| Food drum-linkage bag is a necessary product in people’s daily life,usually made of thermoplastic resin extremely difficult to degrade,is the main cause of white pollution,with the continuous development of food packaging,degradable drum-linkage bag has become a new trend of food packaging,but also one of the main means to solve white pollution today.Polylactic acid(alias polypropylene ester)is a new type of environmental protection material produced by deep processing of maize,which is fermented and polymerized by corn as raw material,and the preparation process is environmentally friendly and pollution-free,and the degradation products are mainly carbon dioxide and water,without causing the secondary pollution.Compared with many biodegradable thermoplastic resins based on chemical raw materials,the excellent properties of polylactic acid make it the best material for the production of degradable food drum-linkage bag.However,polylactic acid blown molding to bags has some limits,such as poor thermal sealing strength,easy to be damaged in the process of use,large total transfer volume,and is not conducive to contact with food,so it is not suitable for directly making food drum-linkage bags.In this study,with different proportions of biodegradable non-polluting materials polylactic acid(hereinafter referred to as PLA)and three kinds of polymers with better physical and chemical properties were selected of polyethylene(hereinafter referred to as PE),polypropylene(hereinafter referred to as PP),poly adipic acid/dibutyl terephthalate(hereinafter referred to as PBAT),modification of polylactic acid degradable food drum-linkage bag,the physical and chemical properties of the modified polylactic acid degradable food drum-linkage bag were analyzed,and the degradation environment and performance were studied through the biodegradable composting experiment,in order to provide theoretical support for the subsequent industrial production.The main research contents and conclusions of this thesis are as follows:Different proportions(PLA accounted for 30 %,40 %,50 %,60 %,70 % and use pure PLA as a control)were prepared,and PLA/PE,PLA/PP and PLA/PBAT blended resin granules,which were blown molding and pressed into corresponding food drum-linkage bags.(1)Through infrared analysis,it is confirmed that the characteristic absorption peaks of the blended food drum-linkage bags are almost identical with the pure PLA and the corresponding PE,PP and PBAT pure characteristic peak positions,and no new peaks appear.In the process of blending,no new radical groups and substances were generated.The intensity change of the peak is caused by the difference of the relative content of PLA/PE,PLA/PP and PLA/PBAT in the blended food drum-linkage bags.Under the conditions of this experiment,PLA/PE,PLA/PP and PLA/PBAT are all mixed in physics.In the ion chromatography test,the content of PLA/PP and PLA/PBAT polylactic acid was consistent with the feed quantity,indicating PLA and PP,The PBAT blending is uniform and has the condition of preparing the food drum-linkage bags.There was no correspondence between the test content of PLA and the feeding ratio of PLA/PE blended food drum-linkage bags,,and the test results were PE1(30 %)28.54 %,25.24 %,27.14 %,PE2(40 %)39.01 %,37.21 %,37.65 %,PE3(50 %)50.87 %,47.64 %,48.34 %,PE4(60 %)56.21 %,59.75 %,57.85 %,PE5(70 %)70.05 %,69.85 %,69.67 %,indicating that the PLA/PE mixing is not uniform under the conditions of this experiment,and does not have the preparation conditions of blended food drum-linkage bags,no follow-up experimental studies are carried out.(2)In the total migration test,the total migration of food simulators at low temperature(20 ℃,40 ℃)of PLA/PP blended food was lower than(or equal to)the control group,the total migration of high temperature(60 ℃,80 ℃)food simulations was higher than that of the control group,and the total migration of each food simulator increased greatly under the condition of 80 ℃.The test results were 4 per cent acetic acid simulator(80 ℃,1 h)control group(%)7.3 mg/L,with a minimum value of 7.5 mg/L for different proportions of PLA/PP blended food,with a maximum value of 9.1 mg/L,all higher than the control group,with different proportions of PLA/ The minimum value of PBAT blended food was 4.2 mg/L and the maximum value was 7.0 mg/L,all lower than the control group;10 per cent ethanol simulator(80 ℃,1 h)control group(%)5.3 mg/L,different proportions of PLA/PP blended food with a minimum value of 5.4 mg/L,with a maximum value of 6.9 mg/L,all higher than the control group,with a minimum value of 3.2 for different proportions of PLA/PBAT blended food coiled bags Mg/L,with a maximum value of 5.2 mg/L,were lower than the control group;the Isobutyl Simulator(80 ℃,1 h)control group(%)9.8 mg/L,and the minimum value of the PLA/PP blended food coiled bag was 10.7 mg/L,with a maximum value of 13.9 mg/L,all higher than the control group,The minimum value of PLA/PBAT blended food with different proportions was 7.2 mg/L and the maximum value was 8.9 mg/L,all of which were lower than the control group.The total transfer volume volume of PLA/PBAT blended food under each condition was lower than that of the control group;In the thermal sealing strength test,the sealing strength of the pure PLA food drum-linkage bag was PLA(100 %)3.8 N/15 mm,PP and PBAT,and the thermal sealing strength of the PLA food drum-linkage bag was modified obviously,and the sealing strength of the plastic bag products could be significantly improved when the content of PP or PBAT was reached 50 %.The sealing strength is PP3(50 %)9.7 N/15 mm,PBAT3(50 %)13.6 N/15 mm.Under the same PLA doping volume,the thermal sealing strength of PLA/PBAT blended food drum-linkage bag was higher than that of PLA/PP food drum-linkage bag.Considering that the food bag should be filled with high temperature food,the total migration volume of PLA/PP blended food was greatly increased under the high temperature condition,which was higher than that of the control group,and the total migration volume was lower than that of the control group under each condition of PLA/PBAT blended food.And when the PLA is mixed with the equivalent ratio,the sealing strength of the PLA/PBAT food drum-linkage bag is higher than that of PLA/PP food drum-linkage bag,and no follow-up experimental study is carried out.(3)The degradation process of blended food is mainly PLA degradation,so select pure PLA food coil bag for composting experiment to screen composting conditions.In the process of composting degradation experiment,the main factors affecting microbial activity were temperature,humidity and pH.On the basis of single factor test,the experimental conditions of composting degradation were optimized by response surface test.The optimum composting conditions were obtained by Design-Expert 8.0.6 Trial Analysis: Temperature: 28 ℃,Humidity: 60 %,and in the initial pH=6.5,The biodegradation rate reached 79.8 % at 90 days,indicating that the model is effective and the optimization results are reliable.(4)The system temperature of composting test system was 28 ℃,humidity 60 %,and initial pH=6.5 were set up by PLA/PBAT mixed food coiled bag composting degradation experiment.The results of composting degradation were PBAT1(30 %)82.3 %t,PBAT2(40 %)85.6 %,PBAT3(50 %)83.4 %,PBAT4(60 %)81.9 %,PBAT5(70 %)80.7 % and the control group(100 %)79.2 %.It is indicated that the decomposition rate of PLA in PLA/PBAT blended food is improved,and the value of PBAT is increased by 1.7%~3.1 %.This may be because the PBAT blending is equivalent to the dispersion of the PLA,making it easier for the experimental group to break down the rolling bag PLA in the later stages of degradation.When the PLA content was 40%,the degradation performance of PLA/PBAT blended coil was the best.The results show that in the scope of this experiment,PBAT is the best modified material for PLA degradable food drum-linkage bag,and its blending products have excellent physical and chemical properties,and the degradation conditions are suitable for landfill and excellent degradation performance.When the PLA feeding ratio is 40 %,the comprehensive performance of the food drum-linkage bag is the best. |
PDF Full Text Request