Polycarbonate weatherability

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

Influence of various UV absorbers (UVA-1 = dimer 2-hydroxyphenyl benzotriazole, UVA-2 = 2-hydroxyphenyl triazine) on yellowing in co-extruded double-skin sheets made of polycarbonate (weathering in a weatherometer black standard temperature 55 °C) [529]... 

Where transparency is required, a range of polymers is available. Polystyrene is the least expensive but polymethylmethacrylate has an outstanding high light transmission combined with excellent weathering properties. Also to be considered are the polycarbonates, glass-clear polyamides, SAN, butadiene-styrene block copolymers, MBS polymers, plasticised PVC, ionomers and cellulose esters such as cellulose acetate. 

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. 

Further, methods for producing a thermoplastic resin with good physical properties and appearance properties and weatherability as well, use a three component blend of ASA, PMMA, and polycarbonate) (20). 

Ultramarine blues, reds and violets are acid sensitive. As such, their thermal and weathering properties are adversely affected in acidic media. Silica-encapsulated versions offer marked improvement in thermal stability and some improvement in weathering properties. The treated versions allow broad polymer usage, even in engineering plastics such as polycarbonate, and provide sufficient durability for automotive interior applications. Weatherability is highly dependent upon the degree of exposure to acid or alkaline conditions. 

Accelerated weathering test was carried out by the exposure of the films to a Sunshine weather meter with Xenon arc type accelerated weathering machine. HS-polymer s fihn does not chalk nor yellow. However under the conditions employed, polyimide (PI) is led to chalking and polyethylenenaphtalate (PEN), polycarbonate (PC) and polyethylenetelephtalate (PET) are led to yellowing (Table 1). 

Polycarbonates prepared by reacting phosgene and bisphenol A and capping with a perfluoroalcohol, (III), were prepared by Davis [3] and used as the surface layer of molded articles in flame retardant and weatherable articles. 

FIGURE 5.3 Accelerated and real-time weathering of polymer materials obtained at NREL. PET, polyethyleneteraphthalate PVDF, polyvinylidenedifluoride PE, polyethylene PC, polycarbonate PMMA, polymethylmethacrylate. 

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. 

Factor, A. Search for the sources of color in thermally aged, weathered, and y-ray irradiated bisphenol A polycarbonate. Angew. Makromol. Chem. 1995, 232, 27 3. 

Medford, G. Pickett, J. Reynolds, C. The next generation of weatherable hardcoats for polycarbonate. PCI, 2001. (accessed October 2004). http //www.pcimag.com/pci/cda/article information/coverstory/bnpcoverstoryitem/ 0,29001,00 + en-uss 01dbc.html (accessed October 2004). 

The particular filter we used for this project has a polycarbonate bowl. Polycarbonate is not well rated for use with potassium hydroxide. We decided to use this however, as the system has a scrubbing system to neutralize and absorb a good portion of the KOH solution, and the system was not intended for long service. Polycarbonate does not stand up well in harsh weather conditions with wide temperature fluctuations, and in general tends to crack quite easily. 

The photo-Fries products are not present in significant amounts in solid polycarbonate degraded under normal weathering conditions. 

The results from this survey indicate that a wide variety of reactions occur in the photodegradation of polycarbonate under natural weathering conditions. Both oxidative and non-oxidative processes are involved, but the oxidative reactions probably cause greater loss in physical properties. Accelerated aging studies should take into account the variables tested here. In particular, acceleration should not be accomplished by the use of very short wavelength light. 

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. 

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