Properties Of Polylactic Acid Films Research Articles

Effects of ZnO nanoparticles, polyethylene glycol 400, and polyoxyethylene sorbitan ester Tween 80 on PLA films properties

Abstract Polylactic acid has the potential to be an alternative to petroleum-based materials in the food packaging industry. In this study, the effect of zinc oxide nanoparticles, polyethylene glycol 400, and Tween 80 as plasticizers on the properties of polylactic acid films was investigated. In order to study the mechanical properties more accurately, the tests were repeated for four months. An experimental design method was used to investigate the effects of additives on the measurement factors and finally to choose the optimal combination with the help of the TOPSIS technique. The results showed that the addition of different materials increased the opacity, most of which being related to P400/ZnO (6.82 ± 0.07 mm−1). The presence of plasticizers increases the hydrophilicity of the film and the water vapor permeability. The highest contact angle (85.33° ± 4.00) and the lowest water vapor permeability (0.074 ± 0.002 g mm/kPa h m2) were related to neat PLA film. The lowest modulus of elasticity, the highest tensile strength and elongation at break were related to P400/T80/ZnO (1.18 ± 0.17 GPa, first month), PLA/ZnO (96.28 ± 3.17 MPa, fourth month), and P400/ZnO (76.82 ± 27.22 %, first month), respectively. The effect of plasticizers was significant in most of the measurement factors, but the effect of nanoparticles was significant in some cases such as opacity and contact angle. The results of an ANOVA analysis showed that the effect of film type on the mechanical properties was significant, and the effect of storage time was only significant on the elongation at break. According to the results obtained from the TOPSIS technique, P400/ZnO was chosen as the combination with the best features among the produced films.

Influence of MgO and ZnO nanofillers on morphology, structural, thermal and mechanical properties of polylactic acid films

Influence of MgO and ZnO nanofillers on morphology, structural, thermal and mechanical properties of polylactic acid films

Smart Film Based on Polylactic Acid, Modified with Polyaniline/ZnO/CuO: Investigation of Physicochemical Properties and Its Use of Intelligent Packaging of Orange Juice

In this study, a biodegradable/conducting film based on polylactic acid (PLA) modified with polyaniline, zinc oxide, and copper oxide (PLA/PAn/CuO/ZnO) was prepared. The effect of polyaniline, zinc oxide, and copper oxide on the electrical, physicochemical, antioxidant, and antimicrobial properties of polylactic acid films by different techniques such as SEM, FTIR, and TGA were investigated. Electricity conductive films were used for intelligent packaging of orange juice. The chemical and microbial properties of orange juice and the electrical conductivity of packaging films during storage time (56 days) were investigated. The results showed that the effect of polyaniline, zinc oxide, and copper oxide greatly increased the antioxidant and antimicrobial properties of polylactic acid film. Polyaniline gave the film good electrical conductivity, but zinc oxide and copper oxide had no significant effect on it. The active film used to package the orange juice increased the chemical and microbial viability of the orange juice. The electrical resistance of the conductive films used for packaging increased over time and a significant mathematical relationship was established between storage time and changes in electrical resistance, which was used to estimate the shelf life and expiration date of orange juice. Examination of the performance of the films showed that these films with an accuracy of over 90% have the ability to estimate the storage time of orange juice. Electricity conductive/antimicrobial/antioxidant film based on polylactic acid as an active and intelligent film has the ability to increase the shelf life and detect spoilage of orange juice.

Improvement of the Structure and Physicochemical Properties of Polylactic Acid Films by Addition of Glycero-(9,10-trioxolane)-Trialeate.

Glycero-(9,10-trioxolane)-trioleate (ozonide of oleic acid triglyceride, OTOA) was introduced into polylactic acid (PLA) films in amounts of 5, 10, 30, 50, and 70% w/w. The morphological, mechanical, thermal, and water absorption properties of PLA films after the OTOA addition were studied. The morphological analysis of the films showed that the addition of OTOA increased the diameter of PLA spherulites and, as a consequence, increased the proportion of amorphous regions in PLA films. A study of the thermodynamic properties of PLA films by differential scanning calorimetry (DSC) demonstrated a decrease in the glass transition temperature of the films with an increase in the OTOA content. According to DSC and XRD data, the degree of crystallinity of the PLA films showed a tendency to decrease with an increase in the OTOA content in the films, which could be accounted for the plasticizing effect of OTOA. The PLA film with 10% OTOA content was characterized by good smoothness, hydrophobicity, and optimal mechanical properties. Thus, while maintaining high tensile strength of 21 MPa, PLA film with 10% OTOA showed increased elasticity with 26% relative elongation at break, as compared to the 2.7% relative elongation for pristine PLA material. In addition, DMA method showed that PLA film with 10% OTOA exhibits increased strength characteristics in the dynamic load mode. The resulting film materials based on optimized PLA/OTOA compositions could be used in various packaging and biomedical applications.

Properties of PLA films with cinnamic acid: Effect of the processing method

Polylactic acid (PLA) is a sustainable material for food packaging applications. The incorporation of cinnamic acid (CA) into PLA films was studied to obtain antimicrobial films, using two different techniques for film production, namely casting and thermal processing (TP). Whereas CA could be successfully incorporated at 5 and 10% w/w into TP films, only 3% w/w could be used in cast films without observing any crystallisation of CA. The acid reduced the glass transition temperature in TP films, while also improving their thermal resistance. Cast films retained a little proportion of the casting solvent which contributed to their plasticisation. The processing method greatly affected the mechanical properties of the films, with the cast films being significantly more plastic and stretchable. CA reduced the film’s stiffness and resistance to break and improved their water vapour and oxygen barrier capacity. Antibacterial assays with Listeria innocua did not show significant growth inhibition for any film, but the observed inhibition could be related to the acid concentration. This suggested that only a small amount of acid near the film surface could be released. Further research to promote the superficial concentration of cinnamic acid into PLA films is required to obtain active materials.

Effect of plasma treatment on the surface properties of polylactic acid films

Plasma treatment is one of the methods currently used to obtain polymeric materials with surface properties appropriate to the functionality for which they were designed. However, the effects achieved after surface modification are not always long lasting and involve chemical and physical changes in the outermost layer. In this context, the effects of both argon and oxygen plasma on polylactic acid (PLA) films deposited on titanium were studied to determine which physical and chemical processes occur at the surface, and their duration. Regarding physical surface changes, there were scarcely any differences between both plasmas: roughness was very similar after treatments, root mean square height (Sq) being 10 times higher than the control, without plasma. Water contact angle (WCA) showed that the surface became more hydrophilic after application of the plasma, although hydrophilization was longer lasting in the case of argon treatment.With regard to chemical changes, it was observed that the argon plasma treatment caused greater fragmentation of the polymer chains, and increased crosslinking between them. ToF-SIMS analysis made it possible to propose mechanisms to explain the formation of the fragments observed.

Preparation of formyl cellulose and its enhancement effect on the mechanical and barrier properties of polylactic acid films

Cellulose was modified by formic acid to prepare formyl cellulose (FC). The amount of formyl groups in FC was adjusted by controlling the reaction time, reaction temperature, and formic acid concentration. Then, FC was used to reinforce polylactic acid (PLA) films prepared by solution casting. Scanning electron microscopy (SEM) shows that long rod-like cellulose particles were broken into short rods after formylation and the introduction of FC made PLA surface rougher. The mechanical properties of PLA/FC films were improved by the inclusion of FC. Compared to pure PLA film, the PLA/FC composite film with 1 wt% FC (containing 15.79% formyl groups) showed a 48.59% increase in tensile strength and a 346% increase in Young's modulus. The addition of FC also resulted in better water barrier properties. The moisture absorption capacity and water vapor permeability were 40.56% and 51.43% lower than those of the pure-PLA film. The enhancement in properties for PLA/FC composites could be ascribed to the improved compatibility between PLA and cellulose with the introduction of hydrophobic formate groups. The PLA/FC composite films developed in this work could be highly potential for food packaging.

Improved water barrier properties of polylactic acid films with an amorphous hydrogenated carbon (a-C:H) coating

For the first time a 120 nm thick layer of amorphous hydrogenated carbon (a-C:H) deposited on top of 50 μm thick polylactic acid (PLA) films with radio-frequency plasma-enhanced chemical vapor deposition has been used as barrier to impede water diffusion through free-standing PLA films. Surface structures were examined by AFM and the water uptake was measured with Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy, a powerful technique for studying the diffusion of water through polymeric membranes. We have compared the water uptake of uncoated and a-C:H coated PLA films by placing the initially dry films in contact with deionized water for 24 h and monitoring the time-dependent absorbance changes in the FTIR spectra of the OH stretching bands of water in the wavenumber region of 2960–3750 cm−1. Mathematical modeling revealed that the water uptake was best described with a model consisting of three diffusion coefficients ascribed to monomeric and dimeric, clustered and bulk water having values between 1.1 × 10−8 and 2.6 × 10−10 cm2s−1. We show that the thin a-C:H layer effectively decreased the water uptake of PLA with 55% after a contact time of 24 h and even more at shorter times.

Effect of processing conditions on the physical, chemical and transport properties of polylactic acid films containing thymol incorporated by supercritical impregnation

This study deals on the supercritical impregnation of thymol in polylactic acid (PLA) in order to obtain biodegradable antimicrobial films by means of a procedure, which is in agreement with the principles of green chemistry, reducing the environmental impact of products and of its preparation processes. The impregnation tests were carried out in a high-pressure cell using supercritical carbon dioxide as impregnation medium at different operational conditions. These assays were implemented at pressures of 9 and 12MPa, a constant temperature equal to 40°C and different values of depressurization rates: 0.1, 1.0 and 10MPamin−1. Depending on the impregnation process conditions, thymol was incorporated into the films at concentrations from 13.5 to 20.5 %w/w. FTIR analyses confirmed the presence of thymol on the surface of the films. Furthermore, the supercritical impregnation process at the conditions used in this work produced a strong modification of the thermal and mechanical properties of the PLA films.On the other hand, release kinetic assays were carried out on the all prepared films. From these experimental results, it can be observed that the highest amounts of released thymol at the slowest depressurization rate were obtained. Meanwhile, the use of a previously reported mass transfer model shows that there is no significant effect of the supercritical impregnation process on the transport properties of PLA.From the experimental and theoretical results obtained in this work, it could be suggested that the impregnation of thymol in PLA using dense carbon dioxide is a promising technique to prepare active biodegradable materials for a wide range of applications.

Cold Oxygen Plasma Treatments for the Improvement of the Physicochemical and Biodegradable Properties of Polylactic Acid Films for Food Packaging.

The effects of cold plasma (CP) treatment on the physicochemical and biodegradable properties of polylactic acid (PLA) films were studied. The PLA films were exposed to CP for 40 min at 900 W and 667 Pa using oxygen as the plasma-forming gas. The tensile, optical, and dynamic mechanical thermal properties, surface morphology, printability, water contact angle, chemical structure, weight change, and biodegradability properties of the films were evaluated during storage for up to 56 d. The tensile and optical properties of the PLA films were not significantly affected by CP treatment (CPT; P > 0.05). The surface roughness and water contact angle of PLA films increased by CPT and further increased during storage for 56 d. The printability of the PLA films increased following CPT and remained stable throughout the storage period. CP-induced hydrophilicity was also sustained during the storage period. The PLA films lost 1.9% of their weight after CPT, but recovered 99.5% of this loss after 14 d in storage. Photodegradation, thermal, and microbial biodegradable properties of the films were significantly improved by CPT (P < 0.05). Accelerated biodegradation of CP-treated PLA sachets with and without cheese was observed in compost. These results demonstrate the potential of CPT for modifying the stiffness, water contact angle, and chemical structure of PLA films and improving the printability and biodegradability of the films for food packaging.

Preparation of Biodegradable Polymer Blended of Poly(L-Lactic Acid)/Cellulose Acetate Films in the Solvent Mixture

Nowadays, bio-plastic is the most popular in packaging field. Green chemistry and environmental responsibility has led it to develop the bio-plastic for use as packaging. Polylactic acid (PLA) is the well known staring material in this area. However, some properties of PLA films have to develop. Polymer blend is the interesting technique, in this work, PLA/Cellulose acetate (CA) blend films were prepare by casting solution at various compositions. Mixing solvent of Chloroform and acetone in acid condition were used, it was found that the mixing solvent can improved the compatibility and mechanical properties of the blend films. From this work CA can significantly increase PLA properties both the usefulness and the possible applications for bio-plastic material.

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