Calcium-rich biowastes offer low-cost functional fillers for engineering polymers, but their use in polyamide 6 requires balanced control of interfacial contact, morphology, moisture response, transport behavior, crystallization, and thermal stability. Waste oyster shells were calcined at 1000 degrees C to obtain CaO-rich thermally treated oyster shell powder (TOS), which was incorporated into polyamide 6 by melt blending and compression molding at 5-25 wt%. Comparative characterization against commercial CaO confirmed that TOS contained 98.70 mass% CaO on an oxide-equivalent basis and retained a CaO/Ca(OH)2-rich mineral structure with minor Mg-containing species. The composites showed loading-dependent mechanical, morphological, moisture-related, oxygen-barrier, thermal, and antibacterial responses. The 10 wt% composite gave the best overall balance, increasing tensile strength from 25.0 to 30.5 MPa while maintaining compact fracture morphology, controlled surface roughness, and the lowest moisture content and water absorption. Surface microscopy and elemental mapping confirmed the distribution of Ca-rich domains, whereas excessive TOS caused particle exposure, surface heterogeneity, and local defects. The oxygen transmission coefficient decreased at moderate TOS contents but increased at 25 wt% because of defect-assisted transport. Thermal and crystalline analyses confirmed crystallization regulation and improved early weight-loss resistance. The 10 wt% composite showed antibacterial efficiencies of 95.45% +/- 1.70% against Escherichia coli and 89.41% +/- 1.46% against Staphylococcus aureus. A screening cradle-to-gate assessment estimated a 7.7% material-level reduction in global warming potential, linking waste valorization to verified multifunctional performance.
The organic electric-field regulator enables the polymer to have nonlinear conductivity and to self-regulate electric field. However, it may migrate out from the polymer matrix due to its small molecular weight, causing nonreversible damage to the electrical performance of the composite. In this work, to improve the long-term stability, the allyloxy polyethylene glycol (APEG) with electron-donating groups was grafted onto the low-density polyethylene (LDPE) chains by chemical grafting method. The composites were mainly characterized by weight loss rate, breakdown strength, conductivity, space charge distribution, and surface potential decay. In addition, the quantum chemical calculations were carried out on APEG and grafting APEG/LDPE composites. The results show that grafting APEG on LDPE macromolecules not only improves the long-term stability but also enhances the nonlinear conductivity, which is attributed to the increase in the electrostatic potential of electron-donating groups of APEG. The nonlinear conductivity helps homogenize the electric field distribution in polymer composites and helps dissipate the surface charges. This work lays a foundation for the improvement of all-organic nonlinear dielectrics.
Poly(vinyl alcohol) (PVA) is a commercial polymer with one of the lowest oxygen transmission rates, demonstrating considerable application potential in high-barrier packaging. However, its poor thermal processability severely limits its practical use. Based on molecular complexation technology for thermal processing of PVA developed in our research group, a small amount of boric acid (BA) was further introduced to form both crosslinking and hydrogen bonding in the system while preserving the excellent thermal processability and biaxial stretchability of PVA. In this way, high-performance modified PVA (G-PVA/BA) films were successfully fabricated via melt extrusion and biaxial stretching, leading to a significant enhancement in mechanical properties and barrier performance. With BA addition of only 0.10 wt.%, the biaxially stretched film exhibited an elongation at break of 434% and a tensile strength of 95 MPa, primarily attributing to the notable increase in crystallinity induced by orientation. The well-ordered crystal structure also provided a robust physical barrier, resulting in the low oxygen permeability coefficient of 1.117 & times; 10-18 cm3 & centerdot;cm/(cm2 & centerdot;s & centerdot;Pa) at 23 degrees C and 50% RH. This high-strength, high-barrier PVA film has broad application prospects in fields such as food, tobacco, electronics, and textile packaging.
ABSTRACT Poly(vinyl chloride) (PVC) is widely used for its versatility and cost‐effectiveness, but its inherent thermal instability requires advanced stabilization and flame‐retardant systems. Simultaneously enhancing thermal stability, flame retardancy, and mechanical performance remains challenging, as conventional additives often act through a single mechanism and suffer from poor PVC compatibility and limited synergy. Overcoming this, particularly through uniform dispersion and strong interfacial interaction between the organic and inorganic components, was a main challenge of this work. A hybrid formulation was developed to improve the thermal stability and fire performance of plasticized PVC by combining a pyridine‐based organotin polymer (PSn) with a multifunctional organo‐modified magnesium dihydroxide (MDH)@Zn‐Al layered double hydroxide (MLDH). Scanning electron microscope (SEM) showed improved dispersion with reduced aggregation in hybrid samples, while the absence of the LDH reflections in X‐ray diffraction (XRD) suggested uniform distribution within the PVC matrix. Thermal analysis revealed an enhancement in stability for the PSL5 sample (containing 2.5 wt.% PSn and 2.5 wt.% MLDH), where the onset degradation temperature increased from 165°C for neat PVC to 229°C, along with an increase in char residue from 10% to 21%. Thermal aging results further demonstrated a clear delay in discoloration compared to neat PVC. Flammability performance evaluation indicated that the total heat release (THR) decreased from 16.9 kJ g −1 (PVC) to 11 kJ g −1 (PSL5), while the limiting oxygen index (LOI) value increased from 26.8% to 28.7%, confirming relatively improved flame retardancy. Mechanical properties were also enhanced, with tensile strength increasing from 59.02 MPa (PVC) to 100.41 MPa (PSL5) and modulus from 2.68 to 4.98 GPa, while maintaining acceptable elongation.
ABSTRACT Polymer films composed of biodegradable polymers containing lignocellulosic fillers have been identified as good candidates for substitution for conventional petroleum‐derived packaging materials. In the current study, polyvinyl alcohol (PVA) biofilms containing 5–25 wt% alkali‐treated Sapindus mukorossi shell filler (at. SMSF) were synthesized through the solution casting method. The objective of this study is to explore the structure of PVA biofilms, thermal behavior, mechanical behavior, optical, surface, and antibacterial properties. The removal of amorphous parts through alkali treatment exposed cellulose‐filled microfibrils, resulting in the development of strong intermolecular hydrogen bonds with the PVA matrix. FTIR showed improvement in interfacial compatibility without the creation of any new chemical bond. On the other hand, XRD analysis depicted an increase in crystallinity from 32.5% to 54.8% and crystallite size from 18.2 to 31.3 nm. Thermal analysis proved that the biofilms exhibited good thermal stability and high degradation temperatures, along with a reduction in heat flow and an increase in char formation. SEM and surface roughness analysis depicted uniform dispersion of fillers and compact morphology, especially in the case of medium loading of fillers. There was significant enhancement in mechanical properties, where tensile strength and Young's modulus increased from 23.5 to 46.8 MPa and from 29.5 to 62.3 MPa, respectively. The contact angle of water increased from 51.3° to 92.5°, showing remarkable improvement in water repellence. Moreover, PVA/25 wt% at. SMSF showed significant UV‐blocking efficiency and very good antibacterial properties toward Escherichia coli and Bacillus cereus . The results showed that alkaline‐treated SMSF can be a very good bio‐component to develop mechanically tough, thermally stable, moisture‐resistant, and antibacterial PVA biofilm for use as a packaging material.
