Multicomponent flame retardant systems containing aluminum diethylphosphinate in thermoplastic styrene-ethylene-butylene-styrene elastomers are investigated (oxygen index, UL 94, cone calorimeter, and mechanical testing). Solid-state nuclear magnetic resonance, scanning electron microscopy, and elemental analysis illuminate the interactions in the condensed phase. Thermoplastic styrene-ethylene-butylene-styrene elastomers are a challenge for flame retardancy (peak heat release rate at 50 kW m 22. 2000 kW m 22 , oxygen index = 17.2 vol%, no UL-94 horizontal burn rating) since it burns without residue and with a very high effective heat of combustion. Adding aluminum diethylphosphinate results in efficient flame inhibition and improves the reaction to small flame, but it is less effective in the cone calorimeter. Its efficacy levels off for amounts .;25 wt%. As the most promising synergistic system, aluminum diethylphosphinate/ melamine polyphosphate was identified, combining the main gas action of aluminum diethylphosphinate with condensed phase mechanisms. The protection layer was further improved with several adjuvants. Keeping the overall flame retardant content at 30 wt%, aluminum diethylphosphinate/melamine polyphosphate/titanium dioxide and aluminum diethylphosphinate/ melamine polyphosphate/boehmite were the best approaches. An oxygen index of up to 27 vol%
Developing
flame retarded thermoplastic elastomers (TPE-S) based
on styrene–ethylene–butylene–styrene, polypropylene,
and mineral oil is a challenging task because of their very high fire
loads and flammability. A promising approach is the synergistic combination
of expandable graphite (EG) and ammonium polyphosphate (APP). Cone
calorimetry, oxygen index, and UL 94 classification were applied.
The optimal EG:APP ratio is 3:1, due to the most effective fire residue
morphology. Exchanging APP with melamine-coated APPm yielded crucial
improvement in fire properties, whereas replacing EG/APP with melamine
polyphosphate did not. Adjuvants, such as aluminum diethyl phosphinate
(AlPi), zinc borate, melamine cyanurate, titanium dioxide, dipentaerylthritol,
diphenyl-2-ethyl phosphate, boehmite, SiO2, chalk, and
talcum, were tested. All flame retardants reinforced the TPE-S. The
combination with AlPi is proposed, because with 30 wt % flame retardants
a maximum averaged rate of heat emission below 200 kW m–2 and a V-0 rating was achieved. Multicomponent EG/APP/adjuvants
systems are proposed as a suitable route to achieve efficient halogen-free
flame retarded TPE-S.
A novel silicon-based linkage and cleavage strategy for solid-phase synthesis of aromatic organic compounds has been developed. The method is based on the following steps: (i)) to a Merrifield resin via R 4 , (ii) reactions with the resin-linked silanes (chemical transformations of the aryl group R 1 ; R 1 f f f R 1* ), and)CH 2 CH 2 -containing resin with 1,2dihydroxybenzene in acetonitrile at 50 °C to give the cleavage products R 1* H (release of the target molecules in a traceless fashion), R 2 H, and R 3 OH, along with the resin-linked zwitterionic pentacoordinate silicate of the formula type (1,2-C 6 H 4 O 2 ) 2 Si(CH 2 ) n N(H)CH 2 -CH 2 N(R 4 )CH 2 CH 2 .
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