Fabrication of poly(lactic acid) films with resveratrol and the diffusion of resveratrol into ethanol

Poly(94% L ‐lactic acid) (PLA) films containing 0, 1, and 3 wt % resveratrol (PR0, PR1, and PR3) were extruded in a pilot‐plant scale blown‐extrusion machine. Yellow‐colored PLA films with reduced crystallinity were obtained, and the films absorbed UV‐visible light at 350–200 nm. The diffusion kinetics of resveratrol into ethanol at 9, 23, 33, and 43°C displayed Fick's behavior, and diffusion coefficients between 10⁻¹³ and 10⁻¹⁰ cm²/s were obtained. According to the Arrhenius equation, the energy of activation for the diffusion of resveratrol from PR1 and PR3 films was 175 and 177 kJ/mol, respectively. The temperature of diffusion had a stronger effect on the reduction of the weight average molecular weight of PLA than the processing conditions and the contact time with ethanol. However, diffusion of resveratrol was not affected by the degradation of PLA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Gas barrier and wetting properties of whey protein isolate‐based emulsion films

The aim of this research was to investigate the effect of rapeseed oil concentration (1–3% w/w) on the water vapor, oxygen and carbon dioxide permeability, water vapor sorption and surface properties of whey protein isolate emulsion‐based films. The water contact angle as affected by oil content, film side and time was analyzed. The effect of temperature (5 and 25°C) on the water vapor permeability (WVP), water vapor sorption kinetics and diffusion coefficient was also studied. The results showed that the incorporation of a lipid phase to whey protein film‐forming solutions was able to decrease the WVP, water hydrophilicity (increasing water contact angle) and water transfer of whey protein films. However, the films containing oil were more permeable to oxygen and carbon dioxide. Significantly higher values of WVP and diffusion coefficient were obtained at 5°C than at 25°C, indicating that storage temperature should be taken into account when designing the composition of edible films and coatings for food applications. POLYM. ENG. SCI., 59:E375–E383, 2019. © 2018 Society of Plastics Engineers     

Water sorption behaviors of the BPDA‐based polyimide films depending upon the structural isomers of diamine

For the biphenyltetracarboxylic dianhydride (BPDA)‐based polyimide thin films, the water sorption behaviors were gravimetrically investigated by using a thin film diffusion analyzer. The water sorption behaviors of the polyimide thin films are quite different and strongly dependent upon the sort of polyimide. The diffusion coefficients of the polyimide thin films vary in the range of 1.6 × 10⁻¹⁰ to 12.4 × 10⁻¹⁰cm²/s and the water uptakes vary from 1.52 to 5.25 wt %. Both the diffusion coefficient and water uptake of the polyimide thin films are in the increasing order: BPDA‐pPDA < BPDA‐p,p′ODA < BPDA‐p,m′ODA < BPDA‐mPDA ∼ BPDA‐p,p′DDS < BPDA‐m,m′DDS. Specifically, the polyimide films with para‐oriented linkages in backbone structure showed relatively lower diffusion coefficient and water uptake than the corresponding polyimide films with meta‐oriented linkages because of the well‐developed crystalline structure and good intermolecular chain ordering. In addition, the polyimide thin films having higher chain order showed relatively lower diffusion coefficient and water uptake. The crystallinity and intermolecular chain ordering in the morphological structure are critical parameters in controlling the water sorption behaviors of the polyimide thin films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2121–2127, 2001     

Water‐sorption behavior of P‐phenylene diamine–based polyimide thin films

Four different p‐PDA–based polyimide thin films were prepared from their respective poly(amic acid)s through thermal imidization at 400°C: poly(p‐phenylene pyromellitimide) (PMDA‐PDA); poly(p‐phenylene biphenyltetra carboximide) (BPDA‐PDA); poly(p‐phenylene 3,3′,4,4′‐oxydiphthalimide) (ODPA‐PDA); and poly(p‐phenylene 4,4′‐hexafluoroisopropylidene diphthalimide) (6FDA‐PDA). Water‐sorption behaviors of polyimide films were gravimetrically investigated at 25°C and 22–100% relative humidity by using the modified electromicrobalance (Thin Film Diffusion Analyzer). The diffusion coefficients of water for the polyimides varies in the range of 1.6 to 10.5 × 10⁻¹⁰ cm²/s, and are in the increasing order: BPDA‐PDA < PMDA‐PDA ∼ ODPA‐PDA < 6FDA‐PDA. The water uptakes of polyimides vary from 1.46 to 5.80 wt %, and are in the increasing order: BPDA‐PDA < ODPA‐PDA < 6FDA‐PDA < PMDA‐PDA. The water‐sorption behaviors for the p‐PDA–based polyimides are closely related to the morphological structure; specifically, the diffusion coefficients in p‐PDA–based polyimide thin films are closely related to the in‐plane orientation and mean intermolecular distance, whereas the water uptakes are affected by the packing order. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1315–1323, 2000     

Water and temperature response of semi‐IPN hydrogels composed of chitosan and polyacrylonitrile

Temperature‐responsive semi‐interpenetrating polymer networks (semi‐IPNs) constructed with chitosan and polyacrylonitrile (PAN) were crosslinked with glutaraldehyde. The semi‐IPN determined the sorption behavior of water at several temperatures and at a relative humidity (RH) of 95% using a dynamic vapor sorption (DVS) system. Water diffusion coefficients of semi‐IPNs were calculated according to the Fickian Law at several temperatures and exhibited a relatively water uptake, 0.1–0.4 at room temperature. The water uptake of hydrogels depended on temperature. The apparent activation energy was dependent of the composition of the semi‐IPN with value of 32.8–34.8 kJmol^?1. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 12: 2721–2724, 2003     

Water‐transport properties in polyetherimide blends with a liquid crystal polymer

The effect of the addition of a liquid crystal polymer (Rodrun^®) on the sorption and transport properties of water through films of a polyetherimide (PEI, Ultem 1000) was investigated. A Cahn electrobalance was employed for measuring the water uptake by the polymer samples. Sorption measurements were made with films of PEI, Rodrun, and heterogeneous PEI/Rodrun blends at different water activities at 30°C. In all cases, diffusion and sorption coefficients decreased when the amount of Rodrun increased. Values of the water‐sorption isotherms were adjusted to different models. Permeabilities for the different samples were indirectly obtained using experimental values of the solubility and diffusion coefficients described above. Furthermore, permeabilities of the binary composite material were calculated on the basis of those of the pure components and some theoretical assumptions concerning blend morphology. Results were consistent with a Rodrun structure in the composite intermediate between a fibrillar and a laminar morphology. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 323–332, 1999     

Sorption and diffusion of water vapor in poly(ethylene terephthalate) film

The sorption and diffusion of water vapor in poly(ethylene terephthalate) (PET) film were measured by applying a thermogravimetric analyzer (TG‐DTA), which customarily has been used to detect the weight loss of a sample with the increase of temperature under a given atmosphere. In this case, we detected the weight gain of PET film by sorption of water vapor under a given humidity at a constant temperature. Sorption‐rate curves were successfully obtained in spite of the low solubility of PET film and the presence of Fickian‐type curves. The solubility was better described according to the dual‐mode sorption model. The diffusion coefficients were determined in their initial slopes by the short‐time method. We found that the diffusion coefficient depended on vapor pressure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 67–74, 2000     

Controlling water permeability of composite films of polylactide acid,cellulose, and xyloglucan

To test the hypothesis that the introduction of a hydrophilic hemicellulose would affect viscoelastic properties and increase water permeability, xyloglucan (XG) was adsorbed onto the surface of microcrystalline cellulose (MCC) in water dispersion prior to the extrusion of 79–80 wt % polylactide acid (PLA), 20 wt % MCC, and 0–1 wt % XG. For comparison, composites of PLA, MCC, and non‐absorbed XG were produced. Analysis of thermal properties showed no differences for glass‐transition or melting temperatures, but the crystallinity of the films increased with the addition of MCC and XG. Storage modulus of the composite materials increased with XG content; however, at higher humidities storage modulus decreased, probably because of lower interfacial adhesion. Water permeability through the films increased more with the addition of XG adsorbed to the MCC than with the MCC and XG simply mixed in the same amounts. © 2014 The Authors. Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41219.     

Micromorphology,mechanical, crystallization and permeability properties analysis of HA/PBAT/PLA (HA,hydroxyapatite; PBAT,poly(butylene adipate‐co‐butylene terephthalate); PLA,polylactide) degradability packaging films

In this study, the self‐made nano‐hydroxyapatite (HA) and poly(butylene adipate‐co‐butylene terephthalate) copolyesters (PBAT) were used as fillers, and composite films of HA/PLA (PLA, polylactide) and HA/PBAT/PLA systems were prepared. The micromorphology, mechanical properties, thermal properties, crystallinity, water vapor permeability and oxygen permeability of the composite films were studied. The results show that the self‐made HA has a porous rod‐like structure with a size of 30–50 nm. PBAT was dispersed uniformly in the HA/PLA matrix in the form of spherical particles and formed many pores and holes. The tensile strength, elongation at break and modulus of elasticity of HA/PLA composite films were increased by adding 10 wt% PBAT. The addition of HA and PBAT played a synergistic function in improving the crystallinity of the composite films. The water vapor and oxygen permeabilities of HA/PLA and HA/10%PBAT/PLA composite films can be regulated by adjusting the amount of HA. The results of this study indicate that composite films with higher water vapor and oxygen permeabilities exhibit great potential for applications in green packaging and fresh‐keeping packaging. © 2019 Society of Chemical Industry     

Water sorption and water‐resistance properties of poly(vinyl alcohol)/clay nanocomposite films: Effects of chemical structure and morphology

A series of poly(vinyl alcohol)/sodium montmorillonite (PVA/NaMMT) nanocomposite films were prepared via a solution method, and their water sorption and water‐resistant properties were investigated as a function of clay content. The water sorption and water resistance properties were strongly dependent on the chemical structure and film morphology originating from the NaMMT content. The water diffusion coefficient and water uptake of the PVA/NaMMT nanocomposite films were obtained by best fits to a Fickian diffusion model. The diffusion coefficient and water uptake in the PVA/NaMMT nanocomposite films varied between 8.16 × 10⁻¹⁰ and 3.60 × 10⁻¹⁰ cm² s⁻¹ and 35.6 and 29.9 wt%, respectively. Both the diffusion coefficient and water uptake decreased as the content of NaMMT in pure PVA was increased. Additionally, the water resistance pressure (mm) of the PVA/NaMMT nanocomposite films increased with increasing NaMMT content. Contact angle analyses showed that the chemical affinity to water and the surface energy of the nanocomposite films decreased with increasing NaMMT content. Furthermore, the well‐dispersed and exfoliated structure in the nanocomposite films not only induced an increased tortuous path for water molecules to pass through, but also increased the molecular order. However, to enhance the water sorption properties and water resistance of hydrophilic PVA, further studies to increase the dispersion of clay particles and ensure desired morphological qualities such as crystallinity and molecular packing order in the PVA/clay nanocomposite films are required. POLYM. COMPOS., 36:660–667, 2015. © 2014 Society of Plastics Engineers     

Desiccant films made of low-density polyethylene with dispersed calcium oxide: Water vapor absorption,permeation and mechanical properties

Polymers with dispersed desiccants are relevant for various packaging applications to protect packaged goods from water vapor. The intention of this study was to analyze and to describe a relevant system. Therefore, films with calcium oxide (CaO) were investigated, because such materials are hardly described in scientific literature. Monolayer films with 0.14 to 0.51 g dispersed CaO per 1 g film (PE-LD) were prepared and they absorbed up to 0.2 g water vapor per 1 g of film. The water vapor absorption was described by effective diffusion coefficients. By the use of effective diffusion coefficients and the absorption capacity, the absorption behavior of layers with various thicknesses can be estimated. The steady state (effective) water vapor permeation coefficients of the films with dispersed CaO were a factor of 2 to 24 (8.4 to 101.5 mg cm [cm² s Pa]^–1 × 10¹², at 23 °C) higher than for pure PE-LD films (4.26 mg cm [cm² s Pa]⁻¹ × 10¹², 23 °C). The tensile stress changed only slightly (pure PE-LD: 9.5 N mm⁻²; PE-LD with 0.14 g dispersed CaO per 1 g film: 8.1 N mm⁻²; PE-LD with 0.51 g dispersed CaO per 1 g film: 10.5 N mm⁻²), while the tensile strain at break was reduced with higher CaO concentration from 318% (pure PE-LD) to 10% (PE-LD with 0.51 g dispersed CaO per 1 g film). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47460.     

The Fabrication and Characterization of Cellulose/Mesoporous Silica Composites Packaging Films with Adjustable Permeability by NMMO Technology

Cellulose-based composites containing various amounts of SBA-15 mesoporous silica were prepared by NMMO-technology, and their morphologies, mechanical properties, permeability for oxygen and water vapor were studied. The investigation suggested that both the modified and unmodified mesoporous silica materials can improve the elongation at break of the cellulose films. However, the incorporation of the mesoporous silica materials can reduce the tensile strength of the films, and the modified one has less effect on that than the unmodified one. The composites films with rational mechanical properties have adjustable oxygen permeability (7.90 × 10^?15–94.6 × 10^?15 cm³ · cm/cm² · s · Pa) and water vapor permeability (7.12 × 10^?13–4.10 × 10^?13 g · cm/cm² · s · Pa).     

Effect of compatibilization on the oxygen‐barrier properties of poly(ethylene terephthalate)/poly(m‐xylylene adipamide) blends

The improvement of the oxygen‐barrier properties of poly(ethylene terephthalate) (PET) via blending with an aromatic polyamide [poly(m‐xylylene adipamide) (MXD6)] was studied. The compatibilization of the blends was attempted through the incorporation of small amounts of sodium 5‐sulfoisophthalate (SIPE) into the PET matrix. The possibility of a transamidation reaction between PET and MXD6 was eliminated by ¹³C‐NMR analysis of melt blends with 20 wt % MXD6. An examination of the blend morphology by atomic force microscopy revealed that SIPE effectively compatibilized the blends by reducing the MXD6 particle size. Thermal analysis showed that MXD6 had a nucleating effect on the crystallization of PET, whereas the crystallization of MXD6 was inhibited, especially in compatibilized blends. Blending 10 wt % MXD6 with PET had only a small effect on the oxygen permeability of the unoriented blend when it was measured at 43% relative humidity, as predicted by the Maxwell model. However, biaxially oriented films with 10 wt % MXD6 had significantly reduced oxygen permeability in comparison with PET. The permeability at 43% relative humidity was reduced by a factor of 3 in compatibilized blends. Biaxial orientation transformed spherical MXD6 domains into platelets oriented in the plane of the film. An enhanced barrier arose from the increased tortuosity of the diffusion pathway due to the high aspect ratio of MXD6 platelets. The aspect ratio was calculated from the macroscopic draw ratio and confirmed by atomic force microscopy. The reduction in permeability was satisfactorily described by the Nielsen model. The decrease in the oxygen permeability of biaxially oriented films was also achieved in bottle walls blown from blends of PET with MXD6. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1361–1370, 2005     

Development and Characterisation of Electrically Conductive Polymeric‐Based Blends for Proton Exchange Membrane Fuel Cell Bipolar Plates

The main objective of this work was to develop films with controlled dimensions for proton exchange membrane fuel cell (PEMFC) bipolar plates (BPPs) using the twin‐screw extrusion process. These films consisted of a low‐viscosity polyethylene terephthalate (PET) in which a mixture of high specific surface area carbon black (CB) and synthetic flake graphite (GR) were dispersed. A third conductive additive, consisting of silver‐coated glass particles (SCG) or multi‐walled carbon nanotubes (MWCNT), was also added at a low concentration (5 wt.‐%) in order to study its synergistic effect on the PET‐based blend electrical conductivity. As the developed blends had to meet properties suitable for PEMFC bipolar plate applications, they were characterised for their electrical through‐plane resistivity, mechanical properties and oxygen permeability. Through‐plane electrical resistivity of about 0.3 Ω·cm and oxygen permeation rate of 3.5 × 10^–8 cc cm^–2 s^–1 were obtained for only 30 wt.‐% of a 60:40 mixture of CB/GR conductive additives. Although the substitution of 5 wt.‐% of CB/GR by the same amount of MWCNT had no significant effect on BPPs' electrical resistivity, it helped to improve their mechanical properties and especially their oxygen permeation, which was decreased from 3.5 × 10^–8 cc cm^–2 s^–1 to around 0.6 × 10^–8 cc cm^–2 s^–1.     

Transport and dielectric properties of poly(ethylene terephthalate) as determined via electrochemical techniques

The electrochemical impedance spectroscopy (EIS) technique was used to evaluate the water transport (diffusion and equilibrium water uptake) and the dielectric properties of free-standing poly(ethylene terephthalate) (PET) membranes at 40°C. Permeability and diffusion coefficients were also obtained using the Payne cup method and the MacBain quartz spring balance to assess the reliability of the EIS method when compared to other techniques. In addition, an electromigration (dc) technique was used to estimate the NaCl diffusion coefficient across PET films. Results obtained indicate that PET is highly permeable to water and much less permeable to salt. The water diffusion coefficient, D, varies from 2.11× 10^?9 to 9.97× 10^?9 cm²s^?1 for thicknesses between 22 and 205μm, whereas the equilibrium water uptake, W, varies from 0.54 to 0.95 wt % for the same given range of thicknesses. The average calculated dielectric constant of the free-standing PET films is 3.6. An estimate of the NaCl diffusion coefficient, D_s, is 9.34× 10^?14 cm²s^?1. Transport properties results obtained via the electrochemical technique are in reasonable agreement with those obtained with the classical gravimetric method. © 1993 John Wiley & Sons, Inc.     

Carbon dioxide sorption and diffusion in poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐CO‐3‐hydroxyvalerate)

CO₂ sorption and diffusion in poly(3‐hydroxybutyrate) and three poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) copolymers were investigated gravimetrically at temperatures from 25° to 50°C and pressures up to 1 atm. The sorption behavior proved to be linear for all the copolymers studied. An additional set of measurements performed in a pressure decay apparatus at 35°C showed that the linearity could be extrapolated to pressures up to 25 atm. The sorption results obtained from both techniques were in good agreement. The poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) sorption kinetics were increasingly non‐Fickian at the higher temperatures, thus preventing the calculation of diffusion coefficients above 35°C. Interestingly, this was not the case for poly(3‐hydroxybutyrate), and diffusion coefficients and permeabilities could be calculated at all of the investigated temperatures. The 35°C permeabilities were fairly low, which is attributed to the high degree of crystallinity of this polyester family. Finally, the poly(3‐hydroxybutyrate) barrier properties against CO₂ are successfully compared with those of some selected common thermoplastics. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2391–2399, 1999     

Effect of hydrophobic hexafluoroisopropylidene group on the water sorption behaviors of rigid poly(p‐phenylene pyromellitimide) polyimide thin films

We prepared poly(p‐phenylene pyromellitimide) (PMDA–PDA), poly(p‐phenylene 4,4′‐hexafluoroisopropylidene diphthalimide), and their copolyimides with various compositions to explore the relationship between the water sorption and structure. The water sorption behaviors were gravimetrically investigated as a function of composition and temperature and interpreted with a Fickian diffusion model in films. Overall, the water sorption behaviors were strongly dependent on the changes in morphological structure, which originated from the variations in composition. When the content of the bulky hexafluoroisopropylidene group (6FDA) was increased, the water uptake decreased from 5.80 to 3.18 wt %, whereas the diffusion coefficient increased from 3.6 × 10^?10 to 11.3 × 10^?10 cm²/s. The relatively high water uptake in the PMDA–PDA polyimide film was successfully healed by the incorporation of 6FDA, which may have resulted from the increases in the intermolecular packing order and hydrophobicity. The degree of orientation and crystallinity, which are in‐plane characteristics, were directly correlated to the diffusion coefficient and activation energy in the polyimide film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3442–3446, 2003     

Water vapor sorption and transport in dense polyimide membranes

The sorption and transport of water vapor in five dense polyimide membranes were studied by thermogravimetry. The sorption isotherms of water vapor in the polyimides could be successfully interpreted by both the dual‐mode sorption model and the Guggenheim–Anderson–de Boer equation. The water vapor diffusion behavior was found to be nearly Fickian at higher water vapor activities, whereas non‐Fickian diffusion was observed at lower water activities. The phenomena could be well described by the mechanism of combined Fickian and time‐dependent diffusion. The diffusion coefficient and water vapor uptake in the polyimides were strongly dependent on the polymer molecular structure. Except for the polyimide prepared from 3,3′,4,4′‐diphenylsulfone tetracarboxylic dianhydride and 1,3‐bis(4‐aminophenoxy) benzene, the permeability of water vapor in the dense polyimide membranes predicted from the sorption measurement at 30°C corresponded well with the water vapor permeability measured at 85°C. Among the polyimides studied, pyromellitic dianhydride–4,4′‐diaminophenylsulfone (50 mol%)/4,4′‐oxydianiline (50 mol%) showed both high water sorption and diffusion and, therefore, high water vapor permeability, which for vapor permeation membranes is necessary for the separation of water vapor from gas streams. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2306–2317, 2003     

Sorption and permeation of acetic acid–water mixtures by pervaporation using copolymer membrane

Poly (acrylonitrile‐co‐methyl acrylate) copolymer designated as PANMA was used for making pervaporation membrane. This membrane was used for separation of acetic acid–water mixtures over the concentration range of 80–99.5 wt% acetic acid in water. Interaction parameters based on Flory–Huggins lattice model and engaged species induced clustering (ENSIC) model was used to explain swelling of the membranes. Coupling in sorption was explained in terms of activity coefficient of water and acid in feed and membrane using Flory–Huggins model and also by interpolating ENSIC parameters. Flow coupling in pervaporation was also determined from phenomenological deviation coefficients. Intrinsic membrane properties like partial permeability and membrane selectivity of the solvents were also determined. Diffusion coefficient and plasticization coefficient of the solvents were obtained using a modified solution–diffusion model. The copolymer membrane showed high flux and water selectivity for highly concentrated acid. Thus, at 30°C temperature 1–20 wt% water in feed was concentrated to 82–84 wt% water in permeate and for 0.95 wt% water in feed, the membrane showed thickness normalized flux and water selectivity of 1.71 kg m^?2 h^?1 mμ and 409, respectively. OLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Sorption and migration of aliphatic organic esters into VITON® fluoroelastomer membranes

Sorption and migration of six aliphatic esters into four VITON^® fluoroelastomers were studied by a gravimetric sorption method in the temperature interval of 30–60°C. Fick's equation was used to obtain diffusion coefficients. The dependence of fluorine contents and the polymer morphology on the sorption and diffusion characteristics of esters was investigated. The permeability coefficients were obtained from the sorption and diffusion data. Fick's equation was solved to compute the concentration profiles of liquids at various locations within the membrane materials using initial and boundary conditions. These profiles were compared with those obtained from the numerical method based on finite difference technique. Activation parameters for diffusion and sorption were calculated using the Arrhenius relationship. These results were discussed in terms of molecular size and shapes of the esters. For higher esters, namely, n- and iso-amyl acetates, a concentration dependency of the diffusion coefficient was investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1223–1235, 1997