In this thesis there were two main purposes, the first one being to investigate effects of zinc borate (ZB) on the flammability behavior of ABS when used with and without a traditional brominated flame retardant (BFR) / antimony trioxide (AO) system. The second purpose was to investigate contribution of nanoclays (NC) to the flame retardancy performance of the same traditional BFR compound with various combinations of AO and ZB again in ABS matrix. For these purposes, materials were melt compounded by using a laboratory scale twin-screw extruder, while specimens were produced by injection or compression molding. Flame retardancy of the specimens were investigated by Mass Loss Cone Calorimeter (MLC), Limiting Oxygen Index (LOI) measurements and UL-94 vertical burning tests. Other characterization techniques required in this thesis were / X-ray diffraction analysis, scanning and transmission electron microscopy, thermogravimetric analysis and tensile tests. Studies for the first purpose indicated that almost all flame retardancy parameters were preserved when antimony trioxide were replaced with zinc borate as much as in the ratio of 1:3. Residue analyses revealed that predominant flame retardancy mechanism of traditional system was gas phase action, while zinc borate contributes especially in the condensed phase action by forming thicker and stronger char layer. Investigations for the second purpose basically concluded that use of nanoclays improved all flame retardancy parameters significantly. Residue analyses pointed out that nanoclays especially contribute to the formation of stronger and carbonaceoussilicate char acting as a barrier to heat and flammable gases and retarding volatilization via tortuous pathway. As an additional third purpose in this thesis, usability of three boron compounds (zinc borate ZB, boric acid BA, boron oxide BO) with two traditional flame retardants (organic phosphinate OP and melamine cyanurate MC) in neat PET and recycled PET were also examined leading to some promising results in MLC parameters.

In this thesis, there were four purposes. The first one was to investigate effects of nanoclays (NC) on the flammability behavior of polystyrene (PS). The second purpose was to investigate contribution of nanoclays to the flame retardancy performance of conventional phosphorus based flame retardant / triphenyl phosphate (TPP) and its synergist melamine cyanurate (MCA). For the third purpose contribution of nanoclays to the flame retardancy performance of another conventional halogenated flame retardant / brominated epoxy polymer (BE) and its synergist antimony trioxide (AO) was investigated. As the fourth purpose, effects of another nanoadditive / carbon nanotubes (CNTs) on the flammability behavior of PS with and without BE-AO flame retardant system was investigated. Materials were prepared via &ldquo / solution mixing&rdquo / method, while test specimens were shaped by compression and injection molding. Flammability behaviors were investigated by Mass Loss Cone Calorimeter (MLC), Limiting Oxygen Index (LOI) and UL-94 Vertical Burning tests. Other characterization techniques required in this thesis were / X-ray diffraction analyses, scanning and transmission electron microscopy, thermogravimetric analyses and tensile tests. It was revealed that use of nanoclays improved flame retardancy of PS significantly, mainly with &ldquo / condensed phase&rdquo / mechanism via formation of strong char barrier layers inhibiting mass and heat transfer. When nanoclays were used together with conventional flame retardant systems TPP-MCA and BE-AO, flame retardancy parameters improved further, this time due to the &ldquo / synergistic action&rdquo / of &ldquo / condensed phase mechanism&rdquo / of nanoclays and &ldquo / gas phase mechanism&rdquo / of the conventional systems. Use of carbon nanotubes also resulted in improvements in the flame retardancy of PS. However, &ldquo / condensed phase mechanism&rdquo / of CNTs were not as effective as the NCs, which might be due to the lower performance of 1D geometry (CNTs) compared to higher efficiency of 2D geometry (NC) in barrier formation. As an additional purpose, effects of mixing methods in the production of PS-Nanoclay composites were also investigated. It was seen that compared to &ldquo / solution mixing&rdquo / use of &ldquo / in-situ polymerization&rdquo / resulted in poorer flame retardancy parameters that might basically be due to residual monomers or oligomers left during polymerization.

Climate change and its accompanying environmental issues have caused the building industry to use more environmentally friendly building materials. Wood have always been a buildingmaterial but due to the renewed interest in imparting sustainability and renewability, its usage has increased over the recent years. With a rising interest in wood, it is of great importance to enhance the knowledge of its burning behaviour in order to predict and prevent fire hazards. Fire development is often characterized in terms of heat release rate (HRR) as a function oftime. Therefore, HRR is considered one of the most important variables in the evaluation of material fire hazards. This study aims to generate greater knowledge of the HRR curve of wood when exposed to heating in the cone calorimeter and how the curve can be described quantitatively. Furthermore, it was attempted to comprehend the properties and functions of char and its effects on HRR during combustion. The study is based on laboratory tests carried out with a cone calorimeter and a Scanning Electron Microscope (SEM). The cone calorimeter was set to generate a heat flux of 35 kWm-2. Spruce wood samples of three thicknesses were analysed, namely 10, 20 and 30mm. The samples were assembled with one of three types of material on the rear side of the samples, which were Kaowool, steel plates and aluminium foil wrapped around wood. The different materials were used as they are greatly dissimilar in their thermal properties. Wood with both low and normal moisture content was also analysed. Char was analysed with SEM. The results show that there are four major points of interest in the HRR curve of wood. The first point is the initial peak heat release rate (PHRR) that occurs when the sample surface ignites causing great production of heat which increases the HRR. The second point of interest is the vast decrease in HRR soon after the first PHRR, this is due to char formation, which acts as a protective barrier preventing the exchange of volatile gases and oxygen. The third point of interest is a second PHRR close to the end of the combustion that occurs as a response to sample burn through, which means that the heat gradient reaches the rear side of the sample. The second PHRR is highly dependent on the boundary condition defined by the rear material, which determines the heat losses at the rear side of the specimen, and consequently the temperature of the specimen. The higher is the specimen temperature, the higher is the pyrolysis rate, and therefore also the higher the second PHRR. Moreover, high moisture content delays the time of occurrence of the second PHRR as more water needs to undergo phase change, which requires a high amount of energy. The final point of interest is the final decrease in HRR as a result of fuel depletion leading to the sample smouldering or the fire being extinguished. Char, formed by mainly lignin and some cellulose in wood, affects the overall HRR. The SEM analysis showed that the char cracks grew wider during the second PHRR. It is, however, observed that char cracking has no significance in the time of occurrence of the second PHRR as this is based on sample burn through, and it was difficult to determine to what extent char cracking affected the intensity of the PHRR. This systematic study is considered adequate to justify the research questions and aim of this study. It has also created new questions for further study in the area as well as provided a deeper understanding of the fundamental burning behaviour of wood. / Klimatförändringen och dess medföljande miljöfrågor har fått byggbranschen att använda mer hållbara och miljövänliga byggmaterial. Trä har alltid varit ett byggmaterial men på grund av ett förnyat intresse för hållbarhet och förnybarhet har användningen av materialet ökat under de senaste åren. Med ett stigande intresse för trä är det av stor vikt att öka kunskapen om dess förbränningsbeteende för att kunna förutse och förebygga brandrisker. Brandutveckling karakteriseras ofta i termer av värmeavgivningshastighet (HRR) som funktion av tid. Det är därför en av de viktigaste variablerna i utvärderingen av brandrisker. Denna studie syftar till att skapa större kunskap om HRR-kurvan för trä när det utsätts för värme i konkalorimetern och hur kurvan kan beskrivas kvantitativt. Vidare, att studera kollagrets egenskaper och funktioner samt hur det påverkar HRR under förbränning. Studien bygger på laborativa försök utförda med en konkalorimeter och ett svepelektronmikroskop (SEM). Konkalorimetern genererade strålning med intensitet 35 kWm-2. Tre tjocklekar av granprover testades, 10, 20 och 30 mm. Proverna placerades ovanpå en av tre typer av material i en provform, Kaowool, stålplattor och trä invirat i aluminiumfolie. Materialen användes då deras termiska egenskaper skiljer sig åt. Vidare testades även trä av både låg och normal fukthalt. Kollagret analyserades med SEM. Resultatet visar att det finns fyra intressanta områden på HRR-kurvan för trä. Det första är den initiala maximala värmeavgivningshastigheten (PHRR) som inträffar när provytan antänder vilket orsakar en stor värmeproduktion som ökar HRR. Det andra är en kraftig minskning av HRR strax efter den första PHRR. Detta beror på att kol börjat bildas på provytan, kollagret fungerar som en skyddande barriär som förhindrar utbyte av flyktiga gaser och syre. Det tredje är en andra PHRR som inträffar nära brandprovets slut. Detta sker till följd av provkroppsgenombränning som innebär att värmegradienten når provets baksida. Intensitetenav PHRR är starkt beroende av materialet bakom provet. Det bestämmer värmeförlusten på provets baksida och därmed även provkroppens temperatur. Ju högre provkroppstemperaturenär, desto högre är pyrolyshastigheten vilket leder till en högre andra PHRR. Hög fukthalt fördröjer även tidpunkten för uppkomsten av den andra PHRR eftersom fasomvandling av vatten kräver en stor mängd energi. Det sista och fjärde området av intresse är en minskning av HRR efter den andra PHRR, detta sker när allt bränsle förbränts och det som kvarstår är endast ett glödande prov. Kollagret, som främst bildas av lignin och en del cellulosa i träet, påverkar den totala HRR. SEM-analysen visade att sprickorna i kollagret blev bredare under den andra PHRR. Däremot observerades det att sprickbildningen inte har någon betydelse för tidpunkten av den andra PHRR uppkomst då denna enbart är baserad på provets genombränning. Det är även svårt att avgöra i vilken utsträckning sprickbildningen påverkar intensiteten av PHRR. Metoden som används för att besvara frågeställningarna och syftet anses vara adekvat. Studien har öppnat upp för ytterligare frågeställningar och idéer till fortsatta försök inom området. Vidare har även studien gett en djupare förståelse om förbränningsbeteendet av trä.

No description available.