Thermoplastics from lignocellulose - bagasse esters and ethers
Presentation held at Cellulose Symposium 2017, Zellcheming, July 6th, 2017, Weiterstadt
Lignocelluloses represent an abundantly available sustainable feedstock for bioplastics and biocomposites. In particular, bagasse as a waste stream in sugar or ethanol production from sugar cane reaches annual quantities of 200 million tons only in Brasil. In the present paper two ways of utilizing this source of lignocellulose are considered: chemical modification, i.e. esterification and etherification of the entire bagasse on the one hand and use of bagasse as a filler in thermoplastic composites with polyolefin matrix, in particular LDPE. While the latter approach resembles the wood plastic composite (WPC) manufacture, the former is similar to plasticizing chemical pulp by esterification to obtain cellulose acetate and other (mixed) esters. On the WPC route, filler loads of up to 8 0 % were reached while maintaining tensile strength, increasing modulus up to more than five times the starting value reaching 3 GPa and increasing HDT from 45 to 105 °C. On the down side, tensile elongation at break and Charpy impact were reduced. For chemical bagasse modification acetylation, propionylation, mixed esterification as well as benzylation were investigated. With the right choice of reaction conditions and catalyst, and using common, low-cost chemicals (not, e.g., ionic liquids) thermoplastic materials could be obtained which adjustable mechanical properties in the range of polyolefins. Tensile elongations tend to be low, but with the appropriate choice of plasticizer and substitutent type and amount, 10 to 20 % could be realized. Both approaches are capable of utilizing the bagasse waste stream for manufacturing thermoplastic materials for extrusion or injection molding. While WPC may figure as a somewhat obvious option, the chemical modification opens up a new variety of (partially) bio-based plastics on the commodity side.