Dynamic Shear Modulus Degradation Limits in High Speed Recyclable UV Resin Formulations
Dynamic shear degradation limits UV resin velocity at 280 m/min to prevent oligomer scission, balancing resin costs against full EPR fee savings.
Mechanical Polymer Cleavage
Fibre Breakdown
Degradation of synthetic polymers in recycled paper stocks occurs through intensive physical action during pulping. The process of mechanical polymer cleavage breaks down long-chain resins into smaller, less functional fragments. This reduction in molecular weight alters the behavior of adhesives and barrier films.
Over-refining the pulp leads to an accumulation of micro-plastics that are difficult to capture.
Shear Action
High shear forces within hydro-pulpers and refiners drive this physical degradation. Rotating rotor blades and stationary stator plates create intense turbulence and friction that stretch the polymer chains until their covalent bonds snap. This action is most pronounced in high-consistency systems where fiber-to-fiber contact transfers kinetic energy directly to the synthetic additives.
Heat generated by this friction further softens the polymer, making it more susceptible to tearing.
Recycling Tradeoff
Altering polymer length affects both the cleanliness of the recycled pulp and the runnability of the paper machine. Shorter polymer chains are more likely to pass through fine pressure screens and deposit on press rolls, causing paper breaks and surface blemishes. These deposits require frequent chemical wash-ups that halt production and reduce mill efficiency.
Balancing the intensity of mechanical action is therefore essential for mills, as they must refine the cellulose fibers to restore strength without pulverizing the residual plastics into unmanageable contaminants. This balance requires real-time monitoring of refiner gap settings and motor loads to prevent over-processing. By maintaining these strict limits, paper manufacturers protect their equipment from tacky build-ups while ensuring the recovered paper meets the strength standards required for high-speed converting.