A review on polymer–layered silicate nanocomposites

Jets, ie collimated streams of matter, occur from the microscale up to the large-scale structure of the universe Our focus will be mostly on surface tension effects, which result from the cohesive properties of liquids Paradoxically, cohesive forces promote the breakup of jets, widely encountered in nature, technology and basic science, for example in nuclear fission, DNA sampling, medical diagnostics, sprays, agricultural irrigation and jet engine technology Liquid jets thus serve as a paradigm for free-surface motion, hydrodynamic instability and singularity formation leading to drop breakup In addition to their practical usefulness, jets are an ideal probe for liquid properties, such as surface tension, viscosity or non-Newtonian rheology They also arise from the last but one topology change of liquid masses bursting into sprays Jet dynamics are sensitive to the turbulent or thermal excitation of the fluid, as well as to the surrounding gas or fluid medium The aim of this review is to provide a unified description of the fundamental and the technological aspects of these subjects

Physics of liquid jets

Plastic waste is currently generated at a rate approaching 400 Mt year–1. The amount of plastics accumulating in the environment is growing rapidly, yet our understanding of its persistence is very...

Degradation Rates of Plastics in the Environment

This article reviews the recent trends, developments, and future applications of bio-based polymers produced from renewable resources. Bio-based polymers are attracting increased attention due to environmental concerns and the realization that global petroleum resources are finite. Bio-based polymers not only replace existing polymers in a number of applications but also provide new combinations of properties for new applications. A range of bio-based polymers are presented in this review, focusing on general methods of production, properties, and commercial applications. The review examines the technological and future challenges discussed in bringing these materials to a wide range of applications, together with potential solutions, as well as discusses the major industry players who are bringing these materials to the market.

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Current progress on bio-based polymers and their future trends

Nanocellulose, a tiny fiber with huge applications

Biodegradable polymeric blends are expected to be widely used by industry due to their environmental friendliness and comparable mechanical and thermal properties. Poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) are such biodegradable polymers which aim to replace commodity polymers in future applications. Since cost and brittleness of PLA is quite high, it is not economically feasible to use it alone for day to day use as a packaging material without blending. In this study, blends of PLA and PBS with various compositions were prepared by using a laboratory-scale twin-screw extruder at 180oC. Morphological, thermal, rheological and mechanical properties were investigated on the samples obtained by compression molding to explore suitability of these compositions for packaging applications. Morphology of the blends was investigated by scanning electron microscopy (SEM). Morphology showed a clear phase difference trend depending on blend composition. Modulated differential scanning calorimetry (MDSC) thermograms of the blends indicated that the glass transition temperature ( ) of PLA did not change much with the addition of PBS, but analysis showed that for PLA/PBS blend of up to 80/20 composition there is partial miscibility between the two polymers. The tensile strength and modulus were measured by the Instron Universal Testing Machine. Tensile strength, modulus and percentage (%) elongation at break of the blends decreased with PBS content. However, tensile strength and modulus values of PLA/PBS blend for up to 80/20 composition nearly follow the mixing rule. Rheological results also show miscibility between the two polymers for PBS composition less than 20% by weight. PBS reduced the brittleness of PLA, thus making it a contender to replace plastics for packaging applications. This work found a partial miscibility between PBS and PLA by investigating thermal, mechanical and morphological properties.

/pdf/compatibility-of-biodegradable-poly-lactic-acid-pla-and-poly-2x1yi5ngqy.pdf

Compatibility of biodegradable poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) blends for packaging application

Morphology, electromagnetic properties and electromagnetic interference shielding performance of poly lactide/graphene nanoplatelet nanocomposites

Dielectric properties and electromagnetic interference shielding effectiveness of graphene-based biodegradable nanocomposites

This paper reports a detailed investigation of the steady shear and extensional properties of mono-disperse polystyrene solutions for a range of molecular weights from 1.95 to 20 million and a range of concentrations from 69 ppm to 777 ppm. The steady shear and dynamic properties are reasonably well described by the Zimm model. The relaxation time and polymer viscosity evaluated using the Zimm model exhibit the expected scaling with concentration and molecular weight for theta solutions. In an extensional flow, these solutions show strain hardening and need about 5.5 to 6 strain units to reach steady state. The stress growth depends both on strain rate and strain. However, at moderate values of strain and when the Weissenberg number exceeds 6, the extensional stress growth depends only on total strain. The steady state extensional viscosity for each fluid was observed to depend on the magnitude of Weissenberg number (Wi). For Wi<6, the steady state extensional viscosity was observed to be an increasing fu...

Extensional viscosity of dilute polystyrene solutions: Effect of concentration and molecular weight

Nanocomposites of ethylene-vinyl acetate copolymer (EVA) with 28 wt.% vinyl acetate content (EVA28) was prepared by melt intercalation with different loadings of organically-modified bentonite clay. The microstructure and morphology of the nanocomposites were examined by X-ray diffraction (XRD) and electron microscopy. XRD and transmission electron microscopy (TEM) indicated that EVA28 nanocomposites had predominantly exfoliated morphologies. The dynamic and steady shear rheological properties of the nanocomposites showed remarkable differences in comparison to that of pure EVA28 copolymer. Linear viscoelastic parameters were enhanced at all frequencies investigated and indicated the presence of a percolated network structure. Steady shear measurements revealed that the elasticity of EVA28 nanocomposites were dependent on the silicate loading at high shear stresses. Uniaxial extensional viscosities were found to increase with silicate loading and in general exhibited strain hardening behavior. Beyond a critical strain, nanocomposite extensional viscosities were almost identical with that of the unfilled EVA28, suggesting that at high strains, silicates have little effect on the extensional viscosities. An attempt has been made to propose a possible mechanism that describes the influence of clay layers on the uniaxial extensional flow field. Images obtained from transmission electron microscopy (TEM) and an environmental scanning electron microscopy (ESEM) were used to support the proposed mechanism.

Rahul K. Gupta

Papers

Compatibility of biodegradable poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) blends for packaging application

Morphology, electromagnetic properties and electromagnetic interference shielding performance of poly lactide/graphene nanoplatelet nanocomposites

Dielectric properties and electromagnetic interference shielding effectiveness of graphene-based biodegradable nanocomposites

Extensional viscosity of dilute polystyrene solutions: Effect of concentration and molecular weight

Shear and extensional rheology of EVA/layered silicate-nanocomposites