Evaluating distillers grains as bio-fillers for high-density polyethylene

Bioactive composite films with improved antioxidant and barrier properties prepared from sodium alginate and deep eutectic solvent treated distillers' grains

In this work, a straightforward approach utilizing distillers' grains (DG) waste and sodium alginate (SA) was developed to prepare functional and bioactive packaging films. Deep eutectic solvents (DESs) were initially synthesized from choline chloride (CO), betaine (BO), glycerol (GO), and oxalic acid. Composite films were then prepared from DES-treated DG slurry and SA at different ratios. Characterization and analysis revealed that adding 75 % CO-treated DG slurry reduced the water vapor permeability (WVP) by over 66 % compared to that of the SA film. Composite films containing CO/BO-treated DG slurry had an ultraviolet light barrier rate exceeding 99 %, while those with 75 % DES-treated DG slurry demonstrated excellent antioxidant activity, with a 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) free radical scavenging rate of 80.14 %-88.35 %, representing a 322.45 %-365.73 % increase compared to that of the pure SA film. These composite films also exhibited favorable mechanical properties (31.58 MPa, 5.53 % EB), thermal stability, and biodegradability, extending the shelf life of grapes by 1.8 times. In conclusion, bioactive composite films derived from DES-treated DG are expected to replace petroleum-based plastics, enhancing sustainable biomass use and environmental responsibility.

Synergistic effect of phytic acid and eggshell bio-fillers on the dual-phase fire-retardancy of intumescent coatings applied on cellulosic substrates

Cellulosic substrates, including wood and thatch, have become icons for sustainable architecture and construction, however, they suffer from high flammability because of their inherent cellulosic composition. Current control measures for such hazards include applying intumescent fire-retardant (IFR) coatings that swell and form a char layer upon ignition, protecting the underlying substrate from burning. Typically, conventional IFR coatings are opaque and are made of halogenated compounds that release toxic fumes when ignited, compromising the roofing's aesthetic value and sustainability. In this work, phytic acid, a naturally occurring phosphorus source extracted from rice bran, was used to synthesize phytic acid-based fire-retardants (PFR) via esterification under reflux, along with powdered chicken eggshells (CES) as calcium carbonate (CaCO3) bio-filler. These components were incorporated into melamine formaldehyde resin to produce the transparent IFR coating. It was revealed that the developed IFR coatings achieved the highest fire protection rating based on UL94 flammability standards compared to the control. The coatings also yielded increased LOI values, indicative of self-extinguishing properties. A 17 °C elevation of the IFR coating's melting temperature and a significant ∼172% increase in enthalpy change from the control were observed, indicating enhanced fire-retardancy. The thermal stability of the coatings was improved, denoted by reduced mass losses, and increased residual masses after thermal degradation. As validated by microscopy and spectroscopy, the abundance of phosphorus and carbon groups in the coatings' condensed phase after combustion indicates enhanced char formation. In the gas phase, TG-FTIR showed the evolution of non-flammable CO2, and fire-retardant PO and P-O-C. Mechanical property testing confirmed no reduction in the adhesion strength of the IFR coating. With these results, the developed IFR coating exhibited enhanced fire-retardancy whilst remaining optically transparent, suggestive of a dual-phase IFR protective mechanism involving the release of gaseous combustion diluents and the formation of a thermally insulating char layer.

Diminishment the gas permeability of polyethylene by "densification" of the amorphous regions

High-density polyethylene/paraffin wax (HDPE/wax) systems with adjustable density of the amorphous regions were prepared by a melt-blending process to optimize/control the final oxygen barrier properties. The introduction of paraffin wax (a low molecular weight modifier) is the key to tune the gas permeability properties of polyethylene-based materials. Density gradient column (DGC) measurements distinctly showed that the incorporation of modifier led to densification of the amorphous phase of semicrystalline HDPE consisting in a decrease in the average fractional free volume confirmed by positron annihilation lifetime spectroscopy (PALS). Polyethylene with "densified" amorphous phase exhibits lower oxygen permeability parameters compared to pristine polyethylene, but it is characterized by similar thermal and thermomechanical properties. An increase in the density of the amorphous regions of polyethylene by about 0.003 g/cm3, which corresponds to 0.3%, reduces the permeability of oxygen by up to 22%. For the first time, it has been proven that by controlling the density of the amorphous regions of semicrystalline polymers, it is possible to obtain materials with appropriate transport properties (without changing other properties) for applications meeting specific requirements.

Dynamic Behavior of Thermally Affected Injection-Molded High-Density Polyethylene Parts Modified by Accelerated Electrons

Polyethylenes are the most widely used polymers and are gaining more and more interest due to their easy processability, relatively good mechanical properties and excellent chemical resistance. The disadvantage is their low temperature stability, which excludes particular high-density polyethylenes (HDPEs) for use in engineering applications where the temperature exceeds 100 °C for a long time. One of the possibilities of improving the temperature stability of HDPE is a modification by accelerated electrons when HDPE is cross-linked by this process and it is no longer possible to process it like a classic thermoplastic, e.g., by injection technology. The HDPE modified in this way was thermally stressed five times at temperatures of 110 and 160 °C, and then the dynamic tensile behavior was determined. The deformation and surface temperature of the specimens were recorded by a high-speed infrared camera. Furthermore, two thermal methods of specimen evaluation were used: differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The result of the measurement is that the modification of HDPE by accelerated electrons had a positive effect on the dynamic tensile behavior of these materials.

Mechanical, thermal, and tribological characterization of bio-polymeric composites: A comprehensive review

The current review extensively discusses the effects of various natural fillers on mechanical, thermal, and tribological characteristics of polypropylene, polyethylene, poly(vinyl chloride), and polyester resin matrices. The discussion has considered all of the tensile, flexural, and impact properties along with the wear rate and thermogravimetric analysis of a wide range of natural reinforcements. Detailed comparative studies about the factors that influence the fillers’ performance in the polymeric composites were also conducted to give the reader a comprehensive understanding to enable a better selection of the optimized characteristics to develop a more sustainable design. This systematic review indicates that the majority of green fillers had an adverse effect on the tensile strength of the considered matrices, but generally improved the tensile modulus. Moreover, the studied fillers enhanced the flexural modulus property for all mentioned matrices. The impact strength was dramatically influenced by the intrinsic characteristic of the filler type.

Preparation, Characterization, and Bioactivity Evaluation of Polyoxymethylene Copolymer/Nanohydroxyapatite-g-Poly(ε-caprolactone) Composites

In this work, nanohydroxyapatite (HAp) was functionalized with poly(ε-caprolactone) (PCL), using 1,6-hexamethylene diisocyanate (HDI) as a coupling agent, and then incorporated into the polyoxymethylene copolymer (POM) matrix using the extrusion technique. The obtained POM/HAp-g-PCL composites were investigated using FTIR, DSC, TOPEM DSC, and TG methods. Mechanical properties were studied using destructive and non-destructive ultrasonic methods, wettability, and POM crystallization kinetics in the presence of HAp-g-PCL. Moreover, preliminary bioactivity evaluation of the POM/HAp-g-PCL composites was performed using the Kokubo method. It was found that the introduction of HAp-g-PCL to the POM matrix has a limited effect on the phase transitions of POM as well as on its degree of crystallinity. Importantly, HAp grafted with PCL caused a significant increase in the thermal stability of the POM, from 292 °C for pristine POM to 333 °C for POM modified with 2.5% HAp-g-PCL. If unmodified HAp was used, a distinct decrease in the thermal stability of the POM was observed. Crystallization kinetic studies confirmed that HAp-g-PCL, in small amounts, can act as a nucleating agent for the POM crystallization process. Moreover, incorporation of HAp-g-PCL, although slightly decreasing the mechanical properties of POM composites, improved the crucial parameter in biomedical applications, namely the in vitro bioactivity.

Barrier performance and biodegradability of antibacterial poly(butylene adipate-co-terephthalate) nanocomposites reinforced with a new MWCNT-ZnO nanomaterial

A new nanomaterial or nano-filler in the form of multiwalled carbon nanotube-zinc oxide (MWCNT-ZnO) was synthesized for the purpose of modifying poly(butylene adipate-co-terephthalate) (PBAT) and its derivative (modified PBAT or MPBAT) through a melt-blending method (MPBAT was obtained by introducing maleic anhydride groups into PBAT). The effect of the new nano-filler on the properties of resultant nanocomposites was determined from the characterization of mechanical properties, morphology, crystallinity, thermal stability, barrier properties, hydrophilicity, conductivity, antibacterial property, and biodegradability. The results showed that MPBAT nanocomposites had stronger mechanical properties, better barrier properties, and higher electrical conductivity than PBAT nanocomposites. Scanning electron microscopy illustrated that MWCNT-ZnO had better compatibility with MPBAT than with PBAT. At 0.2% MWCNT-ZnO, the MPBAT/MWCNT-ZnO nanocomposite film exhibited the greatest mechanical properties (17.74% increase in tensile strength, 22.17% in yield strength, and 14.29% in elongation at break). When the MWCNT-ZnO content was 0.4%, the nanocomposite film demonstrated the best water vapor barrier ability (an increase of 30.4%). The MPBAT/MWCNT-ZnO film with 0.6% MWCNT-ZnO turned out to have the best oxygen barrier performance (an increase of 130% relative to pure PBAT). It was shown from the results of antibacterial evaluation that the new nanomaterial could impart PBAT and MPBAT with antibacterial activity. The biodegradability tests indicated that an MWCNT-ZnO content of 0.2% could slightly reduce the biodegradability, and when the content was higher than 0.2%, the weight loss rate would increase.

Barrier Properties and Hydrophobicity of Biodegradable Poly(lactic acid) Composites Reinforced with Recycled Chinese Spirits Distiller's Grains

Adding natural biomass to poly(lactic acid) (PLA) as a reinforcing filler is a way to change the properties of PLA. This paper is about preparing PLA/biomass composites by physically melting and blending Chinese Spirits distiller's grains (CSDG) biomass and PLA to optimize the composite performance. Composites of modified PLA (MPLA) with varying amounts of CSDG were also prepared by the melt-mixing method, and unmodified PLA/CSDG composites were used as a control group for comparative analysis. The functional groups of MPLA enhanced the compatibility between the polymer substrate and CSDG. The composite water vapor/oxygen barrier and mechanical properties were studied. It was found that the barrier and mechanical properties of MPLA/CSDG composites were significantly improved. SEM was adopted to examine the tensile section structure of the composites, and the compatibility between the filler and the matrix was analyzed. An appropriate amount of CSDG had a better dispersibility in the matrix, and it further improved the interfacial bonding force, which in turn improved the composite mechanical properties. X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry were conducted to determine the crystalline properties and to analyze the stability of the composites. It was found that the CSDG content had a significant effect on the crystallinity. Barrier and biodegradation mechanisms were also discussed.

Characterization of network bonding created by intercalated functionalized graphene and polyvinyl alcohol in nanocomposite films for reinforced mechanical properties and barrier performance

Graphene that consists of less than 10 layers is expensive; moreover, it tends to agglomerate. These disadvantages restrict its utility. In this regard, the present study aimed to reduce the number of layers of a functionalized graphene (FG) with 10-30 layers to less than 10 layers by using an ultrasonic processor. We prepared nanocomposite films of polyvinyl alcohol (PVA) incorporated with FG by a simple hydrothermal method and ultrasonic dispersion. Oxygen transmission rate and water vapor permeability were considerably increased on account of modifying PVA with FG. Furthermore, the mechanical properties, thermostability, and barrier properties were improved. The barrier efficiency of the nanocomposites at different temperatures remained high for long periods of operation because of the network bonding. A simple procedure involving relatively low-cost nanomaterials could unlock the potential of nanocomposite FG/PVA films in the fields of coating, packaging, and semiconductor materials.