difficult to alter. Fibers with good intrinsic fiber strength contribute to various properties like good tear index, CMT/RCT, which are desired by all papermakers. When most of the furnish consist of short fibers which are poor in strength, one of the most common ways to improve strength properties is addition of some long fibers either natural or synthetic. However, these options are expensive and most of the times economically unviable. Our research was concentrating around rejuvenating weak fibers in the furnish chemically, so that the cellulose chains have higher degree of polymerization and give stronger fibers. This has been achieved by cross-linking by formation of covalent bonds between the cellulose chains. Covalent bonds are permanent wowing to their high bond energy compared to very low bond energies of hydrogen bonds. The article also discusses about new chemical and actual results.