The effect of multiple recycles on wheat straw fibers

In this project, the strength properties over four recycles were evaluated for papers which contained only softwood fibers and a 70/30 mixture of softwood and wheat straw fibers. Prior to each recycling, fibers were refined to a constant CSF of 250 mt to have controlled amount of fines. Also, handsheets that contained only wheat straw fibers were produced as a standard for comparison. 100% wheatstraw pulp was not recycled. It is seen from the study, that the presence of fines in wheatstraw pulp actually helps in fiberbonding and at equal freeness values, such handsheets had better burst and tensile index values, and a significantly lower tear resistance. The mixed pulp handsheets had strength properties in between the two. Through each of the recycles, the addition of wheat straw fibers proved not to detract from the paper strength properties. During the process of multiple recycling, sheets made from mixed pulp experienced a comparable or slightly lower strength loss. The presence of fines in such handsheets contributed to a higher air resistance. Since necessary refining controlled the freeness, the fines content during successive recycles were remarkably close. The higher ash content in the handsheets fi-om mixed pulp throughout the four recycles indicated that the wheatstraw pulp was not preferentially lost in handsheet making operations. A distinction between primary and secondary fines was not made in this study.