Study On The Physical Strength Of The Change And Improvement In OCC Recycled Processing

Because of the shortage of wood resources in China, the main material of making corrugated paper is OCC. thanks to the physical strength is inevitably decreasing in the recycled process, so it caused the paper strength decline. This thesis studies the rule of fiber recycled process, and also we used CPAM/CMC to self-assemble on the surface of recycled fiber, in order to improve the physical strength greatly of it.Firstly, the effect of beating on the OCC fiber properties and paper physical strength was studied, and the recycled fiber morphology and fiber filtration property were further characterized. It was shown that fiber beating degree from 19 to 39 can greatly improve the physical strength of recycled fiber, it can make paper breaking length, ring crush index and burst index increase by 39.38%, 59.40%, 66.67%, respectively. However, as can be displayed by DFR detection, fiber filtration property got weak with the rising of fiber's beating degree. In addition, it was also noted by SEM that excessive beating can make the fiber cut off seriously which caused the average length of recycled fiber keep dropping. We got that fiber was beaten to 31°SR was better for OCC fiber.Secondly, the changes of physical strength of recycled OCC fiber were studied, and the surface properties of recycled fiber samples were characterized by SEM and FTIR techniques. It was shown that the physical strength of recycled fiber was dropped sharply with the increase of recycling time. From the beginning to the second-time recycling, the breaking length, folding strength, tear index, ring crush index and burst index of the recycled fiber was reduced by 33.97%, 78.58%, 42.16%, 45.51%, 49.63%, respectively. Up to the fifth-time recycling, a significant change in the physical strength of recycled fiber was happened, correspondingly. Moreover, the water retention value was decreased by 12.54% from the beginning to the second-time recycling, also was decreased by 20.58% from the second to the fifth-time recycling of OCC fiber. It was observed by SEM that the surface feature of recycled fiber seemed to exhibit rougher and rougher even to the trace of crack, which is probably due to the fiber's keratinized in the recycling process. According to the spectra of FTIR, it was inferred that with the recycling time increasing, the hydrogen bond of fiber-fiber was gradually improved which promoted the decay of fiber surface strength.Next, Research on CPAM/CMC layers of self-assembly affected on recycled OCC fiber physical strength properties. At same time the electric charge of fiber and surface properties of self-assembly fiber was studied. Research results showed that: CPAM/CMC in pH=5.5, pH=7.5, pH=9.5 fiber environment, The self-assembly improved the breaking length of paper by 82.82% ,71.37%, 38.93% respectively, while folding strength increased by 550.32%; 442.18%; 532.12%, ring crush index increased by 92.88%; 86.53%;72.75%. Compare and know that the fiber was self-assembled can largest improved the folding strength. Also we can know that the acid environment was better for fiber to self-assembly, it was improved the physical strength greatly. Through the test of fiber Zeta potential showed that CPAM/CMC in pH=5.5 fiber environment, self-assembly had the largest amount of change to Zeta potential and also by the test of SEM and FT-IR, it showed that CPAM/CMC polyelectrolyte was adsorbed onto fiber surface.Finally, we had compared the physical strength and surface property of self-assembly and not assembly fiber. The physical strength and surface property of the recycled fiber was greatly improved when we used CPAM and CMC to assemble it. The physical strength of fifth time recycled fiber was assembly even better than the not recycled and not assembly fiber. Breaking length, folding strength, burst index and ring crush index had been increased by: 24.05%,299.78%,26.67%,41.79%. Through the test of SEM and FT-IR, we can know that as the increasing of recycled times, the adsorption of CPAM and CMC onto the fiber surface became less and less.