Low-density Polyethylene Composite Films Research Articles

Synergistic Antimicrobial Activities of Limonene with Mineral Carriers in LDPE Films for Active Packaging Application

The integration of essential oils (EOs) into polymers to endow antimicrobial properties has received a lot of attention. EOs are remarkable in that they have broad antimicrobial activity from a natural source while also being volatile. Their volatility, on the other hand, makes high-temperature processing techniques difficult to incorporate into polymers. In this study, active films based on low-density polyethylene (LDPE) and limonene essential oil (LEO) were prepared and characterized. Before incorporation of LEO into LDPE, vacuum pulling method was used to load the LEO into five different mineral carriers. All Carrier-LEO complexes were added into LDPE using melt compounding. The goal is to analyze the potential use of these formulations to achieve prolonged antimicrobial film packaging. The halloysite nanotubes (HNTs), kaolinite (Kao), mesoporous silica nanoparticles (MSNs), zinc oxide nanoparticles (ZnONPs), and molecular sieve type 4A (Z4A) were used as mineral carriers for limonene. The functional characterizations including mechanical, thermal, optical, barrier, and antimicrobial properties as well as limonene release behavior from the LDPE composite films were investigated. As expected, free limonene molecules acted as a plasticizer in the LDPE matrix. Thermogravimetric analysis (TGA) showed 20-25% of the initial limonene content was retained against thermal degradation in compounding and film making steps and its release from the films was efficiently delayed. A decrease in optical and oxygen barrier properties, as well as elastic modulus and tensile strength, was obtained for all developed films compared with neat LDPE. Significant antibacterial activities of the films were observed against <i>Escherichia coli DH5-Alpha</i> (<i>E. coli)</i> as a model gram-negative bacterial species. Moreover, the obtained results and the short-term and long-term release studies indicated that both HNTs and the MSNs due to their strong synergistic interactions with limonene exhibited sustained release profiles of limonene from LDPE films. Thus, these new active polymer composites present promising features in controlling microbial contamination, rendering them as excellent candidates in active packaging applications.

Influence of gamma rays on the physico-chemical, release and antibacterial characteristics of low-density polyethylene composite films incorporating an essential oil for application in food-packaging

Abstract We investigated the effect of gamma irradiation on the properties of low-density polyethylene composite films incorporated with the antimicrobial terpene 4-allylanisole (ALY), and the volatile release of ALY. For comparison, wood flour and molecular sieves were used as solid carriers for ALY at loading ratios of 20 and 30 wt.%. Infrared spectroscopy indicated that a proportion of ALY underwent structural change during melt-compounding and irradiation at high doses (> 10 kGy). Thermal and mechanical properties of composites prepared did not alter remarkably after irradiation. The release study of ALY showed that using wood flour and irradiation reduced the volatilization of ALY from the polymer matrix; however, the effect exerted by irradiation treatment was less noticeable than that of the carrier type. The antibacterial activity study demonstrated that irradiation only exerted a pronounced negative effect on samples that contained 30 wt.% of ALY/wood flour when irradiated at 30 and 50 kGy.

LDPE-나노 ZnO 복합필름의 기능성 및 재질안정성 평가

In this work, nano ZnO was introduced into low density poly ethylene (LDPE) composites films with various contents (0, 0.5, 1.0, 3.0 and 5.0 wt%) by melt-extrusion. Their basic properties such as crystallinity, chemical bonds and surface morphology were examined by XRD, FTIR and SEM. XRD patterns and FTIR peaks intensity were increased in proportion to the ZnO contents. SEM images showed well dispersed nano ZnO in LDPE composite films. Antimicrobial functionality of LDPE-nano ZnO composite films was also studied and the presence of nano ZnO resulted in significant improvement of antimicrobial functionality compared to the pure LDPE film. To evaluate influence of nano ZnO on LDPE properties required as packaging material, thermal, mechanical, gas barrier and optical properties of LDPE-nano ZnO composite films were characterized with various analytical techniques including TGA, UTM, OTR, WVTR and UV-Vis spectroscopy. As a result, except optical and mechanical properties of LDPE, no significant effects were found in other properties. Opacity of pure LDPE was greatly increased with increasing concentration of nano ZnO and tensile strength was also improved at 0.5wt% ZnO content.

Physicochemical analysis of linear low-density polyethylene composite films containing chemically treated rice husk

A study was conducted to determine the appropriate surface treatment for rice husks (RH) in polymer composite film to improve the physical properties relative to those of untreated RH/linear low-density polyethylene (LLDPE) film. Pulverized RH was treated with NaOH (RH-m) and acetic acid (RH-ac) to prepare composite films with LLDPE resin. The treated RH showed typical mercerization and acetylation, as confirmed by spectroscopic and thermal analysis methods. The RH-m sample was mercerized, allowing decomposition of hemicellulose and partially amorphous cellulose. The RH-ac sample was processed via acetylation inducing partial lignin decomposition. Field-emission scanning electron microscopy showed smaller gaps at the RH/LLDPE interface for RH-m and RH-ac compared to that with untreated RH, implying increased composite compatibility. RH-m in particular showed superior tensile strength (15.85 N/mm2), elongation (884%), Young’s modulus (60.01 N/mm2), and tear strength (7.71N/mm2) compared to untreated RH and RH-ac.

Water vapor permeability, morphological properties, and optical properties of variably hydrolyzed poly(vinyl alcohol)/linear low-density polyethylene composite films

Poly(vinyl alcohol) (PVA)/ linear low-density polyethylene (LLDPE) composite films were prepared using PVAs of various molecular weights and degrees of hydrolysis. The crystallinity, water permeability, mechanical properties, and optical properties of the composite films were analyzed based on the absorption properties of the different PVAs. The formation of the composite film became increasingly difficult with increase in the molecular weight and the degree of hydrolysis of PVA, because the resulting crystallinity increased the intramolecular hydrogen bonding of the hydroxyl groups on the main chains of PVA. The 4-98/LLDPE composite film absorbed water gradually and continuously for a long time, and its water vapor absorption rate was similar to that of the 4-88/LLDPE film but lower than that of the PVA 205/LLDPE film. The mechanical properties of the 4-98/LLDPE film were slightly better than those of the 4-88/LLDPE film but inferior to those of the PVA 205/LLDPE film.

LDPE composite films incorporating ceramic powder emitting far‐infrared radiation for advanced food‐packaging applications

ABSTRACTA ceramic powder that emits far‐infrared radiation (FIR) was incorporated into low‐density polyethylene (LDPE) via melt‐compounding and subsequent melt‐extrusion processes. To investigate the feasibility of as‐prepared LDPE/FIR composite films for use in packaging applications, the composite films were characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, FIR emissivity and emissive power, antimicrobial activity assays, and storage tests. The physical properties and antimicrobial activities of the composite films were found to strongly correlate with the changes in the chemical and morphological structures that originate from different contents of FIR ceramic powder. A higher content of FIR ceramic powder in the LDPE/FIR composite film provided increased FIR emissivity and emission power of the composite and resulted in good antimicrobial activity. Storage tests also showed that incorporation of FIR ceramic powder into LDPE film was an effective method for maintaining the freshness of lettuce. Furthermore, the incorporation of FIR ceramic powder into LDPE films induced higher thermal stability and crystallinity and enhanced their barrier properties, which suggest these LDPE/FIR composite films are potential candidates for advanced packaging materials for the food and medical industries. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43102.

Ni-coated CaCu3Ti4O12/low density polyethylene composite material with ultra-high dielectric permittivity

We report a novel low-density polyethylene (LDPE) composite filled with nickel-coated CaCu3Ti4O12 ceramic (denoted as CCTO@Ni), prepared by a melt mixing technique, and its prominent dielectric characteristics. The effects of magnetic field treatment on the dielectric properties of CCTO@Ni/LDPE composite films with a low filler concentration of 10 vol.% were investigated. Our results show that the dielectric permittivity, loss tangent, and conductivity of the LDPE composite films initially improved and then decreased with increasing treatment time under the applied magnetic field. Magnetic field treatment for 60 min led to an ultra-high dielectric permittivity value of 1.57 × 104, four orders of magnitude higher than that of the pure LDPE material. Our results indicate that the magnetic treatment may have induced a percolation effect and enhanced the interfacial polarization of the CCTO@Ni/LDPE composite, resulting in the observed changes in its dielectric properties.

Preparation and antimicrobial properties of LDPE composite films melt-blended with polymerized urushiol powders (YPUOH) for packaging applications

Abstract Polymerized solid-type urushiol (YPUOH) with high thermal stability and excellent antimicrobial properties was prepared and incorporated into low-density polyethylene (LDPE) via melt-compounding and subsequent melt-extrusion processes. To investigate the feasibility of as-prepared LDPE/YPUOH composite films for use in packaging applications, the films were characterized as a function of YPUOH using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (WAXD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), contact angle, and antimicrobial activity assays. The physical properties and antimicrobial activities were found to be strongly dependent upon the changes in chemical and morphological structures originating from different compositions of the composite films. The thermal stability of the composite films was effectively improved with YPUOH addition. Incorporating YPUOH caused the water vapor transmission rate (WVTR) to decrease from 10.3 to 6.5 g/m 2 ·day, suggesting that the barrier properties of LDPE, which are relatively good per se, were further improved. Furthermore, the LDPE/YPUOH composite films exhibited good antimicrobial activities against both Gram-negative and Gram-positive micro-organisms. However, the dispersion of YPUOH in the LDPE matrix was not satisfactory due to a weak interaction between LDPE and YPUOH, which may adversely affect the thermal and barrier properties at higher contents of YPUOH. Further studies are required to increase the compatibility and dispersion of YPUOH in the LDPE matrix in order to optimize its performance and expand its applications.

Research in Non-Isothermal Crystallization Kinetics of LDPE Composite Films

By means of melt blending process in a co-rotating twin screw extruder and blow molding , the low density polyethylene (LDPE)/thermoplastic elastomer(TPE) mixed membranes and LDPE/inorganic particles composite membrane were prepared. by differential scanning calorimetry(DSC) to study the non-isothermal crystallization kinetics of the LDPE composite system by differential scanning calorimetry (DSC).Use modified Jeziorny method to process the data ,the results shows that ZMS, SiO2, EVA and EMAA all play a role of heterogeneous nucleation and the crystallization rate of LDPE has been increased,especially the ZMS/LDPE composite system which heterogeneous nucleation is more obvious and crystallization rate is faster.

Research in Non-Isothermal Crystallization Kinetics of LDPE and Inorganic Particle Composite Films

The low density polyethylene (LDPE)/ethylene-octene copolymer (POE) blend films and LDPE/POE/inorganic particle composite films were prepared. By means of DSC method, the crystallization capability and the non-isothermal crystallization kinetics of LDPE composite films were investigated, the results show that the addition of DE can reduce the interfacial free energy of the crystal and the active energy of a nucleus, resulting in stable nuclei can be formed at lower supercooling, which makes the polymer crystallized successfully at high temperatures. By selecting data processing method of Mo ZS and modified Jeziorny, the results indicate that the DE play a role of heterogeneous nucleation agent in the process of crystallization and increased the crystalline rate of LDPE.

Influence of maleic anhydride-grafted polyethylene compatibiliser on the tensile, oxygen barrier and thermal properties of rice husk and nanoclay-filled low-density polyethylene composite films

Rice husk and nanoclay (montmorillonite)-filled low-density polyethylene composite films were prepared by extrusion blown film. Maleic anhydride-modified polyethylene was used as compatibiliser in various concentrations ranging from 0 to 8 parts per hundred. X-ray difractograms showed an increase in interlayer spacing of montmorillonite from the use of compatibiliser when compared to the uncompatibilised composites; an increase of 20, 33, 36 and 38% for 2, 4, 6 and 8 parts per hundred, respectively, of maleic anhydride-modified polyethylene. With the incorporation of maleic anhydride-modified polyethylene, a better dispersion of the fillers was also achieved, as confirmed by scanning electron microscopy. The compatibilised composite films showed improved tensile and barrier properties. The addition of 4 parts per hundred of the compatibiliser resulted in an improvement by 22% in tensile strength. Furthermore, oxygen barrier property of the composite films improved more than twofold by adding 4 parts per hundred of maleic anhydride-modified polyethylene. This improvement in tensile and barrier properties is due to an increase in the interfacial adhesion between the fibre and matrix and better dispersion of impermeable nanoparticles.