Permeation of volatile organic compounds across polymer films—Part I: Development of a sensitive test method suitable for high-barrier packaging films at very low permeant vapour pressures

The development of a permeation measurement cell based on the classical principle of permanent gas permeation testing, according to Barrer, and application of a practical procedure for permeant adsorption and subsequent gas chromatographic determination is described. For validation of the method, the permeation of d-limonene across a biaxially oriented polypropylene film (BOPP) was measured and the results were compared with those obtained according to the pouch method and with permeation data from the literature. The applicability and high sensitivity of the test method was demonstrated by measuring limonene permeation through an acrylic-coated BOPP film and a polyethylene terephthalate (PET) film and using permeants of different polarity and volatility, i.e. menthol and citronellol. From the results obtained from the uncoated and from the acrylic-coated OPP films, the permeation and diffusion coefficients of the acrylic barrier layer were calculated and shown to be three to four logarithmic orders of magnitude smaller than those of BOPP.     

Development and evaluation of organic vapour permeation system for packaging applications

This paper reported the permeability of four different organic compounds in low‐density polyethylene (LDPE), ethylene vinyl alcohol (EVOH), and in a multilayer film composed of them through the isostatic flow permeation measurement system. The methodology assumed that the nitrogen feed stream is saturated with organic vapour, and a chromatographic technique was used as a detector for the quantification of the permeate. The results were in general good agreement with literature reports, providing accuracy and reliability of measurement procedures. The permeability of LDPE increased with increasing hydrophobicity of organic compounds, but hydrophilic EVOH suggesting that there had been an effect of functional groups on permeability behaviour. The multilayer films were observed larger than expected because of the interface responsible for adhesive bonding of tie resins to EVOH by chemical interactions. Nonetheless, as an application of such multilayer structures, we suggested the method studied as feasible and possible tools for characterizing permeation properties against organic vapours.     

Water permeation through organic-inorganic multilayer thin films

We prepared organic (self-assembled monolayer (SAM))-inorganic (TiO₂) multilayer barrier films on polyethylene terephthalate substrate using atomic layer deposition and molecular layer deposition methods in the same deposition chamber. The water permeation was mainly blocked by the inorganic TiO₂ layer. While the lag time was proportional to the thickness of the TiO₂ layer, the steady-state permeation rate was relatively independent of the thickness. The multilayer approach was effective in extending the lag time due to both the tortuous path effect and the internal desiccant effect. Water permeation occurred sequentially in the organic-inorganic multilayer barriers by water accumulation in the organic SAM layers. The water vapor transmission rate was 7.0 × 10^− 4 g/m²·day during the lag time of 155 h at 60 °C and a relative humidity of 85% with 5-dyad barrier film.     

GKSS渗透汽化和蒸气渗透技术

介绍了德国GKSS研究中心高性能渗透汽化膜的开发、膜组件及系统设计．分析了GKSS渗透汽化和蒸气渗透技术的工业应用现状．     

蒸汽渗透法有机溶剂气相脱水

蒸汽渗透法是一种膜法气相脱水技术，与渗透汽化不同，在该过程中，进料的蒸汽与膜直接接触，在高于料液沸点的温度下进行操作，可以采用提高压力和温度等手段提高分离膜的透过通量，并可以与分馏过程集成使用，简化化工操作单元，要求所使用的膜具有更好的高温耐溶性性能。文章综述近几年２５篇有关文献，介绍蒸汽渗透过程的特点、与渗透汽化的对比、使用的膜以及其应用前景。     

聚二甲基硅氧烷膜蒸汽渗透分离低浓度乙醇/水溶液的研究

对聚二甲基硅氧烷(PDMS)膜蒸汽渗透分离低浓度乙醇/水溶液的性能进行了研究,考察了料液浓度、膜器温度、循环气体流量、真空度等因素对PDMS膜蒸汽渗透性能的影响.结果表明,渗透通量和渗透侧乙醇浓度随着料液中乙醇浓度的增大而增大,但分离因子有所降低;随着膜器温度的升高,渗透通量增加,渗透侧乙醇浓度下降,影响显著;随着循环气体流量的增大,渗透通量和渗透侧乙醇浓度均有较大幅度的提升,有利于蒸汽渗透过程的进行;随着真空度的增大,渗透通量上升,渗透侧乙醇浓度下降.     

Sodium alginate/poly(vinyl alcohol) alloy membranes for the pervaporation, vapour permeation and vapour permeation with temperature difference separation of dimethylformamide/water mixtures: A comparative study

In this study, sodium alginate (NaAlg)/poly(vinyl alcohol) (PVA) membranes were prepared for the separation of dimethylformamide (DMF)/water mixtures. The two polymer components were independently crosslinked chemically with glutaraldehyde. The crosslinked membranes were characterized by fourier transform infrared spectrometry (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). The permeation and separation characteristics of water/DMF mixtures were investigated using the vacuum processes pervaporation (PV), vapour permeation (VP) and vapour permeation with temperature difference (TDVP) methods. The effects of NaAlg/PVA ratio, membrane thickness, operating temperature and temperature of the membrane surroundings, feed concentration on the transmembrane permeation rate and separation factor were investigated. Optimum NaAlg/PVA ratio was determined as 80/20 (w/w) for the separation. The permeation rate in VP was lower than those in PV, whereas the separation factors were higher. The activation energies of permeation in PV and VP were calculated to be 5.070 and 2.229 kcal/mol, respectively, for a 20 wt% of DMF solution.     

氢渗透电流法监测海洋大气中钢材的腐蚀速率

用Devnathan-Stachurski双电解池技术,对16Mn钢表面干湿循环时氢渗透现象进行了研究,结果表明不同表面液膜下,都有氢渗透电流的存在.氢离子渗透量与试样腐蚀失重之间存在线性关系.利用此线性关系制作的实时监测氢渗透电流的传感器,用以记录实际海洋大气中氢渗透电流,并根据氢离子渗透量与腐蚀失重之间的线性关系对海洋大气中钢材的腐蚀速率进行预测.结果表明,实际海洋大气中,氢渗透电流与环境湿度存在着对应关系,环境湿度由大变小时,氢渗透电流由小变大.环境湿度交替变化,在试样表面完成干湿循环,促进了氢的渗透,实际海洋大气与摸拟海洋大气失重取得了较好的一致性.可以用氢渗透电流传感器实时监测海洋用钢在大气中的氢渗透情况及腐蚀失重情况.     

预处理剂对陶瓷膜表面性质及渗透通量的影响

考察了不同预处理剂对陶瓷膜表面性质及渗透通量的影响,结果表明:表面活性剂的加入,使陶瓷膜表面的负电性以及亲水性得到提高,膜渗透通量从100L/(m2·h)提高到200L/(m2·h);碱式氯化铝中Al3+在膜表面的吸附,导致膜表面呈现正电位,相应的膜渗透通量只有50L/(m2·h);吸附剂对渗透通量的影响主要体现其在乳化废水中表面电位的不同,呈负电性的二氧化硅有利于渗透通量的提高,而呈正电性的氧化铝会导致膜通量的下降.     

Effect of application volume of ethanol-isopropyl myristate mixed solvent system on permeation of zidovudine and probenecid through rat skin

Permeation of zidovudine (AZT) and probenecid from an ethanol-isopropyl myristate (IPM) mixed system through rat skin was studied in a finite system. Several volume sizes of the ethanol-IPM mixed systems containing AZT and probenecid, both as suspensions, were applied on the skin of the hairless rat using a vertical glass cell, and the fractions of the drugs permeated in 8 hr Q_%,8hr were determined. For the systems containing 40% ethanol, the Q_%,8hr value decreased with the reduction of volume of the system applied, and the decreasing profile was similar to that calculated on the assumption that the permeability of the drug does not change with the volume of the sample applied. On the other hand, in the systems containing 10% or 20% ethanol, the Q_%,8hr value showed a maximum when a specific volume of the sample was applied. Therefore, the effect of sample volume on the Q_%,8hr value was different between the 40% ethanol-IPM system and the 10% or 20% ethanol-IPM system. Following pretreatment of the skin with 0.105 ml/cm² of drug-free 40% ethanol-IPM for 2 hr, several volume sizes of 10% ethanol-IPM systems containing the drugs were applied on the skin to explain why the different profiles were observed in the system containing 10% or 20% ethanol. The results for pretreated skin suggest that the amount of ethanol in the systems with low ethanol concentration and small application volume is too small to exert an effect that enhances permeation of the drugs. In those systems, the integrated effect of ethanol on the skin would be important for the enhancing effect. Total volume, as well as concentration, of an enhancer should be set precisely in designing an efficient transdermal delivery system.     

The effect of relative humidity on the permeability of toluene vapour through a multi-layer coextruded film containing hydrophilic layers

The effect of relative humidity on the diffusion of toluene vapour through a multi-layer coextrusion film structure containing moisture sensitive hydrophilic barrier layers (nylon and EVAL) was evaluated. Two experimental test methods were employed. In Method I, the effect of relative humidity on the diffusion of toluene vapour was evaluated, where the test film was preconditioned to a fixed water activity prior to test. In Method II, the effect of water vapour as a co-permeant was evaluated. Studies carried out by Method I showed the concentration dependency of the diffusion process and the importance of relative humidity on the diffusion of organic vapour through barrier structures. Water vapour was found to exhibit strong interactive effects with the moisture sensitive polymer layers of the laminate, which resulted in an increase in the diffusion of toluene vapour through the barrier structure. When the effect of water vapour as a co-permeant was evaluated (Method II), the direction of permeation (i.e. surface exposed to high relative humidity and vapour concentration) markedly influenced the resultant barrier properties.     

Evolution of CO2 permeation properties of LDPE/LLDPE films upon uni‐axial stretching

A range of LDPE/LLDPE films were manufactured by blown and cast extrusion, which were then uni‐axially stretched at regular intervals. The films were analysed to determine the change of diffusion, solubility and permeation coefficient, and the correlation between crystallinity and molecular orientation. It was found that films exhibited a decrease in permeation coefficient with increased uni‐axial stretch as a result in change in crystal type and higher molecular orientation, resulting in a decrease of diffusion and solubility coefficient. This paper shows how double yield phenomena present in the uni‐axial stretching of the LDPE/LLDPE films affect the permeation properties. Copyright © 2008 John Wiley & Sons, Ltd.     

Modification of gellan gum films by halloysite: physicochemical evaluation and drug permeation properties

The aim of this study was to determine the potential of gellan gum (GG) and halloysite (HS) dispersions at different mixing ratios and to investigate the potential of GG-HS dispersions in film formation. To this end, the dispersions and films were characterized. The dispersions formed films with large particles ranging from 3 to 4?μm in size, with a zeta potential of ～?35?mV. The GG-HS films were fabricated using a solvent-casting technique, which generated films with a white opaque appearance and rough surface. The GG-HS films were formed via hydrogen bonding and electrostatic interactions at the inner cavity and outer surface, as confirmed by ATR-FTIR spectroscopy and X-ray diffractometry. The %water uptake and erosion of the GG-HS film decreased with increasing HS content, whereas both puncture strength and elongation were increased in the GG-HS ratios of 1:0.4 and 1:1.2. Moreover, addition of HS into the GG films could possibly decrease drug permeability coefficient when using higher HS ratio in acidic and neutral media. These results suggested that HS modifies the characteristics of the GG used to coat modified-release tablets.     

Measurement of permeability for packaging films to d-limonene vapour at low levels

A method that utilizes permeation cells in conjunction with gas chromatography was developed to measure permeation of d-limonene vapour through packaging materials at very low gradient concentrations. The same method, when properly adjusted, can be used to determine the effect of temperature and relative humidity on permeation. The suitability of the method for its intended use was demonstrated by generating permeation data for polyester (Mylar) and oriented polypropylene (OPP) films at d-limonene vapour concentration gradients as low as 0.54 ppm. The ability to measure permeability at such low concentration levels, where the permeability coefficient approaches a virtually constant value, is of considerable importance. The permeation behaviour of packaging materials at even lower concentrations, most typical of foods, can be obtained by extrapolation. Thus, flavour loss through the package and shelf-life can be estimated in a more reliable manner.     

Effect of urea and pantothenol on the permeation of progesterone through excised rat skin from polymer matrix systems

Standard in vitro permeation experiments, using excised rat skin, were carried out to establish the release profile and permeation behavior of progesterone from polymethacrylate (PMA), polyvinylpyrrolidon (PVP), and polyvinylalcohol (PVA) transdermal systems. Data obtained show significant differences in release characteristics from each polymer systems. The greatest amount of progesterone was released from the PVA system. The influence of urea and pantothenol on progesterone release was also investigated. Release data were compared with the permeation rates of progesterone across excised rat skin. The highest permeation rates were measured from PVA matrices containing 5% urea (860 ± 138 μg/cm²; cumulative amount permeated in 24 hr) and from PVP matrices containing 6% pantothenol (660 ± 73 μg/cm²; cumulative amount permeated in 24 hr). A good correlation between release and permeation data was found with the polymer matrices; however, this was not the case when additives were included.     

A transient method of measuring the water vapour permeability of packaging films. II. Iterative determination of permeability

Principles of the conversion of a measured electrical signal to the relative humidity units have been worked out according to a theory of the method and the measuring system for water vapour permeability through packaging films measurement. The method and the system were based on sorptive sensor reaction inertia analysis. The constants of the measuring vessel were determined by means of the dish method for fixed measurement conditions. Using the developed theory, water vapour permeability was determined for the chosen films. The results obtained were in close agreement with values determined by the dish method and additionally for PET-50 film also in close agreement with the literature data. The uncertainty of the results obtained by this method was estimated. The relative mean uncertainty (α = 0.05) was B_p ≃ 1.1% and the relative maximum uncertainty of a single result B_pmax = 3.1%.     

A transient method of measuring the water vapour permeability of packaging films I. Dynamic performance of a sorptive sensor

Principles of an analysis of the inertia of a sorptive sensor used for transient measurements of water vapour permeability through packaging films have been developed. The construction of the measuring cell and the method of measurement of water vapour permeation through packaging films have been readjusted to the developed principles. It is shown that the inertia of a sorptive sensor, defined as a difference Δ between measured signal value RH* and an estimated value of air relative humidity RH₁ close to the film surface in an input chamber can be described as a difference of exponential functions Δ = RH₀·[exp(−Aτ) − exp(−Bτ)]. The characteristic parameter determining the sensor inertia is the maximum delay time τ_m; the roots of the function Δ(τ) derivative. The theory and procedure for using τ_m for the iterative determination of water vapour permeability through packaging films based on analysis of the sorptive sensor inertia is presented.     

Influence of sorbed vegetable oil and relative humidity on the oxygen transmission rate through various polymer packaging films

In this study, the effect of a vegetable oil on the oxygen barrier properties of different polymer packaging materials [i.e. amorphous polyethylene terephtalate (APET), polypropylene (PP) and high density polyethylene (HDPE)] was investigated. The influence of both relative humidity and the combination of relative humidity and sorbed oil on the oxygen transmission rate (OTR) was studied. Regardless of the relative humidity, the APET film remained an excellent oxygen barrier even after storage in rapeseed oil for 40 days. An increased OTR was observed in both the PP and HDPE films stored for 40 days in rapeseed oil. The OTR of the HDPE films was altered to a much greater extent than the OTR of the PP film. The OTR of the HDPE film was also significantly increased for films stored for 20 days in rapeseed oil. The increase in OTR of an HDPE film stored for 40 days in rapeseed oil was between 36 and 44%, depending on the relative humidity, compared to the OTR through the virginal polymer. The amount of oil sorbed by the polymer films used decreased in the following order: HDPE ? APET > PP.     

Numerical simulation of permeation through vacuum‐coated laminate films

The material usage in the packaging market of Germany has decreased over the last few years. This trend results from the substitution of heavy packages with light‐weight, flexible materials. In this context, aluminium foil‐based multilayer films have been partly replaced by metallized laminates in food packaging technology. Other coating materials, such as Al₂O₃ or SiO_x, are used where transparent films are desired. The disadvantage of these vacuum‐coated layers is the existence of pinholes which allow diffusion processes, in contrast to aluminium foil‐based multilayer films. In this study the barrier behaviour of vacuum coated laminate films was predicted by numerical simulation. The results are presented in terms of dimensionless parameters so that they may be transferred to analogous problems. This model provides a method to calculate the oxygen permeation through coated laminates. However, it is invalid for condensable gases such as water vapour. The simulation is suited for characterizing the influence of the compound structure on the barrier properties of vacuum coated laminate films. The results are verified by comparing the calculated with measured values. Copyright © 2002 John Wiley & Sons, Ltd.     

Effect of nerodilol and carvone on in vitro permeation of nicorandil across rat epidermal membrane

The objective of the study was to investigate the effect of nerodilol and carvone on the in vitro transdermal delivery of nicorandil so as to fabricate a membrane-moderated transdermal therapeutic system. The in vitro permeation studies were carried across the rat epidermal membrane from the hydroxypropyl methylcellulose (HPMC) gels (prepared with 70:30 v/v ethanol-water) containing selected concentrations of a terpene such as nerodilol (0% w/w, 4% w/w, 8% w/w, 10% w/w, or 12% w/w) or carvone (0% w/w, 4% w/w, 8% w/w, 12% w/w, or 16% w/w). The amount of nicorandil permeated (Q₂₄) from HPMC gel drug reservoir without a terpene was 3424.6 ± 51.4 μg/cm², and the corresponding flux of the drug was 145.5 ± 2.2 μg/cm²· h. The flux of nicorandil increased with an increase in terpene concentration in HPMC gel. It was increased ranging from 254.9 ± 3.1 to 375.7 ± 3.2 μg/cm²·h or 207.6 ± 4.7 to 356.7 ± 15.3 μg/cm²· h from HPMC gels containing nerodilol (4% w/w to 12% w/w) or carvone (4% w/w to 16% w/w), respectively. Nerodilol increased the flux of nicorandil by about 2.62-folds whereas carvone increased the flux of the drug by about 2.49-folds across the rat epidermal membrane. The results of the Fourier Transform Infrared (FT-IR) study indicated that the enhanced in vitro transdermal delivery of nicorandil might be due to the partial extraction of stratum corneum lipids by nerodilol or carvone. It was concluded that the terpenes, nerodilol and carvone, produced a marked penetration enhancing effect on the transdermal delivery of nicorandil that could be used in the fabrication of membrane-moderated transdermal therapeutic systems.