Asian Journal of Chemistry; Vol. 25, No. 10 (2013), 5683-5685
Synthesis and Characterization of Flame-Retardant Polyurethane
Elastomers Using Phosphorus-Containing Chain Extender†
*
WENZONG XU , WENXIU LI, MINGYUAN REN and JIANGUO YIN
School of Materials Science and Chemical Engineering, Anhui University of Architecture, 856 Jinzai Road, Hefei 230022, Anhui Province,
P.R. China
*Corresponding author: E-mail: wenzongxu@sohu.com
AJC-13305
Phenylphosphonic diamine was synthesized from phenylphosphonic dichloride and characterized by Fourier transform infrared spectroscopy
and nuclear magnetic resonance. Then phenylphosphonic diamine was used to prepare a series of phosphorus containing polyurethane
elastomers (PPUEs) with different phosphorus contents. Combustion behaviour and thermal degradation behaviour of the PPUEs and
polyurethane elastomer (PUE) were investigated by macroscale combustion calorimetry and thermogravimetric analysis. The macroscale
combustion calorimetry result reveals that the value of peak heat release rate and total heat release of PPUEs are lower than those of PUE
made by 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA). The TGA result shows that PPUE2 has poorer thermal stability than PUE
when they are obtained from the same soft segment, but the char yield of PPUE2 is higher than that of PUE.
Key Words: Phosphorus-containing diamine, Polyurethane, Flame retardancy, Thermal stability.
INTRODUCTION
EXPERIMENTAL
Phosphorus is an effective element for imparting good
fire resistance to polyurethanes (PUs)1-4. Compounds containing
phosphorus are an important group of environmental friendly
flame retardants which have several advantages such as low
toxicity, no release of poison gas, e.g., dioxin or halogen acids
during combustion, as well as low smoke production during
burning. Generally, modifications of flame retardant polyure-
thane can be roughly grouped into two categories i.e., physical
modifications and chemical modifications.
Polyester diol (Mn = 1213, 1975, 2600) was obtained from
Shandong Xinhuarun Chemical Co. Ltd., 3,3'-dichloro-4,4'-
diaminodiphenylmethane (MOCA) was purchased from
Zhangjiagang Daily Chemical Co. Ltd.
Synthesis of phenylphosphonic diamine: In a four-
necked reactor 80 g phenyl phosphonic dichloride was added
dropwise to 210g ammonia under constant stirring at 0 ºC. A
constant flow of nitrogen gas was maintained to remove the
HCl produced. The reaction solution was maintained at 5-10 ºC
for 6 h to complete the reaction. The crude product was separated
from the reaction mixture by filtration. Finally the product
was recrystallized from absolute ethanol.
The physical modification approach provides a simple
means of flame retardation, but polyurethane materials conta-
ining nonchemical bonding phosphorus are limited in several
areas and the loss of phosphorus compounds is continuous
during storage and processing. Thus, a better approach may
be the incorporation of phosphorus into polyurethane materials
in which phosphorus-containing structures are an integral part
of the polyurethane molecule5-8.
Synthesis of phosphorus-containing polyurethane elas-
tomers: A certain amount of molten phenylphosphonic di-
amine or MOCA was added to stir prepolymer and the mix-
ture was put in a Teflon mould and heated at 75 ºC for 2 h and
115 ºC for another 4 h. Table-1 gives a description of PPUEs
and PUE.
In this paper, we report the synthesis and characterization
of a phosphorus-containing chain extender phenylphosphonic
diamine and a series of phosphorus containing polyurethane
elastomer (PPUEs) synthesized by adjusting the soft segment.
The structures and properties of PPUEs were studied by FTIR,
TGA and macroscale combustion calorimetry.
O
O
NH3-H2O
Cl
P
Cl
H2N
P
NH2
Scheme-I: Synthesis scheme of phenylphosphonic diamine
†Presented to the 6th China-Korea International Conference on Multi-functional Materials and Application, 22-24 November 2012, Daejeon, Korea
Xu, Wenzong
