Highly Transparent and Toughened Poly(methyl methacrylate) Nanocomposite Films Containing Networks of Cellulose Nanofibrils

Abstract

Cellulose nanofibrils (CNFs) are a class of cellulosic nanomaterials with high aspect ratios that can be extracted from various natural sources. Their highly crystalline structures provide the nanofibrils with excellent mechanical and thermal properties. The main challenges of CNFs in nanocomposite applications are associated with their high hydrophilicity, which makes CNFs incompatible with hydrophobic polymers. In this study, highly transparent and toughened poly(methyl methacrylate) (PMMA) nanocomposite films were prepared using various percentages of CNFs covered with surface carboxylic acid groups (CNF-COOH). The surface groups make the CNFs interfacial interaction with PMMA favorable, which facilitate the homogeneous dispersion of the hydrophilic nanofibrils in the hydrophobic polymer and the formation of a percolated network of nanofibrils. The controlled dispersion results in high transparency of the nanocomposites. Mechanical analysis of the resulting films demonstrated that a low percentage loading of CNF-COOH worked as effective reinforcing agents, yielding more ductile and therefore tougher films than the neat PMMA film. Toughening mechanisms were investigated through coarse-grained simulations, where the results demonstrated that a favorable polymer-nanofibril interface together with percolation of the nanofibrils, both facilitated through hydrogen bonding interactions, contributed to the toughness improvement in these nanocomposites.

Self-nanofibrillation strategy to an unusual combination of strength and toughness for poly(lactic acid)

“…75 The additional elastic energy dissipating mechanism is triggered by the formation of nanovoids in the channel base and the anchoring interactions between adjacent nanobrils. Upon increasing deformation aer the yield point, the consumption of deformable phase is accommodated principally by structural regularization within the nanobrils and nanochannels, encouraging a series of energy-dissipating mechanisms: (1) amorphization of excessively extended crystals followed by reorientation of newly unfolded chains, 76 (2) formation and growth of uniform nanovoids to deect crack tips and constrain crack propagation, 77 (3) deection and reorientation of kebabs protruding from the nanobrils, (4) friction between interactional nanobrils and channels due to the displacement incompatibility, (5) gradual evolution into longer, thinner and stronger ultrane nanobrils. The synergistic mechanisms occurring in self-nanobrillar PLA contribute to the combination of strength and toughness until the entire consumption of deformable phase.…”

Effect of Cellulose Nanocrystals and Lignin Nanoparticles on Mechanical, Antioxidant and Water Vapour Barrier Properties of Glutaraldehyde Crosslinked PVA Films

“…They are a balanced mixture of lignin, cellulose, hemicellulose and tannins, containing specific functionalities that permit their conversion, as alternative materials to fossil fuels, to biofuels and other organic compounds [ 1 , 2 ]. Lignocellulosic materials have found many applications as reactive filler in various polymers, including thermoplastics, such as polyethylene [ 3 , 4 ], poly (lactic acid) [ 5 , 6 , 7 ], poly (methyl methacrylate) [ 8 , 9 ], polyurethane [ 10 , 11 , 12 ] etc.) and thermosetting matrices, such as phenolic [ 13 , 14 ] and epoxy resins [ 15 , 16 , 17 ].…”

Effect of Cellulose Nanofibrils and TEMPO-mediated Oxidized Cellulose Nanofibrils on the Physical and Mechanical Properties of Poly(vinylidene fluoride)/Cellulose Nanofibril Composites

“…Conversely, high-aspect ratio cellulose nanofibrils (CNFs) exhibit reinforcing effects that have been attributed to the presence of entangled CNF networks capable of bridging crazes formed in composites during tensile testing [13]. The high-aspect ratio of CNFs facilitates fibril interlocking across crazes as well as forming entangled fibril pullouts that can contribute to the increased tensile strength and strain-at-failure at low loadings [13,14].…”

“…PVDF is extensively used as a membrane or scaffold for water purification and filtration technologies. PVDF is a semi-crystalline polymer with five known crystalline phases (α-, β-, γ-, δ- and ε-) whose nucleation is highly dependent on the processing conditions [14]. The most common phases are the non-polar, non-electroactive α-phase with antiparallel TGTG′ (trans-gauche–trans-gauche) chain formation, the electroactive β- and γ-phases with trans TTT planar and T 3 GT 3 G′ respective chain conformations [14,27,28].…”