Polystyrene production energy requirements

Figure 1.11 Fossil energy requirement for petrochemical polymers and PLA. The cross-hatched area of the bars represent the fossil energy used as chemical feedstock (i.e., fossil resource to build the polymer chain). The solid part of the bars represented the gross fossil energy used for the fuels and operation supplies used to drive the production processes. PC = polycarbonate HIPS = high-impact polystyrene GPPS = general purpose polystyrene LDPE = low-density polyethylene PET SSP = polyethylene terephthalate, solid-state polymerization (bottle grade) PP = polypropylene PET AM = polyethylene terepthalate, amorphous (fiber and film grade) ...

If a polymer product is required in particulate form, then suspension polymerization is especially suitable. The energy required to disperse monomer drops is lower than that required to break up the finished polymer. Also, drop size control before polymerization is easier to achieve than particle size manipulation of granulated polymer. Suspension polymerization provides a good route to functionalized particles such as those used in ion-exchange resins. Expandable polystyrene beads are also made by suspension polymerization. When a product is to be used in bead form , initial drop diameters can be as large as 1-2 mm [1]. 

The cost of manufacturing thermoformed, polystyrene foam sheet parts is less dependent on raw material cost than other extrusion processes. This is largely due to the combined effects of additional energy costs required to operate two extruders, heat removal requirements in the secondary extruder, cost of pelletizing (densifying) regrind and the relatively low output of the process for the equipment scale and cost. Typical cost factors for the manufacture of thermoformed polystyrene foam sheet products include raw materials 35%, labor 27%, sales and administration 16%, depreciation 8%, utilities 7% and other 7%. 

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