Secondary Waste Paper Fiber Cyanide Ethyl Modification And The Preparation Of Composite Materials

Reutilization of waste resources secondary fiber(SF) is a potential alternative to solve the energy and environmental problem in processing regenerated paper. This dissertation evaluated the pretreatment and thermoplasticization of SF materials via microwave technology. And new reutilization method is researched in the dissertation, which is more effective, more environmental friendly and highly additional valuable. The pretreatment, thermoplasticization and composite preparation were systematically investigated. To our knowledge, SF composite material by the method of microwave-assisted pretreatment and thermoplasticization hasn't been reported before.Microwave-assisted alkali pretreatment of SF was evaluated and compared with conventional alkali pretreatmen. SF supramolecular structure was changed after microwave-assisted alkali pretreatment:crystallinity decreased, interplanar crystal spacing increased and polymerization degree decreased, making water retention value and accessibility increased. The synergistic effect mechanism of microwave-assisted alkali pretreatment on SF supramolecular structure was firstly put forward.Thermoplasticization of SF was studied systematically. SF can be converted to thermoplastical material by cyanoethylation. Mechanical properties of CSF are related with nitrogen content. The mechanism of SF thermoplasticization was studied. Flexural strength (TS), tensile strength(FS) and thermal flowability of CSF were improved with increasing reaction degree of cyanoethylation. Microwave-assisted alkali pretreatment increased nitrogen content of CSF, decreased the reaction time, and reduced the dosage of chemicals. The effect of microwave-assisted alkali pretreatment conditions on chemical reaction performance of SF were investigated. The results showed:nitrogen content of CSF enhanced after irradiated by microwave under 200w,400w and 600w. Continuous microwave irradiation showed more effective than discontinuous one.Decrystallization cannot give SF thermoplasticity in alkali and micro-assisted alkali pretreatment. The thermoplasticization of SF is mainly attributed to cyanoethylation which introduces the group—CH2CH2CN onto cellulose, partially deteriorates the ordered structure of the crystalline regions, and promotes cellulose macromolecule and/or chain segment to move.Compared with properties of regenerated high density polyethylene (RHDPE), TS and FS of SF/RHDPE composites were higher, increasing by 34.70% and 77.22% respectively. Because SF was not of thermal flowability, the formability of SF/RHDPE composites decreased with increasing SF dosage. The normalized crystallization degree(XR) of RHDPE matrix in the composites was recorded higherly compared to RHDPE. The crystalline melting temperature(Tm) of the composites decreased with the increasing of fibre content. This phenomenon could be attributed to the fact that strong nucleation existed on fibre surfaces. Coupling agent maleated polyethylene (MAPE) improved the interfacial compatibility between SF and RHDPE, and therefore improved the mechanical properties of SF/RHDPE composite. In the presence of the coupling agent MAPE, the XR of RHDPE matrix in the composites was recorded lower compared to that in uncompatibilized SF/RHDPE composites, but the Tm value was higher. This was due to the fact that coupling agent improve the interfacial compatibility between SF and RHDPE, and weaken the nucleation effects of SF.CSF were used as reinforcement in CSF/RHDPE composites. The mold molding technique parameter and content of CSF were investigated. The optimum mixing temperature, mixing time and molding pressure were 160℃,15 min and 15 MPa, respectively. The content and nitrogen content of CSF affected the mechanical properties of CSF/RHDPE composites. When the content of CSF was same, the mechanical properties of CSF/RHDPE increased with nitrogen content of CSF increasing. When nitrogen content of CSF was 20.36% and content of CSF was 20wt%, TS and FS were 34.79 MPa and 36.27 MPa respectively. CSF weakened melting and crystallization properties of the RHDPE in the composites. The mechanical properties and water absorption performance of CSF/RHDPE composites were better than those of uncompatibilized SF/RHDPE, even better than those of compatibilized SF/RHDPE composites. The influence degree of CSF addition on CSF/RHDPE composites'processability was smaller than SF/RHDPE composites.CSF can be used as reinforcement in CSF/RHDPE composites, and also used as matrix in place of traditional matrix to make SF/CSF composites. The optimum content of SF was 10wt% because the hot melt viscosity of CSF was bigger than that of traditional thermoplastic resins. The effects of combined treatment of alkali and silane coupling agent KH550 were better than alkali treatment. SF/CSF composite is biodegradable based on the trial of cellulase degradation. SF/CSF composite could be used as building materials instead of traditional plant fiber enhanced polymer composite.