* Use the same batch of B components (viscosity at 25 °C 600 mPa·s).   
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Packing
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Keywords Polyurethane sealant Room temperature curing Physical properties Process performance Mechanical properties
1 Foreword In order to ensure the smooth implementation of the Nine Localization Project, the China Aviation Industry Corporation No. 550 Company commissioned our institute to develop and produce room-temperature curing polyurethane sealant to replace the imported product UR 3150. The factory had used other domestic materials and its performance did not reach the level of UR 3150. MF-1 polyurethane sealant formula is reasonable, the process is simple, curing at room temperature for 4 days will be able to achieve the required mechanical properties, can replace imported products.   
2 Experimental Section 2.1 Raw Materials
Polytetramethylene ether glycol (PTMG), with a relative molecular weight of 1,000, Nippon Fortune Valley Company; toluene diisocyanate (TDI), purity >99.5%, Japan Mitsui East Asia Corporation; chain extender, self-aligning; castor oil (CTO) , A product, domestic. 
2.2 Synthesis Method
(1) Synthesis of A component A certain amount of PTMG and CTO are vacuum dehydrated in a three-vial bottle at 110-120° C. and a pressure of 666.6 Pa to a moisture content of less than 0.05%. After cooling to room temperature, it is added to weighed amount. In TDI, the reaction was carried out at 80° C. for 2 h, and the NCO content was used for analysis. 
(2) Preparation of component B The oligomer polyol and the chain extender are mixed and stirred uniformly at room temperature under a certain ratio. 
(3) Sealant test piece preparation
A, B components are weighed in a certain ratio, mixed at 25 °C, fully stirred for 1 ~ 2 min and then vacuum degassed for 3 ~ 5 min and poured into a well-treated mold (25 °C). After the machine is cold pressed, the test piece is demoulded and then cured in an oven at 25°C to be tested. 
2.3 Performance Test
Density according to GB 533-91 test;
Hardness according to GB 531-92 test;
Tensile strength, tensile strength, elongation at break, and permanent tearing are tested according to GB 528-98;
Impact rebound according to GB 1681-88 test;
Tear strength according to GB 529-96 test. LL
3 Results and Discussion
Table 1 Effect of component A on viscosity, process performance, and mechanical properties * A component A component NCO mass fraction /% viscosity (25 °C) / mPa · s 25 °C × 4 d mechanical properties 110 °C × 6 h Mechanical properties A component 2 components mixed rebound/% Shore A hardness elongation/% tensile strength/MPa 300% tensile strength/MPa tensile permanent deformation/% tear strength/kN·m-1 Elastomer/% Shore A Hardness Elongation/% Tensile Strength/MPa 300% Tensile Strength/MPa Tensile Deformation/% Tear Strength/kN·m-12.059.553 3003 950359259029.715.635114.4329240051.623.618121.72.109.454 5004 250319254027.316.235109.3309235047.826.018107.52.209.405 8005 350299246044.124.025108.8289435044.429.315113.02.309.556 2005 450289438040.728.12096.0279432042.040.215102.3
As can be seen from Table 1, the increase in viscosity of the component A increases the viscosity, A, B components showed a trend of increasing viscosity after mixing, the glue is easy to produce air bubbles affect the sealing effect. From the perspective of mechanical properties, room temperature vulcanization 4 d, the mechanical properties of different functionalities of the sealant can reach the technical indicators. The tensile strength and tensile strength of the sealant were significantly higher than the functionalities of 2.1 and 2.05 when the functionalities were 2.2 and 2.3, but the performance difference was not significant after hot vulcanization. Considering comprehensively, it is more appropriate to choose a functional degree of 2.1.
3.2 Effect of NCO content on process performance and mechanical properties
Given that the sealant technology requires a Shore A hardness of 90 to 95, NCO mass fractions of 8.97%, 9.50%, and 10.09% were selected for testing. The results are shown in Table 2. From the perspective of mechanical properties, the NCO mass fraction is 10.09%
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Name
Stainless Steel Propane Fire Pit Burner
Material
Stainless steel
Size
800*800mm
Steel thickness
2mm
Weight
3.5KG
Packing
carton
Square Fire Pit Burner Square Fire Pit Burner,Square Log Burner,Square Fire Pit Burner Kit,Square Fire Pit Insert Kit
Henan Jinbailai Industrial Co.,Ltd , https://www.jblfirepits.com