Viscosity of polycarbonates

BPA polycarbonate becomes plastic at temperatures around 220°C, The viscosity decreases as the temperature increases, exhibiting Newtonian behavior, with the melt viscosity essentially independent of the shear rate, At the normal injection molding temperature of 270-3l5°C, the melt viscosity drops from 1.100 to 360 Pa j s (11.000 to 3,600 poise). Because the viscosity of polycarbonate can only be reduced by increasing the temperature, the ultimate limit on molecular weight is controlled by the processing conditions and the thermal stability of the polymer. 

Figure 9.1. The effect of carbon black on the viscosity of polycarbonate. [Adapted, by permission, from Joo Y L, Lee Y D, Kwack T H, Min T I, Antec 96. Vol. I. Conference Proceedings, Indianapolis, 5th-10th May 1996, 64-8.1...

A. Falah, Behavior and melt viscosity of polycarbonate/low density polyethylene hlend in capillary flow. International Journal of ChemTech Research 6 (1) (2014) 316-323. 

Fig. 12.5 Complex viscosity of polycarbonate with and without CNTs as a function of angular frequency. (Courtesy of Hyperion Catalysis International, Inc.)...

The melt viscosity of a polymer at a given temperature is a measure of the rate at which chains can move relative to each other. This will be controlled by the ease of rotation about the backbone bonds, i.e. the chain flexibility, and on the degree of entanglement. Because of their low chain flexibility, polymers such as polytetrafluoroethylene, the aromatic polyimides, the aromatic polycarbonates and to a less extent poly(vinyl chloride) and poly(methyl methacrylate) are highly viscous in their melting range as compared with polyethylene and polystyrene. 

Figure 10.9. Influence of temperature on the melt viscosity of a typical bts-phenol A polycarbonate (shear stress = l X 10 dyn/cm ). (After Christopher and Fox )...

All of the eommereial alkyl eyanoaerylate monomers are low-viseosity liquids, and for some applications this can be an advantage. However, there are instances where a viseous liquid or a gel adhesive would be preferred, sueh as for application to a vertical surface or on porous substrates. A variety of viscosity control agents, depending upon the desired properties, have been added to increase the viscosity of instant adhesives [21]. The materials, which have been utilized, include polymethyl methacrylate, hydrophobic silica, hydrophobic alumina, treated quartz, polyethyl cyanoacrylate, cellulose esters, polycarbonates, and carbon black. For example, the addition of 5-10% of amorphous, non-crystalline, fumed silica to ethyl cyanoacrylate changes the monomer viscosity from a 2-cps liquid to a gelled material [22]. Because of the sensitivity of cyanoacrylate esters to basic materials, some additives require treatment with an acid to prevent premature gelation of the product. 

Polybutadienes, polycaprolactones, polycarbonates, and amine-terminated polyethers (ATPEs) are shown in Scheme 4.4 as examples of other commercially available polyols. They are all specialty materials, used in situations where specific property profiles are required. For example, ATPEs are utilized in spray-applied elastomers where fast-reacting, high-molecular-weight polyamines give quick gel times and rapid viscosity buildup. Polycarbonates are used for implantation devices because polyuredtanes based on them perform best in this very demanding environment. Polycaprolactones and polybutadienes may be chosen for applications which require exceptional light stability, hydrolysis resistance, and/or low-temperature flexibility. 

ISO 1628-4 1999 Plastics - Determination of the viscosity of polymers in dilute solution using capillary viscometers - Part 4 Polycarbonate (PC) moulding and extrusion materials ISO 7391-1 1996 Plastics - Polycarbonate (PC) moulding and extrusion materials - Part 1 Designation system and basis for specifications ISO 7391-2 1996 Plastics - Polycarbonate (PC) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 11963 1995 Plastics - Polycarbonate sheets - Types, dimensions and characteristics. 

Plasticization of the Polycarbonate. Makrolon S of Bayer A.G. was used in the experiments. The intrinsic viscosity of this polymer is about 0.55 dl./gram. 

Fundamental studies of blends of polycarbonate with aciyloni-trile-buladiene-styrene (ABS) indicate that the presence of ABS greatly decreases the melt viscosity in the blend, enhancing processibility. A synergistic improvement of the notched impact strength at low temperature is also seen for polycarbonate-ABS blends. 

Determining the effect of viscous dissipation in the metering section of a single screw extruder. Consider a 60 mm diameter extruder with a4 mm channel depth and a screw speed of 60 rpm. The melt used in this extrusion system is a polycarbonate with a viscosity of 100 Pa-s, a thermal conductivity of 0.2 W/m/K and a heater temperature of 300°C. To assess the effect of viscous heating we can choose a temperature difference, AT of 30K. This simply means that the heater temperature is 30K above the melting temperature of the polymer. For this system, the Brinkman number becomes... 

The polymer grades of polycarbonate and acrylic designed specifically for molding optical disks have high cleanliness levels, low melt viscosity, and... 

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