Study On Mechanical Properties Of Starch-based Foaming Cushioning Packaging Materials

Under the background of"plastic restriction order",the use of non-biodegradable petroleum-based foams will be gradually restricted and eventually phased out.Starch-based foam cushioning packaging materials as a green environmental protection products gradually into the public’s vision,in the substitution of traditional petroleum based foam packaging materials have shown a broad application prospects.It is very important to study the buffering properties of starch-based foam buffering materials.In this paper,the effects of humidity and initial strain rate on the properties of starch-based foam cushioning packaging materials were studied by static compression test,dynamic impact test and frequency sweep vibration test.Through static compression test,the stress-strain curves of starch-based foam buffer materials under different initial strain rates(0.002s^-1,0.01s^-1,0.017s^-1,0.033s^-1,0.05s^-1)and different relative humidity（50%,70%,80%,90%）were obtained.The effects of initial strain rate and relative humidity on stress-strain curve and energy absorption were investigated.Under static compression,starch-based foamed material has obvious strain rate effect,and its energy absorption increases with the increase of initial strain rate.When the relative humidity is 50%and the strain is 0.6,the stress increases by 5.4%,12.51%,20.97%and 26.3%with the increase of the initial strain rate from 0.002s^-1 to 0.01s^-1,0.017s^-1,0.033s^-1 and 0.05s^-1,respectively.Energy absorption increased by 0.69%,7.18%,12.27 and 19.21%,respectively.Starch-based foamed packaging material is greatly affected by humidity,and its static compression performance decreases with the increase of humidity.When the initial strain rate is 0.017s^-1 and the strain is 0.6,with the relative humidity increasing from 50%to 70%,80%and 90%,the stress of the material decreases by 7.26%,19.39%and 39.42%,respectively.Energy absorption decreased by 17.93%,25.7%and 43.84%,respectively.By fitting the stress-strain curve,the static compression constitutive equation of starch foam material based on strain rate and humidity was constructed,The experimental results are in good agreement with the constitutive model.Through dynamic impact test,the stress-strain curves of starch-based foam buffer materials were obtained at different initial strain rates(30.0s^-1,34.6s^-1,38.6s^-1)and different humidity（50%,70%,90%）,and the effects of initial strain rate and relative humidity on the stress-strain curves were investigated.Under dynamic impact,the strain rate effect of starch-based foam material is obvious,and the energy absorption increases with the increase of initial strain rate.When the relative humidity is 50%and the strain is 0.6,the stress increases by 36.12%and 50.4%with the increase of initial strain rate from 30s^-1 to34.6s^-1 and 38.6s^-1,respectively.The energy absorbed by materials increased by 25.76%and 36.37%,respectively.The dynamic impact property of starch-based foamed packaging material decreases with the increase of humidity.When the initial strain rate is 38.6s^-1,the stress decreases by 9.71%and 11.25%with the increase of relative humidity,respectively.The energy absorbed by materials decreased by 6.57%and 6.68%,respectively.By fitting the stress-strain curve,the dynamic impact constitutive equation based on strain rate and humidity was constructed,and the experimental results were in good agreement with the constitutive model.The transmittance curves of starch-based foam buffer packaging materials under different relative humidity（50%,70%,90%）were obtained through frequency sweep vibration test.The results show that humidity has a great influence on the transmittance.In this experiment,when humidity is 90%,the vibration transmittance decreases obviously.