Tailoring starch-engineered mineral particles towards enhanced interaction with cellulosic fibers

Interaction of unmodified starch with guest molecules or ligands (e.g., fatty acids) as a basis for the formation of starch-encapsulated mineral filler particles is an effective process for mitigating the negative impact of filler addition on the strength properties of cellulosic networks. As unmodified starch is essentially nonionic, the interaction of starch-engineered fillers with negatively charged cellulosic fibers is somehow limited. Here, the concept of substituting unmodified starch with a minor amount of cationic starch in filler engineering with starch inclusion complexes was proposed. It was hypothesized that filler-fiber interaction would be enhanced by cationic-anionic attraction. Encouragingly, the effectiveness of this concept was demonstrated to be very pronounced. For instance, at a cationic starch percentage of 3% (relevant to the weight of total starch), filler retention and filler bondability with cellulosic fibers were significantly improved, leading to further mitigated negative impact of filler addition on tensile strength. Basically, this easily scalable concept may shed light on greener, more efficient use of filler technologies on the basis of starch inclusion complex formation, opening up new possibilities for real commercial applications.