Formation of hydrophilic starch coatings on polyethylene films

Thin starch coatings were deposited onto polyethylene (PE) film surfaces when PE films were immersed in 1% jet cooked starch solutions and the hot solutions were allowed to cool. Normal cornstarch, waxy cornstarch, high amylose cornstarch, and solvent‐extracted normal cornstarch (to remove native lipid) were used in these experiments. Amounts of adsorbed starch varied from about 0.03–0.05 mg per cm² of PE, and these starch coatings imparted hydrophilic properties to film surfaces, as evidenced by contact angle measurements. Although starch could be removed by gently rubbing water‐wet PE surfaces, air‐dried coatings were more firmly attached, and did not separate from the PE surface when films were bent or flexed. SEM images of starch‐coated film surfaces showed that starch was deposited as particles less than 1 μm in diameter, and also as aggregates of these submicron particles. Despite the fact that some starch samples contained only very small amounts of amylose and native lipid, surface‐deposited starch in all experiments contained 90–100% amylose; and exhibited the same V_h X‐ray diffraction pattern, indicative of helical inclusion complex formation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1781–1788, 2002; DOI 10.1002/app.10589     

PBAT/TPS-nanowhiskers blends preparation and application as food packaging

About 85–90% of the market for new materials in biodegradable packaging is served by various blends and composites containing starch in some portion. In an attempt to satisfy the increasing consumer demand, innovative materials are being developed. This includes the concept of active packaging, which, in addition to protecting, interacts with the packaged product. In this context, flexible films have been prepared from blends of poly(butylene adipate-co-terephthalate), thermoplastic starch (TPS), and cellulose nanowhiskers (CNW) at different concentrations (0–3.0 wt %) and with distinct compatibilizing agents (glycerol, stearic acid, and citric acid) by flat extrusion. Palm oil was packaged in the films, and was stored under accelerated oxidation conditions as a model system. The films were also used for packing lettuce. The TPS increased the rate of water vapor permeability of the blends. The micrographs showed the films with very porous surface as a function of the CNW concentration. In addition to the antimicrobial action pronounced within 10 days (fungi—molds and yeasts; bacteria—mesophilic and psychrotrophic), the film showed a prooxidant action, indicating its suitability for fruit and vegetable packaging. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47699.     

Evaluation of starch‐PE multilayers: Processing and properties

Adhesion tests performed on various plasticized starch‐polyethylene multi‐layer systems led to the selection of a suitable combination of polymers compatible with the starch‐based layer. The compatibility of starch and polyethylene was better achieved through maleic anhydride functionalized polyethylene (PEg) than chemically modifying starch. The PEg method proved efficient provided that the water content, and the plasticizer nature and contents of the starch layer were carefully chosen. Computed shear viscosity allowed us to select a suitable botanical origin of starch such that the interfacial instabilities of the coextrusion process were minimized. The use of a multilayer structure (PE/PEg/starch/PEg/PE) improved gas barrier properties at high relative humidity. The higher quantity of water sorbed by thermoplastic starch (as compared to EVOH) coupled with starch's specific water sorption isotherm lengthened the water equilibration time in the hydrophilic inner layer significantly. As a result the gas barrier properties of the starch based multiplayer systems were enhanced as compared to existing commercial multiplayer systems (PE/PEg/EVOH/PEg/PE). This specific “water‐buffering property” of the starch inner layer should prove useful in packaging applications of perishables with extended shelf life in environments of varying relative humidity. Polym. Eng. Sci. 45:217–224, 2005. © 2005 Society of Plastics Engineers.     

Immobilization of a cyclodextrin glucanotransferase (CGTase) onto polyethylene film with a carboxylic acid group and production of cyclodextrins from corn starch using CGTase‐immobilized PE film

Carboxylic acid groups were introduced onto polyethylene (PE) film by radiation‐induced graft copolymerization. Subsequently, the clodextrin glucanotransferase (CGTase) was immobilized on the PE film with a carboxylic acid group. The activity of the immobilized CGTase on PE film was in the range of 0.40–1.04 U/cm² per min. The production of cyclodextrins (CDs) from corn starch was examined using the CGTase‐immobilized PE film. The production ratios of CDs using CGTase‐immobilized PE film was in the following order: α–CD > β–CD > γ–CD. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2451–2457, 2002     

碳酸钙和淀粉对聚乙烯薄膜降解性能影响研究

目的:研究淀粉和CaCO3对塑料薄膜的降解影响。方法:将CaCO3填充膜和淀粉填充膜经自然曝露、紫外线照射和土埋处理,测试拉伸强度、断裂伸长率和分子量的变化。结果:自然曝露30d,CaCO3填充膜和淀粉填充薄膜的平均拉伸强度分别下降80.8%和54.4%,平均断裂伸长率分别下降99.4%和98.3%,分子量分别下降25.3%和13.8%;紫外光照120h,CaCO3填充薄膜和淀粉填充薄膜的平均拉伸强度分别下降14.7%和45.9%,断裂伸长率分别下降97.3%和97.0%,分子量分别下降66.7%和48.3%;土埋203d,CaCO3填充薄膜和淀粉填充薄膜的失重率分别为2.2%和15.0%。结论:CaCO3和淀粉均能加速聚乙烯塑料薄膜的降解,其中CaCO3的光降解性能方面优于淀粉,而淀粉的生物降解性能优于CaCO3。     

Studies on the degradable polyethylenes: Use of coated photodegradants with biopolymers

Three degradable polymer materials such as starch–polyethylene (PE) binary blends, PE containing starch and a photoactivator, and PE containing starch and a photoactivator which was coated with gelatin were prepared and their degrees of photodegradation and/or photodegradation after biodegradation were investigated. The addition of the gelatin-coated ferric salt in PE extended the induction period of degradation and accelerated pho-todegradation after the removal of coating material by biodegradation. This result suggested that the degradation rate of PE could be controlled if more powerful photoactivators and/or coating material are developed and their contents are optimized. © 1996 John Wiley & Sons, Inc.     

Polyethylene‐based nanocomposite films: Structure/properties relationship

Polyethylene (PE) is the most used thermoplastic commodity as a consequence of its convenient cost‐processing‐performance relationship and it can be used in the form of films for food, goods and farming packaging. On the other hand, sepiolite is a high surface area and porosity hydrated magnesium silicate with both remarkable adsorptive and absorptive properties. Thus, PE and sepiolite can combine their properties synergetically to obtain new materials with enhanced properties. In this work, a systematic study of final properties of PE‐sepiolite nanocomposite films was performed to investigate the influence of the sepiolite content and modification on the PE properties. Nanocomposites films with 1, 3, 5 and 10 wt % of sepiolite, with and without surface modification, were prepared by cast film extrusion and tested. The filler dispersion and distribution were evaluated by Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR), whereas the film crystalline morphology was analyzed using Atomic Force Microscopy (AFM), Differential Scanning Calorimetry (DSC) and X‐ray Diffraction (XRD). Final properties as mechanical ones, oxygen permeability and transparency were also studied and related with the film structure. Mechanical properties, crystallization and oxygen permeability were increased maintaining good film translucency. POLYM. ENG. SCI., 54:1931–1940, 2014. © 2013 Society of Plastics Engineers     

Starch–poly(vinyl alcohol) foamed articles prepared by a baking process

Composite foam plates were prepared by baking a mixture of granular starch and aqueous poly(vinyl alcohol) (PVOH) solution inside a hot mold. Foam strength, flexibility, and water resistance were markedly improved by addition of 10–30% PVOH to starch batters. The improvement in strength at low humidity was greater for partially (88%) hydrolyzed PVOH while strength at higher humidities improved most with fully (98%) hydrolyzed PVOH. Foam flexibility increased with higher PVOH molecular weight. Scanning electron micrographs of the surface of the foams revealed a phase-separated morphology in which swollen starch granules were embedded in a matrix of PVOH. The starch component was gelatinized (melted) during baking while the PVOH component crystallized to a high degree during baking. Crosslinking agents such as Ca and Zr salts were added to starch batters to give further increases in water resistance. Respirometry studies in soil showed that the starch component of starch–PVOH foams biodegraded relatively rapidly (weeks) while the PVOH component degraded more slowly (months). Baked foams prepared from starch and PVOH have mechanical properties that are adequate for use as packaging containers over a wide range of humidity. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 2129–2140, 1998     

Preparation of nano-Ag-Bi2WO6–TiO2/starch bionanocomposite membranes and mechanism of enhancing visible light degradation of ethylene

Ag–Bi₂WO₆–TiO₂ (ABT) ternary composite photocatalyst was prepared using solvothermal and surface deposition method. Then, the nano photocatalyst was doped into the starch film liquid through internal loading method, and finally, ABT/starch composite film was constructed using tape casting method for visible light catalytic degradation of ethylene. Characterize and analyze the structure and physical properties of nano ABT/starch composite membranes prepared with different ABT loading amounts, and optimize the reaction conditions (ABT addition amount, light intensity, initial concentration of ethylene) on the visible light catalytic degradation performance for ethylene of the composite membrane. The results show that the nano ABT particles and starch molecules have good biocompatibility, and they can be well fused to form a film, without changing the crystal structure of ABT and generating other chemical bond. The results of photocatalytic degradation of ethylene showed that when the loading amount of ABT was 5 wt%, the light intensity was 60.5 mw/cm², and the initial concentration of ethylene was 0.15 mg/L, the ABT/starch film had the best ethylene degradation performance, with a K′ value of 5.6111 × 10⁻⁴ min⁻¹, which is 17.9 times that of the blank starch film. Under the optimal preparation conditions, the thickness, tensile strength, elongation at break of the starch composite film is 168.33 μm, 5.01 Mpa, 32.4%, respectively, and the maximum thermal decomposition temperature is 320.5 °C, which meets the requirements for food packaging materials. After 4 cycles, the catalytic degradation of ethylene by starch composite membrane only decreased by 13.98%, indicating good reusability.     

Adsorption of polyethylene from solution onto starch film surfaces

We prepared starch films by jet‐cooking aqueous dispersions of high‐amylose starch and then allowing the jet‐cooked dispersions to air‐dry on Teflon surfaces. When the starch films were immersed in 1% solutions of polyethylene (PE) in 1‐dodecanol, dodecane, and xylene at 120°C and the solutions were allowed to slowly cool, PE precipitated from the solutions and adsorbed onto the starch film surfaces. Fourier transform infrared spectroscopy was used to estimate the micrograms of PE adsorbed per square centimeter of starch film. PE was preferentially adsorbed onto the film side that was in contact with the Teflon surface during drying. The amount of PE adsorbed ranged from about 8 to 45 μg/cm² and depended upon the solvent used and the final temperature of the cooled solution. Scanning electron microscopy of the starch film surfaces showed discontinuous networks of adsorbed PE on the Teflon side and widely spaced nodules of adsorbed PE on the air side. NMR analysis showed that the PE adsorbed onto the starch surface was more linear and/or had a higher molecular weight than the starting PE. Possible reasons for the selective adsorption of PE onto the Teflon side of the starch film surface are discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

TiO2‐kaolin‐PE composite film: A study based on photocatalytic degradation and biodegradation

A novel photodegradable and biodegradable polyethylene (PE) film was prepared through a melt blending technique, where nano‐TiO₂ and common kaolin were used as the photocatalyst and biodegradable promoter showing improved degradable efficiency of the waste PE. The photo‐degradation of the composite film was investigated by weight loss monitoring, attenuated total reflection–fourier transformed infrared spectroscopy (ATR–FTIR), and scanning electron microscopy. The aerobic biodegradation of the residue films after photodegradation was investigated by analysis of evolved carbon dioxide of films in aquatic test systems according to the international standards (ISO 14852, 1999). The results showed that the weight loss of as‐prepared photo‐ and biodegradable composite film reached 26.8% after 240 h of UV light irradiation. The big cavities formed not only on the film surface but also inside the bulk film, together with the chalking phenomenon taking place. The biodegradation results revealed that the addition of kaolin enhanced the degradation of UV‐light treated TiO₂‐PE films. The prepared PE based composite films showed promising application as novel photo‐biodegradable environment‐harmless materials. In addition, a degradation mechanism for this composite film was also discussed. POLYM. COMPOS., 37:2353–2359, 2016. © 2015 Society of Plastics Engineers     

Characteristics of acrylic acid and N-isopropylacrylamide binary monomers–grafted polyethylene film synthesized by photografting

Method for introducing grafted chains consisting of two types of monomer components, acrylic acid (AA) and N-isopropylacrylamide (NIPAAm), into low-density polyethylene (PE) film (thickness = 25 μm) was investigated by two photografting technique using xanthone photoinitiator at 60°C. In the first method (one-step method), AA and NIPAAm binary monomers were graftcopolymerized onto PE film. In the second method (two-step method), AA was first photografted onto PE film and then NIPAAm was further introduced into the AA-grafted PE film by a second-step photografting. Water absorbencies of the grafted films (one- and two-step samples) prepared by the one- and two-step methods, respectively, decreased in the order of AA-grafted film > one-step sample > two-step sample > NIPAAm-grafted film. The water absorbency steeply decreased at 20 to 40°C with increasing temperature when immersed in water at the temperatures (5–60°C) for 24 h. Thermosensitivity, which was defined as the ratio of water absorbencies of the grafted samples at 5 and 60°C, was higher for the one-step sample than the two-step one. The different extent of the water absorbency and the thermosensitivity between both samples is discussed in terms of location of grafted chains in the film substrate, which was determined by electron probe microanalysis and attenuated total reflection–infrared measurements, and monomer sequence distribution of the grafted chains. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2057–2064, 1998     

Constructing stable “bridge” structures with compatibilizer POE-g-GMA to improve the compatibility of starch-based composites

With the development of degradation technologies such as chemical-catalysis and bio-catalysis, starch-polyethylene (PE) composites have been revitalized as industrial packaging materials. However, starch and PE suffer from interfacial incompatibility. In this study, poly(octene ethylene) grafted glycidyl methacrylate (POE-g-GMA) was added at relatively low amounts (0–7 wt%) to construct robust structures between thermoplastic starch (TPS) and low-density polyethylene (LDPE). Tensile strength increased by 36.39% with the addition of 1 wt% POE-g-GMA. Meanwhile, a smooth surface was observed by SEM, and a fibrillar cross-linked structure appeared on the fractural surface of the blend. POE-g-GMA formed a stable “bridge” at the interface between TPS and LDPE, which increased the thermal stability of the blend as well. The crystallinity of LDPE increased from 20.5% (without addition) to 32.8% (with 1 wt% addition), whereas the average crystallite size decreased slightly. The optimal POE-g-GMA content was found to be 1 wt% based on mechanical and thermal measurements. The results of this study can provide a reference for improving the interfacial compatibility of biopolymers and fossil-fuel-based polymers.     

Biodegradation dynamics of polymer–starch composites

The dynamics of starch biodegradation in polyethylene–starch (PE–S) composites was investigated by aerobic biodegradation methods and computer simulations, with the starch fraction p above and below the percolation threshold p_c. Two models for starch degradation were considered: (i) microbial invasion through the composite and (ii) macromolecular (enzyme) diffusion which results in the back‐diffusion of small molecules to the surface for further assimilation by microorganisms. The microbial‐invasion model was based on scanning electron microscopy (SEM) studies of PE–S composites that contained a 1–15‐micron distribution of starch particles. Following exposure to soil test conditions, micrographs of thin films clearly showed the colonization of microorganisms within channels of the matrix that were initially occupied by starch. The enzymatic diffusion was based on hydrolytic experiments of PE–S composites. Following exposure of a composite to a hydrolytic test condition, small molecules were produced. The starch accessed by microbes and enzymes was computed by simulating degradation of a monodisperse and polydisperse (starch grains of 1–10‐micron diameter) composite. Aerobic degradation studies in a biometer indicate that the starch accessibility. A follows a power‐law dependence with time A ∼ tⁿ, where the exponent n depends on the fractal dimension of the accessed starch clusters and pathways and approaches unity when p > p_c. Microbial invasion simulations indicate that the average power‐law exponent near p_c is approximately 0.5 and approaches 1.0 at p > pc, whereas the enzymatic diffusion simulations indicate that the average power‐law exponent near p_c is about 0.25 and approaches 0.5 at p > pc. The observed exponent for the aerobic degradation study suggests that for composites with a starch fraction less than and greater than p_c the starch is predominantly accessed by microbial invasion. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1643–1657, 2000     

Effects of polyethylene‐grafted maleic anhydride (PE‐g‐MA) on thermal properties,morphology, and tensile properties of low‐density polyethylene (LDPE) and corn starch blends

The effects of polyethylene‐grafted maleic anhydride (PE‐g‐MA) on the thermal properties, morphology, and tensile properties of blends of low‐density polyethylene (LDPE) and corn starch were studied with a differential scanning calorimeter (DSC), scanning electron microscope (SEM), and Instron Universal Testing Machine, respectively. Corn starch–LDPE blends with different starch content and with or without the addition of PE‐g‐MA were prepared with a lab‐scale twin‐screw extruder. The crystallization temperature of LDPE–corn starch–PE‐g‐MA blends was similar to that of pure LDPE but higher than that of LDPE–corn starch blends. The interfacial properties between corn starch and LDPE were improved after PE‐g‐MA addition, as evidenced by the structure morphology revealed by SEM. The tensile strength and elongation at break of corn starch–LDPE–PE‐g‐MA blends were greater than those of LDPE–corn starch blends, and their differences became more pronounced at higher starch contents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2904–2911, 2003     

Graft copolymerization of 4-vinylpyridine and methyl acrylate onto polyethylene film by radiochemical method

Graft copolymerization of 4-vinyl pyridine (4-VP) and methyl acrylate (MA) onto polyethylene (PE) was studied in aqueous medium in air by the mutual irradiation method. The percentage of grafting was determined as a function of the (i) total dose, (ii) monomer concentration, and (iii) amount of water. The effect of different alcohols such as methanol, ethanol, isopropyl alcohol, butanol, and pentanol on the percentage of grafting of 4-VP and MA was studied. The effects of different amines on the percentage of grafting of 4-VP were also studied. The graft copolymers were characterized by IR spectroscopy and thermal analysis and by identifying the isolated polymer from the grafted film. Grafted PE film was tested for permeability behavior and was found to be permeable to a 0.5% aqueous sodium chloride solution. A plausible mechanism is suggested to explain the grafting of 4-VP and MA onto PE film. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 599–610, 1998     

Electrical and mechanical properties of polyethylene–rubber blends

A systematic electrical and mechanical study was carried out on styrene butadiene rubber (SBR), as a nonpolar rubber, and nitrile rubber (NBR), as a polar one blended with pure and waste polyethylene (PE), low and high density. The compatibility investigations, which were carried out by the dielectric method and confirmed by the calculated heat of mixing, indicate that SBR–PE blends (either low or high density) are compatible, while NBR–PE blends are incompatible. From the electrical and mechanical results, it is found that the addition of waste PE to either polar or nonpolar rubber leads to better electrical and mechanical properties when compared with those for the blends having pure PE. The values of permittivity ε′ are found to increase pronouncely, while the values of dielectric loss ε′ slightly decrease. Shore hardness was also measured for all the investigated systems and found to vary linearly with the permittivity ε′. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 69: 775–783, 1998     

Polymer compatibility and biodegradation of starch–poly(ethylene-co-acrylic acid)–polyethylene blends

X-ray diffraction, CP/MAS C-13 NMR, DSC, FTIR and fluorescence microscopy have been used to study the structure, compatibility, and morphology of films made from starch, poly(ethylene-co-acrylic acid) (EAA), and polyethylene (PE) before and after exposure to a mixture of highly amylolytic bacteria. The components of starch, amylose and amylopectin, interact with EAA via the formation of V-type inclusion complexes and hydrogen bonds. PE appears to be immiscible with the starch–EAA complex, with each forming sheetlike domains. The amylopectin in the films is susceptible to digestion by the bacterial consortium while the crystalline EAA–amylose complex is resistant. Digestion begins at the film surface and then proceeds inwards with sheetlike areas of starch removed. The good compatibility between starch and EAA as well as migration of EAA to the film surface explains the resistance of such films to digestion by conventional amylases.     

高阻隔纳米抗菌包装膜的研制与应用

采用聚乙烯、(乙烯/乙烯醇)共聚物通过流延共挤技术生产出高阻隔纳米抗菌包装膜,考察了包装膜的抗菌性及阻隔性.结果表明,该包装膜具有较好的抗菌性及高阻隔性,与传统铝塑复合槟榔包装相比,可提高槟榔保质期及降低成本.     

Graft polymerization of acrylonitrile onto starch‐coated polyethylene film surfaces

Starch‐coated polyethylene (PE) films were prepared by immersing PE in a hot, jet cooked solution of starch. They were allowed to react with acrylonitrile (AN) in the presence of ceric ammonium nitrate initiator, and the graft polymerization that occurred produced starch‐g‐polyacrylonitrile (PAN) coatings that contained about 25 wt % grafted PAN. The starch‐g‐PAN coatings tightly adhered to the PE film surfaces. When grafted starch coatings were wetted with water and the surfaces vigorously rubbed, less than 20% of the coating was removed. The fact that PAN‐grafted coatings were not removed with boiling water provided further evidence for their strong adherence. When starch was removed from the coating by acid hydrolysis, the residual grafted PAN still remained adsorbed on the PE surface. Because the grafted coating was completely removed by treatment with refluxing 0.7N sodium hydroxide, there is apparently no chemical bonding between starch‐g‐PAN and PE. The dimensional changes associated with the evaporation of water from these PAN‐grafted coatings caused the films to curl during drying. Because the final shape of these coated films depends upon the presence or absence of water in the surrounding environment, these films may be considered to be a type of stimulus‐responsive polymer. Attempts to graft polymerize methyl methacrylate and methyl acrylate onto starch‐coated PE surfaces, under conditions similar to those used with AN, were unsuccessful. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3323–3328, 2003