Melt Molding

A large number of techniques are developed for the manufacturing of scaffolds to control the pore interconnectivity and geometry, which are provided channels to the exchange of nutrient/wast used for cell survival and growth. Melt molding is commonly used for the preparation of porous ceramics and metals [206]. In addition, it is also used to fabricate polymeric materials [207]. Melt molding process is that the Teflon molds are filled with PLGA powder and specific diameter gelatin microspheres, and then heated at a polymer’s glass transition temperature (Tg) under the elevated pressure [185]. This action causes the PLGA particle to be bonded together to form a mold-shaped scaffold. Once the mold is removed, gelatin microspheres are leached out by immersing the mixture into water, and the scaffold in the shape of the mold is then dried. The mold decides the shape of the scaffolds produced by this technique. The melt molding is the most convenient and economical method of making porous scaffolds, for it allows the rapid production of polymer scaffolds with various shapes and sizes and doesn’t require the use of organic solvents to create scaffolds [186]. The shape and size of pores can be controlled by selecting poro- gen. As for the manufacture of scaffolds, Liao et al. [208] incorporated MWNTs of 0.1 and 0.3 wt.% and hydoxyapatite nanorods (nHAs) of 8-20 wt.% into polypropylene (PP) to form biocomposites using melt molding techniques. Although there are few reported about this application, this technique still has the potential to be developed as a new processing technique for forming the reinforced scaffolds with suitable structures and compositions. This method can also be combined with other methods, like the solvent casting technique, to provide a route for the preparation of the reinforced scaffolds.

However, there are some disadvantages of this method, such as the presence of nonporous layers on the surface, the complexity of the design and construction of the mold, the difficulty of leaching out the porogen compound, and the unfavorable high-temperature process [209, 210]. The melt molding technique is mostly used for the preparation of bone scaffolds as it allows the combination of ceramic HA and PU [211, 212].

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