Preparation And Properties Of Flame Retardant Dealcohilized Room Temperature Vulcanized One Component Silicone Sealant

Dealcoholized room temperature vulcanized one component （RTV-1） silicone sealant hastaken an important role in a variety of applications, such as architecture, electron, aerospace,auto, medicine etc. The cross-linked network has excellent sealing adhesion, non-corrosive,no odor, and excellent physical and electrical properties in the harsh environment. Additionalbenefits include convenient for using. Yet RTV-1silicone sealant is flammable, once lights up,it would burn.In this paper, four different flame retardant dealcoholized RTV-1silicone sealants withgood comprehensive properties were prepared. The former two were prepared mainly usingeasily available fire retardant Al（OH）₃, along with chloroplatinic acid as flame retardantsynergist. The last two were prepared by adopting aluminosilicate, compound with flameretardant Al（OH）₃.Universal material testing machine was used to test the mechanical properties of theflame retardant dealcoholized RTV-1silicone sealants. Flame-retardant property has beenstudied by methods of limiting oxygen index（LOI）, UL94, cone calorimeter and TGA.Storage stability was studied by accelerating ageing test. SEM testwas used to investigate thedispersion of Al（OH）₃and aluminosilicate in the sealant matrix. The main research contentsand achievements are as followings:Firstly, Al（OH）₃was used as a flame retardant, and effects of particle size and contents ofAl（OH）₃on physical and flame retardant properties of dealcoholized RTV-1silicone sealantswere studied. Results show that the smaller the particle diameter is, the better the mechanicaland flame resistance properties are, yet worse the storage stabilities. The preferred particlediameter is5μm over all considerations. As the contents of Al（OH）₃increased, LOI increased,vertical firing test first improved to FV-1then remained, curing speed got faster, hardnessincreased, tensile strength first increased then declined, elongation at break decreased. When60phr Al（OH）₃was added, LOI of the flame retardant dealcoholized RTV-1silicone sealantreached to32%, the vertical flame test rating FV-0, tack-free time19min, hardness48A,tensile strength2.6MPa, elongation at break280%and tear strength9.6kN/m. After theaccelerating ageing test, retention rate of tensile strength and elongation at break were76.92%and82.14%respectively, while change rate of tack-free time reached33.3%. Residual contentwas31.5%through thermogravimetry analysis.Secondly, chloroplatinic acid with parts per million（ppm） content was added as flameretardant synergist with Al（OH）₃to enhance the flame retardant efficiency. The synergistic effects between Al（OH）₃and chloroplatinic acid on flame retardant properties of siliconesealant were studied. When the amount of Al（OH）₃was60phr together with15ppmchloroplatinic acid, the LOI of silicone sealant was35%, flame retardant grade of FV-0,tack-free time15min, hardness50.5A, tensile strength2.4MPa, elongation at break230%.Residual mass content through thermogravimetry analysis rose to51.5%, proved to be morethermostable in comparison with the same content of Al（OH）₃added alone.Thirdly, flame retardant dealcoholized RTV-1silicone sealants were prepared usedaluminosilicate as flame retardant alone. The effects of aluminosilicate content on themechanical properties and flame-retardant properties were studied. When the content ofaluminosilicate was100phr, the LOI of flame retardant silicone sealant was35%, flameretardant grade of FV-0. With the combination of aluminosilicate and Al（OH）₃（mass ratio2:1or7:5）, total content of flame retardant declined from100phr to90phr, while flame retardedefficiency elevated. LOI of them were35%, flame retardant grade of FV-0, tensile strength1.95MPa, elongation at break170%.