ABS blends

Brominated C rbon te Oligomers. There are two commercial brominated carbonate oligomer (BrCO) products. Both are prepared from tetrabromobisphenol A and phosgene. One has phenoxy end caps [28906-13-0] and the other trihromophenoxy [71342-77-3] end caps. These are used primarily in PBT and polycarbonate/acrylonittile—butadiene—styrene (PC/ABS) blends. 

Usage of phosphoms-based flame retardants for 1994 in the United States has been projected to be 150 million (168). The largest volume use maybe in plasticized vinyl. Other use areas for phosphoms flame retardants are flexible urethane foams, polyester resins and other thermoset resins, adhesives, textiles, polycarbonate—ABS blends, and some other thermoplastics. Development efforts are well advanced to find appHcations for phosphoms flame retardants, especially ammonium polyphosphate combinations, in polyolefins, and red phosphoms in nylons. Interest is strong in finding phosphoms-based alternatives to those halogen-containing systems which have encountered environmental opposition, especially in Europe. 

There is extensive Hterature on PC blends with ABS, and blends of PC with related materials such as SAN, methacrylate-butadiene—styrene (MBS) emulsion-made core-shell mbber modifiers (297—299), and other impact modifiers. One report reviews some of these approaches and compares PC blends based on emulsion vs bulk ABS (229). In PC—ABS blends, no additional compatihili er is used, because of the near-miscihility of the SAN matrix of ABS and PC. 

The use of PC—ABS blends has grown significantly in the early 1990s. These blends exhibit excellent properties, particularly low temperature ductihty, reduced notch sensitivity, and ease of melt fabrication. The blend morphology (229), ABS composition, thermal history (215), PC content and molecular weight (300), processing conditions, etc, all affect the mechanical behavior of PC—ABS blends. These blends have been most frequently used in automotive and other engineering appHcations. 

Alloys and blends are of great commercial significance. The archetype of "alloys" is the poly(phenylene oxide)—polystyrene resin discussed eadier. Important examples of blends based on immiscible resins are afforded by the polycarbonate—poly(butylene terephthalate) resins and polycarbonate—ABS blends. 

Polycarbonates based on tetramethylbisphenol A are thermally stable and have a high Vicat softening point of 196°C. On the other hand they have lower impact and notched impact resistance than the normal polymer. Blends with styrene-based polymers were introduced in 1980, and compared with PC/ABS blends, are claimed to have improved hydrolytic resistance, lower density and higher heat deflection temperatures. Suggested applications are as dishes for microwave ovens and car headlamp reflectors. 

Figure 32.1. Polar diagrams for three thermoplastic materials, CYCOLOY (a PC/ABS blend), ULTEM (polyetherimide) and NORYL (a styrenic PPO). The shaded area indicates the range...

Since it possesses good properties of both PVC plastics and polyurethane elastomers, it has been used in those areas where PVC and polyurethane have traditionally played dominant roles. For example, it is a very promising replacement for flexible PVC used for medical purposes and in the food industry [I6,l7], because it essentially eliminates the concern regarding plasticizer contamination. It has been used in combination with the copolymer of butadiene and acrylonitrile (NBR) to make the abrasion-resistant aprons and rolls used on textile machines [18]. A PVC/TPU/ABS blend serves as a substitute for leather [19]. This could have a tremendous impact on the shoe industry. It has also been found to have an application as a building coating [20,21]. This trend will certainly grow and more applications will be found. This in turn should bring new developments in the material itself. 

Frounchi and Burford [37] studied the effect of styrene block copolymer as a compatibilizer in isotactic PP-ABS blends. It was found hat in PP-rich blends a marginal improvement in mechanical properties was obtained. However, in acrylo nitrile butadiene styrene (ABS) rich blends no improvement was obtained. The effects of four different block copolymers, SBS, SIS,... 

Most dyes, including sulfonated azo dyes, are nonvolatile or thermally unstable, and therefore are not amenable to GC or gas-phase ionisation processes. Therefore, GC-MS techniques cannot be used. GC-MS and TGA were applied for the identification of acrylated polyurethanes in coatings on optical fibres [295]. Although GC-MS is not suited for the analysis of polymers, the technique can be used for the study of the products of pyrolysis in air, e.g. related to smoke behaviour of CPVC/ABS and PVC/ABS blends [263],... 

Houben [256] has compared the determination of flame-retardant elements Br, P, S, K, Cl and F in polycarbonate using commercial (X40 and UniQuant ) software. For the X40 method, a calibration line for each element in PC or PC/ABS blends was mapped for the conversion of intensities to concentrations. With the universal UniQuant method, sensitivity factors (ks) were calibrated with pure standards. The X40 method turned out to be more reliable than UniQuant for the determination of FRs in PC and PC/ABS blends, even in the case of calibration of k values with PC standards. Standard errors of 5 % were achieved for Br, P, S and K, and 20% for Cl and F the latter element could not be determined by means of UniQuant (Table 8.44). GFR PC cannot be quantified with these two methods, because of the heterogeneous nature of the composites. Other difficult matrices for XRF analysis are PBT, PS and PP compounds containing both BFRs and Sb203 (10-30wt %) due to self-absorption of Sb and interelement effects. 

Commercial examples are notably PVC-ABS blends and the blends of polyphenylene oxide with polystyrene. In the case of PPO-PS blends, it has been shown that the good char forming ability of the PPO greatly helps flame... 

Polycarbonate-ABS blends, 19 824-825 Polycarbonate blends, 20 361-362 Polycarbonate-polyester blends, 19 824, 825 Polycarbonate resin(s)... 

Type 4 Hard matrix 4- hard dispersed phase PPO/PS-Blends PC /ABS-Blends PVC/ABS-Blends... 

PBT has also been blended with styrene-maleic anhydride (SMA) copolymers giving materials similar to the ABS blends. Impact modification appears to be more difficult, and one must always be attentive to possible melt reaction with the anhydride, or its ring-opened acid forms, and the PBT resin. 

PPO/PA blend for passenger cars. A new conductive version of the on-line paintable Triax PA/ABS blend is proposed by Bayer. Heat deflection temperature is in the 180-200°C range ensuring resistance to the temperatures encountered in the drying ovens during cathodic dip coating. 

Dow Automotive is developing blow moulding of rear car seats. The prototype uses Dow Automotive s Pulse 220BG, a PC/ABS blend. 

A prototype heating and ventilation control panel produced by Bayer and Lumitec using a luminescent plastic film system incorporating a special electroluminescent electrode system. The panel can be produced in a single process step using Bayfol films and a PC/ABS blend (Bayblend ). 

Figure 4.13 Melting flux for a PC/ABS blend with an MFR of 1.7 dg/min (260 °C, 3.8 kg). The data were measured using a pressure of 0.7 MPa...

Table 13.11 Screw Channel Dimensions for a 152.4 mm Diameter Extruder for a Large-Part Blow-Molding Process Running a PC/ABS Blended Resin...

Actually, ABS can be considered as an impact modifier for PC. PC/ABS blends have been compatibilized with both maleic anhydride (MA)-grafted poly(propylene) (PP) and a solid epoxy resin of the bisphenol A type. Both compatibilizers are effective for formulations of an ABS content up to 30%. The the impact strength of the compatibilized blends was close to that of PC. However, above 40% ABS content, the impact strength decreases significantly (19). 

Transmission electron microscopy measurements reveal that the nanotubes are selectively located in the PA-6 phase. The selectively filled PA-6/ABS blends show a highly irregular, cocontinuous morphology. 

However, a reactive styrene acrylonitrile copolymer (SAN)/gly-cidl methacrylate copolymer was found to be an effective reactive compatibilizer for the blends. Ethyltriphenyl phosphonium bromide was used as the catalyst. Probably, the epoxide groups react either with carboxyl or with hydroxyl groups of the PLLA end groups. This so modified polymer acts as the compatibilizer. Compatibilized PLLA/ABS blends exhibit an improved impact strength and an im-... 

In blends of PTT and ABS, two separate glass transition temperatures are observed, which indicates that the blends are phase separated in the amorphous phase. A styrene/butadiene/maleic anhydride copolymer or glycidyl endcapped epoxy resin may act as a compatibilizer. Compatibilized PTT/ABS blends show a finer morphology and better adhesion between the phases. 

A series of flame retardant additives for ABS have been discussed, including halogen containing flame retardants, as well as halogen free flame retardants. The latter are being preferred for environmental reasons, however, only a few are as effective as halogen containing flame retardants. For ABS blends, some flame retardants (20) have been described that are summarized in Table 8.9. 

The use of silicones to render PC/ABS blends flame retardant, at least by any economically viable means, is not possible (77). However, by the phosphonation of silanes, flame retardants can be synthesized. The reaction is shown in Figure 8.5. The products of the first step can further undergo oligomerization. 

Kinetic data on the thermal degradation of ABS and PC/ABS blends are available (130,131). Thermogravimetric analysis suggests that the kinetics of the thermal degradation can be modelled by an auto-catalytic process. 

M. Zobel, T. Eckel, T. Derr, and D. Wittmann, Flame-resistant polycarbonate ABS blends, US Patent 6528561, assigned to Bayer Aktiengesellschaft (Leverkusen, DE), March 4, 2003. 

D. Stevanovic, A. Lowe, S. Kalyanasundaram, P.Y.B. Jar, and V. Otieno-Alego, Chemical and mechanical properties of vinyl-es-ter/ABS blends, Polymer, 43(16) 4503-4514, July 2002. 

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