Polycarbonate blend properties

The range of blends now available comprises a broad spectrum of materials superior in many respects, particularly heat deformation resistance, to the general purpose thermoplastics but at a lower price than the more heat-resistant materials such as the polycarbonates, polyphenylene sulphides and polysulphones. At the present time the materials that come closest to them in properties are the ABS/ polycarbonate blends. Some typical properties are given in Table 21.1. 

In multiphase polymeric systems, the properties of the end products do not solely depend on the properties of the pure components, but other various parameters also have a great impact (Fig. 1). In order to emphasize these factors, the following systems are taken into consideration (I) elastomer toughened styrene system, (2) elastomer toughened polycarbonate blends, and (3) direct reactive blend processing. 

Heterogeneous compatible blends of preformed elastomers and brittle plastics are also an important route for the development of blends of enhanced performance with respect to crack or impact resistance. Polycarbonate blends with preformed rubber particles of different sizes have been used to provide an insight into the impact properties and the fracture modes of these toughened materials. Izod impact strength of the blends having 5-7.5 wt% of rubber particles exhibits best overall product performance over a wide range temperature (RT to -40°C) [151-154]. 

Some of these block copolymers have improved low temperature impact strength and higher stress-crack resistance than neat BPA polycarbonate Blends. The concept of blending two or more commercially available materials to create a new material having properties different from either starting material has generated a great deal of interest. Polycarbonate blends are used to tailor performance and price to specific markets. 

Kolarik J, Lednicky F, Locati G, Fambri L (1997) Ultimate properties of polycarbonate blends effects of inclusion plastic deformation and of matrix phase continuity. Polym Eng Sd 37 128-137... 

The above systems are fairly simple, homogeneous systems since they contain only one polymer in the matrix. Blending polymers makes the behavior more complex. In polypropylene/polycarbonate blends, carbon black is preferentially located in the polycarbonate phase. A blend which is better mixed is less conductive than a blend in which carbon black predominantly resides in the polycarbonate phase where it can form a conductive network. These are properties which control morphology (and related electric conductivity) ... 

Even in the phase separated blends, where some degree of partial miscibility or compatibility exists between the components, simple melt blending in an intensive shear mixer is adequate for making a well dispersed, reasonably stable blend product with useful combination of properties, such as polypropylene/ethylene-propyl-ene rubber blend, ABS/polycarbonate blend, etc. The self-compatibUizing nature of these blends stems from partial miscibility and the mutual interpenetration of polymer chains at the interface. Slight modifications of the polymer backbone are often employed, particularly in the case of styrenic and ABS resins to induce partial miscibility with other resins. 

Hence the development of polycarbonate blends was primarily market driven, with a motivation to extend the applications of polycarbonate into areas where improved chemical resistance and processability are required while still retaining high impact strength. In the development of all the polycarbonate blends the common goal was to maintain a very high level of impact strength while improving the properties and cost balance (Table 15.24). 

Table 15.26. Properties of some commercial grades of PBT/polycarbonate blends...

At present, there is only one commercial source of the polyamide/polycarbonate blends (Dexcarb , Dexter Corp.). According to their patent, the blend was compatibilized by using a combination of a polyesteramide elastomer and a maleated olefinic polymer, such as male-ated polypropylene or EP rubber [Perron, 1984 1988]. However the degree or the efficiency of compatibilization achieved is unknown, since the added components are not known to be miscible or compatible with the polycarbonate. Nevertheless, the data sheet indicated good properties including a high notched Izod impact strength of > 700 J/m (Table 15.24). 

Chiu FC, Ung MH (2007) Thermal properties rmd phase morphology of melt-mixed poly (trimethylene terephthalate)/polycarbonate blends-mixing time effect. Polym Test 26 338-350 Chuah HH (2004) Effect of process variables on bulk development of air-textured poly (trimethylene terephthalate) bulk continuous filament. J Appl Polym Sci 92 1011-1017 Chuah HH, Lin VD, Soni U (2001) PTT molecular weight and Mark-Houwink equation. Polymer 42 7137-7139... 

Table 19.8 Properties of some commercial ABS/polycarbonate blends vs. neat polycarbonate ...

Since the early discovery of miscibility between the low-cost polystyrene and PPE, several commercial grades of PPE/HIPS have been developed, which offer a wide choice of heat resistance (DTUL), impact strength, and melt processability (Cizek 1969 Fried et al. 1978). This versatility of PPE/HIPS blends led to their unparalleled commercial success, accounting for nearly 50 % of market volume of all engineering polymers commercial blends. PPE/HIPS blends filled the price-performance gap between the styrenic resins (HIPS, ABS) and the engineering resins such as polycarbonate, polyarylate, and polysulfones. The technology of PPE/HIPS blends has already been discussed previously under the styrenic blends section (Sect. 19.3), and the typical blend properties are shown in Tables 19.6 and 19.32. 

Y. He, A. Kulkarni, K. Van De Wetering, V. Daga, J. DeRudder, Mineral reinforced impact modified polycarbonate blends exploring specific filler surface interactions for property enhancements, in Annual Technical Conference - ANTEC, Conference Proceedings, vol. 1, 2012, pp. 16-20. 

For applications where polycarbonate homopolymers or copolymers lack sufficient thermal performance, blends with polyetherimide (PEI) are often used. PEI, which also contributes excellent flammability and low smoke generation to the alloy, may be combined with either straight polycarbonate or polycarbonate blends, depending on what other properties are required. The most common uses are found in light reflectors for automotive headlamps, components for aircraft interiors (especially wall and ceiling panels), and food-contact applications for microwave-to-table cookware. 

Blends of polycarbonates and polyester have been covered in Section 2, however, the properties of compatible blends of polycarbonate and a copolyester have been described. Polycarbonate blends with poly(pivalolactone) have been found to be completely immiscible. Steric hinderance has been offered as a possible explanation. - ... 

Yarema GE, Besklubenko YuD, Privalko VP (1982) Thermophysical properties of poly-styrene/polycarbonate blends in the melt state under elevated pressures. Dokl Acad Nauk UkfSSR, ser B N 3 54-57... 

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