Polymer additives content protection

The protected amine and primary amine ended polymers show the good molecular weight control and narrow MWD s one expects of anionic polymers. In addition, the hydrolysis of the protecting group does not disrupt polydiene backbones. Such procedures are also gel free. The polymers formed exhibit functionalities approaching the theoretical values, especially for low molecular weight (high amine content) polymers (Table VI), (14, 2). 

Hydrocarbon solubility is important for diene polymerization, where a high 1,4 polymer microstructure is often desired. Polar solvents have a tendency to decrease the 1,4 content and elevate the 1,2 addition product. Hydrocarbon solubility is less of an issue for styrene or epoxide polymerization. Thus, the hydrocarbon soluble t-butyldimethylsilyl (TBDMS) protected initiator (5) (Table I) is recommended for high 1,4 polydienes. Most of the other conpounds in Table I can be used with other anionic monomers or where high 1,4 microstructure is not needed. 

PDBS-80 was the first in the series. This material is a homopolymer of dibromostyrene that contains 59-60% bromine. Its primary applications are in high-temperature polyamides and polyethylene terephthalate (PET) because it has excellent flow characteristics and very good thermal stability. In addition, there are benefits of excellent colour retention. The main weakness of this approach is the bromine content relative to the competitive material. Today s competition contains around 68% bromine. This can translate into a 2-3 parts difference in the load level needed in the protected polymer to give equivalent flame retardancy. 

The main conclusion from all the above is that except of MMT, where contradictory results were reported, in all other nanocomposites the addition of nanoparticles can lead to thermal stabilization effect of polymers during their decomposition. However, in this direction the effect of nanoparticles content is very crucial. In most of the cases the thermal stability enhancement takes place at low loading (4-5 wt%) of nanoparticles while at higher contents thermal stabilization becomes progressively lower. This is because at higher concentrations nanoparticles can form aggregates and thus effective area of nanoparticles in contact with polymer macromolecular is lower. In this case microcomposites may are formed instead of nanocomposites and thus the protective effect of nanoparticles becomes lower [22]. 

---