In this study, the curing and thermal degradation kinetics of epoxidized soybean oil (ESO) were investigated using L-aspartic acid (AA) and DL-malic acid (MA)-two bio-derived dicarboxylic acids-as curing agents, in the presence of aluminium triflate (AT) as catalyst (0.5 and 1 wt%). Reactions were monitored by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and coupled TGA-FTIR techniques, and data were evaluated by model-free and model-fitting kinetic approaches to elucidate cure behavior, degradation mechanisms, and volatile decomposition products. Both ESO/AA and ESO/MA systems exhibited comparable total curing enthalpies, with AA formulations showing consistently higher activation energies, attributed to the zwitterionic nature of the amino acid. Despite the higher energetic demand, ESO/AA compositions demonstrated superior thermal stability, with onset degradation temperatures above 200 degrees C and degradation activation energies (Ea) exceeding 700 kJ & centerdot;mol-1. Model fitting revealed a multi-step degradation mechanism, best described by Avrami-Erofeev (An) and & Scaron;est & aacute;k-Berggren (SB) models, indicating nucleation-dominated behavior with secondary surface contraction. TGA-FTIR analysis confirmed water, carbon dioxide, and carbon monoxide as primary gaseous products. These findings highlight the strong potential of amino acid-cured ESO systems as thermally robust, non-toxic, and renewable alternatives to conventional epoxy resins in applications such as adhesives and composites.
Water solubility of poly(vinyl alcohol) (PVA) advantageously prevents the formation of harmful micro- and nano-plastics, but it currently lacks practical viability due to its poor water resistance. In this study, PVA films were reinforced with acid-treated palm kernel shell biochar to enhance their water resistance and wet strength. Incorporation of the treated biochar resulted in significant improvements in mechanical strength, reduced swelling, and higher gel content upon immersion in water, indicating enhanced network stability. At 5 wt% biochar loading, the films exhibited a significant drop in the swelling ratio, decreasing from 296.2% (neat PVA) to 133.1%, while gel content of the corresponding films increased from 76.5% to 93.0%. The most significant mechanical reinforcement occurred at a 3 wt% loading, which yielded a 25.9% increase in tensile strength. Furthermore, the benefits of biochar incorporation were highly evident in wet strength analyses where the samples were subjected to tensile test right after 24 and 48 h of water immersion. The PVA/biochar films maintained a tensile strength of at least five times greater than that of the neat PVA film. By valorizing a renewable waste material to enhance polymer performance, this approach demonstrates a strategic pathway toward practical yet environmentally friendly plastics.
Traditional sorption materials suffer from several significant drawbacks, including low sorption capacity, poor effectiveness in removing heavy oils, limited efficiency in oil-water separation, and inadequate flame-retardant properties during oil spill incidents. In this study, an environmentally benign and multifunctional composite sponge with enhanced flame-retardant properties was developed by modifying a polydimethylsiloxane (PDMS) sponge fabricated via a low-cost and simple sugar molding method. Boric acid (BA) and borax (BX), both halogen-free and low-toxicity boron-based compounds, were incorporated at different ratios to improve the thermal stability of the sponge, with a 1:1 BA/BX composition showing the most favorable performance. Subsequently, a dispersion containing candle soot (CS), a waste-derived carbonaceous material, was impregnated into the sponge to increase surface roughness and hydrophobicity. The resulting PDMS@BA(1)/BX1@CS sponge demonstrated improved self-cleaning behavior against common contaminants, with a static contact angle of approximately similar to 139 degrees, along with high oil-water separation efficiency. The modified sponges showed sorption capacities ranging from 6.5 to 11.3 g/g for various oils and organic solvents. Moreover, the PDMS@BA1/BX1@CS sponge extinguished the ignited flame within 12 s after adsorbing the flammable solvent. These results reveal that the developed sponge has great potential for applications such as oil-water separation, rapid fire extinguishing, and self-cleaning.
Due to the fine particle sizes and interparticle porous structures, polyvinyl chloride (PVC) paste resin produced by microsuspension polymerization is favorable for forming plastisol. However, it requires high processing temperatures or large amounts of external plasticizers to achieve sufficient plasticization, which causes high energy consumption or the risk of plasticizers' migration. In this work, a hybrid plasticization strategy was demonstrated by introducing butyl acrylate (BA) as an internal plasticizing comonomer into PVC paste resin prepared by microsuspension polymerization. A series of poly(vinyl chloride-butyl acrylate) (PVC-BA) copolymer paste resins with controlled BA contents were synthesized, and the effects of BA incorporation on chemical structure, particle morphology, thermal property, plasticization behavior, and rheological performance were systematically examined. It could be found that BA copolymerization resulted in not only the reduction in glass transition temperature from 77.8 degrees C of PVC paste resin to 71.6 degrees C of the copolymer, but also an increased specific surface area of 40 m2/g. These two structure features had a positive synergistic effect on the practical processing. Plastisol with an efficient plasticizer uptake was achieved at low fusion temperature of 140 degrees C. The modified plastisol exhibited enhanced rheological stability across a broad processing range of 100 degrees C-150 degrees C. Furthermore, PVC foams prepared from the copolymer paste resins displayed refined cellular structures and enhanced mechanical performance, including high ductility and improved elastic recovery. As a result, this work provides an effective strategy for developing high-value PVC products by microsuspension polymerization, and demonstrates its application in producing energy-efficient, high-performance PVC foam.
Protein fouling severely limits the performance of poly(vinylidene fluoride) (PVDF) membranes due to their intrinsic hydrophobicity, which promotes fouling adsorption and pore blockage, leading to rapid flux decline. Herein, we report a facile, environmentally friendly surface modification strategy to enhance the hydrophilicity and antifouling performance of PVDF microfiltration membranes using polydopamine (PDA) and glucosamine. A conformal PDA interlayer was first deposited on the membrane surface, followed by glucosamine grafting to form a durable PDA/glucosamine composite coating. Atomic force microscopy (AFM) revealed an increase in surface roughness from 83.7 nm for unmodified PVDF to 96.5and 98.3 nm for PDA- and PDA/glucosamine-modified membranes, respectively. Filtration experiments using pure water and bovine serum albumin (BSA) solutions demonstrated that glucosamine grafting significantly improved membrane permeability and fouling resistance compared to unmodified and PDA-only modified membranes, achieving a maximum pure water flux of 1423 L/m2 h and a BSA flux of 1194 L/m2 & centerdot;h. Furthermore, PDA-based coatings substantially reduced BSA adsorption compared to unmodified membranes and maintained high permeability and antifouling performance over multiple filtration cycles, particularly for PDA/glucosamine-modified membranes, confirming robust coating stability. Density functional theory (DFT) simulations revealed strong interactions between dopamine and glucosamine, including hydrogen bonding and covalent bonding, which facilitate the formation of durable surface coatings on PVDF membranes and corroborate the observed experimental performance. This environmentally benign and scalable modification strategy offers an effective route to mitigate membrane fouling and enhance the long-term performance of polymeric membranes for sustainable water treatment applications.
Poly(vinyl chloride) has been a key polymeric material since its commercial production in 1931, demonstrating versatility across numerous industries due to its compatibility with various additives. PVC's inherent properties, flame retardance, durability, and recyclability make it ideal for building and construction, which accounts for a significant portion of its consumption in Europe. This paper reviews the thermal degradation, decomposition, and combustion behavior of plasticized PVC, focusing mainly on classical stabilization systems and novel nanostructured additives such as polyhedral oligomeric silsesquioxane (POSS), which offer promising advances in improving PVC's thermal stability and fire performance. The review highlights how these aspects, mainly when addressed with innovative additives, could shape the future of PVC compounds in high-performance applications, especially in the cable industry, where fire performance and regulatory compliance are increasingly important.
This study investigates the use of Posidonia oceanica (PO) leaves, derived from coastal banquette residues, as a filler in PBSA, aiming to valorise a natural biomass typically treated as waste within a circular materials approach, while reducing production costs and enhancing seawater biodegradation of the polymer matrix. Composites containing 5 and 10 wt.% of PO, with and without micro-talc, were prepared via extrusion and injection molding. Materials were characterized morphologically, chemically, thermally, and mechanically, while biodegradation was assessed in a controlled seawater environment. Thermal analyses confirm that both PO and micro-talc do not compromise PBSA thermal stability, with degradation temperatures remaining at approximately 403 degrees C. Calorimetric results highlighted an increment of crystallization temperature and the appearance of a secondary melting peak at similar to 79 degrees C, while the main PBSA melting peak remains at similar to 85 degrees C and overall crystallinity degree is unchanged. Chemical and morphological analyses reveal no chemical interactions and confirm homogeneous filler dispersion with good interfacial adhesion. Mechanical testing shows a moderate stiffening and embrittling effect with the addition of PO, with elastic modulus increasing from 0.32 to 0.51 GPa and elongation at break decreasing from 450% to 325%, while impact toughness is markedly reduced at high filler loadings. Seawater exposure demonstrates accelerated biodegradation for Posidonia-filled composites, showing a similar to 20% mass loss after 4 months and rapid mechanical deterioration. The incorporation of PO fillers constitutes an effective approach to modulate and accelerate degradation under marine conditions.
Developing flame-retardant epoxy resin (EP) with high performance has drawn extensive attention recently due to the growing public concern for fire safety. However, the simultaneous enhancement of flame retardancy and toughness without the sacrifice of mechanical strength and thermal stability is still a challenge for EP. Herein, a novel kind of imidazole-based reactive flame retardant MD containing P/N/Si was synthesized and applied into EP. The results demonstrated that due to the presence of P/N/Si multiple flame-retardant elements, incorporating 4 wt% MD could make EP/MD pass UL-94 V-0 grade and have a limiting oxygen index (LOI) of 29.7%. Meanwhile, compared with pure EP, the peak heat release rate (PHRR), total heat release rate (THR), peak smoke production rate (PSPR), and total smoke production (TSP) of EP composite containing 4 wt% MD exhibited an obvious reduction of 41.5%, 11.4%, 24.2%, and 12.9%, respectively. Moreover, thanks to the high reactivity of imidazole groups, the MD could participate in the cross-linking reactions of EP and form strong interfacial interaction between the matrix and flame retardant. Therefore, the mechanical strength and toughness as well as the glass transition temperature of EP/MD composites could be simultaneously and greatly enhanced (tensile strength +30%, flexural strength +35%, impact strength +22%, and T g + 7 degrees C). This work provided a feasible methodology for the fabrication of highly efficient flame-retardant EP with prominent mechanical and thermal properties.
Pharmaceutical blister packaging, composed of complex multilayer materials such as polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), and aluminum, poses significant recycling challenges due to its intricate structure. This study investigates the feasibility of a dissolution-based recycling process to recover high-purity PVC from pharmaceutical composite packaging. Using specific solvents, PVC was selectively dissolved, enabling the separation of undissolved PVDC and aluminum layers. The process was successfully scaled from laboratory to small-technical scale, achieving a recovery yield of 47% for recycled PVC (rPVC). Comprehensive material characterization, including FTIR and gel permeation chromatography, confirmed the chemical integrity of the recovered PVC, with minimal residual solvent content and no significant degradation. Recycled PVC was incorporated into pharmaceutical film recipes at a 30 phr content, demonstrating comparable mechanical and thermal properties to virgin PVC films. Thermoforming trials further validated the suitability of rPVC-containing films for blister production, with reliable sealing and leak-proof performance. While slight yellowing was observed in rPVC films, this effect is deemed manageable through coloring or enhanced cleaning processes. The study highlights the potential of dissolution-based recycling as a sustainable solution for pharmaceutical blister packaging, offering a pathway to circular use of PVC in the industry. Future work will focus on scaling the process to pilot plant operations and evaluating its economic and environmental viability.
Acrylonitrile-butadiene-styrene (ABS) cantilever beams were reinforced with carbon black (CB) at 0-2 wt% and fabricated by mechanical extrusion (MEX)-based additive manufacturing to improve vibration damping without compromising strength. Free-decay responses were processed with three complementary estimators-logarithmic decrement (time domain), half-power bandwidth (frequency domain), and an envelope-fit that provides an analytic standard error-and the per-run damping ratios were fused by precision (inverse-variance) weighting to obtain a single with 68% confidence intervals. Composition-level results show a clear optimum at 0.3 wt% CB, where the fused damping ratio increased from 5.81 & times; 10-3 (pure ABS) to 7.75 & times; 10-3 (approximate to+33%), while the ultimate tensile strength rose from 9.83 to 18.12 MPa (approximate to+84%). At 1 wt%, the damping remained elevated but strength decreased; at 2 wt% both metrics declined, consistent with agglomeration observed in scanning electron microscope images. A strength-damping Pareto view highlights 0.3 wt% as a practical composition window for balanced performance in MEX ABS/CB parts. The workflow-multi-estimator analysis with uncertainty-aware fusion-provides reproducible damping estimates from short free-decay records and can be applied to other printed polymers and fillers.
A novel epoxidized cashew nut phenol derivative plasticizer (ECAE) was successfully designed and synthesized as a green, bio-based alternative to conventional phthalate plasticizers. Cashew nut phenol was chemically modified via a two-step reaction sequence involving esterification followed by epoxidation, yielding a multifunctional plasticizer that incorporated flexible long-chain alkyl groups, ester functionalities, and epoxy groups. When blended with PVC, ECAE exhibited superior performance: a glass transition temperature of 28.10 degrees C, elongation at break reaching 702.12% at 50 phr loading, and antibacterial activity with a 15 mm inhibition zone against Staphylococcus aureus. It also demonstrated excellent stability, with only 0.3% migration after 240 h in distilled water at 25 degrees C. Quantum chemical calculations elucidated the plasticization mechanism, revealing how the combination of spatial effects from long-chain alkyl groups and anchoring effects from polar functional groups modulates PVC chain segment dynamics. This bio-based plasticizer represents a significant advance in sustainable polymer technology, meeting environmental requirements while maintaining high performance. It holds potential for applications in food packaging and medical device manufacturing, where material performance and safety are paramount.
There has been an increasing demand for carbon allotropes-based composites in 3D printing. Thus, synthesis of carbon allotrope-polymer composite filaments is important for achieving consistent extrusion and reliable fabrication by fused filament fabrication (FFF). In this work, a solvent blending approach was used to prepare polylactic acid-based composite filaments with graphite concentration varying up to 40 wt.%. A binary solvent consisting of dichloromethane and chloroform facilitates effective dispersion of graphite, while polyethylene glycol improved filament flexibility and printability. The extruded filament was evaluated for dimensional deviation, revealing reduced die swell with increase in filler loading. The thermal stability, crystallinity, and microstructural homogeneity of fabricated composite filaments were also investigated. Mechanical and thermomechanical analyses were further performed on 3D printed specimens to assess stiffness, strength, and viscoelastic behavior. Percolation threshold was reached at 20 wt.% graphite doping and is found to give optimal mechanical properties. An increase in graphite concentrations increased the thermal as well as the electrical conductivity. The results demonstrated that solvent blending enables effective incorporation of higher graphite concentrations while maintaining adequate processability and structural integrity for additive manufacturing applications in the domain of 4D printing of structures, polymeric sensors, and energy storage.
Protective materials for bridge main cables face a critical challenge in achieving both flame retardancy and aging resistance simultaneously. Conventional materials are prone to structural and functional degradation in complex service environments, which limits their long-term applicability. Leveraging the intrinsic flame retardancy and weather resistance of chlorosulfonated polyethylene (CSM), this study constructed three distinct flame-retardant systems based on aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), and zinc borate (ZB). Three corresponding composites designated ZR-1, ZR-2, and ZR-3 were successfully prepared. The influence of different flame-retardant mechanisms on microstructure and macroscopic properties was systematically investigated. Results indicated that ZB, owing to its excellent interfacial compatibility and nanoscale dispersion, yielded the composite ZR-3 with superior mechanical properties. It demonstrated a tensile strength of 19.88 MPa and an elongation at break of 133.48%. Furthermore, ZB promoted the formation of a dense char layer at elevated temperatures, resulting in a residual char yield of 23.02%. In contrast, the Mg(OH)2 system endowed ZR-2 with the highest thermal stability, exhibiting a glass transition temperature T g = -35.9 degrees C, and superior UV aging resistance. After UV exposure, tensile strength decreased by only 2.32 MPa, while the limiting oxygen index (LOI) was reduced by merely 0.6%. Notably, in salt spray environments, ZR-3 exhibited exceptional resistance to chloride ion erosion. This advantage stems from the chemical stability and structural reinforcement imparted by ZB, which resulted in a minimal tensile strength decrease of 1.17 MPa and an LOI reduction of 1.8%. This work elucidates the intrinsic relationship between multi-mechanism flame retardancy and material durability. It offers novel insights and robust experimental support for developing advanced, adaptive, and long-life protective materials for bridge cables.
In the present study, biosynthesis of zinc oxide nanoparticles (ZnO NPs) was carried out using the underutilized aqueous sepals extract of Dillenia indica as a natural resource. The synthesized ZnO NPs (0.1%, 0.3%, and 0.5%) were reinforced into a polyvinyl alcohol (PVA) matrix, and their effects on the morphological, thermal, mechanical, and barrier properties of PVA nanocomposite films were reported. The prepared ZnO NPs were characterized to analyze their functional groups, UV absorption properties, crystalline structure, elemental composition, surface morphology, zeta potential, hydrodynamic measurements and antimicrobial activities. The peaks of XRD diffraction were closely aligned with the standard pattern for hexagonal wurtzite ZnO. The mean crystallite size of the ZnO NPs was found to be 12.83 nm. The hydrodynamic diameter of ZnO NPs was 580.2 nm with a polydispersity index (PDI) of 0.606. The maximum antibacterial activity was observed at the concentration of ZnO NPs (0.5%) against E. coli (24.90 +/- 0.656 mm) and S. aureus (21.18 +/- 0.928 mm). The reinforced effects of ZnO NPs significantly enhanced the tensile strength (TA) of the PVA nanocomposites from 39.736 +/- 1.431 MPa to 53.209 +/- 0.983 MPa with the addition of 0.3%, respectively. The water vapor permeability (WVP) of the films was significantly decreased from 36.160 +/- 1.860 (g & centerdot;mm/m2 & centerdot;day & centerdot;kPa) to 10.883 +/- 0.552 (g & centerdot;mm/m2 & centerdot;day & centerdot;kPa) with increasing ZnO NPs concentration. In conclusion, the antibacterial activity of synthesized ZnO NPs and their positive impact on the properties of PVA nanocomposite films make them suitable for food safety applications.
Modifying phosphorus-based flame retardants to balance their flame-retardant and mechanical properties has become an emerging research trend in the field of polylactic acid (PLA). In this study, an attapulgite-based phosphorus-nitrogen-silicon hybrid flame retardant (ATP@PSi-NH2) was designed and synthesized by coating a phosphorus-nitrogen-silicon hybrid flame retardant (PSi-NH2) onto the surface of attapulgite (ATP) using the bridging agent KH560. The effects of ATP-KH560, PSi-NH2, and ATP@PSi-NH2 flame retardants on the thermal stability, flame retardancy, and mechanical properties of PLA composites were compared. The incorporation of ATP@PSi-NH2 significantly enhanced the balance between flame retardancy and mechanical performance of the PLA composites. The PLA composite containing 7.5 wt.% ATP@PSi-NH2 achieved a UL-94V-0 rating, with the limiting oxygen index (LOI) increasing to 27.6%. At the same phosphorus content, the total smoke production (TSP) and total smoke release (TSR) of PLA/10ATP@PSi-NH2 were reduced by 38.6% and 39.3%, respectively, compared to the PLA/5PSi-NH2 composite, demonstrating the smoke-suppressing effect of ATP. Furthermore, due to the enhanced interfacial compatibility of ATP@PSi-NH2 within the PLA matrix and the nail-pull effect of ATP, the PLA/ATP@PSi-NH2 composite exhibited superior mechanical properties. This study successfully combines the benefits of phosphorus-based and nano-flame retardants to improve the flame-retardant performance of PLA, providing an effective approach for the development of multifunctional flame retardants.
Two new antiozonant molecules (for diene rubber compounds) have been synthesized using (1R,4R)(+)-camphor as key raw material derived from the renewable source Cinnamomum camphora tree. The diimine reaction product of p-phenylenediamine (p-PPD) and two molecules of camphor was reduced in situ with NaBH4, yielding N,N '-dicamphyl-p-phenylenediamine (2Cam-PD). Similarly, the imine reaction intermediate between ADPA (4-aminodiphenylamine) and one molecule of camphor was reduced in situ, producing N-camphyl-N '-phenyl-p-phenylenediamine (Cam-PPD). The two new antiozonants were characterized by FT-IR spectroscopy and by DSC analysis in comparison to the diimine (2Cam-PD-diimine) and imine (Cam-PPD-imine) intermediates, respectively. DSC analysis was also made on the starting reagents p-PPD, ADPA, and (1R,4R)(+)-camphor. The properties of 2Cam-PD and Cam-PPD are discussed in comparison to the currently used antiozonants. Particular emphasis is addressed toward the analogies of 2Cam-PD with the "safe" antiozonant CCPD (N,N '-dicyclohexyl-p-phenylenediamine) and Cam-PPD with CPPD (N-cyclohexyl-N '-phenyl-p-phenylenediamine). The raw material fraction derived from the renewable source is 73.8% for 2Cam-PD and 45.2% for Cam-PPD.
In this work, the effect of the cross-linking agent trimethylolpropane triacrylate (TMPTA) and gamma irradiation on commercial rigid PVC compounds were evaluated. Compounds containing 1-5 phr of TMPTA were irradiated at doses of 30, 40, and 50 kGy and subsequently characterized by FTIR, TGA, DSC, gel content, and mechanical testing. The yellowing index was also monitored during thermal aging in an automatic oven. FTIR analysis showed that irradiation induced changes in the PVC structure, while the presence of TMPTA minimized alterations in the characteristic PVC bands, suggesting a protective effect against degradation. Gel content increased with both TMPTA concentration and irradiation dose, confirming cross-linking, which was consistent with thermal residues of up to 20% at 500 degrees C in TGA. The glass transition temperature increased by up to 4 degrees C for the 5 phr TMPTA formulation at 50 kGy, and the Young's modulus reached 3200 MPa, indicating enhanced stiffness. During thermal aging at 180 degrees C, the samples showed progressive yellowing, although no significant changes in chemical functional groups were detected. Overall, TMPTA improved the thermal stability of PVC while preserving its mechanical integrity under irradiation and thermal exposure.
In this study, we addressed the challenge of eliminating, during combustion, the flaming dripping behavior of polybutylene succinate flame retarded with ammonium polyphosphate, a key barrier to achieving a V-0 rating in the UL 94 flammability test without excessive additive loading levels. Different 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-based flame retardants were applied to combine their gas-phase mechanism with the solid-phase mechanisms of ammonium polyphosphate. The flame retardant efficiency was evaluated through several flammability tests, thermogravimetric analysis, thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy, and Raman spectroscopy. The results demonstrated that the combination of gas- and solid-phase flame retardants can be effective in improving the flame retardancy of polybutylene succinate while minimizing the total additive content.
Harsh environmental conditions, such as extreme temperatures, high humidity, and sunlight, are the leading causes of PVC items' degradation during their service life. In particular, light can trigger not only severe weathering of outdoor PVC articles, leading to degradation of the PVC matrix, but also milder phenomena that primarily affect color without compromising the material's mechanical properties. Those phenomena are not of secondary importance because they often require the substitution of damaged items, which impacts the costs and durability (and therefore sustainability) of the article. One of these issues is uracil pinking that occurs when the thermal stabilizer used in the finished item contains 1,3-dimethyl-4-amino uracil. This substance is commonly used as a primary stabilizer; moreover, in items such as PVC pipes, fittings, and roofing membranes. Specifically, PVC pipes containing 1,3-dimethyl-4-aminouracil can undergo severe discoloration, compromising their use. Understanding uracil pinking in terms of its triggering and chemistry, it is essential to prevent or mitigate it. Therefore, in this paper, the aging of several rigid PVC formulations containing 1,3-dimethyl-4-amino uracil was performed. The aging was carried out using natural outdoor and accelerated weathering, both direct and modulated by filters. Specifically, cut-off filters were used to understand which wavelengths are capable of triggering the uracil pinking through colorimetric measurements according to the CIE colorimetric system of ASTM E308-22. In the current literature, uracil pinking has always been associated with the presence of titanium dioxide. Our findings show that the phenomenon occurs even in the absence of titanium dioxide. The investigation on the chemical mechanisms responsible for the uracil pinking is outside the scope of our work and still to be identified, but for sure they do not involve only titanium dioxide.
High-temperature vulcanized silicone rubber (HTV-SR) foams with high loadings of flame retardants typically exhibit poor processability and compromised thermal insulation performance when prepared by compression molding. In this study, a novel flame-retardant system composed of hydrophobic core-shell SiO2@LDH particles and a platinum-amine coordination compound was developed for HTV-SR foams. The core-shell SiO2@LDH particles exhibit ultrathin LDH nanosheets and a high specific surface area of 224.3 m2 g-1, enabling good dispersion in the HTV-SR matrix. Silicone rubber compounds containing a unique core-shell nanostructure of SiO2@LDH show excellent processability, allowing for easy preparation of HTV-SR foam with a high expansion ratio by standard compression molding. SiO2@LDH exert a pronounced flame-retardant effect for HTV-SR foam in both the gas and condensed phases. A synergistic effect is achieved by employing a small amount of platinum-amine coordination compound, which promotes a robust char layer at high temperatures and enhances flame inhibition of the SR/SiO2@LDH foam. With only 15 phr of SiO2@LDH particles, the SR/SiO2@LDH foam achieves a UL-94 V-0 rating and a limiting oxygen index (LOI) of 33.5%. Furthermore, the SR/SiO2@LDH foam shows a high expansion ratio with low density (0.35 g/cm3), low thermal conductivity (0.076 W/(m K)), high tensile strength (237.1 kPa), elongation at break (205.8%), and rebound resilience (7.2%). This study presents an advanced flame-retardant system for HTV-SR foams compatible with continuous compression molding, producing a flame-retardant foam with exceptional mechanical and thermal insulation properties.
