Abstract Rigid polyurethane foam (RPUF) is utilized extensively in many different sectors because of its special benefits. Nevertheless, this also emphasizes how crucial its flame-retardant qualities are. In this paper, a simple and green coprecipitation method was used to prepare cobalt phytate (PA-Co) flame retardant, which was then introduced into silk fibroin (SF)-based RPUF. The successful preparation of PA-Co was confirmed by Fourier transform infrared spectroscopy (FTIR) testing. In addition, thermogravimetric analysis (TG), cone calorimeter test and compression test were employed to systematically analyze the thermal stability, flame retardancy, smoke suppression performance and mechanical properties of RPUF composites. TG results indicated that RPUF-4 composite (containing 5 wt% SF and 6 wt% PA-Co) exhibited the highest decomposition temperature at 50 % mass loss (T50 %), maximum mass loss rate temperature (TMax) and apparent activation energy (E) under three heating rates, thus demonstrating the optimal thermal stability. Specifically, the peak heat release rate (PHRR) and total heat release (THR) of RPUF-4 composite were 55.04 % and 36.08 % lower than those of RPUF-0 (containing 0 wt% SF and 0 wt% PA-Co), respectively. Furthermore, its total smoke release (TSR) and peak smoke production rate (PSPR) decreased by 54.17 % and 60.98 % in comparison with RPUF-0. In addition, the mechanical properties and thermal insulation performance of RPUF-4 composite were superior to those of previously reported PA-Co modified SF-based RPUF. This work realizes synergistic enhancement of flame retardancy, smoke suppression and mechanical properties via component synergy and interface regulation, providing a valuable reference for designing high-performance RPUF composites.
In this work, an alginate and calcium phytate-based complex (AlgCaPA) was synthesised and applied as a flame-retardant additive for poly(lactic acid) (PLA) in the presence of ammonium polyphosphate (APP) as a co-flame retardant. The total additive content was fixed at 15 mass%, and the ratio between AlgCaPA and APP was systematically optimised. To assess potential synergistic interactions between AlgCaPA and APP, the resulting PLA composites were investigated by thermoanalytical and spectroscopic methods, flammability tests, and mechanical measurements. The composite containing 5 mass% AlgCaPA and 10 mass% APP significantly outperformed PLA containing 15 mass% APP in several aspects; cone calorimetry revealed a 18% reduction in total heat release and a 74% reduction in total smoke production, accompanied by the formation of a substantial char residue. This enhanced flame-retardant performance is attributed to the formation of a compact, thermally stable hybrid char arising from calcium-induced crosslinking of phosphate networks and their integration with a carbonaceous matrix, which effectively enhances barrier properties during combustion.
With increasing awareness of fire safety, research on the flame retardancy of rigid polyurethane foams (RPUFs) has attracted extensive attention. However, previous studies on flame retardant formulations are not fully applicable to energy-storing polyurethane foams that require both high flame retardancy and thermal energy storage capabilities for thermal management. In this study, a flame-retardant RPUF containing 12.5 wt% expandable graphite (EG) and 2.5 wt% aluminium hydroxide (ATH) was first prepared. The Limiting Oxygen Index (LOI) of the foam increased from 20.3% for the non-flame-retardant sample to 27.4% after the addition of flame retardants, while the compressive strength and thermal conductivity were 271.10 kPa and 0.02942 W/(m⋅K), respectively. Based on this formulations, flame-retardant RPUFs with different performance characteristics were subsequently fabricated by varying the polyisocyanate index. Performance analysis results revealed that, at a constant flame retardant content, the foam with a polyisocyanate index of 1.44 exhibited the best overall performance compared with those having lower indices (e.g., 1.23); at this optimal index, the LOI reached 28.0%, with a compressive strength of 322.72 kPa, an apparent density of 80.0 kg/m 3 , and a thermal conductivity of 0.03179 W/(m⋅K). Subsequently, phase change microcapsules (PCMs) with polyurethane shells encapsulating n-octadecane were incorporated into the flame-retardant RPUF. Performance evaluation of the resulting RPUF showed that at a PCM loading of 6 wt%, the thermal energy storage performance was significantly enhanced while good flame retardancy was maintained. Under this condition, the LOI and phase change enthalpy were 26.3% and 10.79 J/g, and the compressive strength and thermal conductivity were 219.22 kPa and 0.03671 W/(m⋅K), respectively. These findings were further supported by thermogravimetric, dimensional stability and cone calorimetric analyses.
To address the inherent drawbacks of polypropylene (PP), including high flammability, severe melt dripping during combustion, and significant mechanical property deterioration after flame retardant incorporation, a novel halogen‐free intumescent flame retardant (IFR) system was developed in this work by blending natural polyphenol tannic acid (TA) with piperazine pyrophosphate (PAPP). PP composites were fabricated via melt blending. Systematic characterization of the thermal stability, combustion behavior, mechanical properties, and char layer microstructure of the as‐prepared PP composites revealed that the limiting oxygen index (LOI) increased with an increasing PAPP/TA mass ratio. The optimal PP/7PAPP/TA formulation achieved an LOI of 37%. Compared with PP, the peak smoke production rate (pSPR) of the PP/7PAPP/TA composite decreased by 91.11%, while the peak heat release rate (pHRR) decreased by 90.66%. These results confirm that TA exerts a significant synergistic enhancement effect on the IFR efficiency of PAPP. Specifically, a PAPP/TA mass ratio of 7:1 enables the as‐prepared composite to achieve the optimal balance between flame retardant performance, melt dripping inhibition, and mechanical property retention.
Commercial intumescent flame retardants (IFRs) effectively reduce the flammability of polypropylene (PP) but significantly deteriorate its weather resistance. Although hindered amine light stabilizers (HALS) can improve UV-aging resistance, their intrinsic acid-base antagonism with IFRs limits their combined application. In this study, a bio-based supramolecular approach is proposed by employing chitosan (CS) as a functional shell to encapsulate HALS116, forming a core-shell structured light stabilizer (CS@HALS116). The resulting PP/IFR/CS@HALS116 composites exhibit excellent flame retardancy, achieving a limiting oxygen index (LOI) of 30.0% and a UL-94 V-0 rating. Thermal analysis shows that the chitosan shell broadens the effective thermal action range of HALS116 to above 600 °C, preventing its premature degradation from interfering with char formation while enabling gas-phase radical scavenging. Meanwhile, the composites demonstrate outstanding UV-aging resistance, retaining 95.1% of tensile strength after 120 h of UV exposure and maintaining the V-0 rating. The carbonyl index (CI) is reduced to 0.37, much lower than that of neat PP (0.72). Mechanistic analysis reveals a dual anti-UV effect: the chitosan shell physically shields the NOR structure from acidic attack, while the hydrogen-bond network facilitates proton transfer and enhances nitroxide radical (NO·) regeneration. This work highlights a bio-based supramolecular design strategy for overcoming incompatibility in multifunctional polymer systems, offering a promising route toward durable and sustainable polyolefin materials.
Oilwell cementing in high-temperature, high-salinity reservoirs requires retarders capable of maintaining slurry stability, pumpability, and favorable rheological performance under severe downhole conditions. Conventional retarders, including sodium gluconate (SG) and sodium borate (SB), often suffer from thermal degradation, ionic incompatibility, and unstable rheological behavior at elevated temperatures and salinity. To overcome these limitations, sulfonated lignin nanoparticles (SLNPs) were synthesized from oil palm empty fruit bunch (EFB) biomass through chemical sulfonation and nanoparticle engineering. The sulfonation process enhanced the solubility, surface charge density, and adsorption capacity of the lignin, while nanoscale modification increased the surface area and interfacial reactivity of the particles. Physicochemical characterization confirmed the successful synthesis and functionalization of SLNPs. FESEM analysis revealed uniformly dispersed nanoparticles with an average particle size of approximately 24 nm, smaller than untreated lignin nanoparticles (≈37 nm). ATR-FTIR analysis further verified the incorporation of sulfonate functional groups through characteristic S=O and S–O absorption bands. The synthesized SLNPs also exhibited strong negative surface charge and high thermal stability, demonstrating their suitability for harsh oilwell environments. Rheological evaluation showed that SLNP-modified cement slurries exhibited improved structural stability and superior tolerance to elevated temperature and salinity compared with SG and SB systems. Increasing SLNP concentration enhanced the apparent viscosity (40–55 cP), plastic viscosity (15–25 cP), and yield point (10–18 lb/100 ft2), indicating stronger particle interactions and improved suspension stability. Power-Law modeling (R2 ≈ 0.999) confirmed favorable pseudoplastic and shear-thinning behavior suitable for slurry pumping and placement operations. HPHT thickening-time analysis conducted at 220 °C and 3000 psi further demonstrated the strong retarding capability of SLNPs, extending the thickening time from 263 min for neat cement slurry to approximately 540 min at 0.8 wt.% SLNP without flash setting or consistency bulging. Overall, the findings demonstrate that EFB-derived SLNPs are promising, sustainable HPHT cement retarders that enhance rheological stability, prolong pumpability, and improve hydration control in demanding well-cementing applications.
