August 2019 – Page 2 – Paul Wu's Blog

Study of sub-surface features by laser confocal microscopy

A laser confocal microscope has the ability to isolate a single plane of focus from thick samples or overlapping objects. Therefore it is a powerful tool to image the surface or bulk (in transparent media) features of a specimen.

Cpm

Another type of capability index, Cpm, is much less known and used less frequently than Cpk or Ppk. The main difference between the Cpm and the other capability indices is that the bias from the target, not mean, is directly taken into consideration in the Cpm. The bias is the difference between the process average and the target.

Cp, Cpk, Pp, Ppk

Process capability, Cp, tells how well a process meets customer’s specifications. It is defined as the ratio of engineering tolerance (USL – LSL) to the natural tolerance (-3σ to 3σ) . However, a process can be capable of meeting specifications, but not be meeting specifications if the process is not centered relative to the specifications. Therefore, process capability index, Cpk, is introduced to take into account of the centeredness.

Study the curing reaction of silicone release agent through FTIR

In PSA industry, release liner is one of the key components. The main functions of release liner are to provide protection of the adhesive layer during storage and transportation, and ensure a residue-free removal from the protected adhesive layer without damaging or contaminating it.

Silicone FTIR

The paper, titled with Characterization of Surface Treatments of Cork Stoppers by FTIR-ATR and published in J. Agric. Food Chem. 2006,54, 4932-4936, proposed an analytical method for identification of the presence of surface treatments in cork stoppers. The information about the FTIR bands for silicone is quite useful.

FTIR

Molecular bonds can be considered as stiff springs which can be bent or stretched. The vibration (bending and stretching) energy lies in the infrared (IR) range. Therefore, through the interaction between IR incident beam and molecules in samples to be tested, through transmission or reflection, molecular bonds information can be extracted from the absorption spectra to obtain their molecular structures.

initiators

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.

Viscosity Vs coating method

The coating methods, fluid viscosity, and line speed are correlated with each other in thin film coating process. The following figure is a good guidance for selecting coating methods and coating parameters

Thermal conductivity measurement (ASTM D 5470, E1530, and E1461)

Thermal conductivity measurements can be divided into two groups: steady state and transient state testing methods. Steady state methods also includes guarded hot-plate (GHP) method and Heat-Flow Meter (HFM), while a typical transient method is Laser/Xenon Flash (LFA/XFA) method.