Microencapsulation of bisneopentyl glycol dithiopyrophosphate and its flame retardant effect on polyvinyl alcohol

Innovative engineering of scalable, renewable and spherical organic nanoparticles for high fire safety, UV protection and antibacterial properties of polyvinyl alcohol nanocomposites films

A novel and environmentally friendly route was developed for production of sustainable flame retardant, antibacterial and UV protective nanoparticles for polymeric films nanocomposites. For the first time, dried molokhia leaves were engineered into spherical nanoparticles with an average size of 8.5 nm via an eco-friendly, one-pot solid-state ball-milling method. The engineered nanoparticles were proved using spectroscopic and microscopic techniques. The sustainable nanoparticles were employed as an efficient and green flame retardant, antibacterial and UV protective materials for polyvinyl alcohol (PVA) nanocomposite films. The distinct compatibility between PVA chains and spherical nanoparticles afford excellent homogeneous dispersion of each nanoparticle in the polymer matrix. Compared to blank PVA film which burned at a rate of 125 mm/min, the novel nanoparticles achieved significant flame retardancy for polymer nanocomposites films recording zero rate of burning. Their outstanding charring ability and naturally doped elemental composition were attributed to their higher flame retardancy achieved. Moreover, the newly developed multifunctional nanoparticles integrated outstanding UV protection feature to developed polymer nanocomposite films recording UV protection factor superiority of more than 900% compared to nanoparticle free film. Noteworthy to note that, the nanoparticles afford excellent inhibition to bacterial growth against Escherichia coli and Staphylococcus aureus over the surface of developed polymer nanocomposite films achieving clear inhibition zone of 9 and 7.6 mm compared to zero mm for pristine polymer film, respectively. In addition, a proposed and clarified flame retardancy mechanism was presented. Additionally, an assessment was conducted regarding the economic feasibility of producing sustainable multifunctional nanoparticles on an industrial scale.

Applying pH Modulation to Improve the Thermal Stability of Melamine-Formaldehyde Microcapsules Containing Butyl Stearate as a Phase-Change Material

This paper presents a two-stage microencapsulation process that uses pH modulation to enhance the thermal stability of microcapsules that consist of a melamine-formaldehyde (MF) shell and a butyl stearate core. In the first stage, the pH value was modulated between 6.0 and 8.0. Rising the pH value to 8.0 slowed the polycondensation rate, allowing the MF resin with a lower degree of polymerization to migrate to the capsule surface and form a smooth shell. Lowering the pH value to 6.0 accelerated polycondensation. In the second stage, a relatively fast, continuous reduction in the pH value to 5.0 led to further MF polycondensation, hardening the shell. Post-curing at 100 °C prevented shell damage caused by the liquid-gas phase transition of the core material during the process. The microcapsules produced by increasing the pH value to 8.0 twice demonstrated improved thermal stability, with only a minimal overall weight loss of 5% at 300 °C. Significant weight loss was observed between 350 and 400 °C, temperatures at which the methylene bridges in the MF shell undergo thermal degradation. The results from differential scanning calorimetry, electron microscopy, and thermogravimetry analyses confirmed a successful optimization of the microencapsulation, showing that these microcapsules are promising for thermal energy storage and other applications that require high thermal stability.

A Novel One-Step Reactive Extrusion Process for High-Performance Rigid Crosslinked PVC Composite Fabrication Using Triazine Crosslinking Agent@Melamine-Formaldehyde Microcapsules

In this work, we propose, for the first time, a simple, fast, and efficient strategy to fabricate high-performance rigid crosslinked PVC composites by continuous extrusion. This strategy improves the poor processing fluidity of composites and solves the impossibility of conducting extrusion in one step via using microcapsule-type crosslinking agents prepared by in situ polymerization to co-extrude with PVC blends. The results demonstrate that the PVC/microcapsule composites were successfully prepared. Within the studied parameters, the properties of crosslinked PVC gradually increased with the addition of microcapsules, and its Vicat softening temperature increased from 79.3 °C to 86.2 °C compared with pure PVC. This study shows the possibility for the industrial scale-up of the extrusion process for rigid crosslinked PVC.

Synergistic Effect of Graphene Oxide and Mesoporous Structure on Flame Retardancy of Nature Rubber/IFR Composites

Aiming to improve the flame retardancy performance of natural rubber (NR), we developed a novel flame retardant synergistic agent through grafting of MCM-41 to graphene oxide (GO), named as GO-NH-MCM-41, as an assistant to intumescent flame retardants (IFR). The flame retardancy of NR/IFR/GO-NH-MCM-41 composites was evaluated by limited oxygen index (LOI), UL-94, and cone calorimeter test. The LOI value of NR/IFR/GO-NH-MCM-41 reached 26.3%; the UL-94 ratings improved to a V-0 rating. Moreover, the addition of GO-NH-MCM-41 decreased the peak heat release rate (PHRR) and the total heat release (THR) of the natural rubber composites. Furthermore, the addition of GO-NH-MCM-41 increased the thickness of char residue. The images of SEM indicated the char residue was more compact and continuous. The degradation of GO-NH-MCM-41-based NR composites was completed with a mass loss of 35.57% at 600 °C. The tensile strength and the elongation at break of the NR/IFR/GO-NH-MCM-41 composites were 13.9 MPa and 496.7%, respectively. The results of the rubber process analyzer (RPA) reached the maximum value, probably due to a better network of fillers in the matrix.

The Effects of a Macromolecular Charring Agent with Gas Phase and Condense Phase Synergistic Flame Retardant Capability on the Properties of PP/IFR Composites

In order to improve the efficiency of intumescent flame retardants (IFRs), a novel macromolecular charring agent named poly(ethanediamine-1,3,5-triazine-p-4-amino-2,2,6,6-tetramethylpiperidine) (PETAT) with gas phase and condense phase synergistic flame-retardant capability was synthesized and subsequently dispersed into polypropylene (PP) in combination with ammonium polyphosphate (APP) via a melt blending method. The chemical structure of PETAT was investigated by Fourier transform infrared spectroscopy (FTIR), and ¹H nuclear magnetic resonance (NMR) spectroscopy. Thermal properties of the PETAT and IFR systems were tested by thermogravimetric-derivative thermogravimetric analysis (TGA-DTG) and thermogravimetry–Fourier transform infrared spectroscopy (TG-FTIR). The mechanical properties, thermal stability, flame-retardant properties, water resistance, and structures of char residue in flame-retardant composites were characterized using tensile and flexural strength property tests, TGA, limiting oxygen index (LOI) values before and after soaking, underwritten laboratory-94 (UL-94) vertical burning test, cone calorimetric test (CCT), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDXS), and FTIR. The results indicated that PETAT was successfully synthesized, and when the ratio of APP to PETAT was 2:1 with 25 wt % loading, the novel IFR system could reduce the deterioration of tensile strength and enhance the flexural strength of composites. Meanwhile, the flame-retardant composite was able to pass the UL-94 V-0 rating with an LOI value of 30.3%, and the peak of heat release rate (PHRR), total heat release (THR), and material fire hazard values were considerably decreased compared with others. In addition, composites also exhibited excellent water resistance properties compared with traditional IFR composites. SEM-EDXS and FTIR analyses of the char residues, as well as TG-FTIR analyses of IFR were used to investigate the flame-retardant mechanism of the APP/PETAT IFR system. The results indicated that the efficient flame retardancy of PP/IFR composites could be attributed to the synergism of the free radical-quenching and char layer-protecting mechanisms in the gas phase and condense phase, respectively.

Efficient flame retardant polyvinyl alcohol membrane through surface graft method

This paper introduced an efficient charring method through surface graft. The flame retardant was grafted on membrane surface through the chemical reaction between the reactive groups of the P–Si compound and hydroxyl ones of PVA.

A novel method to prepare a flame-retardant polyvinyl alcohol fiber with modified acrylonitrile coatings

A novel fiber with a PVA substrate and modified PAN coating was constructed, which has favorable tensile strength and flame retardance.