Polyurethane-based matrix systems

Surfactants are added to a thermoset resin system to promote the dispersion of fillers in the resin matrix. Recently, surfactants have been used to disperse carbon nanotubes in polymer matrices [48-50]. Surfactants are of two types neutral and ionic. Surfactants have many applications in coating industries for the development of a water-based resin system [51]. Surfactants are added to phenolic or polyurethane foam formulation in which they facilitate formation of small bubbles. The size and uniformity of bubble formation results in a fine cell structure. A surfactant reduces the surface tension of resin formulations and provides an interface between the highly polar resin and the non-polar blowing agent. The surfactant for a particular resin system must be selected carefully so that it is compatible with the resin and resistant... 

The systems shown in Fig. 7 are compared with Cr-containing control systems. Optimized coating systems aU performed well over 2000 h in the test, which is usually a typical requirement in the industry. The polyurethane-based system on AA 6061 even survived 4000 h in ASTM B-117 (Fig. 7d). This gives ample proof of that the modification of the resin matrix might be a key factor in order to make the Cr-free pigments work on metals in a similar way as the strontium chromate works in traditional coatings. 

Composite Particles, Inc. reported the use of surface-modified rubber particles in formulations of thermoset systems, such as polyurethanes, polysulfides, and epoxies [95], The surface of the mbber was oxidized by a proprietary gas atmosphere, which leads to the formation of polar functional groups like —COOH and —OH, which in turn enhanced the dispersibility and bonding characteristics of mbber particles to other polar polymers. A composite containing 15% treated mbber particles per 85% polyurethane has physical properties similar to those of the pure polyurethane. Inclusion of surface-modified waste mbber in polyurethane matrix increases the coefficient of friction. This finds application in polyurethane tires and shoe soles. The treated mbber particles enhance the flexibility and impact resistance of polyester-based constmction materials [95]. Inclusion of treated waste mbber along with carboxyl terminated nitrile mbber (CTBN) in epoxy formulations increases the fracture toughness of the epoxy resins [96]. 

Delivery appheations are based on the fact that polyurethanes swell when exposed to solvents. Once a material is imbedded in a polyurethane matrix, the matrix can deliver the solvent or active ingredient in a number of ways including solubility and vapor pressure. Other polymer systems have this abihty, but the versatility of the polyurethane molecule (e.g., hydrophilicity or hydropobicity) gives it special properties. The abihty to produce polyurethanes as foams or elastomers grants product designers additional degrees of freedom. 

As a means of incorporating the fiber sensors into systems, incorporation of in-line fiber sensors into non-woven fabrics was explored. In order to incorporate an in-line sensor into a textile fabric, a spun-bonded base fabric was taken and an in-line fiber sensor was placed on top of it. Subsequently, non-woven fibers of polyurethane were electrospun on top of the optical fiber sensor to hold the sensor fiber in its position, thereby incorporating it in a non-woven fabric matrix. The electro-spinning was carried out at a voltage of 18 KV using a solution of polyurethane in the solvent DMP. 

---