P, N-decorated halloysite nanotubes for flame retardancy enhancement of polyamide 6/aluminum diethylphosphinate

A thermosensitive luminescence halloysite-based nanocomposite enabling encryptable thermal printing

In situ formation of carbon dots on halloysite nanotubes is demonstrated by treating polyacrylamide-grafted halloysite nanotubes with polycarboxylic acid without the recourse to extremely high temperatures or solvents. Thermosensitive luminescence and phosphorescence properties are carefully investigated. The polyacrylamide-grafted halloysite nanotubes are further processed as composite films for encryptable thermal printing.

How the chemical structure of phosphoramides affect the fire retardancy and mechanical properties of polylactide?

Phosphoramides, as a kind of high-efficient fire retardants, have been designed in many structures and endowed exceptional fire retardancy to polylactide (PLA). However, due to ignorance of the structure-property correlation, the effect of phosphoramides' structure on the fire retardancy and mechanical properties of PLA is still unclear. Herein, a series of biobased phosphoramides (phosphoramide (V1), linear polyphosphoramide (V2) and hyperbranched polyphosphamide (V3)) were designed and incorporated into PLA, and the structural effect of phosphoramides on the fire-retardant and mechanical properties of PLA was deeply researched. Among three kinds of phosphoramides, the hyperbranched polyphosphoramide is more effective than the corresponding linear polyphosphoramide and phosphoramide in improving the fire-retardant and anti-dripping properties of PLA, and only linear polyphosphoramide shows a positive effect in the mechanical strength of PLA. This work provides a feasible strategy for creating mechanically robust and fire-retardant polymer composites by molecularly tailoring the structure of fire retardants and uncovering their structure-property relationship.

Synchronous preparation and modification of LDH hollow polyhedra by polydopamine: Synthesis and application

Layered double hydroxides (LDH) have irreplaceable advantages in the field of polymer flame retardancy, but their thermal stability and compatibility with matrix still need to be improved. In this paper, the bottom-up method is adopted, and the phosphorus series flame retardant triphenyl phosphate (TPP) was first encapsulated inside ZIF-67. On this basis, ZIF-67 was etched to produce LDH while modified by polydopamine (PDA) concomitantly. An organic coated polydopamine hollow cage lamellar LDH microstructure loaded with TPP was constructed, and its structure-performance relationship was verified. When 2 wt% TPP@LDH@Co-PDA was added to the epoxy resin, the LOI value of the composite was increased to 29.4 %, the peak heat release was reduced by 43.1 %, and the smoke release was significantly reduced. The unique microstructure endows epoxy composites with good flame retardancy, improves mechanical properties, and provides a new solution to the migration problem of phosphorous based flame retardants.

Influence of the Crystal Structure of Melamine Trimetaphosphate 2D Supramolecules on the Properties of Polyamide 6

To explore the influence of the crystal structure difference of melamine trimetaphosphate (MAP) on the application performance of its polymer composites, an intumescent flame retardant with the optimal crystal type was designed and synthesized to improve the mechanical properties and flame retardancy of polyamide 6 (PA6). I-MAP and II-MAP were obtained using different concentrations of MA and sodium trimetaphosphate (STMP) in an acidic aqueous solution. The morphology, chemical composition, and thermal stability were comprehensively characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The dispersion, mechanical properties, and flame retardancy of PA6/I-MAP and PA6/II-MAP were evaluated by SEM, stress and strain, limiting oxygen index test (LOI), vertical burning test (UL-94), cone calorimetry (CONE) test, and char residue analysis. The conclusion is as follows: I-MAP and II-MAP have a greater influence on the physical properties of PA6 but less influence on the chemical properties. Compared with PA6/I-MAP, the tensile strength of PA6/II-MAP is 104.7% higher, the flame rating reaches V-0, and PHRR is reduced by 11.2%.

Terminal group effects of DOPO-conjugated flame retardant on polyamide 6: Thermal stability, flame retardancy and mechanical performances

Two DOPO-conjugated flame retardants with or without amino terminal groups (DOPO-NH₂ and DIDOPO, respectively) were synthesized and incorporated into polyamide 6 (PA6). Results demonstrated the DOPO-NH₂ endowed superior thermal, flame retardant and mechanical performances to PA6 composites. With the same loading of 15 wt%, DOPO-NH₂ can catalyze the PA6 matrix more effectively and result in more residues at high temperature. The PA6 composites containing DOPO-NH₂ exhibited higher LOI (28.0%) compared to 25.0% for the sample containing DIDOPO, and the lower heat release capacity and peak heat release rate. Furthermore, the overall mechanical properties of PA6 composites containing DOPO-NH₂ outperformed the samples containing DIDOPO, even superior to that for PA6. Such a significant difference can be mainly attributed to the existence of amino-terminal group, which can interact with carboxyl group in PA6 as confirmed by dynamic mechanical analysis, improving the compatibility between the flame retardant and PA6 matrix.