Modification of cellulose acetate with oligomeric polycaprolactone by reactive processing: Efficiency, compatibility, and properties

Abstract

Oligomeric polycaprolactone (oPCL) was used for the modification of cellulose acetate by reactive processing in an internal mixer at 180 C, 50 rpm, 60 min reaction time, and 45 wt % caprolactone (CL) content. The product of the reaction was characterized by several analytical techniques and its mechanical properties were determined by dynamic mechanical thermal analysis and tensile testing. The synthesized oPCL contained small and large molecular weight components. The small molecular weight fraction plasticized cellulose acetate externally and helped fusion. Although composition and structure did not differ considerably from each other when CL monomer or polycaprolactone oligomer was used for modification, the grafting of a few long chains had considerable effect on some properties of the product. The large molecular weight chains attached to CA increased the viscosity of the melt considerably and resulted in larger deformability. oPCL homopolymer is not miscible with cellulose acetate and migrates to the surface of the polymer. Exuded polycaprolactone oligomers crystallize on the surface but can be removed very easily. More intense conditions may favor the grafting of long chains leading to polymers with advantageous properties.

Long-Chain Anhydride Modification: A New Strategy for Preparing Xylan Films

“…For biomacromolecule (e.g., cellulose, starch) films with or without external plasticizers, mechanical strength mainly depends on the hydrogen bonds. External plasticization (a replacement of hydrogen bridges acting among the chains by the interaction of the plasticizer and the groups forming those bridges) leads to a considerable decrease of strength because of the decreasing hydrogen bonds. ,, In other words, external plasticization can improve the film-forming performance of biopolymers at the cost of decreasing their tensile strength. In this work, continuous xylan film without external plasticizer cannot be formed because strong hydrogen bonds caused strong internal stress, resulting in cracks and defects within the film .…”

Study of Reactive Melt Processing Behavior of Externally Plasticized Cellulose Acetate in Presence of Isocyanate

“…They also explain this with an increase in viscosity due to branching reaction and network structure formation. Furthermore, Klébert [ 19 ] as well as Klébert et al [ 20 ] reported a similar strong increase in torque during melt grafting of CA with different caprolactones.…”

“…Often, external plasticizers were added to improve processing and homogenization and to facilitate the grafting reaction in the molten state due to better access to the functional groups. Nevertheless, in most cases long reaction times and large quantities of catalysts and monomers are necessary for sufficiently high grafting yields [17,18,19,20,21,22]. Thus, most of the processing conditions used in these studies are not viable for typical compounding processes prohibiting economic feasibility of the processes.…”

“…Consequently, lots of studies describe the chemical modification of CA in solution [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. During melt processing, mainly graft reactions onto CA have been studied [ 8 , 17 , 18 , 19 , 20 , 21 , 22 ]. Often, external plasticizers were added to improve processing and homogenization and to facilitate the grafting reaction in the molten state due to better access to the functional groups.…”

Hemicelluloses/montmorillonite hybrid films with improved mechanical and barrier properties

“…For the biomacromolecule films (e.g., cellulose, starch) with or without external additives, mechanical strength mainly depends on the hydrogen bonds. External additives leads to a considerable decrease of strength due to the decreasing hydrogen bonds 49 50 . In other words, the additives can improve the film-forming performance of biopolymer at the cost of decreasing their tensile strength.…”