Treatments of Recycled Pulps from Old Corrugated Containers. Part II. The Effects of Boron Compounds on Strength Properties

The paper from secondary fibers has generally considered to be used in corrugated cardboard production. For this purpose, Sack Corrugated Test (SCT) and Corrugated Medium Tests were used to determine the strength resistance behaviors. The highest CMT value of 73.5 N was found with first recycling stage of control samples. For boron treated pulps, the highest CMT of 63.3 N was found at 10% boric acid treatment at second recycling phase followed by 5.0% boric acid treatment at second recycling phase, respectively. However, some level improvement of SCT properties was observed at certain level both boric acid and sodium borohydride treatment conditions. the highest improvements of SCT of test papers was found with 5.0% boric acid treatment at forth recycling phase that show approximately 39.74% improvement compared to control. Moreover, at the fifth recycled stage, quite high burst strength values observed with both selected boron treatment conditions that approximately 32.31% and 35.94% higher burst strengths at 5.0% level while 20.32% and 14.06% higher burst strengths at 10% boric acid and sodium borohydride level compare to control sample at similar recycling phase. The more less similar trend was also observed for tensile strength properties of test papers. The highest tensile strength (index) of 19.74 Nm/g and tensile stiffness value of 386 kN/m was observed at second recycling phase with boric acid. For tensile energy absorption (TEA) properties, only 10% sodium borohydride treated test papers showed higher TEA of 23.25 j/m2 compared to counterpart control samples (C2: 20.60 j/m2).