| In this paper,in order to solve the problem of difficult resource and scale utilization of the large amount of recovered algae from Lake Chao and penicillin residue produced by the pharmaceutical industry,and overcome the shortcoming of low mechanical properties of biomass/low density polyethylene(LDPE)composites and low degradation ability of LDPE resin material,a method for preparing filled biodegradable plastics by blending LDPE resin with algae from Lake Chao and penicillin residue were proposed.The process combination and parameter configuration were optimized by single factor combined with response surface method.The mechanism changes during the experiment were analyzed by means of ultraviolet-visible spectroscopy,surface topography analysis,X-ray diffraction,infrared spectroscopy,and some other means.At the same time,the properties of biomass/LDPE composites were further analyzed by means of mechanical property test,melting temperature test,penicillin residue test and weight loss rate test.The main research contents and results were as follows:(1)The drying technology of algae in Lake Chao was studied,the mechanical properties of the composites were inversely related to the water content and particle size of algae powder,and the optimum drying process and parameters of algae powder were obtained as follows: freeze-thawing(-13°C,room temperature)2 times,microwave vacuum drying(40°C,700 W/h,0.08,1 h),crushing for 30 s.Under these conditions,the water content of algae powder was about 6.71% and the average particle size was 25.397 ?m.(2)The effects of the additions of polyethylene wax and white oil as lubricant,titanate coupling agent,aluminate coupling agent and maleic anhydride grafted polyethylene(PE-g-MAH)as compatibilizer,glycerin,triethanolamine and formamide as plasticizer on the mechanical properties of the composites were investigated.The experimental results demonstrated that when the addition of algae powder and LDPE resin were 15.00% and 85.00%,the optimum addition of lubricant(polyethylene wax and white oil)was 2.67%(2.00% and 0.67%),the tensile strength,flexural strength and flexural modulus of the composites were 10.10 MPa,8.23 MPa and 193.00 MPa,respectively.PE-g-MAH was chosen as compatibilizer and the optimum addition of PE-g-MAH was 3.00%,the tensile strength,flexural strength and flexural modulus of the composites were 11.20 MPa,8.45 MPa and 212.00 MPa,respectively.When glycerin or triethanolamine was selected as plasticizer and the amount of their addition was 3.00%,the tensile strength,flexural strength and flexural modulus of the composites were 9.90 MPa/9.80 MPa,8.25 MPa/8.05 MPa and 202.00 MPa/199.00 MPa,respectively.The mechanical properties of the composites without any additives were 9.80 MPa,7.22 MPa and 168.00 MPa.And compared with it,the mechanical properties of composites with additives were improved effectively.(3)In the preparation of algae powder/LDPE composites,through single factor experiment and response surface methodology optimization,the optimum formula parameters were as follows: the additions of algae powder,LDPE resin,lubricant(polyethylene wax and white oil),PE-g-MAH,glycerin were 15.00%,85.00%,2.61%(1.96% and 0.65%),4.06%,3.08%,respectively.The tensile strength,flexural strength and flexural modulus of the composites were 11.60 MPa,9.95 MPa and 241.00 MPa,respectively.And the melting temperature was 108°C.(4)In the preparation of algae powder-penicillin residue /LDPE composites,it was found that the infrared spectrum of penicillin residue was similar to that of algae powder,and it was rich in protein,amino acid,carbohydrate and so on.When the algae powder was added to penicillin residue,the dispersion of penicillin residue particles could be improved.However,the compatibility between the two substances with LDPE resin was poor.Through single factor experiment and response surface methodology optimization of the blending ratio of algae powder with penicillin residue,and the additions lubricant,PE-g-MAH and triethanolamine,the optimum formula parameters were as follows: the blending ratio of algae powder with penicillin residue was 1:2,and the additions of blend powder,LDPE resin,lubricant(polyethylene wax and white oil),PE-g-MAH,triethanolamine were 15.00%,85.00%,3.08%(2.32%? 0.76%),4.33%,4.23%,respectively.The tensile strength,flexural strength and flexural modulus of the composites were 12.30 MPa,9.03 MPa and 220.00 MPa,respectively.The melting temperature was 109°C,and the sample extract of the composites was lower than the detection limit of the instrument in penicillin residue test.(5)The action mechanism of auxiliaries was studied.The results demonstrated that the addition of lubricant could reduce the friction between biomass powder and LDPE in the composite system,between the composite and the mold,and the compliance and surface smoothness of the spline were improved.In the experiment of compatibilizer,the isopropoxy end of titanate coupling agent and aluminate coupling agent interacted with the hydroxyl in algae powder,the cyclic anhydride at one end of the PE-g-MAH is tightly linked to the hydroxyl in the algae powder,and the other long chain carbon end was entangled with LDPE.In the experiment of plasticizer,the hydroxyl groups of glycerin and triethanolamine could form hydrogen bond with the hydroxyl group in algae powder,and the amino and carbonyl groups of formamide could form hydrogen bond with the hydroxyl group in algae powder at the same time.And the hydrogen bond between the molecules in the algae powder was weakened,the agglomeration of the algae powder was decreased,and the compatibility of the algae powder with LDPE resin was enhanced.However,because of the formamide molecules could still make the molecules in algae powder have enough space for chain segment movement in the cooling composite system,which leaded to the increase of flexibility and the weakness of strength of the composites.By comprehensive consideration of the mechanical properties of materials and reaction mechanism,the lubricant(polyethylene wax and white oil),PE-g-MAH and glycerin or triethanolamine were selected as the higheffective additives.Furthermore,the mechanism of the lubricant(polyethylene wax and white oil),PE-g-MAH and triethanolamine in preparing algae powder-penicillin residue/LDPE composites was similar to that of algae powder.(6)When using soil and soil mixed with pseudomonas fluorescent as substrate for landfill degradation,the weight loss rates of algae powder/LDPE composites and algae powder-penicillin residue/LDPE composites prepared with the optimum technological parameters were 7.73%/180 d and 7.86%/180 d,8.98%/180 d and 9.12%/180 d,respectively.During this period,the average degradation rates were about 0.0429%/d and 0.0437%/d,0.0499%/d and 0.0507%/d.The model predicted that the degradation periods of the above two composites were about 2300 d and 2000 d,1500 d and 1600 d,the average degradation rates of the above two composites were about 0.0435%/d and 0.0506%/d,0.0690%/d and 0.0640%/d after 180 days,the degradation rates were increased compared with the previous experiment obviously. |
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