Preparation and Characterization of Films Extruded of Polyethylene/Chitosan Modified with Poly(lactic acid)

Preparation, characterization, and life cycle assessment of banana rachis-recycled high-density polyethylene composites

Agro-industrial wastes are sustainable resources that have advantages as a reinforcement for polymeric matrices. This study examined the use of banana rachis fiber (BRF) in reinforcing the recycled high-density polyethylene (rHDPE) matrix. For this purpose, polymer composites with 5-20 wt% of BRF were prepared by the extrusion process using a twin-screw extruder and followed a hot press method. The structure of rHDPE/BRF composites and their characteristic peaks of degradation were successfully identified by the Fourier-transformed infrared spectroscopy and thermogravimetric analysis techniques, respectively, revealing a good dispersion of BRF in rHDPE. Differential scanning calorimetry results of the composites demonstrated that melt enthalpy decreases as the amount of BRF increases. XRD diffractograms revealed a crystallinity reduction of rHDPE due to the increase of fiber within the polymer matrix, which is reflected in the characteristic peaks' intensity decrease of HDPE. Variation in thermal and chemical properties with the addition of BRF in rHDPE was successfully evaluated in this study. Life cycle assessment for 1 kg composite production has also been evaluated. The banana rachis-rHDPE composite materials reduce the overall environmental impacts when the filler concentration increases.

Bioactive antioxidant coatings for poly(lactic acid) packaging films: polyphenols affect coating structure and their release in a food simulant

BACKGROUND

Poly(lactic acid) (PLA) has limited uses for moist and acidic foods due to its barrier properties, which are fairly poor, and its sensitivity to moisture.

RESULTS

Deposition of thin coatings based on natural biopolymers (gelatin) incorporating bioactive agents has allowed the development of active packaging materials while maintaining their biodegradability and their food contact material ability. Gelatin coatings containing two phenolic acids (tannic and gallic) have been tested. These coated PLA films displayed a reduction of the moisture permeability and a slight modification of the thermal properties of PLA. The antioxidant properties of the films and their release kinetics in a simulant medium have been studied and modelled.

CONCLUSIONS

Incorporation of phenolic acids induced interactions with the gelatin that modified the structure of the network and positively affected the retention, diffusivity, and transfer rate of the bioactive compounds when coated PLA films were in contact with the liquid simulant. © 2022 Society of Chemical Industry.

Preparation, Characterization and Evaluation of Antibacterial Properties of Polylactide-Polyethylene Glycol-Chitosan Active Composite Films

Chitin is a natural biopolymer obtained from the exoskeleton of crustaceans. Chitosan is a derivative of chitin, which has antimicrobial properties and potential applications in several industries. Moreover, the composites of chitosan with other biodegradable polymers, such as polylactide (PLA) as packaging film, have shown promising results. In this study, chitosan was obtained and characterized from shrimp shells. Then, polylactide-chitosan composite films were prepared by a solvent casting technique using various amounts of chitosan (0.5–2% w/w) and polyethylene glycol as plasticizer (10% w/w). Thermal, mechanical properties, Fourier-transform infrared, scanning electron microscopy, as well as antibacterial properties of composite films were determined. It was found that adding chitosan (CH) into PLA films has a significant effect on tensile strength and no effect on thermal properties. The results showed a reduction on average of 1 log of colony-forming units against Staphylococcus aureus, while there is no antibacterial effect against Salmonella typhimurium. The study proved the antibacterial effect of CH in films of PLA against Gram-positive bacteria and appropriate mechanical properties. These films could be used for the development of biodegradable/eco-friendly food packaging prototypes, as a potential solution to replace conventional non-degradable packaging materials.

Optimization of Thermoplastic Blend Matrix HDPE/PLA with Different Types and Levels of Coupling Agents

High-density polyethylene (HDPE) and poly(lactic) acid (PLA) blends with different ratios of both polymers, namely, 30:70, 50:50, and 70:30, were produced. Polyethylene-grafted maleic anhydride and a random copolymer of ethylene and glycidyl methacrylate were also considered as compatibilizers to modify HDPE/PLA optimal blends and were added in the amounts of 1, 3, and 5 wt.%. Different properties of the blends were evaluated by performing tensile tests and scanning electron microscopy to analyze blend and interfaces morphology. Moreover, thermomechanical analysis through differential scanning calorimetry, thermo-gravimetric analysis, and infrared spectroscopy were also performed. The blend containing equal amounts of HDPE and PLA seemed to present a good balance between amount of bio-derived charge and acceptable mechanical properties. This suggests that these blends have a good potential for the production of composites with lingo-cellulosic fillers.

Degradation of polyethylene microplastics in seawater: Insights into the environmental degradation of polymers

Microplastic contamination of aquatic environments has become an increasingly alarming problem. These, defined as particles <5 mm, are mostly formed due to the cracking and embrittlement of larger plastic particles. Recent reports show that the increasing presence of microplastics in the environment could have significant deleterious consequences over the health of marine organisms, but also across the food chain. Herein, we have studied the effects of artificial seawater on polyethylene (PE)-based beads by exposing them up to eight weeks to saltwater in stirred batch reactors in the dark and examined the structural and morphological changes these endured. Electron microscopy observations showed that artificial seawater induces severe microcracking of the pellets' surfaces. Additionally, Fourier transform infrared spectroscopy (FTIR) analyses evidenced the formation of oxidized groups whenever these particles were exposed to water and an increase in organic matter content of the waters in which the pellets were kept was evidenced by Raman spectroscopy. There were also noticeable consequences in the thermal stability of the polyethylene pellets, as determined by thermogravimetric studies (TGA). Furthermore, the parallel exposure of polyethylene pellets to UV radiation yielded less pronounced effects, thus underscoring its lower preponderance in the degradation of this material. These results highlight the importance of determining the mechanisms of degradation of microplastics in marine settings and what the implications may be for the environment. Overall, the herein presented results show that a relatively short period of time of accelerated exposure can yield quantifiable chemical and physical impacts on the structural and morphological characteristics of PE pellets.

HDPE/Chitosan Blends Modified with Organobentonite Synthesized with Quaternary Ammonium Salt Impregnated Chitosan

In this study, blends based on a high density polyethylene (HDPE) and chitosan (CS) were successfully prepared by melt processing, in a laboratory internal mixer. The CS biopolymer content effect (up to maximum of 40%), and, the addition of bentonite clay modified with quaternary ammonium salt (CTAB) impregnated chitosan as a compatibilizing agent, on the properties of the blends was analyzed by Fourier transform-infrared spectroscopy (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analyses (TG), tensile strength, and scanning electron microscopy (SEM). The use of clay modified with CTAB impregnated chitosan, employing a method developed here, improved the compatibility of HDPE with chitosan, and therefore the thermal and some of the mechanical properties were enhanced, making HDPE/chitosan blends suitable candidates for food packaging. It was possible to obtain products of synthetic polymer, HDPE, with natural polymer, chitosan, using a method very used industrially, with acceptable and more friendly properties to the environment, when compared to conventional synthetic polymers. In addition, due to the possibility of impregnated chitosan with quaternary ammonium salt exhibit higher antibacterial activity than neat chitosan, the HDPE/chitosan/organobentonite blends may be potentially applied in food containers to favor the preservation of food for a longer time in comparison to conventional materials.

Insight into the significant roles of microstructures and functional groups on carbonaceous surfaces for acetone adsorption

To understand the roles of pore structures and functional groups on acetone adsorption, activated carbons (ACs) with different properties were obtained by surface modification. XRD, SEM, TEM and nitrogen adsorption were used to identify the structural characteristics of the ACs, while TG-DTA, FTIR, XPS and Boehm titration were applied to analyse the surface chemistries. The microporous surface areas showed a positive linear correlation to the acetone adsorption amounts, and increasing the carboxylic groups could improve the uptake of strongly adsorbed acetone. HNO₃ modified AC (AC-N) was found to exhibit an excellent adsorption capacity of 5.49 mmol g⁻¹, which might be attributed to the developed microporous structures and abundant carboxylic groups. The desorption activation energies (E_d) of strongly adsorbed acetone on AC-N and AC were both determined to be 81.6 kJ mol⁻¹, indicating the same adsorption sites on different activated carbons, suspected to be carboxylic groups. The possible adsorption mechanism of acetone on carbonaceous surfaces was also proposed.

To understand the roles of pore structures and functional groups on acetone adsorption, activated carbons (ACs) with different properties were obtained by surface modification.

Preparation and Characterization of Extruded Composites Based on Polypropylene and Chitosan Compatibilized with Polypropylene-Graft-Maleic Anhydride

The preparation of composites of synthetic and natural polymers represent an interesting option to combine properties; in this manner, polypropylene and chitosan extruded films using a different proportion of components and polypropylene-graft-maleic anhydride (PPgMA) as compatibilizer were prepared. The effect of the content of the biopolymer in the polypropylene (PP) matrix, the addition of compatibilizer, and the particle size on the properties of the composites was analyzed using characterization by fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), tensile strength, and contact angle, finding that in general, the addition of the compatibilizer and reducing the particle size of the chitosan, favored the physicochemical and morphological properties of the films.