Associação de micro/nanofibrilas celulósicas e silicatos: estudo da suspensão, filmes e performance no revestimento de papel cartão

Abstract

Chemical pretreatments facilitate the production of cellulosic micro/nanofibrils (MFC/NFC) and expand the possibilities of using these materials in coatings and packaging films. The objective was to evaluate the effect of pretreatment with sodium silicate (Na2SiO3) on the chemical and morphological properties of Eucalyptus sp. and Pinus sp. pulps and energy consumption during MFC/NFC production using an ultra-refiner. We also evaluated the chemical, morphological, physical-mechanical properties and the quality index (QI) of the produced MFC/NFC. We also aimed to evaluate and apply MFC/NFC produced from Eucalyptus sp. pulps pretreated with magnesium silicate (MgO3Si) and calcium silicate (Ca2O4Si) as paperboard coatings regarding barrier, surface and mechanical properties. Eucalyptus sp. pulp pretreated with 10% Na2SiO3 showed the highest water retention. The lowest energy consumptions during fibrillation were obtained for Eucalyptus sp. pulp pretreated with 5% Na2SiO3 (~4100 kWh/t). The pretreated MFC/NFC showed higher frequency of diameters below 45 nm. The zeta potential indicated moderate stability of the suspensions (-24 ~ -18 mV). Pretreatments with Na2SiO3 reduced the transparency of the films by ~25% for Eucalyptus sp. and ~20% for Pinus sp. The films showed adequate barrier to UVC radiation, water vapor and oil. The tensile strength of the films was increased by 20% using 10% Na2SiO3. This concentration of Na2SiO3 resulted in IQ of ~70 for the MFC/NFC of Eucalyptus sp. Pretreatments with Ca2O4Si and MgO3Si reduced energy consumption by ~30% in MFC/NFC production. MFC/NFC layers added to paperboard reduced water vapor permeability, especially for MFC/NFC pretreated with 5% MgO3Si (~98 g mm/kPa -1 -day m2). MFC/NFC suspensions with 5% and 10% Ca2O4Si increased the dispersion of liquids and printing ink on the paper surface. The coatings increased the formability of the paper. Na2SiO3 showed efficiency for MFC/NFC production due to reduced energy consumption and allowed to obtain films with properties suitable for packaging. The suspensions have compatible characteristics for application as stabilizer of colloidal systems and reinforcement of composites. Optimization of application and drying techniques for MFC/NFC formulations and silicate coating can improve the mechanical and barrier properties of coated papers for multilayer packaging.