Abstract
Recent studies have shown interest in flame retardants containing phosphorus, nitrogen and sulfur a combination small molecule with a promising new approach in preparing an important class of flame retardant materials. Tetraethyl piperazine-1,4-diyldiphosphonate (TEPP) and O,O,O’,O’- tetramethyl piperazine-1,4-diyldiphosphonothioate (TMPT), based on Piperazine derivatives, were prepared successfully and their structures were proved by means of 1H, 13C and 31P NMR. Cotton twill fabric was treated with both compounds to provide different add-on levels. Thermogravimetric Analysis (TGA), microscale combustion calorimeter (MCC), vertical and 45° flame test and limiting oxygen index (LOI) were performed on the treated cotton fabrics and showed promising results. When the treated twill fabrics (5 wt% - 7 wt% add-ons) were tested using the vertical flammability test (ASTMD6413-11), we observed that the ignited fabrics self extinguished and left behind a streak of char. Limiting oxygen index (LOI, ASTM 2863-09) was utilized to determine the effectiveness of the flame retardant on the treated fabrics. LOI values increased from 18 vol% oxygen in nitrogen for untreated twill fabric to a maximum of 30 vol% for the highest add-on of twill. Furthermore, Scanning Electron Microscope (SEM), Attenuated Total Reflection-Infrared (ATR-IR), and Thermogravimetric Analysis-Fourier Transform Infrared (TGA-FTIR) spectroscopy were employed to characterize the chemical structure on the treated fabrics, as well as, the surface morphology of char areas of treated and untreated fabrics. Additionally, analysis of the release gas products by TGA-FTIR shows some distinctive detail in the degradation of the treated fabrics during the burning process.
Highlights
Utilization of cotton is encouraged in a variety of consumer markets because cotton is abundant, low cost, and is an adaptable starting material for new products development [1]
TEPP and TMPT were prepared in excellent yields of 93% and 96%, respectively (Scheme 1), and all starting materials were available at low cost
These differences imply that Thermogravimetric Analysis (TGA) data is supported by FTIR data that the more gas products are released from the thermal decomposition of 3-TMPT fabric, the less char is formed at the end
Summary
Utilization of cotton is encouraged in a variety of consumer markets because cotton is abundant, low cost, and is an adaptable starting material for new products development [1]. Unlike the halogen-containing compounds, which generate toxicity or may produce toxic gases, corrosive smoke, or harmful substances [7], the phosphorous-containing flame retardants are known to transform into phosphoric acid during combustion or thermal degradation This further causes the formation of non-volatile polyphosphoric acid that can react with the decomposing polymer by esterification and dehydration to promote the formation of char residue [8] [9]. Emphasis was placed on the synthesis and characterization of the phosphorus-nitrogen base tetraethyl piperazine-1,4-diyldiphosphonate (TEPP) and phosphorus-nitrogen sulfur base O,O,O’,O’-tetramethyl piperazine-1,4-diyldiphosphonothioate (TMPT) piperazine derivatives. Both flame retardant small molecules can be prepared from low cost materials and are the products of a coupling reaction between piperazine and phosphate or phosphonothioate derivative (Scheme 1). Showed good flame resistance at low add-on levels due to the generation of high char content upon thermal decomposition and pyrolysis
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