Properties of BPA-PC blends

The effects of BPA-PC molecular weight dominate the properties of blends that contain this material. Modifications are also made by blending with other polymers and the use of additives to achieve specific effects. These additives may be UV stabilizers, thermal stabilizers, flame retardants, mold release agents, fillers, colorants, impact modifiers, etc. Blends are made with 

Blends of BPA-PC can be immiscible, semimiscible, or fully miscible. Most commercial blends are either compatible or have been compatibi-lized. An example of an immiscible compatible blend would be PC/ABS (commercial examples would be Cycoloy [75] and Bayblend [76] resins). In this case, the ABS needs to be selected to be compatible with the BPA-PC phase. Examples of semimiscible compatible blends would include BPA-PC with either PET or PBT (a commercial example would be Xenoy [77] resin), with PBT showing greater partial miscibility than PET. Fully miscible blends would include examples such as BPA-PC with various wclo-hexane dimethanol polyesters (a commercial example would be Xylex [78] resin). Miscibility or partial miscibihty leads to Tg suppression and products with lower heat resistance. Compatibility without miscibihty may lead to a slight depression in Tg, which may be due to shght miscibihty. 

Other polymers are also blended with BPA-PC to enhance properties. For example, blending with ABS will significantly enhance low-temperature impact and flow and also yield a modest improvement in chemical resistance. However, the greatest property loss from neat polycarbonate is in heat resistance, and the improvement in chemical resistance is less than what can be attained by blending with crystalline polymers, but it 

BPA-PC copolymers are often copolyester carbonates that include ester linkages mixed into the carbonate linkages. The monomers are added to achieve specific effects, such as UV resistance for the Lexan [79] SLX grades, or higher heat resistance as in the case of Lexan PPC 4701R or Makrolon [80] APEC 1805 materials. 

Polycarbonates also have the ability to transesterify with other polyesters. This leads to jumbling of the repeat units and is likely to lead to undesirable properties, such as low thermal resistance. In commercial products, such undesirable side reactions need to be controlled. 

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