Effects Of Melamine Research Articles

Harnessing Enhanced Flame Retardancy in Rigid Polyurethane Composite Foams through Hemp Seed Oil-Derived Natural Fillers.

Over the past few decades, polymer composites have received significant interest and become protagonists due to their enhanced properties and wide range of applications. Herein, we examined the impact of filler and flame retardants in hemp seed oil-based rigid polyurethane foam (RPUF) composites' performance. Firstly, the hemp seed oil (HSO) was converted to a corresponding epoxy analog, followed by a ring-opening reaction to synthesize hemp bio-polyols. The hemp polyol was then reacted with diisocyanate in the presence of commercial polyols and other foaming components to produce RPUF in a single step. In addition, different fillers like microcrystalline cellulose, alkaline lignin, titanium dioxide, and melamine (as a flame retardant) were used in different wt.% ratios to fabricate composite foam. The mechanical characteristics, thermal degradation behavior, cellular morphology, apparent density, flammability, and closed-cell contents of the generated composite foams were examined. An initial screening of different fillers revealed that microcrystalline cellulose significantly improves the mechanical strength up to 318 kPa. The effect of melamine as a flame retardant in composite foam was also examined, which shows the highest compression strength of 447 kPa. Significantly better anti-flaming qualities than those of neat foam based on HSO have been reflected using 22.15 wt.% of melamine, with the lowest burning time of 4.1 s and weight loss of 1.88 wt.%. All the composite foams showed about 90% closed-cell content. The present work illustrates the assembly of a filler-based polyurethane foam composite with anti-flaming properties from bio-based feedstocks with high-performance applications.

Enriched Ti3+ in TiONC electrocatalyst for efficient H2O2 generation via 2-electron oxygen reduction reaction

The 2-electron electrochemical oxygen reduction reaction (ORR) is considered a viable method for synthesizing H2O2 because of its efficiency and environmental friendliness. However, conventional catalysts for this reaction predominantly rely on high-cost metals and require complex preparation procedures. Herein, we synthesized an electrocatalyst containing TiN and N-doped carbon via the pyrolysis of melamine and MIL125(Ti)–NH2. The effects of melamine and pyrolysis temperature on the chemical composition and defect site formation were investigated. Importantly, the obtained results suggest that the generated Ti3+ sites are more important in enhancing the performance of the 2-electron ORR, surpassing defective carbon and oxygen functional groups. In particular, the resulting TiONC-MA-1000 catalyst prepared through pyrolysis at 1,000 °C contained abundant Ti3+ sites, resulting in high 2-electron ORR activity with a molar selectivity exceeding 91 % and high stability over a 12 h testing period. The electrochemical H2O2 generation experiments conducted in an H-cell configuration employing TiONC-MA-1000 as the electrocatalyst yielded 6.99 mol⋅gcatalyst−1⋅h−1 H2O2. Therefore, the present study proposes a facile approach for fabricating highly active electrocatalysts suitable for large-scale H2O2 production.

Enhancement of the ORR Activity and Durability of Pt/C by the Modification with Melamine and N-Containing Aromatic Compounds

The ORR activity and durability of Pt catalysts have to be enhanced for the wider spread of PEFCs. We pay special attention to possibility that surface modification of a Pt catalyst increases its ORR activity. On the Pt surface, Pt-OH species is stabilized too much by network structure of water molecules adsorbed there [1]. The overstabilization of Pt-OH impedes the ORR because this species is an intermediate of ORR. Then, we try to enhance the ORR activity by destabilizing Pt-OH. The perturbation of the water network would destabilize Pt-OH. We try to perturbate the water network by adding an external organic compound to enhance the ORR activity.We tested a wide variety of compounds as an enhancer of ORR of Pt. Although most of compounds tested exhibit no influence of inhibitory effects on the ORR, we found that certain kind of N-containing aromatic compounds -melamine (and tetraazaporphyrin)- enhance the ORR activity of Pt catalysts significantly [2-4]. With the addition of melamine, ORR activity at 0.9 V vs. RHE is increased by 1.6 times although the ECSA decreased (Fig. 1). The enhancement of the ORR activity is reasonably ascribed to the destabilization of Pt-OH, judging from the change of cyclic voltammograms of Pt/C after the addition of melamine.This melamine modification method is also applied for another highly active catalyst (Pt/Pd/C core-shell catalyst) to obtain a further activated catalyst. The mass activity of Pt/Pd/C core-shell catalyst increases by 2.4 times after melamine modification and reaches 3600 AgPt -1 at 0.9 V vs. RHE [5].Melamine also enhances the durability considerably. Under an accelerated durability test (ADT) (80 °C, 0.6 V (3s) - 1.0 V (3s), square wave, 10000 cycles), Pt/C undergoes severe degradation; the ECSA significantly decreases because of the increase in the size of Pt nanoparticles (Fig. 1). However, after the ADT in the presence of melamine, the decrease in ECSA is significantly suppressed [6]. This beneficial effect is due to the suppression of the increase in size of Pt nanoparticles. A melamine polymer (poly-melamine sulfonate)-modified Pt/C also exhibits higher durability than unmodified Pt/C [7]. The suppression of Pt-OH by melamine participates in the enhancement of the durability.In this talk, we introduce discovery of melamine as an ORR enhancer, effect of melamine on the ORR activity/durability of Pt/C, and mechanisms of functions of melamine.This paper is based on the results obtained from projects, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Effects of melamine and cyanuric acid on placental and fetal development in rats.

Melamine or cyanuric acid alone has low toxicity, but combined exposure to melamine and cyanuric acid was reported to cause unexpected toxicological effects. This study investigated the potential effects and toxic mechanism of combined exposure to melamine and cyanuric acid on placental and fetal development in rats. Exposure to melamine and cyanuric acid caused maternal toxicity manifested by increased abnormal symptoms and decreased body weight gain. Developmental toxic effects included a decrease in placental and fetal weights with increased fetal deaths and post-implantation loss. Melamine and cyanuric acid induced oxidative stress in the developing placenta and fetus. The placentas from rats treated with melamine and cyanuric acid showed shortening of the placental layers with histological changes, decreased cell proliferation, increased apoptotic changes, and decreased insulin-like growth factor (IGF)/IGF-binding proteins (IGFBPs) and placental lactogen (PL) expression levels. Fetuses from melamine- and cyanuric acid-treated dams showed increased apoptotic changes and suppressed cellular proliferation in their livers and vertebrae. Consequently, combined exposure to melamine and cyanuric acid resulted in high levels of oxidative stress and impaired placental development associated with impairment of the IGF/IGFBP and PL systems, resulting in increased apoptotic changes and reduced fetal cell proliferation.

Microalgae biomass as a sustainable precursor to produce nitrogen-doped biochar for efficient removal of emerging pollutants from aqueous media

Preparing sustainable and highly efficient biochars as adsorbents remains a challenge for organic pollutant management. Herein, a novel nitrogen-doped carbon material has been synthesized via a facile and sustainable single-step pyrolysis method using a wild mixture of microalgae as novel carbon precursor. Phosphoric acid (H3PO4) was employed as activation agent to generate pores in the carbon material. In addition, the effect of melamine (nitrogen source) was evaluated over the biochar properties by the N-doping process. The results showed that the biochar's specific surface area (SSA) increased from 324 to 433 m2 g−1 with the N-doping process. The N-doping process increased the percentage of micropores in the biochar structure. Chemical characterization of the biochars indicated that the N-doping process helped to increase the graphitization process of the biochar and the contents of oxygen and nitrogen groups on the carbon surface. The biochars were successfully tested to adsorb acetaminophen and treat two synthetic effluents, and the N-doped biochar presented the highest efficiency. The kinetics and equilibrium data were well represented by the General-order model and the Liu isotherm model, respectively. The maximum sorption capacities attained were 101.4 and 120.7 mg g−1 for the non-doped and doped biochars, respectively. The acetaminophen adsorption mechanism suggests that the pore-filling was the dominant mechanism for acetaminophen uptake. The biochars could efficiently remove up to 74% of the contaminants in synthetic effluents.

Does melamine exposure during infancy cause rhabdomyolysis?

ABSTRACT We investigated the possible toxic effects of melamine on muscle tissue in rats using biochemical, hematological and histopathological methods. We used three groups of female albino Wistar rats. The first group was given 0.1 ml saline. The second and third groups were given 50 and 75 mg/kg melamine dissolved in 0.1 ml saline, respectively, daily for 21 days. On day 45, all rats were sacrificed, and whole blood and plasma were analyzed for hematologic and biochemical characteristics. Muscle samples were stained with hematoxylin and eosin for histopathological investigation. Other sections were immunostained for matrix metalloproteinase-9 (MMP-9) and type IV collagen. We found a significant increase in the lymphocytosis-compliant leukocyte number in the 75 mg/kg melamine group compared to the other groups. We also found significant decreases in the hemoglobin levels and hematocrit values in the 75 mg/kg compared to the other groups. We found that the 75 mg/kg melamine group exhibited a significant increase in plasma aspartate aminotransferase (AST) activity compared to the other groups. Changes in plasma creatine kinase and lactate dehydrogenase activity were not statistically significant. Plasma AST activity and mean corpuscular hemoglobin levels were correlated with the lymphocyte:neutrophil ratio. We found mononuclear cell infiltration at the periphery of muscle bundles and in the connective tissue bundles in the melamine treated group. We found MMP-9 expression in muscle cell membranes and type IV collagen expression in degenerative connective tissue fibers. Whole blood, plasma and muscle tissue analysis indicated that the 75 mg/kg melamine group exhibited rhabdomyolysis that was associated with lymphocytosis and anemia. The underlying mechanisms by which melamine causes rhabdomyolytic effects remain unclear.

The effects of melamine on the formation of carbon xerogel derived from resorcinol and formaldehyde and its performance for supercapacitor

Carbon aerogel/xerogel can be easily tuned to have hierarchical pores ranging from micropores to macropores. Nitrogen doping is considered to enhance the wettability and conductivity of the carbon electrode, hence improve the electrochemical performance. To prepare N-doped carbon xerogel and study the effects on the structure and the electrochemical performance of resorcinol and formaldehyde derived carbon xerogel, a series of Resorcinol-Melamine-Formaldehyde derived N-doped carbon xerogel were prepared by a facile sol-gel process and ambient drying method. With the increasing amount of melamine, the inside channels become larger, which contributes to faster ion transport and smaller charge transfer resistance (Rct). The Nitrogen content in carbon xerogel is also increased, enhancing the capacitance of carbon electrode by pseudocapacity effect, while damaging the rate performance by introducing more defects and larger degree of disorder. As a result, the best electrochemical performance is achieved in the RM-6-4 sample (resorcinol:melamine = 6:4), showing the largest capacitance of 139 F g−1.

Reproductive toxicity of melamine against male mice and the related mechanism

Melamine is a nitrogen-containing heterocyclic organic compound with a triazine skeleton, which has been widely applied in industrial and chemical fields. Previous toxicity studies of melamine mainly focused on renal toxicity and hepatic pathological changes, but its toxicity against the reproductive system has seldom been assessed. We investigated the effects of melamine on the reproductive system of male mice. Forty healthy male Kunming mice were randomly divided into a normal saline negative control group, a low-dose melamine group, a medium-dose melamine group and a high-dose melamine group (n = 10). The mice were administered for five consecutive days and killed on the 35th day after first administration. In melamine administration groups, seminiferous tubules had disordered, loose arrangement, and spermatogenic cells at all levels obviously decreased. The sperm count and motility decreased significantly, and the sperm deformity rate increased significantly. Melamine induced apoptosis of testicular spermatogenic cells. To further explore the mechanism, we detected metabolism-related enzymes sorbitol dehydrogenase (SDH) and lactate dehydrogenase (LDH) as well as oxidative stress indices superoxide dismutase (SOD) and malondialdehyde (MDA). The activities of SDH, LDH and SOD in melamine treatment groups decreased significantly, and the MDA level increased obviously. The expressions of apoptosis-related proteins Bcl-2, Bax and caspase-3 were detected by immunohistochemistry. The expression of Bcl-2 significantly increased, but those of Bax and caspase-3 significantly reduced (p < 0.05). In conclusion, melamine damaged the reproductive system of mice via the oxidative stress pathway and by inducing cell apoptosis.

Cytotoxicity, organ distribution and morphological effects of melamine and cyanuric acid in rats

Melamine (Mel) is used widely as a basic organic chemical intermediate in several products. Within the last 10 years there have been two high-profile Mel exposures that caused toxicological concern, especially regarding food adulteration. Objective: This study aimed to determine the toxicity of Mel and one of its homologs, cyanuric acid (Cya), in vitro and in vivo. Materials and Methods: The IC50 of Mel and Cya was determined by the MTT assay in NRK-52E and 293T cell lines. Organ-specific toxicity was assessed using the following dosing paradigm of Wistar rats: group 1: normal saline; group 2: Mel (180 mg/kg); group 3: Cya (150 mg/kg); and group 4: Mel (180 mg/kg) + Cya (150 mg/kg). Results: The NRK cell toxicity studies on Mel and Cya revealed IC50 values of 1.89 mg/mL and 4.20 mg/mL, respectively. Similarly, Mel and Cya IC50 values in 293T cells were 2.07 mg/mL and 3.71 mg/mL, respectively. Histopathologic studies revealed crystals in the renal medulla-cortex and loss of chief cells in the lining of the stomach in the group receiving Mel plus Cya. HPLC-MS analysis of organ homogenates showed that the concentration of Mel was greatest in the animals receiving a combination of both Mel and Cya. Discussion and conclusion: Mel is more toxic than its homolog Cya. The kidney is the most affected organ. Mel was present at high concentration not only in the kidneys, but also in the uterus and liver, informing the scope of future studies on the mechanism of Mel and Cya toxicity.

Hemato-immunologic impact of subchronic exposure to melamine and/or formaldehyde in mice

The aim of the present study was to explore the potential hematotoxic and immunotoxic effects of melamine (MA) in the absence and presence of formaldehyde (FA) in mice. Forty adult Swiss mice were equally allocated into four groups and daily treated with water, MA (50 mg/kg), FA (25 mg/kg), and MA + FA respectively via feeding needle for 60 consecutive days. Hematological status was evaluated using erythrogram and leukogram profiling. Innate immune functions were assessed by measuring white blood cells lysozyme and phagocytic activities. Serum immunoglobulin levels were evaluated as indicators of humoral immunity. In addition, histologic and immunohistochemical evaluations of splenic tissues were performed. The results indicated that either MA or FA treatment resulted in significant decreases in RBCs, Hb, MCHC, total WBC, lymphocyte, and basophile levels as well as in WBCs phagocytosis and lysozyme activity. In contrast, MCV, PCV%, and reticulocyte levels were significantly increased in these hosts. The total IgM level was significantly reduced in the MA-only-exposed mice but markedly increased in the FA-only-treated ones. A significant decrease in serum IgG levels was detected following either MA or FA treatment. The combined exposure to MA and FA, compared to levels of either toxicant alone, was revealed to evoke a significant improvement in Hb, PCV%, MCV, MCHC, neutrophil, eosinophil, total IgM level, and lysozyme activity; however these values did not reach that of the controls. Furthermore, compared to control mice, both MA-only- and FA-only-treated mice showed a strong distribution of CD4+ and CD8+ cells in their spleens, while a moderate presence of the former cells was obvious at their co-exposure. Taken together, these findings revealed that exposure to MA or FA resulted in significant alterations in hemato-immune parameters at variable degrees while a co-exposure resulted in the mitigation of most effects of either toxicant alone.

Effect of melamine and cyanurid acid contaminated diets on blood indicators in broiler chickens

The effect of melamine and cyanuric acid contaminated diets on basic haematological and biochemical blood indicators in male broiler chickens (Ross 308) was studied. The chickens were divided into 6&amp;nbsp;experimental groups (30 birds per group) and fed diets with an addition of 50 or 100 mg of melamine or 50 or 100 mg of cyanuric acid per kg of feed, with the contaminants added separately (either melamine or cyanuric acid) or in combination (melamine + cyanuric acid). The control group (C) was fed a diet without melamine or cyanuric acid. At the end of the experiment (day 40), 8 birds per treatment group were randomly selected for haematological and biochemical examination of blood. Red blood cell count, haemoglobin concentration, haematocrit value, mean corpuscular haemoglobin concentration, mean corpuscular haemoglobin, mean cell volume, and total leukocyte count did not differ significantly among the respective groups of broiler chickens (P &amp;gt; 0.05). The concentrations of melamine and cyanuric acid used in the contaminated diet for broiler chickens led to highly significant changes in the content of total protein (TP), glucose (Glu), Ca, P, Na, and K (P &amp;lt; 0.01) and to significant changes in the content of Mg (P &amp;lt; 0.05) in their blood plasma. In comparison to the C&amp;nbsp;group, the decrease in the content of TP, Glu, Ca, P, Na, K, and Mg in blood plasma was most pronounced in broilers fed the diets contaminated with cyanuric acid only or diets with the simultaneous contamination with melamine and cyanuric acid. On the basis of our results, it can be concluded that the contamination of feed with melamine and cyanuric acid, separately or in combination, results in impaired renal function and probably also in partial liver damage. &amp;nbsp;

A study on growth, histopathology and oxidative stress in Asian sea bass on diets with various loadings of melamine and cyanuric acid adulterants

Effects of melamine (MEL) and its analogue, cyanuric acid (CYA) at various doses on Asian seabass (Lates calcarifer Bloch) are described. Diet 1 (a basal diet without MEL and CYA); diets 2–5 (with MEL and CYA at inclusion levels 2.5, 5, 7.5, 10 g/kg diet, each); diet 6 (with only MEL at 10 g/kg diet); and diet 7 (with CYA alone added at 10 g/kg diet) were examined. It is obvious that those fish that received combined MEL–CYA as follows had low growth and feed conversion ratio (FCR) (P < 0.05): 7.5:7.5, 10:10 or MEL alone diets. Abnormalities were observed in the liver and kidney of fish with combined MEL and CYA supplementation. The renal tubules of fish that were fed with diets 2–5 had golden-brown melamine–cyanurate crystals. Fish given only one type of supplementation did not have such crystals in the kidneys. The highest MEL residue in fillet was detected in the fish that ingested MEL alone (10 g/kg diet). Levels of heat shock protein (Hsp) 70 were elevated in the liver of fish that had ingested MEL/CYA, in combination or alone (diets 2–7) (P < 0.05). There were no significant differences between the treatments (P > 0.05) in the level of Hsp70 in the kidneys of the fish. High dosages of MEL–CYA induced the activities of catalase and glutathione peroxidase in liver and kidneys.

Visual Detection and Determination of Melamine Using Synthetic Dyes

We have used spectroscopic technique for the detection of melamine. The effect of melamine on the colour as well as the pH of bromophenol, methyl red and alizarin red dye solutions was examined at different mole ratios. It is found that we observe color transition and the absorption maxima for bromophenol were at 598 nm, while for methyl red, and alizarin red-S dye they are at 520 nm and 423 nm, respectively. We observe an increase in the absorption intensities at 598 nm with increase in the concentration of melamine in bromophenol blue dye. The absorption intensities at 520 nm decreases and new peak at 420 nm emerges in methyl red dye-melamine mixture. While the absorption intensities at 420 nm decreases and 520 nm peak emerges in alizarin red S dye-melamine at higher mole ratios. The results indicate that we can choose the appropriate dye of suitable range to detect the concentration of melamine from 3 to 206 mg dm−3. The results demonstrate possible use of the simple method for the qualitative and quantitative detection of melamine in adulterated food samples.

Effect of Melamine / Urea Modified Phenol Formaldehyde Resin Binder on the Mechanical Properties of Glass-Fiber Felt

The use of melamine / urea modified phenol formaldehyde resin binder in the glass-fiber felt has led to products with lower free formaldehyde, higher water repellency and flexibility. This study gives a detailed description of the influence on the mechanical properties of the glass-fiber using the phenol formaldehyde resin with different levels of melamine and urea. Results show that, the free formaldehyde content reduced with the increase of the amount of urea and melamine, a small molecule of melamine and urea destroy the macromolecular chain of phenol formaldehyde resin leading to the decrease of breaking strength. At the same time, the decrease of the molecular chain is accompanied by the increase of flexibility.

Bioactive Natural Matrices and Compounds

The demand for healthy ingredients and a natural way of preventing diseases is contributing to the increased use of natural matrices. There has been a lot of research indicating that general antioxidant properties are not the contributing factors to improving human health but rather the antioxidant properties of specific compounds involved in specific cell signaling mechanisms that need to be elucidated. In this way, beyond the composition of the usual macronutrients and micronutrients, it seems important to also provide information on the composition of natural bioactive compounds. Phytochemicals such as phenolic compounds, essential oils, steroids, vitamins, or pigments should assume high importance due to their documented antioxidant, antimicrobial, antitumour, and anti-inflammatory properties, among others, but the knowledge of the mechanisms of action involved is mandatory. The contributions for this special issue consist of five papers covering several aspects of nutraceuticals and phytochemicals in natural matrices with proven activities in various in vitro or in vivo models. The paper by R. P. Constantin et al. evaluated the effects of three citrus flavanones (hesperidin, hesperetin, and naringenin) on several parameters linked to fatty acid oxidation in mitochondria, peroxisomes, and perfused livers of rats. These results confirm the hypothesis that citrus flavanones are able to induce a more oxidised state in liver cells, altering parameters related to hepatic fatty acid oxidation. The prooxidant effect is most likely a consequence of the ability of these substances to oxidise NADH upon production of phenoxyl radicals in the presence of peroxidases and hydrogen peroxide. A. Chennuru and M. T. S. Saleem described the cardioprotective effects of sesamol against doxorubicin-induced cardiomyopathy in rats. The authors concluded that, sesamol has significant cardioprotection against doxorubicin that induced cardiomyopathy via amelioration of oxidative stress, lipid lowering, and membrane stabilization effect. C. Chaotham et al. evaluated the oral toxicity of a partially purified plaunotol extract (PPE), which is traditionally consumed for its antigastric ulcer properties, using in vivo assays. The acute toxicity study demonstrated that PPE was practically nontoxic based on its high median lethal dose value. The chronic toxicity studies also showed the absence of mortality and clinical symptoms in all treated rats. Therefore, the authors concluded that these results suggest that PPE is potentially safe for further development as a therapeutic agent in humans. In the research study presented by H. A. E. Rabey et al., the protective effect of natural bees' honey on the liver of male albino rats against melamine toxicity was reported. Treating the male albino rats (that were presupplemented regularly with 20000 ppm melamine) with natural bees' honey at a dose of 2.5 g/kg body weight for 28 days improved both liver functions and increased serum protein. In addition, a positive impact on the shape of the cells after treatment with honey, compared to the positive melamine supplemented group, was observed. The authors concluded that the use of natural bees' honey has the ability to protect the livers of rats against the toxic effects of melamine. A. Rasul et al. reviewed recent data on primary flavonoids isolated from plants. Pinocembrin exhibits pharmacological effects on almost all systems, and the authors reviewed its pharmacological and therapeutic applications with specific emphasis on mechanisms of actions. The review suggested that pinocembrin is a potentially promising pharmacological candidate, but additional studies and clinical trials are required to determine the specific intracellular sites of action and derivative targets in order to fully understand the mechanism of its anti-inflammatory, anticancer, and apoptotic effects to further validate pinocembrin medical applications.

Impairment of Cognitive Function and Synaptic Plasticity Associated with Alteration of Information Flow in Theta and Gamma Oscillations in Melamine-Treated Rats

Changes of neural oscillations at a variety of physiological rhythms are effectively associated with cognitive performance. The present study investigated whether the directional indices of neural information flow (NIF) could be used to symbolize the synaptic plasticity impairment in hippocampal CA3-CA1 network in a rat model of melamine. Male Wistar rats were employed while melamine was administered at a dose of 300 mg/kg/day for 4 weeks. Behavior was measured by the Morris water maze(MWM)test. Local field potentials (LFPs) were recorded before long-term potentiation (LTP) induction. Generalized partial directed coherence (gPDC) and phase-amplitude coupling conditional mutual information (PAC_CMI) were used to measure the unidirectional indices in both theta and low gamma oscillations (LG, ∼30–50 Hz). Our results showed that melamine induced the cognition deficits consistent with the reduced LTP in CA1 area. Phase locking values (PLVs) showed that the synchronization between CA3 and CA1 in both theta and LG rhythms was reduced by melamine. In both theta and LG rhythms, unidirectional indices were significantly decreased in melamine treated rats while a similar variation trend was observed in LTP reduction, implying that the effects of melamine on cognitive impairment were possibly mediated via profound alterations of NIF on CA3-CA1 pathway in hippocampus. The results suggested that LFPs activities at these rhythms were most likely involved in determining the alterations of information flow in the hippocampal CA3-CA1 network, which might be associated with the alteration of synaptic transmission to some extent.

Preparation and Characterization of Hexadecane Microcapsule Phase Change Materials by &lt;i&gt;In Situ&lt;/i&gt; Polymerization

Hexadecane microcapsule phase change materials were prepared by the in-situ polymerization method using hexadecane as core materials, urea-formaldehyde resin and urea-formaldehyde resin modified with melamine as shell materials respectively. Effect of melamine on the properties of microcapsules was studied by FTIR, biomicroscopy (UBM), TGA and HPLC. The influences of system concentration, agitation speed and mass ratio of wall to core were also investigated. The results indicated that hexadecane was successfully coated by the two types of shell materials. The addition of melamine into the urea-formaldehyde resin microcapsule reduced microcapsule particle size and microencapsulation efficiency. The influences of factors such as system concentration, agitation speed and mass ratio of wall to core to different wall materials microcapsules presented different variety trends of the microcapsule particle size.

Synergistic effect of melamine in combination with cyanuric acid on urinary tract toxicity in rats

The present study investigated the urinary tract toxicity of melamine alone or in combination with cyanuric acid in rats. Male rats were orally administered melamine alone (800 mg/kg) or melamine plus cyanuric acid (50 mg/kg each) for 3 consecutive days. Although melamine treatment did not show any significant difference in body weight, kidney or urinary bladder weight, serum blood urea nitrogen (BUN) or creatinine levels, it caused a decrease in urinary pH and mild histopathological alterations in the kidney and urinary bladder. In contrast, co-administration of melamine and cyanuric acid induced a decrease in body weight, an increase in kidneys and urinary bladder weights, and an elevation in serum BUN and creatinine levels, which were not observed in animals treated with melamine alone. Histopathological examination showed that the incidence and severity of histopathological lesions in the kidney and urinary bladder were much higher than those in the melamine group. Urinalysis revealed an increase in urine occult blood, leukocytes and protein and a decrease in urinary pH. These results indicate that concomitant administration of cyanuric acid synergistically potentiated the urinary tract toxicity induced by melamine in rats. In this study, we first demonstrated the synergistic toxic effects of melamine in combination with cyanuric acid on urinary bladder and urinalysis in rats.

Synergistic flame retardant effect of melamine in ethylene–vinyl acetate/layered double hydroxides composites

Mg–Al–Fe ternary layered double hydroxides (LDHs) were synthesized based on Bayer red mud by a calcination–rehydration method, and characterized by X-ray diffraction (XRD) and thermogravimetric analysis (TG). The synergistic effects between melamine and LDHs in ethylene–vinyl acetate (EVA) composites were studied using limiting oxygen index (LOI), UL 94, cone calorimeter test (CCT), smoke density test (SDT), and thermogravimetry–fourier transform infrared spectrometry (TG–IR). Though melamine decreases the LOI values of EVA/LDHs/melamine composites, a suitable amount of melamine can apparently improve UL 94 rating; the composite with 45 % LDHs and 5 % melamine can pass UL 94 test. The CCTs results indicate that heat release rates (HRR) of EVA/LDHs/melamine composites decreased in comparison with that of EVA/LDHs composites. The SDT results show that melamine is helpful to smoke suppression. The TG–IR data show that the ternary composites have a higher thermal stability than that of the binary composites.

Toxicity of melamine, an adulterant in fish feeds: experimental assessment of its effects on tilapia

Unscrupulous inclusion of melamine in fish feeds can be harmful to fish and may be hazardous to human health. An eight-week feeding trial examined the effects of melamine (inclusion levels; 5-30 g kg⁻¹ feed) on the growth performance, feed efficiency, histopathological changes and melamine residues in sex-reversed red tilapia, Oreochromis niloticus (L.) × O.mossambicus (Peters). Fish which received melamine-containing feeds grew less, utilized feeds less efficiently and performed poorly, besides exhibiting defects such as fin erosion, anorexia, sluggish swimming behaviour, paling/darkening of skin and low survival. Melamine concentration in the fish reflected its inclusion level in the feeds, and the content was higher in the viscera than in the fish fillet or whole fish. Histopathological alterations were evident in the kidney, liver and gills of fish subjected to melamine treatment - the severity of lesions corresponded to its dosage. Enlargement of renal tubules was observed in the kidney of fish fed with ≥10 g melamine kg⁻¹ feed, although, crystals were not deposited. Fish subjected to melamine insult had more prominent lesions in liver than in kidney. Toxic effects on the gills manifested as epithelial hyperplasia of the primary and secondary lamellae. The anomalies were severe at higher intake levels of melamine.