Interface modifications optimized for fire retardancy require detailed research. Confocal Raman microscopy was used to analyze the degradation locally in the area of the nanotube and clay additives. The double‐walled carbon nanotube (DWCNT), containing Co catalyst residue, accelerates the deacetylation process of poly(ethylene‐co‐vinylacetate) (EVA) considerably, while the montmorillonite (MMT) has no significant influence under static circumstances. The compounding process influences the effect of MMT, which causes partial crosslinking in EVA during the compounding. This mechanochemical reaction is catalyzed by uncovered MMT particles, while organophillized MMT promotes the charring process. Inorganic surface modification with various metal ions has also some stabilizing effect. Spray drying of MMT results in microparticles of increased surface area and improved thermal stability of the EVA system. The lowest rate of flame spreading was achieved using uncoated MMT, while coating with cationic surfactant was most efficient for hindering dripping. The rate of heat release (RHR) of the organically modified and the spray dried MMT was approximately the same. The combined organic‐inorganic modified clay moderates both the dripping and the flame spreading in the EVA. Copyright © 2006 John Wiley & Sons, Ltd.

No abstract

Beech wood boards were studied with a cone calorimeter. As the specific density of these materials is greater, the total amounts of CO and CO 2 produced were bigger than values measured on spruce specimens. Also, the shape of the heat release rate (HRR) curve was different as its second peak was bigger than the one observed on spruce wood. It was shown that impregnation of wood with water solutions of H 3 BO 3 resulted in decreased HRR values with increasing acid concentrations. Mass loss and CO and CO 2 production rates also decrease in the same way. Impregnation with water-soluble NaOH-silica resulted in improved data, when compared to untreated specimens, but were not better than those obtained with H 3 BO 3 . Simple mixing of both fire retardants gave no improvement, nor was the two-step impregnation with drying effective after the first step. When the second step-treatment with acid was followed without drying after impregnation with NaOH-silica in the first step, then improvement was evident. This is explained by precipitation of the silica content inside the material when the NaOH was neutralized with H 3 BO 3 , which could penetrate inside when the material was not dried before the second step. The improvement resulted in lower smoke production and longer times to ignition.

SUMMARYSpruce wood boards impregnated with Na 2 S 2 O 3 or Na 2 S 2 O 5 were studied with the cone calorimeter. The presence of Na 2 S 2 O 3 lowered the average heat release rate in comparison to untreated material. The total amounts of CO and CO 2 production were reduced by the treatment and also the specific extinction area and mass loss rate decreased. Washing of the salt from the material with water caused partial loss of the properties. Addition of the second impregnation step using acids (HCOOH, H 3 BO 3 or H 3 PO 4 ) resulted in the fixation of the sulphur in wood, but gave not the results of single-step modification for thiosulphate. With Na 2 S 2 O 5 and without acid, the CO and time-to-ignition values were higher and average heat release rate smaller in comparison to unmodified material. Combined one step Na 2 S 2 O 5 /H 3 BO 3 treatment lowered the CO, CO 2 and specific extinction area values in comparison to the modification with Na 2 S 2 O 5 , similarly like it was observed for Na 2 S 2 O 3 /H 3 BO 3 two-step-treatment. According to time-to-ignition values, Na 2 S 2 O 5 alone at 5% addition is a better flame retardant than Na 2 S 2 O 3 at 7%, but the effect is diminished at 10% amount or presence of acids. The total smoke release curves showed decrease due to modification in both phases of the process. Introduction of water washing as well as the acid treatment further lowered the values. The best results were achieved with 15% Na 2 S 2 O 3 -2% H 3 PO 4 -H 2 O system. According to the total smoke release curve the specimen produced more than five times smaller amount of smoke than untreated material in the first phase of the process. It seams that the concentration of Na 2 S 2 O 5 is less affecting the properties than the synergistic effect of the Na 2 S 2 O 3 or Na 2 S 2 O 5 /H 3 BO 3 system. Although the level of smoke is low, the presence of elemental sulphur causes smaller times-to-ignition than on starting material.