Moisture absorption behavior and its impact on the mechanical properties of cellulose whiskers‐based polyvinylacetate nanocomposites

Abstract

Cellulose nanowhisker (CNW) reinforced polyvinyl acetate (PVAc) nanocomposites were prepared by meltextrusion using a master batch process. Microscopy images showed no visible aggregation of whiskers in the matrix. The influence of CNWs and moisture absorption on the mechanical behavior of the nanocomposites was studied. The water sorption studies indicated low water uptake (<10 wt%) for all the materials. However, higher moisture uptake was obtained in the nanocomposites compared to the matrix though the diffusion co-efficient of the nanocomposites was lower. The tensile strength and modulus were decreased with the addition of CNWs to PVAc, but the reduction is lower at higher CNW concentration indicating that the plasticizing effect of the moisture was counteracted to some extent by the reinforcing effect of CNWs. Higher tensile ductility and toughness, which were dependent on moisture absorption, were achieved in the nanocomposites than pure PVAc. POLYM. ENG.

Water transport properties of bio-nanocomposites reinforced by Luffa cylindrica cellulose nanocrystals

“…It is a general observation that the diffusion pathway is increased by tortuosity effect generating a barrier effect in polymer film which causes a change in the diffusion of small molecules and, hence, in the permeability [8,[11][12][13]. To date, and according to our current knowledge, few works dedicated to transport properties against water, organic solvents, gases for cellulose nanowhisker reinforced biobased materials are reported [2,14,[15][16][17][18][19][20][21], considering the rising interest in both academia and industry since 15 years. Generally, barrier properties obtained when nanofillers are dispersed within a polymer matrix are dependent on the free volume in material, the polymer chain segment mobility, size of diffusing molecules as well as on the dispersion level, the orientation, the amount of dispersed nanoparticles, the formation of dense cellulose network, the interfacial compatibility between nanocomposite elements, or presence of additional additives, etc.…”

“…Some authors mentioned that the water vapor barrier properties are found to be increased upon the nanofiller loading and its improved dispersion for cellulose whiskers/ plasticized-carboxymethyl cellulose films [14], surface-carboxylated whiskers/poly(vinyl alcohol) films [2], modified microcrystalline cellulose/plasticized-starch films [16], for instance. A higher water uptake is reported at high water activity (a w ¼ 0.98) for cellulose whiskers/polyvinylacetate nanocomposites [19] Contents lists available at SciVerse ScienceDirect compared with pure matrix and attributed to preferential diffusion pathways with water-rich domains formed at the nanofiller-matrix interfaces. This observation was consistent with previous results on sisal whiskers/polyvinylacetate films [22].…”

Performance of poly(lactic acid)/ cellulose nanocrystal composite blown films processed by two different compounding approaches

“…Cellulose nanomaterials such as cellulose nanocrystals (CNC) are often added to the PLA matrix to overcome few of its drawbacks . For instance, well‐dispersed nanocrystals can improve PLA's mechanical properties by improving stress transfer from the matrix to the CNCs .…”

“…For instance, well‐dispersed nanocrystals can improve PLA's mechanical properties by improving stress transfer from the matrix to the CNCs . Additionally, CNCs can act as nucleating agents to increase PLA's crystallinity . Increased crystallinity is known to improve the barrier properties of materials because of the increase in packing efficiency of polymer chains, leading to a decrease in free volume .…”

“…CNC particles tend to agglomerate due to their high surface area to volume ratio when the aqueous medium that they are produced in is eliminated by freeze or spray drying. Moreover, CNC particles are difficult to disperse in non‐polar polymers due to their high polarity and strong hydrogen bonding forces . Various approaches, such as solvent casting and melt‐compounding, have been investigated to disperse nanocelluloses into a polymer matrix .…”