Weather-resistant polycarbonate

Colorless clear polycarbonate has a distinct bluish tint which is added to mask its natural straw color. Several medium-density tints are available as well as a number of translucent colors. Over the years the weatherability of polycarbonate has been the subject of much discussion and conflicting claims. Efforts are continuously being made to improve or extend its retention of appearance after prolonged exposure outdoors. The use of coatings holds some promise in this regard. Nonetheless, polycarbonate remains the material of choice when impact resistance is required, for example, to withstand attack by vandals or for safety guards and other industrial plant applications that must meet OSHA requirements [86,95]. 

Abrasion-Resistant Polycarbonate Sheet. Abrasion-resistant polycarbonate sheet retains the extremely high impact properties and also provides resistance to abrasion. The surface coating also gives some added protection against weathering. 

Weather-Resistant-Grade Polycarbonate. Weather-resistance-grade polycarbonate is material with a surface coating which, it is claimed, provides improved resistance against weathering. 

These copolymers, containing a high level of ITR, have also been commercialized in a highly weather-resistant film that has the appearance of a paint film. The film is available in transparent and opaque colors. In addition, the film can be made with a metallic look. The film can be used with in-mold-decoration (IMD) (see the section Processing Polycarbonates ) molding processes to produce class A automotive exterior parts. Because the film contains very high levels of the ITR resin, it has an excellent balance of scratch resistance, weatherability, chemical resistance, and thermal performance. 

The reason for the different weathering behavior in PMMA and PC is their chemi-cai structure. Due to its aromatic structure, polycarbonate absorbs UV light to a much higher degree than polymethyl methacrylate [68], At the same time, PMMA is sensitive to standing moisture while radiation at high levels of humidity is particularly detrimental to scratch resistant polycarbonate [650],... 

The other important attributes of polycarbonate are transparency (a quality shared with all other unadulterated amorphous thermoplastics) and nonflammability the critical oxygen index is 25% for unfilled polymer. However, with this index, it is likely that PC would continue to burn in a hot environment. Also on the debit side, the chemical resistance is not outstanding, and satisfactory weathering resistance is only achieved with additives. 

Polycarbonate It is a tough, transparent plastic that offers resistance to bullets and thrown projectiles in glazing for vehicles, buildings, and security installations. It with stands boiling water, but is less resistant to weather and scratching than acrylics. It is notch-sensitive and has poor solvent resistance in stressed molded products. Use includes coffee makers, food blenders, automobile lenses, safety helmets, lenses, and many nonburning electrical applications. 

Polycarbonates are amorphous and highly transparent thermoplastics like acrylics, but with excellent impact strength, a higher price and lower resistance to UV and weathering. 

In the case of acrylic molding sheets and semi-fmished products, Wacker have elaborated a product concept based on silicone core-shell technology, which enables the manufacture of highly transparent particle-modified materials with improved RT and low-temperature (-40 C) impact resistance and high weatherability [4]. Other transparent plications (e.g., epoxy resins, polycarbonates) are showing encouraging results, too. 

D1SHP40L [GE Silicones] Primo used as adhesion promoter for weatherable abrasion-resistant silicone hardcoat on Lexan polycarbonate. 

Blends of polycarbonate with other styrenic resins are relatively new and therefore their current market volume is low. They have been developed primarily to upgrade the performance of such styrenic resins as styrenic-maleic anhydride (SMA), styrene-methyl methacrylate (S-MMA), acrylic-sty-rene-acylonitrile (ASA) resins primarily for impact strength and to some extent for DTUL improvement (Tables 15.7, 15.8 and 15.23). These blends uniquely combine high notched Izod impact strengths (ranging from 500 J/m to > 1000 J/m) with better UV resistance or weatherability than ABS. 

Chemical properties Polycarbonate is a generic term for polymers that contain carbon acid esters in the chains of their molecules. Pale yellow colour on manufacture due to impurities in the monomers (bisphenol-A), which is masked with blue dyes. PC is a polar polymer and is dissolved by chlorinated solvents. Almost self-extinguishing on burning. Poor resistance to chemicals and weathering. 

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