| With the problems of energy shortage andenvironmental pollution increasing, renewable resources-Biomass resources received extensive attention. Alkali lignin is the main by-product of pulp and paper industry. Due to lack of application ways, Lignin can only be burned or discarded. Therefore, finding new ways of utilization to improve the utilization value of lignin through appropriate chemical and physical methods is necessary. In paper, with alkali lignin and PVA as primary material, alkali lignin/PVA reaction film and polyelectrolyte reaction film were prepared by casting. First, the structure and properties of the films was illustrated. Second, the utilization of film in releasing was sdudied. Third, the aging degradable of films was analyzed. Alkali lignin/PVA reaction film and polyelectrolyte cross-linked film can be used as a new type of green packaging materials, such as seed packaging etc. This research has provided a theoretical basis for the application of film in agriculture. The main results can be summarized as follows:(1) With glutaraldehyde as crosslinker, alkali lignin/PVA cross-linked reaction film was prepared by casting. The reparation condition of reaction film was as follow:the mass ratio of alkali lignin/PVA 1/5, glutaraldehyde content 1.67%, and glycerol content 7.1%(w/w) of the dry matter. Under the best conditions, Elongation-at-break (EB) of PVA film and AL/PVA reaction film was 254% and 283% respectively and Tensile strength (TS) was 30 MPa and 36 MPa, respectively. With AL added, the mechanical properties of film increased. UV absorbance of the reaction films was increased and in the visible area transmissivity was decreased. Alkali lignin had a great influence on films of absorbance and transmissivity. The surface of reaction films was smooth. Compared with PVA film, the crystallinity of the reaction film decreased a little and the thermal stability of the reaction film was higher. The FT-IR analysis showed that a cross-linking reaction occurred between alkaline lignin and PVA. But the aldol reaction between the alkaline lignin and PVA was weak.(2) With formaldehyde as crosslinker, AL/PVA reaction film was prepared by casting. The optimum condition to prepare films of best mechanical properties was that the mass ratio of alkaline lignin (AL) and polyvinyl alcohol (PVA) 2:8, formaldehyde 8.8% of the dry matter, reaction time 40 min, the solution temperature 90℃, and pH 9. Incorporation of 20% alkaline lignin material into PVA improved the tensile properties of films. Under the best conditions, Elongation-at-break (EB) of PVA film and AL-PVA reaction film were 205% and 236% respectively and Tensile strength (TS) were 52 MPa and 46 MPa. Alkaline lignin had a great influence on the absorbance and transmittance of films. The UV absorbance of the reaction films was nearly 100% among 200-400nm and the transmittance decreased during 400-800nm in visible area. The more formaldehyde, the higher transmittance of the reaction films in visible area. Both the carbon dioxide and oxygen transmittance were reduced after adding alkaline lignin, increased with the formaldehyde added and first increased then decreased with the pH value changing from 5 to 11. The surface of reaction films was smooth. Lignin and the cross-linking reaction both improved the water resistance of films. Compared with PVA film, the crystallinity of the reaction film decreased slightly; the Tg and the tanδ magnitude of the AL/PVA reaction film both decreased slightly; the thermal stability of the reaction film was higher. The cross-linking reaction between AL and PVA (1799) was present. Whether with glutaraldehyde as crosslinker or with formaldehyde as crosslinker, the mechanical properties of AL/PVA reaction film were better than that of PVA film. Compared with glutaraldehyde crosslinking film, the change of functional groups in the infrared image of the formaldehyde crosslinking film was obvious. And the content of AL in formaldehyde crosslinking film can be up to 20%. The crosslinking effect of formaldehyde was better than glutaraldehyde.(3) In order to expand the application range of lignin, the trimethyl-lignin quaternary amine salt (TLQA) and carboxymethylated polyvinyl alcohol (CMPVA) were prepared by chemical modification. The ionic strength of polyelectrolyte solution was characterized by the conductivity. The composite film (TLQA/CMPVA)n was prepared by electrostatic layer-by-layer self-assembly using the traditional immersion method. The nitrogen content of TLQA was 3.56% and the carboxyl content of CMPVA was 0.62mmol/g. ATR spectra showed that TLQA and CMPVA were fabricated and (TLQA/CMPVA)n was assembled successfully. The concentration of TLQA had the polynomial correlation with the conductivity (correlation coefficient R2=0.9953) and the concentration of CMPVA was linear with the conductivity (R2=0.9819). For TLQA assembled film, when the conductivity of TLQA was less than 2.0mS*cm-1, the assembly process was linear. For CMPVA assembled film, when the conductivity of CMPVA was less than or equal to 2.5mS*cm-1, the assembly process was linear. The absorbance of (TLQA/CMPVA)n increased linearly and the linear equation was y=0.0267x+0.07453, R20.9735. The assembled TLQA surface was smooth, while the assembled CMPVA surface was rough. With the number of the layers increasing, the film surface roughness increased. (TLQA/CMPVA)n film was stable in the water.(4) Polyelectrolyte crosslinked films:The reparation condition of TLQA/CMPVA reaction film was as follow:The solid content of polyelectrolyte crosslinked film was 10%; The PVA accounted for 30% of the solid content and TLQA and CMPVA accounted for 70% of the solid content(mass ratio of TLQA and CMPVA 3:7); Formaldehyde content 3.88%, pH 9. Elongation-at-break (EB) and Tensile strength (TS) of TLQA/CMPVA reaction film were 222.13% and 6.80MPa, respectively. UV absorbance of the reaction films was increased and transmissivity in the visible area was decreased. After formaldehyde crosslinking, the light transmittance of TLQA/CMPVA reaction film was increased. Meanwhile oxygen and carbon dioxide permeability of TLQA/CMPVA reaction film were decreased. The electrostatic force between carboxylicions and quaternary ammonium cationic in TLQA/CMPVA reaction film existed.The ether bond was formed in TLQA/CMPVA reaction film. The surface of reaction films was smooth and the section was uneven. The thermal stability, wettability and water resistance of TLQA/CMPVA reaction film were increased after formaldehyde crosslinking. Compared with PVA, the crystalline structure of CMPVA disappeared. The thermal stability of CMPVA was greater than PVA. Compared with AL/PVA reaction film, the thermal stability and surface hydrophilicity of TLQA/CMPVA reaction film increased, while the mechanical properties, permeability and transmittance of TLQA/CMPVA reaction film were reduced. And Elongation at break and Tensile strength of TLQA/CMPVA reaction film decreased 12.20% and 86.02%, respectively.(5) Pesticide release film:The thermal stability of TLQA/CMPVA/pesticide reaction film was greater than that of AL/PVA/pesticides reaction film. Abamectin in the form of particles blend with AL and PVA. In 46 h, TLQA/CMPVA/Abamectin reaction film had a less cumulative release rate for the abamectin than AL/PVA/Abamectin reaction film. The release mechanisms of TLQA/CMPVA/Abamectin reaction film and AL/PVA/Abamectin reaction film for abamectinwere were different. The former was by diffusion mechanism and the latter mechanism was the comprehensive effect of diffusion and erosion. The cumulative release rate of Hymexazol in TLQA/CMPVA/Hymexazol reaction film and AL/PVA/Hymexazol reaction film were high and the slow release rate was fast. In 33 h, almost all the Hymexazol dissolved out. The release mechanism of Hymexazol in TLQA/CMPVA/Hymexazol reaction film was first carrier dissolution and then swelling; however, it was the opposite for AL/PVA/Hymexazol reaction film.(6) Metal release film:The coordination complexes were formed between metal (Fe and Cu) and oxygen atom (C=O and OH). The contact angles of AL/PVA/FeCu reaction film and TLQA/CMPVA/FeCu reaction film were 90.0° and 23.67°, respectively. The cumulative release rate for Cu of TLQA/CMPVA/FeCu reaction film was greater than that of AL/PVA/FeCu reaction film. However, the cumulative release rate for Fe of TLQA/CMPVA/FeCu reaction film was greater in the early release and less in the late release than that of AL/PVA/FeCu reaction film. The release mechanism of FeCu in AL/PVA reaction film was first carrier swelling diffusion and then dissolution; however, the release mechanism of FeCu in TLQA/CMPVA reaction film was first dissolution, and then swelling diffusion, finally corrosion diffusion.(7) PVA film, AL/PVA reaction film and TLQA/CMPVA reaction film were degraded after UV aging and thermal aging. The quality retain rate change of TLQA/CMPVA reaction film changed greatly, followed by PVA film and AL/PVA reaction film. After UV aging, the smaller convex appeared on the surface of PVA film, while the surface morphology was nearly unchanged after thermal ageing. For AL/PVA reaction film, the matte and rough surface appeared after UV aging and thermal ageing. For TLQA/CMPVA reaction film, the flake and pore appeared after UV aging. FT-IR analysis showed that the absorption peak intensity of-OH decreased, the absorption peak intensity of C=O at 1730cm-1 disappeared and the absorption peak of CH2 strength reduced. These were mainly caused by the degradation of Lignin and PVA. |
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