Behavior Of Poly Research Articles

Composition-Dependent Dielectric Properties of Poly(vinylidene fluoride-trifluoroethylene)s Near the Morphotropic Phase Boundary

The discovery of relaxor behavior in poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymers plays a crucial role in driving the formation of a morphotropic phase boundary (MPB) near which large enhancements of dielectric and piezoelectric responses are achieved. Here we study the dielectric spectra of P(VDF-TrFE)s near MPB and analyze the relaxor behavior using two different theoretical models. We observe the largest dielectric constant of ∼76 at 1 kHz in morphotropic composition P(VDF-TrFE) 50/50 mol % at around 69 °C. We show that the compositional dependence of dielectric peak temperature changes dramatically in the vicinity of VDF = 49 mol %. Moreover, we find that the parameters (i.e., dielectric relaxation strength) deduced from the fit of the experimental data by different models also changes abruptly at VDF = 49 mol %. These findings clearly signify the destabilization of normal ferroelectric phase occurring at the critical VDF content of 49 mol % and explicitly mark one boundary of ...

Optical characterization of salt-induced swelling behavior ofpoly(N-isopropylacrylamide) terpolymer hydrogel layers

Optical characterization of salt-induced swelling behavior ofpoly(N-isopropylacrylamide) terpolymer hydrogel layers

Thermal phase transition of poly(N-vinyl caprolactam)-based copolymers: the distribution of hydrophilic units within polymeric chains

Here, cloud temperature and aggregation behaviors of poly(N-vinyl caprolactam)-based polymer were investigated with the addition of hydrophilic units. Copolymers composed of N-vinyl caprolactam and polyethyleneglycol methylacrylate (POEGMA) were firstly synthesized through a reversible addition fragmentation chain transfer technology with benzylsulfanylthiocarbonylsulfanyl propionic acid (BPA) as chain transfer agent and 4,4′-azobis(4-cyanovaleric acid) as initiator. The cloud points measurements indicated that comparing with pure poly(N-vinyl caprolactam), little amount of POEGMA would dramatically decrease copolymers’ cloud temperature while further addition of POEGMA would inversely increase the cloud temperature. The contribution of POEGMA within polymeric chains was modulated by adding POEGMA after 30 min of initiating polymerization. Both the DLS and TEM measurements showed that micelles instead of random structures were formed through a self-assembling process above the cloud temperature. These results emphasized the importance of the contribution of hydrophilic units in predicting the thermal phase transition behavior of poly(N-vinyl caprolactam)-based materials.

Thermal, Mechanical Properties and Rheological Behavior of Poly(Propylene Carbonate)/Poly(Ethylene Glycol)/Graphene Oxide Nanocomposites

Graphene oxide (GO) is an efficient nanofiller for polymers and a good dispersion of GO in polymer matrix is most important to enhance properties. Poly(propylene carbonate) (PPC)/GO nanocomposite was prepared by a method with solution blending and melt mixing for improvement of GO dispersion. First, GO was prepared using an improved Hummers method. In the solution blending, GO was well dispersed in water and another low molecular weight polymer, poly(ethylene glycol) (PEG), was also dispersed in water, as a dispersion medium for next melt mixing of PPC and GO. Then PPC and PEG/GO was melt-mixed in a HAAKE mixer. The dispersion of GO in PPC matrix and effect of GO content on properties of PPC/PEG/GO nanocomposites was investigated. Results show that tensile strength of nanocomposites with the content of 0.5 wt% GO increased from 17.51 MPa (pure PPC) to 21.61 MPa and elongation at break can be kept high. The complex viscosity, storage and loss modulus is the highest for nanocomposites with the content of 0.5 wt% GO. This illustrated that a lower content of GO can improve the properties of PPC, owing to the good dispersion of GO in PPC matrix. Based on dispersion of GO and chemical structure of PPC, PEG, and GO, the reinforcement mechanism of GO in PPC was analyzed.

Substituent engineering of electrooptic chromophores to suppress their aggregation

Chromophores composed of 4-cyano-5-dicyanomethylene-2-oxo-3-pyrroline (CDCOP) and a donor have been synthsized for electrooptic applications. Three substituents of [5-(4-aminophenyl)-2-thienyl]-substituted CDCOP 1 and (4-aminophenyl)-substituted CDCOP 2 were modified to suppress the aggregation for effective poling. To 1, bulky and branched 2-ethylhexyl groups were introduced instead of linear alkyl groups. Less aggregation was confirmed in the polymer dispersion films, and the corona poling behaviors were examined. To 2, we introduced norbornyl epoxide groups as bulky and thermally crosslinkable moieties. The aggregation was suppressed as well, and the thermal crosslinking of the epoxide with acid anhydride in the presence of a base was investigated.

Tuning crystallization and hydrolytic degradation behaviors of poly(lactic acid) by using silver phosphate, zinc oxide and their nano-hybrids

ABSTRACTThe promising potential of silver phosphate (Ag3PO4) nanoparticles is shown in improving the properties of polylactic acid (PLA) by preparing PLA/Ag3PO4, PLA/ZnO and PLA/Ag3PO4/ZnO nanocomposites. The dispersion quality of nanoparticles was significantly improved once the nano-hybrids were used. It was found that Ag3PO4 acts as efficient nucleating agents in the solution-induced crystallization. Generally, ZnO was not as efficient as Ag3PO4 in improving the PLA crystallinity. Hydrolytic degradation experiments revealed that Ag3PO4 could notably retard the degradation process while it was accelerated in the presence of ZnO. Therefore, Ag3PO4 and ZnO would be desirable for long- and short-life biological applications, respectively.

Pseudo‐ductile behavior of poly(vinyl alcohol) fiber‐reinforced polypropylene

Composites based on two different polypropylene (PP) grades reinforced with poly (vinyl alcohol) (PVA) fibers were prepared by compounding and injection molding. Very high residual fiber length values of up to 2,500 μm were achieved. The impact performance of a PP homopolymer can be improved dramatically by reinforcement with the PVA fibers, even below the glass transition temperature of the matrix. For a high impact PP heterophasic copolymer, the fiber reinforcement interferes with the elastomer toughening. Scanning electron microscopy and X‐ray computer‐tomography analysis indicate that the specific composite microstructure has very long, entangled fibers and a low fiber matrix interaction allowing for pseudo‐ductility. Analysis of the micromechanical deformations by volume strain and acoustic emission measurements during tensile testing supports this hypothesis. POLYM. COMPOS., 40:4067–4078, 2019. © 2019 Society of Plastics Engineers

Modeling and experimental verification of nonlinear behavior of cellulose nanocrystals reinforced poly(lactic acid) composites

Abstract In this paper, a constitutive modeling framework was introduced to characterize the time-dependent behavior in poly(lactic acid) reinforced by cellulose nanocrystals (CNCs). The mechanical properties of PLA and its corresponding nanocomposites were analyzed at three different extension rates (1, 5, 10 mm/min) using a stress relaxation test. Six hyperelastic strain energy functions were employed to describe the instantaneous mechanical behavior. The deviatoric and volumetric material constants were verified using Drucker stability criterion, and the instability limits of each model were reported. Furthermore, a hyper-viscoelastic model consisting of Neo-Hookean strain energy function and time-dependent Prony series was used to study the viscoelastic behavior of PLA and the corresponding nanocomposites. The model constants were determined using finite element (FE) simulations through an iterative process for the whole loading history of the relaxation test. Nelder–Mead Simplex method was applied to optimize the results of the FE simulations using the experimental data. The mechanical response observed for PLA and nanocomposites from model exhibited a good agreement with both short and long-term experimental data, suggesting the applicability of the estimated material parameters by this technique.

The Impact of Molecular Weight on the Behavior of Poly(propylene glycol) Derivatives Confined within Alumina Templates

In this paper, we explored the influence of both the variation in the molecular weight (Mn = ∼400, 2000, 4000 g/mol) and the terminal groups (hydroxyl, amino, and methoxy) on the molecular dynamics of poly(propylene glycols) confined within anodic aluminum oxide membranes of different pore diameters. All confined samples revealed the presence of two glass transition temperatures related to the vitrification of two, core and interfacial, fractions of polymers. As found, the glass transition temperature of PPG adsorbed on the pore walls increases with a decrease in polymer Mn and scales with the H-bonding ability of a given material. Surprisingly, the glass transition temperature of the core macromolecules decreases with respect to the bulk sample with increasing Mn. To gain insight into the observed quite unexpected anti-correlated behavior of both Tg values, we performed the additional contact angle and surface tension measurements together with the annealing experiments. As shown, there were no differenc...

Influence of Musa acuminate bio-filler on the thermal, mechanical and visco-elastic behavior of poly (propylene) carbonate biocomposites

Biocomposites were fabricated using poly(propylene) carbonate as matrix and cellulosic polysaccharide banana (Musa acuminate) peel powder as filler in varying concentrations (5–25 wt.%) and were characterized for their functional properties. Microscopic analysis indicated the uniform distribution and existence of microfibrils in the filler. The thermal stability of the composites was lower than the matrix till 320 °C, beyond which it increased. The visco-elastic and mechanical behavior of the biocomposites was found to be enhanced with the addition of fillers. Thus, with better thermal, visco-elastic, and mechanical properties, the biocomposite films can be a replacement for the non-biodegradable polymers for packaging applications.

Synthesis, Characterization, and Micellization Behavior of Poly(L-lactide) and Poly(ethylene glycol) Block Copolymers in the presence of a Novel Organocatalyst

Synthesis, Characterization, and Micellization Behavior of Poly(L-lactide) and Poly(ethylene glycol) Block Copolymers in the presence of a Novel Organocatalyst

Analysis of complex viscosity and shear thinning behavior in poly (lactic acid)/poly (ethylene oxide)/carbon nanotubes biosensor based on Carreau–Yasuda model

Abstract The complex viscosity of poly (lactic acid) (PLA)/poly (ethylene oxide) (PEO) blends and PLA/PEO/carbon nanotubes (CNT) biosensor as a function of frequency is measured and analyzed by Carreau–Yasuda model. This model correlates the complex viscosity to zero complex viscosity, relaxation time, power-law index as well as the shear stress and the width of the transition region between Newtonian and power-law behavior. The impacts of these parameters on the complex viscosity are justified to confirm the Carreau–Yasuda model. The calculations of Carreau–Yasuda model successfully agree with the experimental data at different frequency ranges. The prepared samples show different levels for parameters explaining the shear thinning behavior. A high zero complex viscosity, poor relaxation time, high power-law index, low frequency and a wide transition region between Newtonian and power-law behavior enhance the complex viscosity of samples. Among the studied parameters, the power-law index and the width of the transition region significantly change the complex viscosity. The prepared samples can develop the nano-bio-sensors for detection of various diseases such as cancer.

The behavior of compatibility of Ap-g-PHMA to impact polypropylene/kenaf fibres composites

In this research, the behavior of poly(hexyl methacrylate (PHMA) grafted to Amylopectin (Ap-g-PHMA) as a compatibilizer on isotactic polypropylene (iPP)/kenaf fibres composites was studied. In order to improve interfacial interaction between hydrophilic kenaf fibre and hydrophobic matrix polypropylene (PP), Ap-g-PHMA is used as a compatibilizer. Field Emission Scanning Electron Microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), and mechanical testing were used for the composite characterization. The properties of binary and ternary systems have been analysed as a function of both fibre and compatibilizer content. All compatibilizer systems showed enhanced fibre dispersion and interfacial adhesion. It was found that using Ap-g-PHMA has a significant effect on composite properties. Fibre loading at 40% ratio showed very good effect regarding mechanical properties with 1% compatible agent. It is concluded, that incorporation of coupling agent had shown a better result than that of without it at a certain level of fibre loading.

Three different mechanisms of self-discharge behavior in poly(vinylidene fluoride-hexafluoropropylene) for dielectric energy storage

Poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) has attracted attention as a matrix material for nanodielectrics, combining the high electrical breakdown of the polymer with the high permittivity of nanoparticles for improved energy storage properties. Although a large number of published works have reported increased discharged energy density for various nanocomposites, polarization and conduction loss mechanisms are rarely investigated. The latter are closely linked to the self-discharge behavior, which is crucial for future applications. This work aims to improve knowledge about loss and self-discharge mechanisms in doctor-blade-coated P(VDF-HFP) since its role in nanodielectrics is not fully understood. Combined analysis of cyclic unipolar electric displacement–electric field (D–E) characteristics and charging–lift–discharging measurements, where the measurement tip is lifted for a specific time between charging and discharging processes, reveals three Debye processes with different relaxation times: 20, 130 and 1340 s. The fast one correlates with the intrinsic conductivity of the polymer, which is dominated by space charge at high electric fields. The other two processes appear to saturate at an electric field of 100 MV m−1 so that their contribution to permittivity drops.

Effects of magnetic field and temperature on the density of states of the poly(dA)-poly(dT) DNA molecule

Charge-transport behavior in poly(dA)-poly(dT) DNA molecules is indicated by the distribution of density of states (DOS) at different electron energies. The DOS of DNA molecules in the presence of magnetic field and temperature is calculated using the tight-binding Hamiltonian and Green’s function. The molecule in question consists of 32 base pairs of adenine (A) and thymine (T) in the interior, and a sugar phosphate backbone as the exterior. Electron hopping along the backbone sites is possible with this structure. The DNA molecule is connected to metallic electrodes at both ends. In the model, an external magnetic field modifies the electron-hopping constant through the Peierls transition. Temperature affects the molecule by generating a twisting motion among the base pairs. The results show that temperature and magnetic field limit the DOS of the DNA molecule for a given electron energy. Electrons can occupy all states in the energy spectrum, which are localized states, at temperatures considerably higher than zero.

RAFT mediated miniemulsion copolymerization of ethylene and BMA and their non-isothermal model-free kinetic analysis

Miniemulsion copolymerization of ethylene and butyl methacrylate (BMA) was carried out at 60 °C using 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid as the reversible addition fragmentation chain transfer (RAFT) agent, sodium dodecyl sulphate as emulsifier and potassium per sulphate as free radical initiator under extremely low ethylene feed pressure of 5–20 bar. In the absence of a co-stabilizer, very stable emulsion was obtained, wherein the RAFT agent acted both as the chain transfer agent and as the co-stabilizer. FT-IR as well as NMR analysis established the formation of poly(ethylene-co-BMA) copolymer nanoparticles. The SEM analysis was used to study the morphological behaviour of poly(ethylene-co-BMA) copolymer nanoparticles. DLS analysis confirmed that the particle diameter Zavg of copolymer nanoparticles is in the range 100–140 nm and confirmed miniemulsion polymerization. In order to establish the stability of copolymers against thermal degradation, the kinetics and mechanism of thermal degradation of copolymers were investigated by thermogravimetric analysis. Thermogravimertic analysis established that thermal decomposition of poly(ethylene-co-BMA) copolymer nanoparticles occurred in the range 250–450 °C. This range is lower than the decomposition temperature of neat polyethylene (350–580 °C). Kinetic parameters were determined according to the model-free approaches of Friedman and Flynn–Wall–Ozawa. The multivariate nonlinear regression analysis was performed to determine the kinetic model and the corresponding kinetic triplets.

Synthesis of chloromethyl benzimidazole grafted polybenzimidazole with enhanced UV absorption and its effect as a stabilizer on the ultraviolet‐aging behaviors of poly(vinyl chloride) films

ABSTRACTPoly(vinyl chloride) (PVC) is particularly susceptible to UV damage, and its durability can be reduced substantially when it is exposed to outdoor environments. In this study, high‐molecular‐weight polybenzimidazole (PBI) was synthesized and then grafted with 2‐chloromethyl benzimidazole. The polybenzimidazole grafted with 2‐chloromethyl benzimidazole (PBI‐g‐CMBeIm) could absorb over 99% of UV light in the region 220–420 nm. Then, PVC–PBI‐g‐CMBeIm blend films were prepared by a solution‐casting method, and the effects of the PBI‐g‐CMBeIm content and UV‐irradiation time on the properties of these films were investigated. The results show that the benzimidazole moieties incorporated into the macromolecular chain of PBI provided additional conjugation units, and this allowed the films to have a stronger UV absorption and broader λ range. The yield strength of the PVC–PBI‐g‐CMBeIm blend films irradiated for 1000 h ranged from 16.5 to 27.7 MPa; this increased 3.2–14.4 MPa compared with that of the pure PVC. The strength retention rate of the pure PVC was 28.8%, whereas that of the PVC–PBI‐g‐CMBeIm blend films was in the range 34.1–55.2%. The addition of PBI‐g‐CMBeIm also effectively increased the thermal degradation temperature of the blend films and slowed down their thermal degradation rate. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47626.

Spatial patterns of travel behaviour in Poland

Abstract Proper investigation of travel behaviour – its spatial variability and determinants, is a key factor in correct national and local policy-making on transport. In this paper we try to identify the main features of travel behaviour in Poland as well as its relationship to travellers’ places of residence and destinations. This is the first such an attempt in Poland, and is based on the travel behaviour data of 26,000 Poles. The data was obtained in 2015 and released by the Central Statistical Office; previously such information hasn’t been available. The survey reveals that despite the different path of socio-economic and political development, the travel behaviour of Poles isn’t very different from that observed in Western and Northern Europe. The car is the dominant means of transport; our travelling relies heavily on commuting; and we also tend to cover similar distances. What makes Poland a little bit different is that fewer journeys are made each day. Travel behaviour is affected more by the type of area where the travellers live (urban/rural) than by the location of this area in the settlement system (urban/peripheral regions).

Analysis of orientation behavior in poly(lactic acid) billets during extrusion using a finite element method and chain network model

Analysis of orientation behavior in poly(lactic acid) billets during extrusion using a finite element method and chain network model

Novel biodegradable composites based on PHBV: Effect of nanocellulose incorporation on the non‐isothermal crystallization kinetic and structural parameters

This study presents the non‐isothermal behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) biodegradable films with 1–5 wt% of cellulose nanoparticles (CNs) manufactured by solution casting using N,N‐dimethylformide and chloroform as the solvents. X‐ray diffraction and scanning electron microscopy with field emission gun were performed for CNs in order to determine its morphology and crystalline properties. The effect of non‐isothermal crystallization of PHBV and its nanocomposites was studied using differential scanning calorimetry technique. The incorporation of CNs increases the crystallization rate with up to 3 wt%. Structural parameters were studied using positron annihilation lifetime spectroscopy and small‐angle X‐ray scattering. The free volume does not change upon CNs addition in spite of form less perfect crystals and increase the lamellar thickness. POLYM. COMPOS., 40:3156–3165, 2019. © 2018 Society of Plastics Engineers