Enhancing Polyvinyl Alcohol Nanocomposites with Carboxy-Functionalized Graphene: An In-Depth Analysis of Mechanical, Barrier, Electrical, Antibacterial, and Chemical Properties

To enhance the various properties of polyvinyl alcohol (PVA), varying concentrations of carboxy-functionalized graphene (CFG) were employed in the preparation of CFG/PVA nanocomposite films. FTIR and XRD analyses revealed that CFG, in contrast to graphene, not only possesses carboxylic acid group but also exhibits higher crystallinity. Mechanical testing indicated a notable superiority of CFG addition over graphene, with optimal mechanical properties such as tensile and yield strengths being achieved at a 3% CFG concentration. Relative to pure PVA, the tensile strength and yield strength of the composite increased by 2.07 and 2.01 times, respectively. XRD analysis showed distinct changes in the crystalline structure of PVA with the addition of CFG, highlighting the influence of CFG on the composite structure. FTIR and XPS analyses confirmed the formation of ester bonds between CFG and PVA, enhancing the overall performance of the material. TGA results also demonstrated that the presence of CFG enhanced the thermal stability of CFG/PVA nanocomposite films. However, analyses using scanning electron microscopy and transmission electron microscopy revealed that a 3% concentration of CFG was uniformly dispersed, whereas a 6% concentration of CFG caused aggregation of the nanofiller, leading to a decrease in performance. The incorporation of CFG significantly enhanced the water vapor and oxygen barrier properties of PVA, with the best performance observed at a 3% CFG concentration. Beyond this concentration, barrier properties were diminished owing to CFG aggregation. The study further demonstrated an increase in electrical conductivity and hydrophobicity of the nanocomposites with the addition of CFG. Antibacterial tests against E. coli showed that CFG/PVA nanocomposites exhibited excellent antibacterial properties, especially at higher CFG concentrations. These findings indicate that CFG/PVA nanocomposites, with an optimized CFG concentration, have significant potential for applications requiring enhanced mechanical strength, barrier properties, and antibacterial capabilities.

Development and Characterisation of Composites Prepared from PHBV Compounded with Organic Waste Reinforcements, and Their Soil Biodegradation

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biobased and biodegradable polymer. This polymer is considered promising, but it is also rather expensive. The objective of this study was to compound PHBV with three different organic fillers considered waste: human hair waste (HHW), sawdust (SD) and chitin from shrimp shells. Thus, the cost of the biopolymer is reduced, and, at the same time, waste materials are valorised into something useful. The composites prepared were characterised by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile strength and scanning electron micrograph (SEM). Tests showed that chitin and HHW did not have a reinforcing effect on tensile strength while the SD increased the tensile strength at break to a certain degree. The biodegradation of the different composites was evaluated by a soil burial test for five months. The gravimetric test showed that neat PHBV was moderately degraded (about 5% weight loss) while reinforcing the polymer with organic waste clearly improved the biodegradation. The strongest biodegradation was achieved when the biopolymer was compounded with HHW (35% weight loss). The strong biodegradation of HHW was further demonstrated by characterisation by Fourier-transform infrared spectroscopy (FTIR) and solid-state nuclear magnetic resonance (NMR). Characterisation by SEM showed that the surfaces of the biodegraded samples were eroded.

Poly(Lactic Acid)-Based Graft Copolymers: Syntheses Strategies and Improvement of Properties for Biomedical and Environmentally Friendly Applications: A Review

As a potential replacement for petroleum-based plastics, biodegradable bio-based polymers such as poly(lactic acid) (PLA) have received much attention in recent years. PLA is a biodegradable polymer with major applications in packaging and medicine. Unfortunately, PLA is less flexible and has less impact resistance than petroleum-based plastics. To improve the mechanical properties of PLA, PLA-based blends are very often used, but the outcome does not meet expectations because of the non-compatibility of the polymer blends. From a chemical point of view, the use of graft copolymers as a compatibilizer with a PLA backbone bearing side chains is an interesting option for improving the compatibility of these blends, which remains challenging. This review article reports on the various graft copolymers based on a PLA backbone and their syntheses following two chemical strategies: the synthesis and polymerization of modified lactide or direct chemical post-polymerization modification of PLA. The main applications of these PLA graft copolymers in the environmental and biomedical fields are presented.

Long Chopped Glass Fiber Reinforced Low-Density Unsaturated Polyester Resin under Different Initiation

Long chopped glass fiber reinforced low-density unsaturated polyester resin (LCGFR-LDUPR) composite materials with light weight and excellent mechanical properties were prepared. It was proved that long chopped glass fiber, which was in length of 15.0 mm and chopped from ER4800-T718 plied yarn, was suitable for the preparation of LCGFR-LDUPR composite samples. With the coexistence of 1.50 parts per hundred of resin (phr) of methyl ethyl ketone peroxide (MEKP-II) and 0.05 phr of cobalt naphthenate, optimal preparation parameters were obtained, which were 20.00 phr of long chopped glass fiber, 2.50 phr of NH₄HCO₃, at a curing temperature of 58.0 °C. The lowest dosage of activated radicals produced by MEKP-II and cobalt naphthenate enabled the lower curing exothermic enthalpy and the slowest crosslinking for unsaturated polyester resin to carry out, resulting in a higher curing degree of resin. It was conducive to the formation, diffusion, and distribution of bubbles in uniform size, and also to the constitution of ideal three-dimensional framework of long glass fibers in the cured sample, which resulted in the LCGFR-LDUPR composite sample presenting the apparent density (ρ) of 0.68 ± 0.02 g/cm³, the compression strength (P) of 35.36 ± 0.38 MPa, and the highest specific compressive strength (P_s) of 52.00 ± 0.74 MPa/g·cm³. The work carried out an ideal three-dimensional framework of long chopped glass fiber in the reinforcement to low-density unsaturated polyester resin composite samples. It also presented the proper initiator/accelerator system of the lower curing exothermic enthalpy and the slowest crosslinking for unsaturated polyester resin.

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.

Antibacterial Property and Cytotoxicity of a Poly(lactic acid)/Nanosilver-Doped Multiwall Carbon Nanotube Nanocomposite

A novel method was used to synthesize a nanosilver-doped multiwall carbon nanotube (MWCNT-Ag), and subsequently, the novel poly(lactic acid) (PLA)- and MWCNT-Ag-based biocompatible and antimicrobial nanocomposites were prepared by melt blending. Based on energy dispersive X-ray spectrometry images, an MWCNT-Ag was successfully synthesized. The effect of the MWCNT-Ag on the PLA bionanocomposites was investigated by evaluating their thermal and mechanical properties, antifungal activity, and cytotoxicity. The nanocomposites exhibited a high degree of biocompatibility with the MWCNT-Ag content, which was less than 0.3 phr. Furthermore, tensile strength testing, thermogravimetric analysis, differential scanning calorimetry, and antibacterial evaluation revealed that the tensile strength, thermostability, glass transition temperature, and antibacterial properties were enhanced by increasing the MWCNT-Ag content. Finally, hydrolysis analysis indicated that the low MWCNT-Ag content could increase the packing density of PLA.