Requirements, matrix resins capability

Thermoplastic additives in SMC and BMC accounted for nearly 8 kton/y consumption in the USA [Skeist, 1992]. A primary requirement for the polymer additive is that it must be amorphous with a low to moderate T and fairly soluble or dispersible in the resin matrix initially, but capable of phase separation during the polymerization. 

To solve this problem, Maruo et al. [10] proposed a two-photon laser rapid prototyping technology, now known as two-photon photopolymerization. In this scheme the laser was directly focused inside a liquid resin droplet and it polymerized the focal point volume by TPA. This technology firstly eliminates the requirement of thin additive liquid film and controls the longitudinal spatial resolution by focal spot size itself, and secondly, it provides the capability of writing arbitrary 3D patterns within the droplet volume, as can be done in 3D laser writing in solid matrix only if the resin viscosity is reasonably high. From this sense, the laser focus functions as a real 3D laser pen. 

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