Synthesis and Application of Hybrid Aluminum Dialkylphosphinates as Highly Efficient Flame Retardants for Polyamides.

Hybrid aluminum dialkylphosphinates were synthesized from mixed diethyl-, ethylisobutyl-, and diisobutylphosphinates and Al3+ in water. The XRD, DSC, and TGA results of these Al phosphinates established that phosphinate ligands are randomly distributed in the species. The thermal and thermoxidative stabilities of the hybrid phosphinates were easily adjustable by varying the ratio of phosphinate ligands, a desirable feature for efficient flame retardants. The hybrid aluminum dialkylphosphinates with a relatively low ratio of diethylphosphinate demonstrated higher efficiency than Al diethylphosphinate and Al diisobutylphosphinate in flame-retarding polyamide 66. Detailed investigations on the thermal and thermoxidative stabilities of Al dialkylphosphinates and the morphologies of char obtained in UL-94 tests revealed that timely vaporization of degradation products of hybrid dialkylphosphinates at a temperature which closely matches the degradation temperature of polyamides and their ability to promote char formation of polyamides are two key factors which contribute to the excellent performance of hybrid aluminum dialkylphosphinates.

Real-world NOx emissions from heavy-duty diesel, natural gas, and diesel hybrid electric vehicles of different vocations on California roadways.

This study assessed the real-world nitrogen oxide (NOx) emissions from 50 heavy-duty vehicles of different vocations and engine technologies using portable emissions measurement systems (PEMS). This is one of the most comprehensive in-use emissions studies conducted to date, which played a key role in the development of CARB's (California Air Recourses Board) updated EMission FACtor (EMFAC) model, especially for natural gas vehicles. In-use emissions testing was performed on school and transit buses, refuse haulers, goods movement vehicles, and delivery vehicles while were driven over their normal operating routes in the South Coast Air Basin. Engine technologies included diesel engines with and without selective catalytic reduction (SCR) systems, compressed natural gas (CNG) engines and liquified petroleum gas (LPG) engines, and SCR-equipped diesel hybrid electric vehicles. For most vehicles, the in-use NOx emissions were higher than the certification standards for the engine. Diesel vehicles generally showed higher brake-specific NOx emissions compared to the CNG vehicles. NOx emissions were strongly dependent on the SCR temperature, with SCR temperatures below 200 °C resulting in elevate brake-specific NOx. The 0.02 g/bhp-hr certified CNG vehicles showed the largest reductions in NOx emissions. The diesel hybrid electric vehicles showed important distance-specific NOx benefits compared to the conventional diesel vehicles, but higher emissions compared to the CNG and LPG vehicles. Overall, average NOx reductions were 75%, 94%, 65%, 79%, respectively, for the 0.2 CNG, 0.02 CNG, diesel hybrid electric, and LPG vehicles compared to diesel vehicles, due in part to some diesel vehicles with particularly high emissions, indicating that the widespread implementation of advanced technology and alternative fuel vehicles could provide important NOx reductions and a path for meeting air quality targets in California and elsewhere.

An Extremely Efficient Silylated Benzensulfonate Flame Retardant for Polycarbonate.

An extremely efficient flame retardant with low water solubility has been developed for bisphenol-A based polycarbonate. Potassium trimethylsilylbenzenesulfonate (KTSS) combining trimethylsilyl and sulfonate groups in its molecule is 7 times less water soluble and 5 times more effective in flame retardancy than potassium benzenesulfonylbenzenesulfonate (KSS), the commercial workhorse for polycarbonate (PC). At a loading of 0.02%, KTSS enables PC to achieve a solid UL-94 V0 rating and a limiting oxygen index (LOI) value of 34.4%, representing an increase of 8.5 units. The extremely high efficiency of KTSS stems from its great migration ability to the burning polymer surface facilitated by trimethylsilyl group, its timely release of active alkaline species that promote the charring process of PC, and the stabilization of char by silicon. In addition to the exceptional flame retardancy, PC/KTSS retains excellent physical properties of PC.