Judgment based on time and reaction process
Pre set reaction time: In the early stage of conducting a large number of laboratory small or pilot experiments, based on established reaction conditions (such as specific temperature, catalyst dosage, raw material ratio, etc.), explore the approximate reaction time range required to achieve the expected product performance. For example, in a conventional hydrolysis and condensation reaction of silicone resin, it has been determined through multiple experiments that at a temperature of 60 ℃, using a specific catalyst and corresponding raw material ratio, the reaction can take about 3-5 hours to obtain a product that meets the requirements. Therefore, when scaling up production under the same conditions, this time range can be used as a reference for preliminarily judging the reaction endpoint.
Observing changes in reaction phenomena: As the reaction progresses, some intuitive phenomena may change. For example, in the hydrolysis condensation reaction, the system may present a uniform solution state at the initial stage of the reaction. As the reaction continues, the solution may gradually become turbid, showing a trend of gel (for cross-linked silicone resin synthesis), or stratification. When these phenomena are observed to develop to a state consistent with past experience where the product is close to completion, it can be preliminarily judged that the reaction is approaching the endpoint. For example, when a solution begins to appear slightly turbid and no longer shows significant changes for a period of time, it may indicate that the reaction has reached a later stage.
Judging through physical property testing
Viscosity measurement: The viscosity of silicone resin is closely related to its molecular weight, crosslinking degree, etc. As the reaction proceeds, the molecular weight of the product continues to increase, and the crosslinking structure gradually forms, resulting in a corresponding increase in viscosity. A viscometer can be used to regularly measure the viscosity of the reaction system, and a curve of viscosity over time can be drawn during the laboratory trial stage to determine the corresponding time point when the viscosity reaches the target value (which is related to the expected product molecular weight, application scenario requirements, etc.). Subsequently, the reaction endpoint can be determined based on this. For example, for silicone resin used in the field of coatings, it is required to reach a specific viscosity range at a certain temperature. When the actual measured viscosity reaches this range, the reaction can be considered to have reached the endpoint.
Refractive index detection: The refractive index of silicone resin is also one of its important physical properties, and it will change with the change of product structure during the reaction process. Regularly detect the refractive index of the reaction system using a refractometer, and establish the corresponding relationship between refractive index, reaction process, and product state through preliminary experiments. When the refractive index stabilizes near the value required for the target product, it can be determined that the reaction is approaching or has reached the endpoint.

Room termperature curing polysilazane, pls check IOTA 9150, IOTA 9150K. 
High termperature curing polysilazane, pls check IOTA 9108, IOTA 9118.