Weekly topic: 8 wealth points for those who answer correctly, 2 wealth points for participation； Question 122!
Thread Content
Short answer: What are the methods to control the size of spherulites? Answer: 1? Control the cooling rate; 2? Control the shaping speed; 3? Control the nucleation time.
Answer: Methods to control the size of spherulites: (1) Control the formation rate: Rapidly cool the melt (at lower temperature ranges) to produce smaller spherulites； Slow cooling results in the formation of larger spherulites. (2) Using the copolymerization method: disrupting the uniformity and regularity of the chains to produce smaller spherulites. (3) Exogenous nucleating agents: can yield small or even extremely small spherulites.
Crystallization temperature, solvent type, solution concentration, cooling rate, etc
Yes: 1. Controlling the cooling rate； 2. Control the molding speed ； 3. Control the nucleation time.
Increase supercooling, use stirring for crystallization, add second-phase particles to suppress crystallization
The spherulite size is closely related to the number of nucleation centers. Generally, crystalline polymers have an optimal crystallization temperature. When the crystallization temperature is below the optimal crystallization temperature, increasing it leads to an increase in the number of nucleation sites, an increased likelihood of collisions between spherulites, and smaller spherulite sizes ； Above the optimal crystallization temperature, increasing the temperature reduces the number of nucleation sites, thereby decreasing the likelihood of collisions between spherulites, allowing them to grow larger
What are the methods for controlling the size of spherulites? Controlling the nucleation time, controlling the cooling rate, controlling the molding speed
What are the methods to control the size of spherulites? In actual production, small spherulites are often obtained through rapid cooling (quenching), and the size of the spherulites can also be reduced by adding nucleating agents such as sodium benzoate.
What are the methods to control the size of spherulites? Different conditions under which crystalline polymers are crystallized affect the size of spherulites: 1. Under rapid cooling conditions, the degree of crystallization is low, resulting in small spherulite sizes; 2. Under slow cooling conditions, the degree of crystallization is high, leading to larger spherulite sizes; 3. Crystallization at higher temperatures results in larger spherulite sizes and a higher degree of crystallization; 4. Crystallization at lower temperatures results in smaller spherulite sizes and a lower degree of crystallization
Increase the supercooling, use stirring crystallization and add second-phase particles to suppress crystallization
Answer: By controlling the conditions under which spherulites are formed, namely: crystallization temperature, solvent type, solution concentration, cooling rate, etc.