Compatibility of chitosan in polymer blends by chemical modification of bio-based polyesters

For some applications of bioplastics like food packaging or medical devices, applying additives can be necessary to avoid microbial activity and hinder biofilm or fouling formation. A currently promising additive is chitosan (CS), the deacetylated form of the biogenic scaffolding material chitin. Due to its hydrophilicity, chitosan is not compatible with most of the thermoplastic bio-based polymers like poly(lactic acid) (PLA) or polyhydroxyalkanoates (PHA). In this work, compatibilization between chitosan and two selected bio-based polyesters, PLA and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), was enhanced by grafting maleic anhydride (MAH) and glycidyl methacrylate (GMA), respectively, onto polymer chains using peroxide. The success of grafting was confirmed via titration methods. The effects of grafting agent and peroxide concentrations on grafting reaction and the physical and thermal properties of the functionalized polyesters were investigated. Compounding of the functionalized polyesters with different weight portions of chitosan was accomplished in a discontinuous internal mixer by in-situ functionalization, followed by blending with chitosan. The titration method, scanning electron microscopy, DSC, FTIR and mechanical characterization of the composites showed good interfacial adhesion and suggest the formation of covalent bonds between functional groups of the polyesters and chitosan, especially for the samples functionalized with GMA. The molecular weights (Mw) of the samples showed a change in the molecular weight related to the thermal degradation of the sample. The Mw of the samples grafted with MAH are lower than those functionalized with GMA. Furthermore, integration of chitosan into non-functionalized PLA polymer matrix showed a nucleating effect, while for PHBV, the increase of crystallinity with the content of chitosan was only observed for grafted PHBV

Thermo-rheological effects of plasticizer types and concentrations on cellulose diacetate with varying molar masses

The thermo-rheological effects of adding different types and amounts of plasticizer to cellulose diacetate were studied using Dynamic Mechanical Thermal Analysis (DMTA) and Oscillation shear rheology (SAOS). Depending on the plasticizer type and concentration the zero shear viscosity, i.e. the first Newtonian plateau, can be adjusted before shear-thinning behavior occurs. The control of the viscoelastic performance is of special interest for extrusion foam processes (comparable to XPS-processes), where low shear rates between 1 and 30 s-1 arise. In this study, the effects of the type of plasticizer and its concentration as well as the molar mass of cellulose diacetate on the entanglement density and the viscoelastic properties of the material are examined. Three different plasticizers have been used in the cellulose acetate blends in concentrations between 15 to 40 wt.-%. The plasticizer concentration and temperature affect the viscosity more pronouncedly than the plasticizer type used does. Furthermore, the plasticizer significantly influences the apparent measured entanglement density of cellulose acetate

Development and processing of flame retardant cellulose acetate compounds for foaming applications

Cellulose acetate (CA) is a bio‐based polymeric material suitable to replace foamed polystyrene (PS) boards in applications for building insulation. Foam boards can be produced by extrusion foaming with physical blowing agents. In addition, the high heat deflection temperature and good mechanical properties (e.g., tensile and compression strength) of CA make it suitable for the injection molding of technical parts. In general, flame retardancy of foamed products is often required in building or electronic applications. This article presents the effects of various flame retardant (FR) additives, process settings, and the calibration of the foam board on flammability, foam morphology, and mechanical properties of extruded CA boards. Different formulations of FR additives and foaming agents were investigated regarding density and morphology of the foamed boards. Furthermore, investigations on foam behavior for foam injection molding with physical blowing agents were conducted. The foamed parts were characterized with regard to their flammability