Starch Gelatinization And Its Effects On Starch Grafting Modification

Nowadays, pulp and paper industry has formed relatively complete production system. It's popular with the papermaking process to reduce energy consumption in the form of optimizing production technology, saving resources and protecting the environment. Because of its widespread source and moderate price, starch is widely used in papermaking industry. It is always gelatinized at 92? in the process of papermaking, which is not distinguished between different types of starch. It will influence the gelatinization efficiency and the effect of starch. So it has far-reaching significance to explore the optimal temperature of different kinds of starch for improving producing efficiency and its performance on paper strength. This article is focused on optimizing gelatinization temperature of several kinds of starch and its influence on starch grafting-copolymerizing reaction and paper strengthen.Stereo Microscope and rotary viscometer were used to observe the morphology and viscosity transformation of starch in the process of gelatinization. It can be found that the optimal gelatinization temperature of initial cassava starch, low DS cationic starch, middle DS cationic starch, and high DS cationic starch were 85?, 90?, 80? and 75?, respectively. While, the optimum temperature of low DS amphoteric starch, middle DS amphoteric starch, and high DS amphoteric starch were 85?, 90? and 70?.Three kinds of cationic starch gelatinized at five different temperature, including the initial gelatinization temperature, the optimal gelatinization temperature and the complete gelatinization temperature, were used in paper formation as a strengthen agent. The pulp used here was commercial bleached eucalyptus pulp with 36°SR of beating degree. The effect of starch gelatinization temperature on the paper physical strength includes tear, burst and tensile strength. It can be concluded that the low DS cationic starch NC-1 gelatinized at 90? gave the maximum paper strengthening. The tearing index, burst index, and tensile index were 5.127 mN?m2/g, 2.44 KPa?m2/g and 37.645 N?m/g, respectively. The middle DS cationic starch NC-2 gelatinized at 80? presented the maximum paper strengthening. The tearing index, burst index, and the tensile index of the strengthened paper were 4.966 mN?m2/g, 2.717 KPa?m2/g and 41.525 N?m/g. The high DS cationic starch NC-3 gelatinized at 75? showed the maximum paper strengthening, and the tearing index, burst index and the tensile index were 4.901 mN?m2/g, 2.716 KPa?m2/g and 41.538 N?m/g, separately.Gelatinization temperature and reaction temperature were taken as the main effectors to the grafting of starch with acrylamide. The gelatinized cassava starch at 85? was grafted with acrylamide first, then gelatinized and used in paper formation. During these procedure, the stereo Microscope and rotary viscometer were also used to measure the optimal gelatinization temperature of the grafted cassava starch. Comparing with amphoteric starch and cationic polyacrylamide, the optimal gelatinization temperature of grafted starch decreased to 75? and its optimum usage amount was 1%, which could give the maximum paper physical strength.