Study On Preparation And Properties Of Plant Leaves/Bio-gel Fully Degraded Biomass Composites

A year ever increasing number of plastic production in China caused serious ’White pollution’ due to its nondegration and improper disposal and became the main pollution sources.Biomass composites,as a new environmental-friendly materials,have been widely studied in recent years,using natural renewable plant resources as raw materials to prepare biomass composites is considered to be a crucial method to alleviate energy shortage and environmental pollution,also conforms to sustainable development strategy in China.This paper chooses three types of plant leaves(lotus leaves,reed leaves,banana leaves)and four types of bio-gel(cassava starch,carrageenan,gelatin,guar gum)as raw material to prepare leaves/bio-gel biomass composites by laminated molding.The properties of lotus leaves/gelatin biomass composites with different pretreatments were investigated,the effects of different leaves,different bio-gel and different contents of gelatin on mechanical properties,moisture absorption and other performance were compared and analyzed.It’s necessary to conduct an in-depth study on the properties of this type of composites since this material will not cause harm to environment from production to utilization.The main conclusion are as follow:(1)Comparison of lotus and lotus leaves/gelatin biomass composits’ properties with different pretreatments(untreatment,hot water treatment,alkali treatment)shows that both pretreatments can remove the waxy surface of lotus leaves to a certain extent,and alkali treatment has a greater degree of damage to cellulose molecular chain than hot water treatment,the residual mass of lotus leaves pyrolysis was improved.The mechanical properties of lotus leaves/gelatin composites with pretreatments are better.No matter what kind of fibers orientation,hot water treatment on the mechanical property of lotus leaves/gelatin composites have the most significant improvement.when the vascular bundle fibers are longitudinal,The tensile strength,impact strength,flexural strength,flexural modulus are the highest,which are1l.77 MPa,4.73 KJ/m2,14.06 MPa,618.79 MPa.The composites prepared by hot water have the minimum moisture absorption rate of 18.50%.The contact angle from high to low is untreatment>hot water treatment>alkaline treatment.It can be seen from the internal microstructure of the composites that the pretreatment of lotus leaves improves binding property with gelatin,making the interlayer binding more compact and dense.However,the composites with untreatment have the best thermal insulation performance,with a thermal conductivity of 0.094W/(m·k).(2)Comparison of four types of bio-gel(cassava starch,carrageenan,gelatin and guar gum)and the properties of the composites prepared with hot water lotus leaves.The results showed that:the four kinds of bio-gel have hydrophilic groups,can react with lotus to form hydrogen bonds,The thermal stability of cassava starch is relatively good,the lotus leaves/gelatin composites have the best mechanical properties,the lotus leaves/guar gum composites have the minimum moisture absorption rate of 6.50%.According to the microstructure,there are many gaps between lotus leaves/cassava starch and lotus leaves/guar gum composites,resulting in relatively low thermal conductivity,which are 0.080W/(m·k),0.039W/(m·k).(3)The content of gelatin is controlled to be 10wt%,20wt%,25wt%and 30wt%,which is prepared with hot water treated lotus leaves.Its properties show that the maximum tensile strength,flexural strength and flexural modulus are 11.77MPa,14.06MPa and 618.79MPa when the content of gelatin is 30wt%.The maximum impact strength is 5.36KJ/m2 at 25wt%gelatin,and the moisture absorption rate is also the lowest at 5.19%.With the increase of gelatin content,the interlayer bonds become increasingly tight and the porosity decreases.The thermal conductivity of the composites are significantly reduced to 0.042W/(m·k)when the content of gelatin is 10wt%due to the filling of air in the internal cracks of the composites,which are 61.47%,63.48%and 64.10%lower than that of the composites with gelatin content of 20wt%,25wt%and 30wt%.(4)Comparison of three types of leaves with hot water treatment(lotus leaves,reed leaves,banana leaves)and the properties of the composites prepared with gelatin shows that the three kinds of leaves are similar in composition but different in content.There are more cellulose and lignin in banana leaves and more hemicellulose in reed leaves.The mechanical properties of the composites are as follows:reed leaves/gelatin,banana leaves/gelatin,lotus/gelatin.The tensile strength,impact strength,flexural strength,flexural modulus of reed leaves/gelatin composites are 26.07MPa,9.87KJ/m2,41.12MPa,869.13MPa,and the contact angle from high to low in turn is:banana leaves/gelatin composites,lotus leaves/gelatin composites,reed leaves/gelatin composites.According to microstructure,the combination between lotus leaves/gelatin composites are better,so lotus leaves/gelatin composites have the minimum moisture absorption rate of 18.50%,reed leaves/gelatin composites have the lowest thermal conductivity of 0.109W/(m·k).(5)Three factors and three levels orthogonal tests are designed to verify the effects of different plant leaves,the content of bio-gel and the types of bio-gel on the moisture absorption and mechanical properties of the composites.The test results shows that the optimal level of each factor is consistent with the above.Based on the range analysis,it is concluded that the types of plant leaves and bio-gel are the main factors,and the content of bio-gel is the secondary factor.