Polycarbonate packaging applications

Yu et al. reported that poly[lactic acid]-block-[polycarbonate diol] [PLA-PCD] copolymers were synthesized using a two-step process with polycondensation and chain extension reactions [shown in Fig. 23.5]. The PLA-PCD copolymers obtained could crystallize, and the crystallinity decreased with chain-extension reaction. The products exhibited superior mechanical properties with elongation at break above 230%, which was much higher than that of PLA chain-extended products. The products had a good potential for packaging applications [20]. 

Another polyester, polycarbonate (PC), is a glassy, amorphous thermoplastic material. It has excellent balance of toughness and clarity. Commercial production of PC is based on bisphenol A. The heat deflection temperature of about 130°C, and its glass-transition temperature is 149°C. Polycarbonate has good potential for packaging applications. Commonly, polycarbonate is produced by the reaction of bisphenol-A and carbonyl chloride. 

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Polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), and PUR are the most common foams however, PP foams can provide favorable properties at a lower material cost. PP is stiffer than PE and can perform better in load bearing or structural applications. The low glass transition temperature of PP compared to PS provides increased flexibility and impact strength. Use of PP foams include packaging, automotive, insulation, and protection of underground pipe. 

These polymers have excellent mechanical, thermal, and chemical properties due to their stiffened main backbone chains. Polyacetals and polysulfones are being tested as implant materials, while polycarbonates have found their applications in the heart/lung assist devices, food packaging, etc. 

The optical properties, clarity and gloss, are also improved and biaxially oriented polystyrene and polypropylene films are used for envelope windows and overwraps. Biaxially oriented polyvinylidene chloride film is also used for food packaging in view of its good mechanical and optical properties, but for economic reasons it is only used if its low permeability to gases, especially oxygen, is required. The electrical properties are improved by biaxial orientation and the applications of polyester, polycarbonate and polypropylene films in capacitors are expected to show a rapid growth. In these electrical applications crystalline films are always annealed in order to improve the dimensional heat stability. 

In addition, isosorbide and other l,4 3,6-dianhydrohexitols (isomannide derived from D-mannose, isoidide derived from L-fructose) are also attractive to serve as monomers for polymer production due to their rigidity, chirality, and non-toxicity (Fig. 6). Such features may introduce special properties into the polymers formed, such as enhanced Jg and/or special optical properties. Their innocuous nature also opens the possibility of applications in packaging or medical devices. As a bifunctional monomer, isosorbide can be polymerized with other bifunctional monomers via condensation polymerization. A recent review described various isosorbide-based polymers synthesized, including polyesters, polyamides, poly(ester amide)s, poly(ester imide)s, polycarbonates, polyurethanes, and so on [308], and the present... 

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