Summary
The effect of zinc borate (ZnB) was studied on the flame retardant and thermal properties of thermoplastic polyurethane containing huntite‐hydromagnesite. The flame retardant properties of thermoplastic polyurethane–based composites were investigated using limiting oxygen index, vertical burning test (UL 94), thermogravimetric analysis, and mass loss calorimeter. No remarkable effect of ZnB was observed on the flammability properties of composites. UL 94 rating did not change regardless of the added amount of ZnB, and the slight increase in limiting oxygen index value was observed at ratio of 1:1. The adjuvant effect of ZnB was observed during the mass loss calorimeter studies by increasing the barrier effect of the residue in the condensed phase and by increasing the formation of incombustible gasses in the gas phase. The highest fire performance was achieved at ratio of 1:1.
This article describes micro‐ and nanostructural, mechanical, and thermal properties of nanocomposites based on polyvinyl chloride (PVC) and graphene nanoplatelets (GNP). The primary objective of this study was to extend restricted application area of PVC due to its low thermal stability and limited mechanical properties. GNP‐filled PVC nanocomposites were prepared (0, 0.1, 0.3, 0.5, and 1.0 wt%) by colloidal blending method and characterized in detail. The highest value of the tensile strength 13.73 MPa (an increase of 58%) and the highest value of microhardness 83.42 MPa (an increase of 82%) were obtained with GNP loading content of 0.5 wt% compared neat PVC. The mechanical properties started to decrease at loading higher than 0.5 wt%; however, the thermal properties continued to increase. The differential scanning calorimetry and Fourier transform infrared analysis results of this nanocomposite confirmed that the increase in glass transition temperature from 34.99°C to 44.36°C and the decrease in the height of functional groups peaks proved to prevented segmental relaxation and intermolecular vibrations of PVC, respectively. Thermogravimetric analysis results were showed that the percentage of carbonaceous residue increased to 15.77% by increasing the GNP content from 0.1 to 0.5 wt%. As a result, the best GNP loading was at 0.5 wt% for PVC/GNP nanocomposites where mechanical and thermal properties of PVC/GNP were both enhanced.
The effects of carbon fiber amount and length were studied on the flame retardant, thermal, and mechanical properties of the intumescent polypropylene composites. The flame retardant properties of the intumescent polypropylene-based composites were investigated using limiting oxygen index, vertical burning test (UL-94), and mass loss calorimeter. The mechanical properties of the composites were studied using tensile test and dynamic mechanical analysis. According to the flammability tests results, the antagonistic interaction was observed between carbon fiber and ammonium polyphosphate. The limiting oxygen index value reduced steadily as the added amount of carbon fiber increased. Mechanical test results revealed that the addition of carbon fiber increased the tensile strength and the elastic modulus as the added amount increased. No effect of carbon fiber length was observed on the flammability, fire performance, and tensile properties of composites, whereas the elastic modulus increased as the carbon fiber initial length increased.
In this study, organoclay-containing polystyrene (PS)-based nanocomposites were fabricated by extrusion in the presence of thermoplastic elastomer modifiers. Styrene–butadiene–styrene (SBS) rubber was used as the elastomeric compatibilizer and maleic anhydride (MA) was grafted onto SBS rubber at different ratios. Grafting was made via melt blending. Cloisite® 30B was used as the organoclay and it was added to PS and PS/SBS blends using a corotating twin-screw extruder, followed by injection molding. Clay loading was kept constant as 2 wt%, and the elastomer content was varied between 0 and 40 wt% throughout the study. MA grafted SBS enhanced the intercalation/exfoliation of clay layers resulting in higher tensile strength, modulus, elongation at break, and impact strength with respect to neat PS. Composites containing 15 wt% MA grafted SBS displayed the optimum average domain size resulting in the high impact strength without deteriorating the tensile strength and modulus values. Elastomer addition increased the glass transition temperature of the samples due to branching or cross-linking during extrusion. PS and PS/SBS exhibited similar melt flow index values with their organoclay-containing composites. MA acted as a plasticizer and decreased viscosity. Scanning electron microscopy study indicated that dispersion of clay layers was observed at the PS-SBS interphase and also in the elastomer phase. Intercalated and exfoliated structures of organoclay layers were confirmed by X-ray diffraction and transmission electron microscopy analyses.
In this study, short carbon fiber (CF) surface was coated with jeffamine, isocyanate, and polyamide (PA). Surface-coated layers of CF samples were confirmed by infrared spectroscopy. Desized and coated CFs were incorporated to PA6 by melt-compounding method with a constant ratio of 20 wt%. Tensile testing, shore hardness, dynamic mechanical analysis (DMA), and melt flow rate (MFR) test of composites were performed. Adhesion of CF to the polymer matrix was investigated by scanning electron microscopy (SEM) of composites. Mechanical characterization of composites implied that tensile strength, tensile modulus, percent elongation, and shore hardness of unfilled PA were extended to higher values by the addition of surface-coated CFs. The highest improvement was observed for isocyanate-modified CF-loaded PA-based composites. According to DMA results, storage modulus and loss modulus of PA increased with the incorporation of sized CF into polymer matrix. CF containing composites showed higher glass transition temperature with respect to unfilled PA. Addition of CF caused no significant change for MFR of PA. Poor adhesion of desized CF and relatively strong adhesion of surface-coated CFs to PA matrix were confirmed by SEM analysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.