Additives – Paul Wu's Blog

Formation of Bénard cells

There is a drying pattern called “Bernard cell”, which is particularly easy to present in solvent borne solution drying.

In optically clear adhesive synthesis, free radical initiators can be photoinitators or thermal initiators. The amount of the free radical initiator is often in a range of 0.05 to 5 weight percent based on a total weight of monomers used. The following are some examples of initiators including both thermal and photo-initiators:

Inhibitors

In silicone addition curing, inhibitors must be used to exclude the vinyl groups from the platinum at temperatures around room temperature to have enough pot life. At elevated temperatures, e.g. above 80°C, these inhibitors evaporate and dissociate from the platinum, or react with the SiH and become part of the cured matrix. In either case, they can no longer exclude the polymer vinyl groups, and cure takes place rapidly.

Photoinitiator

According to the radical generation mechanisms, radical photoinitiators can be divided into three categories:

Polymeric Photoinitiator

Polymeric photo initiators have at least two advantages: (1) low migration rate due to their long polymer chain compared with small molecular counterparts; (2) higher cross linking efficiency since only one step reaction is needed to form bridges between two polymer chains, while small molecular initiators need two steps.

SiO2

Introduction*

Nano-silica particles according to their structure are divided into two types: P-type (Porous particles ) and S-type (Spherical particles). P-type nano-silica surface contains a number of nano-porous with the pore rate of 0.611ml /g; therefore, P-type has much larger SSA comparing to S-type. S-type’s SSA is ~170-200m²/g. Further more, P-type ultraviolet reflectivity is >85% , S-type: >75%.