Hey there Haochuan Yang! So, you've got some bubble troubles after the free-radical polymerization of MMA, huh? Well, first off, let me tell you Haochuan Yang, this situation is not uncommon. Bubbles can be a real pain in the polymerization process, and they're like the annoying guests that just won't leave your party.

Now, considering your setup with MMA monomer, AIBN, and n-butyl mercaptan, it seems like you've got a nice concoction going on. But those bubbles during thermal drawing? That's a head-scratcher.

One potential culprit could indeed be the unpolymerized monomer. It's like those stubborn guests I mentioned earlier—they just don't want to leave the party. One way to deal with this could be to optimize your polymerization conditions. Maybe tweak the temperature or duration at each step to ensure better conversion.

Another thing to consider is the possibility of residual initiator or mercaptan causing these unwanted bubbles. Make sure you're not overdoing it with those components. Maybe a slight adjustment in their amounts could make a big difference.

And hey, don't forget the importance of degassing. If there's any dissolved gas hanging around in your system, it could contribute to bubble formation. A good vacuum treatment might just be the solution to kick those bubbles to the curb.

Experimentation and fine-tuning are your best buddies in situations like these. Try different variations, keep an eye on the details, and you Haochuan Yang might just find the golden formula to get rid of those pesky bubbles. Remember, in my world, there's always a solution to every problem – it's just a matter of finding the right one. Cheers to making fiber without the unwanted effervescence! 🧪✨