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Hybrid interaction/co-working mechanisms of waste cellulose (WC) fibers and expanded vermiculite (V) in polypropylene (PP) resulted in stronger, stiffer, and thermally durable composites are presented. Fibrous WC and particulate V inclusions were mixed with the PP matrix via high shear thermokinetic mixer under 4000 rpm. Thermal and mechanical characterization efforts assisted with ffactographic investigations are performed on five sample sets such as (i) two-phase WC fibrous PP composites and (ii) three-phase WC-V hybrid composites. Results suggested that as the main reinforcement agent WC is able to increase the axial stiffness of PP (1.7 GPa) up to 4 GPa (30WC) as the weight fraction increases with a reduction in ductility. However, a strength threshold due to WC cluster entanglement, which leaves partially non-wet clusters of WC and limited crystallization volume for PP at high WC weight fractions, is noted. In situ formed V platelets placed between WC fibers are proven to provide PP crystallization loci to further increase the axial stiffness (4.1 GPa) and matrix brittleness. When used with 10WC, they significantly increased the ability of PP matrix r to resist the failure events associated with the presence of randomly aligned WC fibers. Such ability is further highlighted in the 20WC10V case where the inherent problem of WC entanglement increased the contribution of polymer shear failure to the overall tensile response of manufactured composites. A significant increase in tensile strength (55%) for this case was recorded which makes the proposed hybridization effort more advantageous to conventional short fiber reinforcing strategies. Highlights * Stiffer and stronger PP-based hybrid composites with waste cellulose and vermiculite. * Tensile failure/toughening mechanisms in hybrid PP composites * Sustainable approach for reinforcement selection. KEYWORDS clay, composites, fracture, mechanical properties, microscopy, 1 | INTRODUCTION There exists an accelerating demand for stronger and lighter thermoplastic composites with a strong emphasis on environmental concerns. (1-3) This demand is mainly driven by recyclability, (4) [...]

There is currently considerable interest in developing stiff, strong, tough, and heat resistant poly(1actide) (PLA) based materials with improved melt elasticity in response to the increasing demand for sustainable plastics. However, simultaneous optimization of stiffness, strength, and toughness is a challenge for any material, and commercial PLA is well-known to be inherently brittle and temperature-sensitive and to show poor melt elasticity. In this study, we report that high-shear mixing with cellulose nanocrystals (CNC) leads to significant improvements in the toughness, heat resistance, and melt elasticity of PLA while further enhancing its already outstanding room temperature stiffness and strength. This is evidenced by (i) one-fold increase in the elastic modulus (6.48 GPa), (ii) 43% increase in the tensile strength (87.1 MPa), (iii) one-fold increase in the strain at break (~6%), (iv) two-fold increase in the impact strength (44.2 kJ/[m.sup.2]), (v) 113-fold increase in the storage modulus at 90[degrees]C (787.8 MPa), and (vi) [10.sup.3]-fold increase in the melt elasticity at 190[degrees]C and 1 rad/s (~[10.sup.5] Pa) via the addition of 30 wt% CNC. It is hence possible to produce industrially viable, stiff, strong, tough, and heat resistant green materials with improved melt elasticity through high-shear mixing. KEYWORDS cellulose nanocrystals, green nanocomposites, high-shear mixing, PLA, 1 I INTRODUCTION Biodegradable polymers [1-3] have attracted considerable interest in the plastics market in recent years as promising alternatives to petroleum-based commodity polymers. However, their implementation remains a challenge [...]

The morphological transformation of expanded vermiculite (VC) during injection molding with brittle PLA and ductile PP polymers along with its positive and negative contribution to mechanical response is investigated. Polymer/VC mixtures with 30 wt. % VC are prepared by thermokinetic high shear mixing at 4000 rpm without any ex‐situ exfoliation agents or compatibilizers. Obtained composite mixtures are then injection molded onto three‐point bending and tensile test specimens. Performed mechanical tests suggested a significant increase in tensile (110%) and flexural modulus (112%) of PP30VC samples. Presented fractographic and morphological investigations suggested that the root cause of measured improved tensile (36%) and bending strength (26%) of PP is the fibrillation of VC associated with PP/VC interactions under high shear. A similarly increasing trend for tensile (147%) and bending modulus (137%) was observed for PLA30VC samples. Contrary to PP30VC, a decreasing pattern was present in the case of tensile (−40%) and bending strength (−13%) of PLA30VC. The root cause for such reduction is determined to be (i) in situ exfoliation of VC inside PLA matrix and transformation of VC into micrometer‐sized platelets; (ii) evaporation of trapped water/crystalline water in the interlayer region of VC which caused in situ degradation of PLA during manufacturing. Highlights: Vermiculite‐loaded PP and PLA composites are produced at high shear.Composites have superior modulus compared to neat polymers.Fibrillation of platelet vermiculite is observed in only the PP matrix. [ABSTRACT FROM AUTHOR]

Poly(ethylene oxide) (PEO) based polyurethaneurea-silica nanocomposites were prepared by solution blending and characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Differential Scanning Calorimetry and tensile testing. The colloidal silica nanoparticles with an average size of 50 nm were synthesized by modified Stober method in isopropanol. Silica particles were incorporated into three cycloaliphatic polyurethaneurea (PUs) copolymers based on PEO oligomers with molecular weights of 2,000, 4,600, and 8,000 g/mol. Hard segment content of PUs was constant at 30% by weight. Silica content of the PU nanocomposites varied between 1 and 20% by weight. Soft segment (SS) glass transition and melting temperatures slightly increased with increasing filler content for all the copolymers. Degree of SS crystallinity first increased with 1% silica incorporation and subsequently decreased by further silica addition. Elastic modulus and tensile strengths of PU copolymers gradually increased with increasing amount of the silica filler. Elongation at break values gradually decreased in PEO-2000 based PU copolymer with increasing silica content, whereas no significant change was observed in PUs based on PEO-4600 and PEO-8000. Enhancement in tensile properties of the materials was mainly attributed to the homogeneous distribution of silica filler in polymer matrices and strong polymer-filler interactions., INTRODUCTION Polymeric nanocomposites have been a focus of attention particularly because of their enhanced physicochemical, thermal, mechanical, and other engineering properties, enabling their use in a wide range of applications, [...]

Tissue-engineered skin substitutes have great potential to treat chronic wounds and high-degree burns. Existing solutions, such as Integra Dermal Template, are extensively used for skin defects. However, these templates are still lacking in terms of recreating the functionality of the native tissue and providing scarless healing. In this study, polycaprolactone/silk fibroin (PCL/SF)-based nanofibers with varying blends were fabricated and characterized to develop a novel skin substitute. Morphological analysis showed that the nanofiber distribution of each sample was homogenous without showing any beads. In terms of mechanical properties, all the samples other than SF showed sufficient mechanical strength. It was observed that adding a specific amount of SF into the PCL nanofiber improves the tensile strength of the samples due to the introduction of intermolecular interactions from the functional groups of SF. In addition, incorporating SF into PCL improved Young's modulus of the PCL nanofibers since SF provides stiffness and structural integrity to the overall structure. Water contact angle analysis was performed as the hydrophilicity of a biomaterial is a significant factor in cell functionality. Each sample had a contact angle between 33° and 48°, indicating the adequate hydrophilicity of nanofibers for advanced cell proliferation other than PCL. Cell proliferation and viability studies were conducted with the seeding of primary human keratinocytes on the samples. It was examined that scaffolds containing blends of PCL and SF resulted in higher cell proliferation and viability after 7 days compared to pure PCL and SF nanofibers. [ABSTRACT FROM AUTHOR]