Flame-retardant Rigid Polyurethane Foams Derived From Phosphorus-containing Soybean Polyol

Rigid polyurethane foam?RPUF?is a kind of broad-spectrum organic polymer materials with excellent performance due to many advantages,such as lightweight,low thermal conductivity,high compressive strength,good dimensional stability,fast curing speed,good adhesion,and easy construction,which is widely used in refrigeration equipment,chemical pipelines and building insulation and other fields.On view of raw materials,most of the raw materials for preparing RPUF derived from non-renewable fossil fuel resources,which makes the traditional polyurethane industry has been deeply affected by the petrochemical industry.On view of behavior,RPUF is also a kind of flammable materials,and the LOI of the non-flame-retardant polyurethane foam is only 18%to 20%.The flammability of RPUF not only poses a great threat to safety for people's life and property and environmental safety,but also limits its application.Therefore,it is the two key points urgently needed to address in the field of RPUF that the development of bio-based materials and imparting good flame retardancy to them.This paper focuses on these two points proposed above,developping three new flame-retardant soybean oil-based polyols?PBSO,PCSO PDSO?made respectively from three kind of organic phosphorus compounds?BBPA,CEPPA,DMP?and epoxy soybean oil?ESO?.Furthermore,three intrinsic flame-retardant soybean oil-based RPUFs?RPUF-PBSO,RPUF-PCSO,RPUF-PDSO?were prepared successfully that can fully replace traditional polyether polyol 4110.In addition,our group carried out some meaningful researchs to compare the flame retardant property of these obtained RPUFs,and draw a conclusion that RPUF-PCSO have the best flammability.Finally,a flame-retardant mechanism of RPUF-PCSO and synergistic flame-retardant effect system were put forward to further enhance the flame retardancy of RPUF-PCSO.It is briefly summarized as follows:?1?Firstly,three potential flame-retardant soybean oil-based polyols named PBSO,PCSO and PDSO were synthesized respectively from three kind of organic phosphorus compounds?BBPA,CEPPA,DMP?and ESO.Secondly,the physic parameters and molecular structure of them were characterized by chemical titration,FT-IR,¹HNMR,³¹PNMR and GPC.Finally,the experiment result indicated that the phosphorus-containing flame retardant unit in flame retardant molecule was successfully introduced into the molecular chain of ESO by ring opening reaction under high temperature.In other words,PBSO,PCSO and PDSO were synthesized successfully,and the OH Value were 130±10 mgKOH/g,200±10mgKOH/g,300±20 mgKOH/g orderly.?2?Three intrinsic flame-retardant soybean oil-based RPUFs named RPUF-PBSO,RPUF-PCSO and RPUF-PDSO were prepared successfully.The Compression strength,thermal conductivity,dimensional stability,flame retardancy and thermal stability of obtained RPUFs were characterized,and the results showed that all soybean oil-based polyols were able to replace polyether 4110 completely to prepare RPUF,and the obtained RPUFs had comparable mechanical properties to Neat RPUF.The LOI were 21.5%,22.0%and 21.5%respectively;Happily,the UL-94 grade of RPUF-PCSO was V-0,which showed good flame retardant performance.The thermal stability of all RPUFs were good,and final char yields were 27%,28%,and 28%respectively,which were higher than Neat RPUF?18%?.After comprehensive comparison,we can draw a conclusion that RPUF-PCSO enjoyed the greatest mechanical properties and flame retardance.?3?In order to improve the flame retardancy and thermal stability of RPUF-PC in development,different amounts of expanded graphite?EG?were added into the foaming formulation of RPUF-PCSO.During foaming process,the phosphorus-containing liquid flame retardant BY30 was added to adjust the viscosity of mixture to make foam normally.The Compression strength,thermal conductivity,dimensional stability,flame retardancy and thermal stability of obtained RPUFs were characterized,and the results show that adding 5%EG into the formulation formula of RPUF-PCSO can increase LOI to 27.0%surprisingly.With continued addition of EG,the LOI has improved to a certain extent.Then the LOI can reach 35.0%when 20%EG is added,and the flame retardant performance is greatly improved.However,the mechanical properties of RPUFs were greatly affected after addition of 15%EG or more.Finally,the thermal stability of all RPUF-PCSO/BY30/EG were improved significantly after adding EG.?4?For the combustion characteristics of RPUF-PCSO and RPUF-PCSO/BY30/EG composite foams,our group carry out some significative experiment to analyze the composition of pyrolysis gas,the apparent morphology and phosphorus content of the residual carbon after combustion by TG-IR,SEM and ICP-AES.Then a reasonable flame retardant mechanism was proposed to explain combustion phenomena of them.