1. Why prepolymer are used for this polymerization of PMMA?, Why different step of
thermal polymerization are applied?
Solution:
Prepolymer are used to modify PMMA such as addition of some artwork additives
example favorite colours.
Other reasons of using prepolymer for this polymerization of PMMA are
1. Improved handling since prepolymers is liquid storage stable when kept in
oven (dry).
2. Allows one to “prebuild in” the final PMMA polymer properties and obtain a
more uniform final PMMA structure.
3. Prepolymer offers an attractive approach allowing one to prepare PMMA
system from entirely liquid components. Using pure MMA , for instance
would require that ingredients (mixed with BPO) be heated to the
temperature higher than melting point of MMA, which could shorten the
window for convenient processing. As a liquid it is convenient to begin with
a system that is as low viscosity as possible to avoid problems such as
entrainment of air during processing.
Different step of thermal polymerization is applied because it is easy to control thermal
process since typically reaction has both modest activation Energy Ea and Enthalpy of
polymerization ΔH with modestly exothermic.
The other reason is that temperature control / thermal polymerization step is applied in
order to allow viscosity build up and allow post polymerization of the prepolymer.
, 2. If there are some bulb in the system can you explain why?
Solution:
The presence of some bulb in the system is due to the bulk polymerization happened very
fast and heat was concentrated in the local position. This will affect the quality of the
PMMA polymer materials Therefore, the need to control polymerization temperature and
evolve of the heat of the reaction is the key factor in this system.
The autoacceleration behavior during polymerization of Methyl-methacrylate occurred as
the polymerization rate of reaction increases with conversion. The figure below indicates
the 10% of methyl methacrylate solution shows the behavior that would generally be
expected. The plot for neat (pure) monomer shows a dramatic autoacceleration in the
polymerization rate.
Fig.1 Autoacceleration of Benzoyl peroxide-initiated polymerization of methyl
methacrylate in benzene at 50°C. The different plots shows various concetrations of
monomer in solvent. After Schulz and Haborth [1948] (by permision of Huthig and Wepf
Verlag, Basel).
thermal polymerization are applied?
Solution:
Prepolymer are used to modify PMMA such as addition of some artwork additives
example favorite colours.
Other reasons of using prepolymer for this polymerization of PMMA are
1. Improved handling since prepolymers is liquid storage stable when kept in
oven (dry).
2. Allows one to “prebuild in” the final PMMA polymer properties and obtain a
more uniform final PMMA structure.
3. Prepolymer offers an attractive approach allowing one to prepare PMMA
system from entirely liquid components. Using pure MMA , for instance
would require that ingredients (mixed with BPO) be heated to the
temperature higher than melting point of MMA, which could shorten the
window for convenient processing. As a liquid it is convenient to begin with
a system that is as low viscosity as possible to avoid problems such as
entrainment of air during processing.
Different step of thermal polymerization is applied because it is easy to control thermal
process since typically reaction has both modest activation Energy Ea and Enthalpy of
polymerization ΔH with modestly exothermic.
The other reason is that temperature control / thermal polymerization step is applied in
order to allow viscosity build up and allow post polymerization of the prepolymer.
, 2. If there are some bulb in the system can you explain why?
Solution:
The presence of some bulb in the system is due to the bulk polymerization happened very
fast and heat was concentrated in the local position. This will affect the quality of the
PMMA polymer materials Therefore, the need to control polymerization temperature and
evolve of the heat of the reaction is the key factor in this system.
The autoacceleration behavior during polymerization of Methyl-methacrylate occurred as
the polymerization rate of reaction increases with conversion. The figure below indicates
the 10% of methyl methacrylate solution shows the behavior that would generally be
expected. The plot for neat (pure) monomer shows a dramatic autoacceleration in the
polymerization rate.
Fig.1 Autoacceleration of Benzoyl peroxide-initiated polymerization of methyl
methacrylate in benzene at 50°C. The different plots shows various concetrations of
monomer in solvent. After Schulz and Haborth [1948] (by permision of Huthig and Wepf
Verlag, Basel).
