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1.
Three different plastic films of biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET) and low‐density polyethylene (LDPE) were perforated using Nd‐YAG laser. Effects of laser pulse energy were examined by varying energies from 50 to 250 mJ where the pulse duration and pulse repetition were kept constant at 10 ns and 1 Hz, respectively. It was found that perforation diameters of all films increased with increasing pulse energies. Observed perforations were different among the three film types. Explanation was contributed to material inherent property and its interaction with laser. Incorporation of an inorganic filler (i.e. silica based anti‐blocking agent used in packaging film) of 0.5 wt% into the LDPE films (0.5Si‐LDPE) could improve perforation performance for LDPE. This was attributed to an increased thermal diffusivity of the 0.5Si‐LDPE film. Commercial BOPET and BOPP films containing 97 microholes/m2 (hole diameter of ~100 µm) showed an improvement in oxygen transmission rates (OTR) of 18 and 5 times that of the neat films without perforation. In the case of perforated 0.5Si‐LDPE films having similar perforations of 97 microholes/m2 and perforation diameter of 100 µm, a two‐fold increase of OTR was obtained. Gas transmission rates of the microperforated films were measured based on the static method. Measured OTR and CO2TR values of the three films with varying perforation diameters in a range of ~40–300 µm were compared and discussed. Overall results clearly indicate that perforation by laser is an effective process in developing breathable films with tailored oxygen transmission property for fresh produce packaging. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

2.
The biaxially oriented poly(lactic acid) films prepared using simultaneous biaxial stretching were perforated by CO2 laser with the power of 60 W. The focal spot diameter was fixed at 103 μm. Pulse durations were varied from 1 to 30 μs, which corresponds to the fluence from 1.4 to 42.6 J/cm2. The perforated microhole size increased with increasing laser energy. The shape of microholes was circular for the films of equi‐biaxial stretching, whereas elliptical microholes were formed with its long and short axes corresponding to the directions of higher and lower stretch ratios, respectively. Comparing the laser perforation behavior of the as‐drawn films and annealed films, the opening of a microhole in the annealed films started at higher laser fluence, and at the same fluence the size of microhole was smaller. Gas transmission rates of the biaxially oriented poly(lactic acid) films with different thicknesses were examined. The oxygen transmission rates (OTR) of film improved with increased microhole diameter. The OTR of films containing 1 microhole/103 cm2 (hole diameter of ~110 μm) was 184, 150, and 98 cm3/d in comparison with the OTR for the original films without microhole of only 16, 10, and 8 cm3/d, respectively. Packaging films with OTR higher than 100 cm3/d (equivalent to the 9700 cm3/m2/d) are required to create a modified atmosphere inside the package of fresh produce for shelf‐life extension. Measured OTR and CO2TR values of the 3 different shapes of microhole were compared and discussed.  相似文献   

3.
盒式气调包装下温度对薄膜透气性能的影响   总被引:4,自引:3,他引:1  
以高阻隔膜、双层膜、聚丙烯(PP)膜及双向拉伸聚丙烯(BOPP)膜为材料,采用小袋法,分析了盒式气调包装下,各薄膜在4,10,25,30℃温度下的薄膜透气系数和透气系数比的变化规律。结果表明:随着温度的升高,4种薄膜的透气系数都呈上升趋势;同时,高阻隔膜和双层膜的透气系数比显著降低,而BOPP膜和PP膜的透气系数比则逐渐升高。同一温度条件下,PP膜的透气性能最好,BOPP膜次之,双层膜和高阻隔膜的透气性能较低。试验中,透气系数的自然对数与绝对温度的倒数满足阿累尼乌斯方程,以此可求得不同薄膜材料在其他温度下的透气系数。  相似文献   

4.
Antimicrobial enzyme, glucose oxidase (GOX), was covalently immobilized onto amino‐ and carboxyl‐plasma‐activated biorientated polypropylene films (BOPP) via glutaraldehyde and carbodiimide chemistries. N2‐plasma + NH3 and N2‐plasma + CO2 treatments were utilized to create amino (1.1 nmol/cm2) and carboxyl (0.9 nmol/cm2) groups densities onto the surface of BOPP films. GOX‐immobilized onto amino‐activated BOPP films using 2.5% glutaraldehyde produced higher enzymatic activities than GOX‐immobilized by 0.4% carbodiimide. Further immobilizations were carried out with glutaraldehyde as the coupling agent at temperatures of 4–75°C at pH 5.6 and 7.2. 10 s treatment was sufficient to immobilize GOX at high temperatures in both pH conditions, producing enzymatically active films which remained active over 30 days of storage. GOX covalently immobilized onto BOPP films completely inhibited the growth of Escherichia coli and substantially inhibited the growth of Bacillus subtilis; thus, they may have great potential to be exploited in various antimicrobial packaging film applications. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

5.
目的研究常见类型添加剂对BOPP(双向拉伸聚丙烯)薄膜表面光泽度和雾度的影响。方法通过测试BOPP薄膜的表面光泽度、雾度,对比分析不同类型添加剂对BOPP薄膜光学性能的影响。结果氢化石油树脂与芯层PP有良好的相容性,有利于改善BOPP薄膜的表面光泽度和透明性,质量分数为5%~20%的氢化石油树脂可以使BOPP薄膜的光泽度由88%提高到95%,雾度由1.7%降至0.8%,增透效果明显。抗静电剂(烷基二乙醇胺、单甘酯)和爽滑剂(硅酮类、芥酸酰胺)与PP有部分相容性,在迁移过程中不同程度地影响了BOPP薄膜的光学性能。在烷基二乙醇胺与单甘酯复配的抗静电体系中,烷基二乙醇胺的添加有利于BOPP薄膜光学性能的提高,单甘酯含量的提高明显恶化了薄膜的光学性能,芥酸酰胺的添加造成BOPP薄膜光泽度下降,雾度增加,苯基改性硅酮比普通硅酮更有利于提高BOPP薄膜表面的光泽度与透明性。抗粘连剂二氧化硅与表层PP不相容,形成了界面,在二氧化硅含量大于0.15%(质量分数)时,雾度迅速提高,光泽度下降。结论薄膜生产配方中添加剂的选择与优化是开发高表面光泽度低雾度BOPP薄膜的关键。  相似文献   

6.
To protect sensitive food products from oxidative deterioration, multilayer barrier film systems and also modified atmosphere packaging are widely applied. However, the preservation of food quality in such packaging systems may be compromised by the presence of defects in the sealing layer of the films, especially when these are below a critical size, typically the detection limit of standard leak testers of 10 µm. The addition of an oxygen scavenger (OS) layer in barrier film structures could therefore provide extended protection against O2 penetration through such defects. In this study, O2 absorption of different multilayer film structures including an iron‐based OS were investigated under defined gas atmospheres. Measurement cells were thereby covered with plastic films of defined O2 permeability to simulate conditions in a food package during storage with pinhole defect sizes of 10 and 17 µm. The results indicated that the OS film structures applied could only compensate for a defect size of 10 µm in the sealing layer. Analysis of the O2 absorption of different multilayer film structures at 85% and 100% relative humidity showed that higher humidity accelerates the activation of the scavenger. After full activation, the scavenger kinetics are the same for 85% and 100% relative humidity. Long‐term storage experiments using the most effective film structure from the preliminary experiments were carried out to compare O2 absorption of a snack food product in packages with and without an OS. The analyzed linear gradient of the reaction of the OS film and food product, respectively, indicated first‐order reaction kinetics with corresponding reaction constants calculated to be K (food product) 0.021 mg (O2) mbar (O2)?1 day?1 and K (OS film) 0.066 mg (O2) mbar (O2)?1 day?1. The reaction velocity of the OS was thus three times faster than that of the food. The applicability of OS multilayer film systems to compensate a critical pinhole defect size of 10 µm for sensitive food products could therefore be confirmed. The measurement of quality parameters for the status of lipid oxidation processes would help to verify this result. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

7.
Packaging of foods in high barrier and strong materials is essential to attain food safety, and nanocomposite technology leads in search of the above kind of packaging material. The effect of compatibilizer (1.6, 5, 10, 15 and 18.4%), nanoclay (0.6, 2, 4, 6 and 7.4%) and thickness of film (35, 50, 75 100 and 120 µm) on oxygen transmission rate (OTR), water vapour transmission rate (WVTR), tensile strength and per cent elongation of polypropylene (PP)‐based nanocomposite films was studied using response surface methodology. The maximum reduction in OTR of PP‐based nanocomposite films over the control was 21.4% in treatment having 10% compatibilizer, 4% nanoclay and 120 µm thickness. A maximum of 28.1% reduction in WVTR for the treatment with 5% compatibilizer, 2% nanoclay and 100 µm thickness over the control was achieved. The regression models were developed for the prediction of OTR and WVTR of nanocomposite films. The maximum increase in the tensile strength of PP‐based nanocomposite films over the corresponding control was 71.7%. The elongation percentage of nanocomposite films was less than the control and increased with increase of thickness of film and decrease of both nanoclay and compatibilizer. Treatment having 5% compatibilizer, 2% nanoclay and 100 µm thickness of nanocomposite films showed better barrier and strength characteristics than other treatments. This paper helps to design the packaging films according to the requirement of foods to be stored using the developed regression models. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

8.
Modified atmosphere packaging (MAP) storage has become a useful technique for extending the shelf life of fruit and vegetables. However, the success of MAP depends on many factors, including types of fresh products, storage conditions, and the characteristics of the packaging films. To achieve the optimal gas composition in the package headspace and improve the postharvest quality of fresh produce, the packaging film with appropriate barrier properties needs to be selected. This study aimed to predict the film thickness by applying produce respiration rate and package film permeability data measured in given product weight and storage conditions. An available film (eg, 25‐μm‐thick low‐density polyethylene) was used to pack fresh produce, and the respiration rate of fresh produce and in‐package O2 and CO2 concentrations at steady state were measured. Permeability of the film was calculated based on mass balance, and the thickness of the film could be predicted if the recommended target O2 and CO2 concentration was obtained from the literature. To validate the predicted thickness value, an experiment was conducted by packaging fresh table grapes in bags of the predicted thickness. The effect of packaging with different film thicknesses on the quality of the fruit was determined. The results showed good agreement between the predicted and the experimental in‐bag O2 and CO2 concentrations, and the MAP with predicted thickness (90 μm) film was more effective in maintaining postharvest quality of grapes during low‐temperature storage than the thinner films (30 and 60 μm) and the control.  相似文献   

9.
This study compared the effects of the use of various types of packaging films in maintaining quality, preserving bioactive compounds and extending shelf life of the ‘Nam Dok Mai’ mango. The principal techniques for maintaining the quality of mangoes are based on modified atmosphere packaging using highly gas‐permeable films and an ethylene‐removing mechanism. The films studied were non‐perforated highly gas‐permeable film, non‐perforated ethylene‐absorbing highly gas‐permeable film (HNPE), micro‐perforated highly gas‐permeable films (HMP) and common non‐perforated polyethylene film (LNP). These films were compared with non‐packaging treatment, which served as a control (C). Gas composition (O2, CO2 and C2H4) in the package headspace was monitored during storage at 12°C. The quality of mangoes were assessed by weight loss, colour (L* a* b*), texture, total soluble solids, titratable acidity, total phenolics, total flavonoids, ethanol concentration and sensory quality. Equilibrium‐modified atmospheres of 5 kPaO2 + 5 kPaCO2 and 4 kPaO2 + 5 kPaCO2 were achieved in the non‐perforated highly gas‐permeable film and HNPE packs, respectively. Carbon dioxide accumulation was observed in the HMP and LNP packs where CO2 reached 17 and 10 kPa, respectively, after storage for 10 days. The shelf life of mangoes was extended to 40 days with HNPE, 35 days with HNP, and 30 days with HMP, as compared with 20 days with control and 5 days with LNP. HNPE, the film incorporated with fine particles of mordenite framework inverted‐type zeolite with ethylene‐absorbing ability, could further extend the shelf life of mangoes in addition to modified atmosphere packaging alone. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

10.
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.  相似文献   

11.
Plasma‐activated biaxially oriented polypropylene (BOPP) films and paper substrate have been coated with functional chitosan solutions. Plasma treatment increased the amount of surface peroxide groups and carboxyl groups on the BOPP films. As a result of plasma activation, the surface energy increased from 30 to 50 dynes/cm. The enzyme tyrosinase catalysed the grafting of octyl gallate and dodecyl gallate to amino groups of chitosan polysaccharide. Resulting coatings exhibited strong antimicrobial activity against Gram‐positive Staphylococcus aureus and Gram‐negative Listeria innocua. After 24 h of incubation, a total reduction in both bacteria cell numbers varied between >4.9 and 1.4 logarithmic units. Grafted dodecyl gallate and octyl gallate at pH 6 were found to have the lowest reduction values of <3 logarithmic units for S. aureus, while 1.4 logarithmic reduction value was obtained for grafted dodecyl gallate at pH 6 against L. innocua. Chitosan coatings were also effective barrier layers against oxygen transmission although the transmission rates clearly increased in high‐humidity conditions. In dry conditions, however, the transmission rate of 2 cm3/(m2 · 24 h) was obtained with chitosan‐coated BOPP. Coatings did not have any effects on water vapour transmission. Both gallates were successfully grafted at pH 6. As increased flocculation and colour formation indicated, the tyrosinase‐catalysed grafting was more powerful with octyl gallate. Dodecyl gallate containing chitosan coatings was more hydrophobic as compared to octyl gallate. Total migration of substances into 95% ethanol was ≥5 mg/dm2, thus materials may be exploitable in packaging purposes in direct contact with certain foodstuffs. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

12.
Passive daytime radiative cooling (PDRC) is a promising strategy to realize surface cooling of objects without any external energy consumption. While such materials typically exhibit dazzling white appearances, developing pleasingly looking colored radiative cooling materials is greatly significant but remains an arduous challenge. Herein, self-standing, flexible colored films available on both sides are prepared by using a facile and scalable strategy. The films are asymmetrically designed. One side is SiO2-filled porous structure with highly reflective pigment distributed that can selectively reflect solar light to generate specific color, and the other side is hierarchically porous three-phase composite with less SiO2, which maximizes the solar reflection. The breathable film achieves a relatively high near infrared reflectance on the colored side (up to 89%), and a broadband solar reflectance on the reverse side. Moreover, both sides exhibit extremely high mid-infrared emissivity (98%) allowing significant radiative heat loss. With the diverse but efficient reflectance and emittance, different sides of three colored films yield temperature drops ranging from 2.0 to 11.1 °C during daytime. Building energy simulation indicates that 655 MJ m−2 energy can be saved over the whole summer if the dual-sided available colored film is deployed in China.  相似文献   

13.
Recycled cardboard has been identified as a major source of mineral oil hydrocarbon (MOH) contamination of foods. Identifying and using appropriate functional barriers is a mechanism through which this problem can be addressed. A number of cellulose‐based and biaxially oriented polypropylene (BOPP) films were evaluated as potential functional MOH barriers. The films were tested using a donor material, a paper containing MOH placed on one side of the film barrier and a paper which acted as the receptor on the other. Testing was performed at accelerated conditions of 60°C, the receptor analysed periodically for MOH. The results demonstrated that the cellulose‐based film types provided an MOH barrier of >3.5 years. This contrasted with the BOPP selected films, for which only the proprietary acrylic‐coated BOPP film provided an effective barrier to MOH migration. Further investigation of the MOH barrier properties of the proprietary acrylic‐coated BOPP film was undertaken. Various coating strategies were employed including increasing the coating application weight, increasing the number of coating lay downs and coating one or both surfaces of the film. It was found that an MOH barrier of 1.5 years when tested at 40°C could be achieved for the proprietary acrylic‐coated BOPP film; however, barrier effectiveness was dependent on the coating integrity of the film. Further work with a vertical form filler packaging machine and the use of a staining technique with transmission microscopy proved effective at highlighting and assessing the coating integrity of packets during a typical packaging operation. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

14.
Here, room‐temperature solution‐processed inorganic p‐type copper iodide (CuI) thin‐film transistors (TFTs) are reported for the first time. The spin‐coated 5 nm thick CuI film has average hole mobility (µFE) of 0.44 cm2 V?1 s?1 and on/off current ratio of 5 × 102. Furthermore, µFE increases to 1.93 cm2 V?1 s?1 and operating voltage significantly reduces from 60 to 5 V by using a high permittivity ZrO2 dielectric layer replacing traditional SiO2. Transparent complementary inverters composed of p‐type CuI and n‐type indium gallium zinc oxide TFTs are demonstrated with clear inverting characteristics and voltage gain over 4. These outcomes provide effective approaches for solution‐processed inorganic p‐type semiconductor inks and related electronics.  相似文献   

15.
A new dynamic accumulation method for measuring the oxygen transmission rate (OTR) of packages and packaging films using robust and inexpensive fluorescence oxygen sensing technology has been developed. The method allows for oxygen to transfer through a given area of packaging or sample film and accumulate over time. The test volume incorporates a fluorescence‐based oxygen sensor that does not consume oxygen and therefore does not interfere with the real‐time measurement of oxygen concentration. The new method was tested against a widely used, commercially available instrument (Mocon Oxtran 2/20; Mocon, Inc., Minneapolis, MN, USA) designed around the steady‐state gas permeation measurement approach described by ASTM D3985. Sample films were chosen to provide comparison over several orders of magnitude of OTR. Specifically, sample films with OTR values in the range of 101, 103 and 104 ml O2/m2/day were measured, and results using the two methods were compared. Results showed that the new dynamic accumulation method provides comparable results with the steady‐state method (ASTM D3985). Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

16.
We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi0.65Fe0.35O3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe4+) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The kchem values obtained by OTR were significantly lower than the AC-IS derived kchem values and kq values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in kchem and kq values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived kchem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ, and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films.  相似文献   

17.
高性能薄壁化和多层复合是当前塑料包装薄膜的发展趋势。双向拉伸多层共挤复合薄膜不仅可以满足包装行业对薄膜多功能性的要求,还具有"减薄"功能,可大幅度减少同类塑料薄膜的用量,降低生产成本。文中分别介绍拉伸取向和多层共挤关键技术、商业化薄膜生产设备和几种主要的薄膜产品,如双向拉伸聚丙烯(BOPP)薄膜、双向拉伸聚酯(BOPET)薄膜、双向拉伸聚酰胺(BOPA)薄膜、双向拉伸聚乳酸(BOPLA)薄膜和双向拉伸聚乙烯(BOPE)薄膜,着重讨论了BOPE薄膜研究现状及未来展望。  相似文献   

18.
Abstract

Porous germanium films with good adhesion to the substrate were produced by annealing GeO2 ceramic films in H2 atmosphere. The reduction of GeO2 started at the top of a film and resulted in a Ge layer with a highly porous surface. TEM and Raman measurements reveal small Ge crystallites at the top layer and a higher degree of crystallinity at the bottom part of the Ge film; visible photoluminescence was detected from the small crystallites. Porous Ge films exhibit high density of holes (1020 cm?3) and a maximum of Hall mobility at ~225 K. Their p-type conductivity is dominated by the defect scattering mechanism.  相似文献   

19.
Although the hot‐casting (HC) technique is prevalent in developing preferred crystal orientation of quasi‐2D perovskite films, the difficulty of accurately controlling the thermal homogeneity of substrate is unfavorable for the reproducibility of device fabrication. Herein, a facile and effective non‐preheating (NP) film‐casting method is proposed to realize highly oriented quasi‐2D perovskite films by replacing the butylammonium (BA+) spacer partially with methylammonium (MA+) cation as (BA)2?x(MA)3+xPb4I13 (x = 0, 0.2, 0.4, and 0.6). At the optimal x‐value of 0.4, the resultant quasi‐2D perovskite film possesses highly orientated crystals, associated with a dense morphology and uniform grain‐size distribution. Consequently, the (BA)1.6(MA)3.4Pb4I13‐based solar cells yield champion efficiencies of 15.44% with NP processing and 16.29% with HC processing, respectively. As expected, the HC‐processed device shows a poor performance reproducibility compared with that of the NP film‐casting method. Moreover, the unsealed device (x = 0.4) displays a better moisture stability with respect to the x = 0 stored in a 65% ± 5% relative humility chamber.  相似文献   

20.
Gas permselective plastic films have been in a great deal of attention in the area of modified atmosphere packaging of fresh produces. Such films must allow transport of the respiring gases, i.e. oxygen and carbon dioxide, in a controlled manner and, moreover, should efficiently remove ethylene gas. Therefore, the development of highly permeable films with high ethylene permselectivity, i.e. high in both permeability and selectivity, was carried out. The concept of ‘mixed matrix membrane’, by which enhanced gas permselectivity can be obtained by incorporation of zeolite particles into the polymeric film, was applied. Fine particles of hydrophobic zeolites, i.e. zeolite beta and ZSM‐5, and the surface‐modified zeolites were used in this study. The films with uniform distribution of zeolite particles (10% w/w) in 70LDPE/30SEBS (styrene‐b‐(ethylene‐ran‐butylene)‐b‐styrene block copolymer) matrix can be prepared by blow film extrusion. Significantly high ethylene permselectivity, i.e. ethylene permeability of 1.78–2.67 × 103 cm3 ? mm/m2 ? day ? atm and ethylene/O2 selectivity of 4.67–8.26, was obtained from the films containing octyl‐modified and phenyl‐modified zeolites. Particular enhancement was observed on the films containing phenyl‐modified zeolites. Crystallinity of polyethylene, transition temperatures and decomposition temperature were, however, indifferent among the studied films. Nevertheless, elongation at break and toughness of the films containing surface‐modified zeolites were superior. Particle–polymer interface could thus be improved. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

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