Abstract
Two types of externally plasticized cellulose acetate (CA) were chemically modified using 4,4'-methylene diphenyl diisocyanate (MDI) as crosslinking agent. Crosslinking was performed in the molten state by means of melt mixing in an internal mixer. The viscoelastic properties of the non-crosslinked, externally plasticized CA show typical temperature dependence, similar to conventional thermoplastics. A strong increase in storage modulus is observed with increasing crosslink density indicating that the crosslinked compounds exhibit predominately elastic response. The complex viscosity also increases considerably with increasing crosslink density and does not reach the typical Newtonian plateau at low radial frequencies any more. The viscoelastic properties correlate well with the data recorded online during reactive melt processing in the internal mixer. In comparison to the non-crosslinked CA, the crosslinked compounds show higher glass transition temperature, higher VICAT softening temperatures, improved thermal stability and lower plasticizer evaporation at evaluated temperatures.
Highlights
Cellulose acetate (CA) was first invented by Schützenberger [1] in 1865 and is one of the oldest bio-based polymers in the world
The aim of this paper is to present recent results of reactive melt processing of externally plasticized cellulose acetate (CA) in presence of a crosslinking agent under residence times typical for compounding processes
Plasticized CA was successfully crosslinked via melt mixing in sufficiently low reaction times using 4,4'-methylene diphenyl diisocyanate (MDI) as crosslinking agent
Summary
Cellulose acetate (CA) was first invented by Schützenberger [1] in 1865 and is one of the oldest bio-based polymers in the world. It is produced from cellulose via esterification. In comparison to conventional thermoplastics such as polystyrene (PS) or polyolefins, CA is principally not melt processible without further modification. This is due to the narrow temperature window between melting and decomposition [2]. External plasticization has several drawbacks such as evaporation of plasticizer during melt processing at evaluated temperatures or leaching of plasticizer accompanied with property loss during service life
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