Polymer melts show complex response under the act of deformation. This response has direct relation to their molecular structure. The purpose of this study was to investigate the rheological behavior of branched polymers and the effect of branching on linear and nonlinear viscoelastic flow for usage in various industrial applications.

Novel thin sheets based on poly (lactic acid)/poly (caprolactone)/thermoplastic starch ternary blends were fabricated by incorporating thymol, zinc oxide nanoparticles (ZnO-NPs) and thymol/ZnO-NPs at different concentrations (6, 9, 12 wt% thymol and 1, 3, 5 wt% ZnO). The gas/water vapor barrier properties of the nanocomposites comprising the effects of polar and non-polar molecules and their leading mechanisms were thoroughly discussed. Moreover, the localization preference of ZnO-NPs, morphology along with mechanical, and thermal properties of the nanocomposites were investigated. A significant improvement of 58% in the water vapor impermeability by 5 wt% ZnO and 12 wt% thymol loading was achieved. Finally, the fitting of the Maxwe

Chain extension/branching by reactive processing is a well‐known method to enhance the rheological properties of polymers. In this study, pyromellitic dianhydride, poly(glycolic acid), triglycidyl isocyanurate, and bisphenol A diglycidyl ether were used as chain extender/branching agents to produce branched Polyethylene terephthalate (PETs) with four different molecular structures. According to the linear rheological characterizations, the storage modulus and complex viscosity of modified PET samples enhanced significantly after branching. The shear viscosities of modified PET show a pronounced shear‐thinning behavior and a remarkable increase at low frequencies, which can be an indication of the existence of long‐chain branches (LCB

A biocompatible synthetic polymer, poly(vinyl alcohol) (PVA), and a water-soluble derivative of chitosan, (N-[(2-hydroxy-3-trimethyl-ammonium)-propyl] chitosan chloride) (HTCC), were blended and electrospun to develop a scaffold with good biocompatibility and mechanical properties in order to mimic skin. The optimum conditions to prepare PVA/HTCC fibers with minimum diameter determined as 80/20 and 13 kV. Then collagen, the most abundant material in the extracellular matrix (ECM) of skin, was co-electrospun with PVA/HTCC (80/20). Using HTTC provided excellent antibacterial properties (>99.9%). Also crosslinking improved all mechanical properties of the scaffold, except strain at break. The crosslinked PVA/HTCC (80/20) scaffold showed desi

Polymers and polymeric composites are widely used for various applications due to their outstanding and wide range of properties. Polyurethanes, existing in different types, are novel and versatile polymers with excellent mechanical properties. Thermosetting polyurethane resins are among the most widely used polyurethanes wherein their manufacturing and developing have been introduced during the last few years. Self-healing materials have been inspired by biological systems in which damages provoke healing responses. It is almost cost-effective to use self-healing materials in commercial applications. This study investigates a novel self-activated approach in thermosetting polyurethane resins. A tungsten (VI) chloride () catalyst, a co-acti

Research subject: Increasing plastic wastes of the packaging industry and concerns about their environmental problems, have attracted many researchers to use biopolymers. Therefore, the preparation of cheap biodegradable films with desirable properties for using in the packaging industry can be an attractive challenge.Research approach: In this study, poly (lactic acid)(PLA) based ternary blends were prepared by experimental design (mixture method). For this purpose, thermoplastic starch (TPS) was first prepared using 28 wt% sorbitol and 14 wt% glycerol. Then, PLA/PCL (poly (caprolactone), PCL)/TPS ternary blends at different concentrations were prepared using the melt mixing method. Morphological, physical (tensile, water vapor permeabilit

In the present study, ternary blends based on poly (lactic acid)/poly (ε-caprolactone)/thermoplastic starch were prepared at different concentrations of synthesized zinc oxide nanoparticles (ZnO-NPs) and thymol. The sizes of ZnO-NPs with an average diameter of about 30–50?nm were detected by FE-SEM analysis. Moreover, the effect of ZnO-NPs and thymol on morphological, FT-IR spectrum, UV absorption, thermal stability, cytotoxicity, and antibacterial properties of neat blend was investigated. TGA analysis showed that the addition of ZnO-NPs and/or thymol diminished thermal stability of the system. Incorporating ZnO-NPs improved antibacterial activities of the neat blend, but MTT-assay and AO fluorescent staining test results depicted a dec

Polymeric composites as materials with special engineering structure and favorable properties are widely used in different industries. The concept of self‐healing in polymers, inspired by biological systems, has been introduced in recent years. Growing applications of thermosetting polyurethanes have also resulted in their extensive use in engineering applications. There are various methods for self‐healing mechanisms, one of which involves microcapsules containing healing agents. Given that the most past research on encapsulation‐based methods carried out for self‐healing epoxy resins, the present work aims to develop the in situ technique and examine the healing efficiency for thermosetting polyurethanes due to their wide variety

In recent years, patterning has become a highly interesting approach for creating anti-bacterial surfaces. Since bacteria have become adept at protecting themselves against their killing agents, creating surfaces that able to repel bacteria solutions are simple and eco-friendly emerging approaches to overcome the new generations of bacteria. Extrand’s model presents a methodology for calculation of dynamic contact angles by considering the contact line fraction of solid asperities. In this study, a simulation of this model is presented with the aim of understanding the effect of surface patterns parameters on superhydrophobicity. The results demonstrate that a pattern with hexagonal array of circle pillars leads to the most achievable con

Aims: The study of the behavior of active suspended fluid introduced a new topic for a wide range of applications such as reactors, microfluidic pumps, cultivating surfaces and antibacterial surfaces. The motility of bacterial suspension has generated a shear force (Hydrodynamic interaction) across the cells, which has an effect on the fluid viscosity. In this study, shear rheometer was used to evaluate the viscosity behavior of Escherichia coli (E. coli) in a water/polymer environment as a function of bacteria concentration and shear rate.Materials and Methods: In the experimental study, the activity of E. coli was evaluated by choosing the constant concentration (0.01 g/ml) and molecular weight of polyvinylpyrrolidone (360KDa). Also, the

During some investigations on compatibilizing poly(ethylene terephthalate) (PET) blends by maleic anhydride–grafted polyolefins (PO‐g‐MA), the reaction between PET and PO‐g‐MA and the formation of PO‐g‐PET were proposed. However, the effect of PO‐g‐MA on the rheological properties of PET has not been the aim of any specific study. In our study, polypropylene (PP)‐g‐MA was melt reacted with PET, and the effects of its content and grafting degree on the intrinsic viscosity and linear viscoelastic properties of PET were investigated. The results reveal that the addition of PP‐g‐MA leads to increasing intrinsic viscosity, which confirms the reaction between PP‐g‐MA and PET. Rheological measurements suggest that th

Antibacterial and biodegradable whey protein isolate (WPI-) gelatin nanocomposites were prepared using natural orange peel extract (OPE) in percentage of 7, 14, and 21% (v/v solution) and Cloisite 30B (5% w/w dry whey protein) made by a casting method. Mechanical, physical, and antibacterial properties of prepared films were measured as a function of OPE concentration. Higher concentrations of OPE led to higher antibacterial activity, tensile strength, and water solubility, but lower moisture content and transparency. The films microstructures were studied by field emission scanning electron microscopy (FESEM) and ATR-FTIR. Overall, the film containing 21%(v/v) OPE resulted in the best antibacterial, mechanical, and physical performance. Ad

Many hierarchical structures are used to create self-cleaning capability. The stability and durability of superhydrophobic surfaces are still questionable in various applications. In this article, the effect of annealing process and wax-coating approach was considered to create nanostructures on micro-rice-like patterns. The morphology of resultant structures was analysed by FE-SEM and AFM instruments. The presence of nanostructures significantly increased contact angles on the hydrophobic surfaces (from 138? to 158? in the annealed process and to 161? in the wax-coating method). The decreased sliding angle from 60? in smooth surface to 10? and 6? in both superhydrophobic surfaces demonstrated a clear correlation between hierarchical struct

In this paper, we introduced thermal annealing treatment as an effective way of increasing the nanoscale roughness of a semi-crystalline polymer surface. Annealing treatment applied to a biomimetic microscale pattern of rice leaf to achieve a superhydrophobic surface with a hierarchical roughness. Resulted surfaces was characterized by XRD, AFM and FE-SEM instruments and showed an increase of roughness and cristallinity within both time and temperature of treatment. These two parameters also impact on measured static contact angle up to 158?. Bacterial attachment potency has an inverse relationship with the similarity of surface pattern dimensions and bacterial size and due to that, thermal annealing could be an effective way to create anti

Coaxial electrospinning is a method for producing fibrous mats with optional features, such as antibacterial properties, controllable release, and hydrophobicity based on shell materials. Because these features are important in biomedical applications, in this study, biocompatible hydrophobic polymer (polycaprolactone) and hydrophilic polymer [poly(vinyl alcohol)] with silver nanoparticles loaded in the core solution were coaxially electrospun. The effect of silver addition on the conductivity and viscosity of the solutions, chemical structure of the fiber mats, mechanical properties, porosity, hydrophobicity, water vapor transmission rate (WVTR), silver release, and antibacterial properties were investigated. Fibers with silver exhibited

In this study, the relation between the permeation properties and structural characteristics of thermoplastic polyurethane based on polycaprolactone diol, TPU (PCL), and polycaprolactone (PCL) blends is investigated. for the purpsoes of this study, PU, PCL, and TPU/PCL blends containing 20 wt.% and 40 wt.% PCL were prepared via a solution blending method. The miscibility and good distribution of PCL in the soft segment of PU were represented by the reduced intensity of the band attributed to the NH band at 3400 cm-1 in the Fourier transform infrared (FTIR) spectra. X-ray diffratcion (XRD) results indicated that the amorphous structure of TPU changed to a crystalline one when PCL was added. These results were further confirmed by FTIR and di

The aim of this study was to compare the rheological behavior of branched polypropylene and linear PP by reactive extrusion process. Samples were modified in the presence of a peroxide initiator, i.e., 2,5-dimethyl-2,5(tert-butyl peroxy) hexane which was dispersed at 45?wt% in (DHBP45), multi-functional monomer trimethylol propane triacrylate (TMPTA) as a graft monomer, and co-agent tetraethyl thiuram disulfide (TETDS) as a co-reactant, in an internal mixer. Rheological measurements and thermal analysis were used to characterize the structure of the modified PP samples. Using PP powder instead of PP granule, it was concluded that the elastic response of branched PP at low frequency was enhanced in comparison with linear PP.