Recycling Effects on the Properties of Pulp Fiber Sheets Produced from Oil Palm Empty Fruit Bunch

Empty fruit bunch (EFB) is a residual biomass produced from the processing of palm oil. Although the application of EFB to papermaking has been studied, there are no reports concerning recycled paper made from EFB pulp. In this study, the effects of recycling on the properties of EFB fiber sheets were investigated and compared to the recycling of hardwood kraft pulp fiber sheets. Following recycling, EFB sheets had lower tensile index than that of hardwood sheets but higher tensile elongation and tensile energy absorption (TEA). To explain this observation, the fiber strength index and bond strength index following recycling were calculated using Page's equation, and the results showed that the EFB sheets exhibited a lower fiber strength index. The lower tensile index of the EFB sheet is attributed to this reduced fiber strength. Observed changes in the tensile elongation of EFB sheets with increasing recycling treatments were almost the same as variations in the retention values of EFB pulps, while the bond strengths calculated from Page's equation for EFB and hardwood sheets showed little difference before and after recycling. Therefore, the significant decrease observed in the tensile elongation is attributed to a drop in the elongation-potential of the EFB pulp due to increased hornification during recycling. Furthermore, the TEA values of EFB sheets were found to be strongly dependent on the tensile elongation value as opposed to the tensile index. It is evident that the differences in the tensile index, tensile elongation and TEA values of hardwood and EFB sheets during recycling exhibit a significant dependence on the properties of the pulp rather than the bonding strength of the sheets.