What are the factors affecting the application of polyacrylamide dry strength agents?

(1) Relative molecular weight In obtaining a good drying strength effect, relative molecular weight is an important factor, requiring the dry strength agent to have a certain length to provide good adsorption properties and have sufficient number of hydrogen bonds. However, the relative molecular weight can not be large enough to bridge the fibers to cause flocculation or even damage the evenness of the paper, for most polyacrylamide dry strength agents, the appropriate relative molecular weight is 100,000-500,000.

(2) The dosage is generally 0.5%-1%, which can improve the break resistance and tensile strength of about 20%-40%, and has little impact on the tearing degree.

(3) When the two resins are used together apam and cpam, good enhancement effects can be achieved. The specific method is to mix the anion and cationic enhancer before adding the slurry, and quickly add it to the slurry, but be careful not to place the two polymers for a long time after mixing, because electrostatic adsorption will quickly produce flocculant, if not dispersed, it will affect the evenness of the paper and cause the reduction of application effect.

(4) A small amount of alum can be added to improve the adhesion of apam on the fiber, and the amount is determined according to the rosin filler and other auxiliaries, generally 1.5%-3.0%. The addition of alum is large, and it is unfavorable to improve the dry strength, because the retention of alum flocculate becomes a new filler, which prevents the fiber bonding. However, alum had no significant effect on enhancing cpam.

(5) The improvement of ph dry strength is achieved by adsorbing the resin in the fixed fiber, and the ph value of the paper is 4.2-5.0. cpam needs to show its cationic properties under acidic conditions to form electrostatic adsorption bonds with fibers.

(6) Adding order first add rosin gum, then add alum, then add pam.

(7) With the increase of beating degree, the strength of the paper with pam is higher than that without pam, indicating that the increase of beating degree is conducive to increasing the hydrogen bonding point between pan and fiber.