suspension polymerization polystyrene 1

[hoidap]

Dear members

I am doing suspension polymerization of polystyrene,
BPO is used as initiator (~1wt % of monomer)
PVA as dispersed agent (0.4 -> 1wt% of water)
monomer/water : 1/10 and 2/10 and 4/10

I tried to vary monomer/water ratio, PVA ratio, and i always fail to obtain the bead but an aggregated mass.
The coalescence always happens at sticky stage.
please advice how to overcome this and obtain bead PS
Thank you so much
Best regards

 

[Demon3]

Stirring is really important and also make sure you are using the right kind of PVA. PVA comes in many types. You need PVA to act as a steric stabilizer, that means that you probably don't want the kind that is 100% hyydrolysed. PVA is made by hydrolysing polyvinylacetate. You need some hydrophobic acetate groups left on the PVA, they adsorb to the PS particle to help stabilize it. As an alternative try PVP instead of PVA. Having said all of that I am not an expert on suspension polymerization so if someone more experienced chips in then listen to them.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[hoidap]

Thank Demon3,

PVA used is
341584
Aldrich Poly(vinyl alcohol)
average Mw 89,000-98,000, 99+% hydrolyzed
I am not really sure whether it is suitable.
I need to keep on with PVA, thank you for your suggestions.
Best regards

 

[Demon3]

Steric stabilizers work by adsorbing on the particle and being water soluble. In order to do that they need hydrophobic parts that adsorb and hydrophilic parts that dissolve the rest of the PVA in the water to make what is called a protective colloid. If you use PVA that is 99+% hydrolysed then you have a polymer that only has hydrophilic, water soluble units so it won't adsorb onto the PS particle and won't stabilize it so you will get precipitate / coagulum. Normally PVA is about 88% hydrolysed, this gives a nice mixture of 12% hydrophobic groups so the PVA adsorbs and 88% water soluble groups to make a steric barrier around the particle. So, I suggest you buy the 88% hydrolysed PVA from Aldrich and try that.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[hoidap]

Hello Demon3

I get it, the PS particles with the new PVA of 87-89% hydrolyzed,
Thank Demon3.

 

[Demon3]

Excellent!!

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell