Melt granulation advantages

An additional advantage of the polyhydroxyalkanoates is that the polymers can be produced by fermentation. Certain types of bacteria produce PHAs for energy storage when they are grown in glucose solution in the absence of specific nutrients. The polymer forms as discrete granules within the bacterial cell, and it is then removed by extraction to give a white powder that can be melted and modified into a variety of different products. 

These can be prepared by techniques like wet granulation, extrusion—spheronization, and hot melt extmsion, as illustrated in Figure 4.8. Solid self-nanoemulsifying pellets are documented to possess several advantages, such as flexibility of manufacturing, reduced intra- and/or intersubject variation in plasma profiles, and minimal G1 irritation (Serratoni et al., 2007). 

An exceptional advantage of self-reinforced thermoplastic composites is that they can be thermally recycled, but also reprocessed due to their polymer purity. This can be done by either returning the composite to a melted state or by simply re-granulating it. Thus, this process does without the complicated and expensive separation of the components, because an actual single-material system is on hand. Such a simple and useful recycling concept (in regard to material reuse) for the quantities currently in circulation has yet to be developed for the established foreign fiber reinforced thermoplastics. 

Hot-melt systems are usually flexible and tough. They are used extensively for sealing applications involving paper, plastic films, and metal foil. Table 7.29 offers a general comparison of hot-melt adhesives. Hot melts can be supplied as (1) tapes or ribbons, (2) films, (3) granules, (4) pellets, (5) blocks, or (6) cards, which are melted and pressed between the substrate. The rate at which the adhesive cools and sets is dependent on the type of substrate and whether it is preheated. Table 7.30 lists the advantages and disadvantages associated with the use of water-based, solvent-based, and hot-melt thermoplastic adhesives. 

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