Transparent polyurethanes processing

This process involves the suspension of the biocatalyst in a monomer solution which is polymerized, and the enzymes are entrapped within the polymer lattice during the crosslinking process. This method differs from the covalent binding that the enzyme itself does not bind to the gel matrix. Due to the size of the biomolecule it will not diffuse out of the polymer network but small substrate or product molecules can transfer across or within it to ensure the continuous transformation. For sensing purposes, the polymer matrix can be formed directly on the surface of the fiber, or polymerized onto a transparent support (for instance, glass) that is then coupled to the fiber. The most popular matrices include polyacrylamide (Figure 5), silicone rubber, poly(vinyl alcohol), starch and polyurethane. 

As we will show, biocompatibility of a device can be approached from two perspectives. This is most clearly established in a discussion of how blood or plasma interacts with a foreign body. We can approach a project with the goal of allowing the body to react to the device and encapsulate it by a natural process, or alternatively, adopt a strategy to make the material as transparent as possible. Both techniques have been used with some degree of success. It is testimony to the versatility of polyurethanes that either approach can be accomplished with a simple change in the polyol. 

Aerogels are particularly well suited for insulation applications because of their exceptionally low density, thermal stability, and high transparency. In fact, they can have a thermal conductivity only one-third that of polyurethane or polystyrene foam, and with recent process improvements that reduce the cost of manufacmre by an order of magnitude their practical use in certain construction applications is now feasible [31]. The insulating properties can be enhanced through the addition of IR opacifiers [32]. The high transparency of aerogels makes them suitable as insulation in windows or translucent panels. 

Another successful example is a commercialized product of dodecylbenzene sulfonic acid-doped polyaniline (PANI-DBSA) in xylene solution/dispersion in combination with matrix such as polyurethane, polyester, and so on. Thanks to the counterion-induced processability of polyaniline, pale green color antistatic coating with surface resistivity of 10 -10 Q/D can be produced (Figure 10.9), which has shown great success in antistatic application in electronic industry, mainly due to its good transparency, low cost, and long-term stability. 

PROCESSING OF TRANSPARENT THERMOPLASTIC POLYURETHANE ELASTOMER BY INJECTION MOULDING... 

A statistical model is discussed which will help to understand the sequence length distribution of thermoplastic polyurethane block copolymers. Using this model processing range and transparency of some TPU materials were correlated to the theoretical segment length distribution. 

---