Where to add retention aid: issues of time and shear.Application: Papermakers can adjust the balance between retention efficiency and formation uniformity by adding high-mass acrylamide acrylamide /acryl·a·mide/ (ah-kril´ah-mid) a vinyl monomer used in the production of polymers with many industrial and research uses; the monomeric form is a neurotoxin. copolymer retention aids earlier or later to the process. ********** Papermakers can choose to add high-mass retention aids either before or after pressure screens in the approach flow to a paper machine. Early addition provides more opportunity for breakage of chemically induced fiber flocs, possibly leading to more uniform formation. Early addition also provides more chance for chemicals to become degraded or lost in the porosity of fiber cell walls. Later addition tends to maximize chemical efficiency in terms of first-pass retention. We applied a new method of fiber floc floc n. A flocculent mass formed in a fluid through precipitation or aggregation of suspended particles. [Short for flocculus.] Noun 1. evaluation in the case of headbox-consistency fiber slurries to help understand what happens to chemically induced fiber flocs when exposed to increased time and shear. We determined the extent of flocculation flocculation /floc·cu·la·tion/ (flok?u-la´shun) a colloid phenomenon in which the disperse phase separates in discrete, usually visible, particles rather than congealing into a continuous mass, as in coagulation. by the force required to move a pair of 6-mm probes through furnish samples. Supplementary tests of the streaming potential of fibers were used to help explain the separate effects of time and hydrodynamic hy·dro·dy·nam·ic also hy·dro·dy·nam·i·cal adj. 1. Of or relating to hydrodynamics. 2. Of, relating to, or operated by the force of liquid in motion. shear on the state of flocculation. We compared two contrasting types of pulp furnish--chemithermomechanical pulp (CTMP CTMP Comprehensive Treatment and Management Plan CTMP Chemico-Thermomechanical Pulping CTMP CONUS Telephone Modernization Program CTMP Cisco Technology Migration Program CTMP Competitive Technology Migration Plan CTMP Cisco Technology Migration Plan ) with 10% ground calcium carbonate on fiber solids and well-refined southern U.S. bleached kraft with 70 parts hardwood and 30 parts softwood. We found that the polymer-induced flocs formed by cationic cationic having qualities dependent on having free cations available. cationic detergents are wetting agents that disrupt or damage cell membranes, denature proteins and inactivate enzymes. poly-acrylamide treatment of CTMP furnish were very persistent over time in the absence of hydrodynamic shear. Similar experiments with bleached kraft furnish showed more rapid decay of flocs in the absence of shear. Both types of furnish responded to agitation in approximately the same manner after flocculant treatment High-shear agitation in a blender reduced the viscometer output to the same level as untreated pulp. This result is consistent with the irreversible breakage of polymer bridges. Hubbe and Wang conducted this study through the Dept. of Wood & Paper Science, North Carolina State University History
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