Polycarbonate viscosity

Functionality Internal/External Use Level 1.2 phr max Comments Will lower polycarbonate viscosity recommended for use with regrind. 

Fig. 1. Melt viscosity as a function of shear rate for (—) linear BPA polycarbonate and (-) branched polycarbonate. To convert Pa-s to poise, multiply...

Fig. 6. Melt viscosity dependence on shear rate for various polymers A, low density polyethylene at 210°C B, polystyrene at 200°C C, UDEL P-1700 polysulfone at 360°C D, LEXAN 104 polycarbonate at 315°C and E, RADEL A-300 polyethersulfone at 380°C.

Workers at the General Electric Co. have described a new procedure using low viscosity cycHc intermediates to prepare polycarbonate composites (14,15). This work is discussed in the section dealing with novel methods. 

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. 

The polymerization of cyclic low-molar-mass polycarbonates, polyarylates, and PBT to high-molar-mass thermoplastics has been extensively studied by the General Electric Company during the last decade.57,58 Due to very low viscosity, cyclic oligoesters can be processed like thermosetting resins but retain thermoplastic properties in the final state, after polymerization in the presence of suitable... 

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. 

P.R.149 also lends color to cast resins made from materials such as unsaturated polyester or methacrylic acid methylester, which are polymerized with peroxide catalysts. P.R.149 is equally lightfast in these media. In polycarbonate, the pigment tolerates exposure to more than 320°C. This is an asset in view of the fact that polycarbonate shows high melt viscosity and is thus processed at up to 340°C. The list of applications also includes other media, such as PUR foams and elastomers, for which P.R.149 is recommended because of its good heat stability and its coloristic properties. 

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. 

Figure 4.13 Effect of fiber content on shear viscosity for long glass fibers in polycarbonate. Reprinted, by permission, from J. P. Green and J. O. Wilkes, Polym. Eng. ScL, 32(21), 1670. Copyright 1995 Society of Plastics Engineers.

Bartosiewicz and co-workers (205) used both GPC data combined with intrinsic viscosities, and the MWD, to make estimates of the degree of branching in polycarbonate. The first method, using the assumption gf—g%, gave absurdly high estimates of the number of branches, but the latter one gave an estimate considered to be reasonable. ... 

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. 

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