ABS polymer melt

Li L, Masuda T and Takahashi M (1990) Elongational flow behavior of ABS polymer melts. J Rheol 34 103-16. 

Fig. 13.23. Shear thinning behavior of an ABS polymer melt at three different temperatures. Broken lines are power law fits and solid lines represent the Cross model, (from C. W.

Plot of viscosity versus shear rate for an ABS polymer melt at three temperatures (Cox and Macosko, 1974) dashed lines, power law fit solid line represents a Cross or Ellis mcxiel. See Table 2.4.1. 

Shear stress versus parent shear rate for two capillaries of different diameter but the same L/R = 60. ABS polymer melt squares, R = 0.26 mm, 230°C barrel circles, R = 1.6 mm, 232°C barrel. The solid line represents isothermal flow estimated at high Y from the viscosity master curve (Hg-ure 2.6.1) the dashed line, adiabatic boundary condition, viscous dissipation with no heat transfer to the wall, for / = 1.6 mm. Replotted from Cox and Macosko (1974a) and Cox (1973). 

Transition from liquid behavior to solid behavior has been reported with fine particle suspensions with increased filler content in both Newtonian and non-Newtonian liquids. Industrially important classes are rubber-modified polymer melts (small rubber particles embedded in a polymer melt), e.g. ABS (acrylo-nitrile-butadiene-styrene) or HIPS (high-impact polystyrene) and fiber-reinforced polymers. Another interesting suspension is present in plasticized polyvinylchloride (PVC) at low temperatures, when suspended PVC particles are formed in the melt [96], The transition becomes evident in the following... 

Let us consider two hypothetical phases in our composite, A and B, without specifying their physical state. They conld be a polymer melt and a glass fiber reinforcement during melt infiltration processing, a metal powder and ceramic powder that are being snbjected to consolidation at elevated temperatnre and pressure, or two immiscible polymer melts that will be co-extruded and solidified into a two-phase, three-dimensional object. In any case, the surface that forms between the two phases is designated AB, and their individual surfaces that are exposed to their own vapor, air, or inert gas (we make no distinction here) are labeled either A or B. The following three processes are defined as these surfaces interact and form ... 

Weld lines (also known as knit lines) are a potential source of weakness in molded and extruded plastic products. These occur when separate polymer melt flows meet and weld more or less into each other. Knit lines arise from flows around barriers, as in double or multigating and use of inserts in injection molding. The primary source of weld lines in extrusion is flow around spiders (multiarmed devices that hold the extrusion die). The melt temperature and melt elasticity (which is mentioned in the next section of this chapter) have major influences on the mechanical properties of weld lines. The tensile and impact strength of plastics that fail without appreciable yielding may be reduced considerably by in doublegated moldings, compared to that of samples without weld lines. Polystryrene and SAN copolymers are typical of such materials. The effects of weld lines is relatively minor with ductile amorphous plastics like ABS and polycarbonate and with semicrystalline polymers such as polyoxymethylene. Tliis is because these materials can reduce stress concentrations by yielding [22]. 

Hilliard theory is used, thereby introducing k as another parameter, see 2.6.9. For the latter, the assumption is made that the entropy only depends on the local density and not on the gradient. This is van der Wacds assumption. Obviously this model contains less detail than given in fig. 2.18 nevertheless the results for y and dy/dT for a number of oligo- and polyhydroccirbons were satisfactory. The value of K remciins to a certain extent adjustable which renders it less ab initio than the previous model. For polymer melts this theory overestimates S . With k optimized it was found that y decreases with in the homologeous series. 

Polymer melts can be classified based on their viscosity low viscosity melts for polyacylamide polyethylene, polypropylene and polystyrene medium viscosity melts for ABS, cellulose acetate, POM and styrene butadiene and high viscosity melts for polycarbonate, polymethylmethacrylate, polypropylene oxide and polyvinyl chloride. 

The color concentrates (masterbatches) used for ABS are of the universal or of the ABS-based types. A typical let down ratio (concentration) for the universal type is 1 to 2% whereas a ratio of between 3 to 7% is used for the ABS based master-batch. Before using a universal masterbatch it is important to ascertain it s compatibility with ABS. Pastel shades can now be readily achieved due to the availability of polymers with a lighter (i.e. whiter) base color. Back pressure is often used with masterbatches so as to assist in the dispersion of the pigment within the polymer melt. 

A broad molecular-weight distribution (MWD) typically increases the shear and pressure sensitivity of polymer melts. However, the effect of MWD on zero shear-rate viscosity varies a broad MWD increases the zero shear-rate viscosity of polyethylene and HIPS, but decreases t o for ABS and poly(vinyl chloride). The effect of MWD on temperature sensitivity also seems polymer-dependent. 

Han, C.D. (1971) Measurement of the rheological properties of polymer melts with slit rheometer. I. Homopolymer systems n. Blend systems ni. Two phase systems - higfi impact polystyrene and ABS resins, /. Appl Polym. Set., 15,2567-77,2579-89, 2591-6. 

IR process control systems have also been used to determine the chemical composition of copolymers and polymer blends (PP/PE, PC/PBT/PET, PC/ABS, EVA) and to control PET, PA6 and EPDM polymerisation processes (end-group determination, etc.) [70, 92]. Partial least squares (PLS) analysis of ATR-FTIR absorbance spectra has provided an accurate, precise, rapid and cost effective method both for off-line and on-line compositional analysis at production sites of EO/FO copolymers in the range of 0-10 wt.% co-polymerised ethylene sites [104]. Proper examination of the statistics underlying the PLS model is essential in providing a robust calibration model. Gotz et al. [80] showed that the composition of ethylene/propylene copolymers could be determined at 200°C by means of an IR sapphire fibre-optic sensor. Similarly, monomer residuals and additives in polymer melts may be determined. 

It is clear that this model is difficult to apply even to simple geometries. Also, the great body of data on polymer melts shows that, once clearly above the Newtonian, low-shear region, they are well represented by the Power Law and do not become increasingly more pseudoplastic (Harper CA (ed) (2002) Handbook of plastics, elastomers and composites, 4th edn. McGraw-Hill, New York Strong AB (2000) Plastics materials and processing. Prentice-Hall, Columbus, OH). 

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