Calcium Hypophosphite Research Articles

Effect of Gaseous Atmosphere Composition on the Thermal Decomposition of Calcium Hypophosphite

Effect of Gaseous Atmosphere Composition on the Thermal Decomposition of Calcium Hypophosphite

Phosphorus features halogen –calcium hypophosphite replaces antimony trioxide, reduces smoke, and improves flame retardancy

Replacing antimony trioxide (ATO) in flame retardant formulations is an urgent task due to its toxicity. There are indications that calcium hypophosphite (CaP) may be a promising replacement. This study investigates the decomposition, fire behavior, and smoke release of brominated flame-retarded acrylonitrile butadiene styrene (ABS) under various fire scenarios like ignition, developing fire and smoldering, while replacing ATO with CaP and CaP/talc. Adding 4 wt.-% of talc to CaP formulations showed beneficial effects on flammability due to changes in the viscosity and barrier properties. Synergism between 8 wt.-% talc and CaP improved the protective layer in the developing fire scenario, resulting in a ∼60 % decrease in the peak of heat release rate and reduction of ∼21 % in total smoke production (ref. ABS+Br+ATO). With a conventional index of toxicity (CIT) of below 0.75, ABS+Br+CaP passes the highest requirements according to EN 45545-2. Overall, the CaP/talc materials improve flame retardancy, show less smoke emission under forced flaming conditions, and prevent chronic intoxication and environmental pollution through smoke particles contaminated with antimony.

Enhancement of Flame Retardancy of Cotton Fabrics by Calcium Hypophosphite-Chitosan Solution Compound Silica Sol

To enhance the thermal stability and flame retardancy of cotton fabrics, a hybrid sol was prepared by using silica (SiO2) sol, calcium hypophosphite (CaHP) and chitosan (CS), then finished on the surface of cotton fabrics through dipping-baking (drying) method. The results show that the CaHP-CS and SiO2 are successfully attached to the cotton fabric surface. Remarkably, the limiting oxygen index (LOI) value of the CaHP-CS-SiO2@COT was 31.30 % ( the highest of all samples). In the cone calorimetry test (CCT), the study revealed that the CaHP-CS-SiO2@COT has the lowest peak heat release rate (PHPP), fire growth rate (FGR) and CO2/CO. Its flame retardancy is mainly enhanced by the SiO2 (provides a gel coating with dimensional structure to block the transmission of oxygen and heat, CaHP (promotes cotton cellulose to dehydrate and form aromatic chars) and CS (dilute gaseous products and cool down heated areas).

Bacteriostatic coatings formed on titanium dental implants for veterinary applications

Titanium (Ti) dental implants were anodized in calcium hypophosphite solution to obtain a porous, bioactive layer. The anodized implant surface was covered by a poly(sebacic anhydride) (PSBA) layer with amoxicillin. SEM analysis showed an irregular distribution of the antibiotic on the surface. However, confocal microscopy images revealed the formation of a uniform polymer layer. The thickness of the oxide and polymer layers was similar, between 6 and 9 μm. PSBA is an easy, hydrolysable polymer. After the polymer with amoxicillin was immersed in phosphate buffered solution (PBS) for 1 h, >53 % of hydrolysis products were detected by 1H NMR spectroscopy. After 9 days of polymer immersion, the hydrolysis product content was >67 %. Drug release was analyzed using high-performance liquid chromatography (HPLC). After 1 h of implant immersion in PBS an average of 6.0 μg/mL of amoxicillin was released. Importantly, the released concentration of amoxicillin was enough to inhibit S. aureus and S. epidermidis growth, minimal inhibitory concentration (inhibition zones between 27 mm and 30 mm) and decrease bacteria adhesion to the implant surface were achieved. This paper presents the cytocompatibility results of PSBA, amoxicillin, and extracts collected from the implants exposed to mouse fibroblast L929 and osteoblast-like MG-63 cells. PSBA concentrations up to 1 % did not significantly affect cell viability. Amoxicillin concentrations up to 150 μL/mL were cytocompatible with both cell lines. Cell viability was >70 % for both cell lines after 24 h of treatment with extracts from modified implants that were immersed in PBS for 72 h prior to viability experiments. This work presents a simple method to obtain a hybrid, bacteriostatic and biocompatible layer on long-term implant surfaces. These techniques may find application in the surface treatment of various Ti implants with a variety of shapes and sizes for veterinary applications.

Kalsiyum Hipofosfit ve Magnezyum Hipofosfit Emdirilmiş Jüt Elyaf Katkılı Poli (Laktik Asit) Biyokompozitlerinin Isıl Ve Güç Tutuşurluk Özelliklerinin İncelenmesi

The aim of this study is to investigate the thermal and flammability properties of poly(lactic acid) (PLA) biocomposites reinforced with calcium hypophosphite (CHP) and magnesium hypophosphite (MHP) impregnated jute fiber (JE). For this purpose,biocomposites were produced by adding the jute fibers (JEs), which are treated separately with 5% and 10% CHP and MHP solutions and dried, to the PLA at a constant rate (20% wt) by melt blending method. Thermal properties of the PLA biocomposites produced were evaluated by thermogravimetic analysis (TGA), also their flammability properties were investigated by using limit oxygen index (LOI), vertical (UL-94V) and horizontal burning (UL-94HB) tests. As a result of the TGA tests, it was determined that the addition of JEs impregnated with CHP and MHP, the thermal stability and char residue amount of PLA biocomposites increased, and consequently the flame retardancy of the composites were also improved. From the LOI test results, it was observed that the LOI values of PLA biocomposites increased as the percentage of hypophosphites in the JE treatment solution increased. UL-94V and UL-94HB tests indicate that PLA biocomposite reinforced with JEs treated with 10% wt CHP has the highest flame retardancy performance.

Thermal stability and flame retardant properties of calcium- and magnesium-hypophosphite-finished cotton fabrics and the evaluation of interaction with clay and POSS nanoparticles

The aim of this study was to investigate the effect of calcium hypophosphite (CaHP) and magnesium hypophosphite (MgHP) on the thermal stability and fire retardant properties of cotton fabrics. The effects of water-soluble nanoparticles, namely Na-montmorillonite and octaammonium polyhedral oligomeric silsesquioxane (OA-POSS), in the presence of CaHP were also investigated. The characterizations of flame-retardant-treated cotton fabrics were performed using thermogravimetric analysis, limiting oxygen index (LOI) and mass loss calorimeter studies. The residues remained after mass loss calorimeter test were characterized by conducting attenuated total reflectance Fourier-transform infrared spectroscopy and scanning electron microscopy with a wavelength-dispersive X-ray spectrometer. The results showed that the fire performance of cotton fabric increased as the treated amount of both hypophosphite compounds increased. CaHP showed better fire performance than MgHP. The fire retardant performance of CaHP was further improved when used with nanoparticles. The highest LOI value of 24.2 and the lowest peak heat release rate (PHRR) of 43 ± 3 kW m−2 were achieved with the use of CaHP and OA-POSS at a ratio of 19:1.

Safer plasticized polyvinyl chloride synthetic leathers for the automotive industry: Evaluation of alternatives to antimony compounds as flame retardants

Automotive interiors materials, like plasticized polyvinyl chloride (pPVC) synthetic leathers (SLs), require additives for improving their flame behavior. The preferred flame retardant (FR) used in pPVC is antimony trioxide (Sb2O3, ATO), though the use of antimony poses several issues, for both human health and the environment, related to its extraction, processing, and use. In order to investigate alternatives to ATO in high‐performance pPVC SLs, various commercial FRs have been selected and tested in a typical, highly plasticized formulation. These additives have been used either alone or combined to evaluate synergistic effects. Samples have been tested to assess mechanical properties, thermal stability, and flame resistance. Data have been compared with those of neat pPVC and a foil with 2 phr of ATO. Several FRs are effective in improving the flame response compared with neat pPVC, without compromising the other properties, in detail calcium hypophosphite and mixtures containing zinc hydroxystannate (ZHS). Finally, aluminum hydroxide and ZHS (ATH + ZHS) yields the cheaper among the alternatives here proposed, even though higher than ATO (+193%) whose price/performance ratio is difficult to overcome. POLYM. ENG. SCI., 59:2488–2497, 2019. © 2019 Society of Plastics Engineers

The flame‐retardant effect of calcium hypophosphite in various thermoplastic polymers

SummaryThe flame‐retardant behavior of calcium hypophosphite (CaHP) was investigated in different thermoplastic polymers including polyamide 6 (PA), poly (lactic acid) (PLA), thermoplastic polyurethane (TPU), and poly methyl metacrylate (PMMA). CaHP was used at three different amounts of 10, 20, and 30 wt%. The characterization of the composites was performed using limiting oxygen index (LOI), vertical burning test (UL 94), thermogravimetric analysis (TGA), and mass loss calorimeter test. According to the test results, CaHP enhances the fire‐retardant properties in different levels depending on the polymer type. The CaHP exhibits its flame‐retardant effect via the formation of foamed char structure in the condensed phase and via the dilution and radical scavenging effect in the gas phase.

Calcium hypophosphite mediated deiodination in water: mechanistic insights and applications in large scale syntheses of d-quinovose and d-rhamnose

A practical and green synthesis of d-quinovose and d-rhamnose was achieved based on the mechanistic studies of hypophosphite mediated deiodination.

Reduction of aromatic nitriles into aldehydes using calcium hypophosphite and a nickel precursor.

Herein we report the reduction of aromatic nitriles into aldehydes with calcium hypophosphite in the presence of base and nickel(ii) complex in a water/ethanol mixture. This catalytic system reduced efficiently a series of aromatic nitriles bearing different functional groups such as -Cl, -CF3, -Br, -CH3, -OCH3, -COOCH2CH3, -OH and -CHO. The corresponding aldehydes were isolated in moderate to excellent yields (30-94%).

Solid–Liquid Phase Equilibria of (Ca(H2PO2)2 + H2O), (Ca(H2PO2)2 + CaCl2 + H2O), and (Ca(H2PO2)2 + NaH2PO2 + H2O) Systems

Fine calcium hypophosphite can be synthesized by sodium hypophosphite and calcium chloride via the replacement reaction, and sodium hypophosphite can be synthesized from phosphorus via the intermediate of Ca(H2PO2)2. Both processes involve the interactive quaternary system of (Ca2+ + Na+)//(Cl– + (H2PO2)− + H2O) and its subsystems. In this study, the (solid + liquid) phase diagrams of the (Ca(H2PO2)2 + H2O) binary system from freezing to boiling point at normal pressure, and (Ca(H2PO2)2 + CaCl2 + H2O), (Ca(H2PO2)2 + NaH2PO2 + H2O) ternary systems at 273.15 K were experimentally determined via the classical isothermal solubility equilibrium method. It was found that (1) one anhydrous salt of Ca(H2PO2)2 occurs in (Ca(H2PO2)2 + H2O) binary systems with temperatures ranging from freezing to boiling points, (2) two solid salts of Ca(H2PO2)2 and CaCl2·6H2O exist in the (Ca(H2PO2)2 + CaCl2 + H2O) system, and (3) Ca(H2PO2)2, NaH2PO2·H2O and one incompatible double salt of NaCa(H2PO2)3 exist in the (Ca(H2PO2)2 + N...

(Solid + liquid) phase equilibria of (Ca(H2PO2)2 + CaCl2 + H2O) and (Ca(H2PO2)2 + NaH2PO2 + H2O) ternary systems at T = 323.15 K

Calcium hypophosphite has been widely used as an anti-corrosive agent, flame retardant, fertilizer, assistant for Ni electroless plating, and animal nutritional supplement. High purity calcium hypophosphite can be synthesized via the replacement reaction of sodium hypophosphite and calcium chloride. In this work, the (solid+liquid) phase equilibria of (Ca(H2PO2)2+CaCl2+H2O) and (Ca(H2PO2)2+NaH2PO2+H2O) ternary systems at T=323.15K were studied experimentally via the classical isothermal solubility equilibrium method, and the phase diagrams for these two systems were obtained. It was found that two solid salts of CaCl2·2H2O and Ca(H2PO2)2 exist in the (Ca(H2PO2)2+CaCl2+H2O) system, and three salts of Ca(H2PO2)2, NaH2PO2·H2O and one incompatible double salt, NaCa(H2PO2)3 occur in the (Ca(H2PO2)2+NaH2PO2+H2O) system.

Biofunctionalization of Ti–13Nb–13Zr alloy surface by plasma electrolytic oxidation. Part I

The surface of Ti–13Nb–13Zr alloy was modified in 0.1M calcium hypophosphite (Ca(H2PO2)2) solutions via the addition of tricalcium phosphate, wollastonite or silica powders using a plasma electrolytic oxidation process. Depending on the anodizing bath chemical composition and applied voltage, various oxide layers were formed on the substrate. The morphology, cross-section and chemical composition of the Ti–13Nb–13Zr alloy surface were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (TL-XRD) and Raman spectroscopy. The surface roughness of the oxide layers was also measured. The corrosion behavior of the coatings was examined using potentiodynamic polarization in Ringer's solution. The surface modification improved their corrosion resistance in physiological fluid.

Biofunctionalization of Ti–13Nb–13Zr alloy surface by plasma electrolytic oxidation. Part II

The surface of Ti–13Nb–13Zr alloy was modified in 0.1M calcium hypophosphite (Ca(H2PO2)2) solutions via the addition of tricalcium phosphate, wollastonite or silica powders using a plasma electrolytic oxidation process. Depending on the anodizing bath chemical composition and applied voltage, various oxide layers were formed on the substrate. The water contact angle of the oxide layer was measured. The biological investigations using osteoblast-like cells MG-63 showed that the suspensions utilized during anodization strongly influenced the oxide layer bioactivity. Only the traces of the alloy elements were involved in Ringer solution after 5months of immersion.

Solid–liquid phase equilibria of Ca(H2PO2)2–CaCl2–H2O and Ca(H2PO2)2–NaH2PO2–H2O ternary systems at 298.15 K

Calcium hypophosphite has been widely used as an anti-corrosive agent, flame retardant, fertilizer, assistant for Ni electroless plating, and animal nutrition supplements. High purity calcium hypophosphite can be synthesized via the replacement reaction of sodium hypophosphite and calcium chloride. In this work, the solid–liquid phase equilibria of Ca(H2PO2)2–CaCl2–H2O and Ca(H2PO2)2 –NaH2PO2–H2O ternary systems at 298.15K were studied experimentally via the classical isothermal solubility equilibrium method, and the phase diagrams for these two systems were obtained. It was found that two solid salts of Ca(H2PO2)2 and CaCl2∙6H2O, and three solid salts of Ca(H2PO2)2, NaCa(H2PO2)3, and NaH2PO2∙H2O can form in the corresponding systems under phase-equilibrium conditions. Ca(H2PO2)2 has low solubility in the Ca(H2PO2)2–CaCl2–H2O system. NaCa(H2PO2)3 occupies a large solid field in the ternary system of Ca(H2PO2)2 –NaH2PO2–H2O.

Acrylonitrile–Butadiene–Styrene Terpolymer with Metal Hypophosphites: Flame Retardance and Mechanism Research

Three metal hypophosphites, including aluminum hypophosphite (AP), magnesium hypophosphite (MP), and calcium hypophosphite (CP), were applied to flame retard acrylonitrile–butadiene–styrene (ABS). Thermal stability of three flame-retardant ABS were evaluated, and the enhancement of thermal stability were found. Flammable properties of flame-retardant ABS were investigated by Underwriters Laboratories 94 vertical burning test (UL-94), limit oxygen index (LOI), and cone calorimetry. Results suggested that AP could endow the best flame retardance for ABS with a UL-94 V-0 rating and LOI value of 25.1%. The peak heat release rate of ABS-AP reduced to 174.8 kW/m2, and the total heat released was decreased to 40.9 MJ/m2. Thermogravimetric Fourier transform infrared (TG-FTIR), FTIR, and scanning electron microcsopy–energy-dispersive X-ray spectrometry (SEM-EDX) were used to characterize the gaseous products and condensed residue respectively. Results showed that the flame-retardant mechanism was attributed to the formation of a two-layer protective barrier consisting of an organic P–O–C char layer and an inorganic layer to insulate material from fire and oxygen in the condensed phase, and the generation of P• and PO• to capture the reactive radicals in the vapor phase.

Combustion properties and thermal degradation behaviors of biobased polylactide composites filled with calcium hypophosphite

In this work, calcium hypophosphite (CaHP) was introduced into polylactide to prepare flame retardant polylactide composites (FR-PLA). Thermal gravimetric analysis (TGA) was used to investigate the thermal degradation properties of CaHP and FR-PLA composites. It was found that CaHP presented a different thermal degradation process in air atmosphere compared with that in nitrogen. The flame retardancy properties of the composites were evaluated by limiting oxygen index (LOI), underwriter laboratories 94 testing (UL-94), microscale combustion calorimetry (MCC) and cone calorimetry. LOI and UL-94 testing showed that the incorporation of CaHP can significantly improve the flame retardancy of FR-PLA composites. MCC and cone calorimeter tests showed that the values of heat release rate (pHRR) and total heat release (THR) of FR-PLA composites were significantly decreased compared with those of pure PLA. The thermal degradation processes of PLA and FR-PLA were researched by real time Fourier transform infrared spectra (RT-FTIR). The crystallization behavior of FR-PLA composites was investigated by differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) revealed that the addition of CaHP promoted the formation of condensed char residue which contained aromatic structure and phosphorous-rich inorganic structure. The condensed char could inhibit the inner material from being attacked by the heat flux and flame during combustion, resulting in improved flame retardance of FR-PLA composites.

Characterization of passive films formed on titanium during anodic oxidation

The purpose of the study is to characterize the passive films formed on titanium during anodic oxidation in solutions of osteoinductive components: calcium cations and phosphate anions and to determine the electrochemical characteristics of the so modified titanium. Anodic oxidation was carried out in two solutions. The first Ca(NO 3) 2 20 g dm −3 (NH 4) 2HPO 4 20 g dm −3, NaNO 3 10 g dm −3 (K1), whereas the other, 20 g dm −3 Ca(H 2PO 2) 2 in 4.3 M H 3PO 4 (K2). Samples anodised in the bath K1 were additionally anodised in the bath K2 containing calcium hypophosphite and phosphoric acid at the voltage 150 V. SEM, EDX, TL-XRD, OCP, CV and EIS methods were used to characterize of obtained layers on titanium. It has been found that it is possible to incorporate Ca and P into the emerging passive layer. The application of the voltage of 150 V makes it very porous. It has been also demonstrated that the modified titanium presents higher resistance to corrosion in the investigated environment than unmodified titanium in Ringer's solutions.

Electrochemical study of growth behaviour of plasma electrolytic oxidation coating on Ti6Al4V: Effects of the additive

The growth behaviour of plasma electrolytic oxidation (PEO) coating on Ti6Al4V was studied by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test, focusing on effects of the electrolyte additive – calcium hypophosphite. The EIS analysis of the outer layer of the PEO coating provided insight into the structure of the coating, which was confirmed by SEM results. The EIS analysis of the inner layer of the PEO coating provided information matching well with the results of the potentiodynamic polarization test.

A Review of Recent Progress in Phosphorus-based Flame Retardants

Recent patent and technical works indicate a growing interest in halogen-free solutions with the predominance of the literature focusing on phosphorus-based flame retardants. Patents published on the flame retardancy of polycarbonate and its blends significantly exceed the number of patents on flame retardancy of any other polymer. Bridged aromatic diphenyl phosphates, especially resorcinol bis(diphenyl phosphate) and bisphenol A bis(diphenyl phosphate) have found broad application because of their good thermal stability, high efficiency, and low volatility. Another actively reported group of compounds are the metal salts of dialkylphosphonic acid as well as calcium hypophosphite, which have recently been found to be particularly effective in poly(butylene terephthalate) and polycarbonate. These products are synergistic with a number of phosphorus and nitrogen-containing compounds, such as melamine salts, which seem to be very efficient and commercially useful in nylons. Printed wiring boards comprise the largest market for flame-retardant polymeric materials. Recently, there has been a strong interest in halogen free solutions in East Asia and Europe. A recent halogen-free introduction is the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, which can be reacted into epoxies. Another reactive product with some processing and property advantages is poly(m-phenylene methylphosphonate). Because of the banning of pentabromodiphenyl ether in Europe and voluntary withdrawal of this product from the market in the US, the polyurethane (PU) industry is searching for a more environmentally acceptable low-scorch alternative. Both halogenated and halogen-free solutions are being considered but the PU industry seems to have a preference for the halogen-free products, generally containing phosphorus.