Water‐assisted melt processing of cellulose biocomposites with poly(ε‐caprolactone) or poly(ethylene‐acrylic acid) for the production of carton screw caps

Abstract

Composites in 25 kg batches were compounded of cellulose nanocrystals (CNC) and thermomechanical pulp (TMP) and shaped into caps at industrial facilities on a pilot-plant scale. Some of the material was also injection molded into plaques to compare the effect of laboratory-scale and pilot-scale compounding of poly(ethylene-co-acrylic acid) (EAA7) and poly(caprolactone) composites reinforced with 10 wt% CNC and TMP. The materials compounded under laboratory-scale conditions showed a different morphology, improved mechanical properties, and a higher viscosity, than the materials compounded on a pilot-scale.

Reactive melt crosslinking of cellulose nanocrystals/poly(ε-caprolactone) for heat-shrinkable network

“…The addition of CNC does not affect the PCL rheological behavior, because of the observed poor adhesion and CNC aggregation, despite the high CNC content selected. These results confirm that traditional melt processing does not lead to a CNC percolating network, as previously observed [32]. By waterassisted REx design, an increase of gel content enhances PCL viscosity and moduli up to two and four orders of magnitude, respectively (Fig.…”

“…The mechanical behavior of the materials has also been assessed by tensile tests to evaluate the effect of REx on PCL deformability and toughness. The unreacted bionanocomposite shows the detrimental effect of CNCs on PCL tensile properties, as previously reported for extruded PCL-CNC at the same ratio [32]. Increasing the crosslinking degree (PCL-CNC-1L) reduces the deformability, consistent with shorter chain lengths between crosslinks (Fig.…”

“…The final amount of CNC was targeted at 10 wt% of the total bionanocomposites mass, well above percolation threshold to ensure CNC network formation taking into account the challenges of CNCs individualization in melt compounding and the possible inclusion of redispersing agents such as polyethylene glycol in CelluForce CNC [31]. Effective stiffening has been previously achieved even in melt processing [32] and even in solvent casted [33] poly(ε-caprolactone) (PCL) bionanocomposites at a CNC content ≈ 5 times the percolation threshold (Equation S1), CNC morphology and other details in SI.…”

Acetylation of Nanocellulose: Miscibility and Reinforcement Mechanisms in Polymer Nanocomposites

“…The final amount of CNC was targeted at 10 wt % of the total composite mass, just above the percolation threshold. 3 For this comparably high CNC content, a sensitivity to aggregation effects can be expected. The fraction of water was reduced to 50 wt % by evaporating under a fume hood and then during the melt-blending at 393 K using a DSM twin-screw microcompounder (DSM, Holland, Explore, 15 cc).…”

“…In particular, when the different nanocomposite phases (nanoparticle and matrix, respectively) have different hydrophilic/hydrophobic character, the intended nanocomposite becomes, in fact, a microcomposite since the nanoparticles cluster and form micrometer-sized aggregates. One such example is composites based on natural nanoparticles and conventional thermoplastic matrices. − Increasing the “compatibility” between the polymer matrix and the nanoparticle by tailoring the surface chemistry of the latter has often been reported as the key to improve dispersion and interface adhesion, i.e., stress transfer . One prominent example is the successful surface topochemistry performed in natural clay to improve their dispersibility in conventional thermoplastics .…”