Compatibilizers for impact-modified

Chapter 13) and continues with melt processing, including injection molding, extrusion, films, and fibers (Chapter 14). Chapter 15 goes on to describe applications of SPS polymers themselves, followed by a discussion of blends with polyamides in Chapter 16 and with conventional polystyrenes in Chapter 17. Compatibilizers for impact-modified SPS are covered in Chapter 18. 

Tables 5 and 6 summarize key properties and appHcations for miscible and immiscible blends which are either commercial as of 1996 or were commercialized in the past (2,314—316,342,343). Most of the Hsted blends contain only two primary components, although many are compatibiLized and impact-modified. Consequently, an immiscible system consisting of two primary components or phases may contain impact modifiers for each phase and a compatihilizer copolymer, for a total of five or more components.

Himont (now Montell Polyolefins) introduced a family of PP-based blends under the trade name of Hivalloy . Some grades seem to be mechanical alloys of PP/PS, compatibilized and impact modified by incorporation of SEBS and EPR. Others are reactor-made — here porous grains of PP serve as reaction beds for the polymerization and grafting of PS, SMA, acryhcs, etc. 

Polymethylacrylate (PMA) and polymethylmethacrylate (PMMA) were discovered, respectively, in 1880 and 1930. The resins have been used for the production of transparent plastic sheets, viz. Plexiglas or Perspex , used for the military aircraft cockpit canopies, gunner s turrets and the like [Riddle, 1954]. Acrylic elastomers (ACM or ANM) were developed by Rohm in 1901, and commercialized in 1948 as Hycar vulcanizable copolymers of ethyl acrylate, allyl maleated lactones, chloroethyl vinyl ether, butadiene, isoprene, acrylonitrile, etc. [Mast et al., 1944]. Since the 1950 s, a wide variety of acrylic compatibilizers and impact modifiers have been developed. 

Poly(styrene-co-maleic anhydride) (SMA) is frequently mixed with SAN before the reactive blending with PA [Takeda and Paul, 1992]. Much attention has been paid to morphology control during the reactive processing [Serpe et al, 1990 Campbell et al., 1990 Willis and Favis, 1990]. Frequently, a third polymer is added as a com-patibilizer for binary systems, e.g., MA-grafted SEES to compatibilize (and impact-modify) blends of PE with PET [Carte and Moet, 1993]. 

Proprietary compatibilizers-cwm-impact modifiers offer a more economic solution and are widely used. These materials are formulated for specific types of polymer mixtures, viz. Blendex — polybutadiene-type compatibilizer for styren-ics, PVC, TPU, PET, EXL — an acrylic-based additive for PEST, Fusabond — maleated-PO compatibilizer for PO/PET blends, Vector — is SBS-type block copolymers with stabilizers, designed for PO/PS commingled mixtures, etc. 

Frequently, the recycled blends must also be impact-modified. There are two reasons for this (i) contamination of the composition by other polymers, and (ii) degradation of the usually less stable compatibilizers and impact modifiers. 

Blending PPE with either PEST or PC poses similar problems - the polymers are immiscible and brittle, hence require compatibilization and toughening. The PEST/ PPE blends are multicomponent systems, with > 5 components PEST, PPE, styrenic copolymer, compatibilizer, and impact modifier. Examples of commercial blends are Dialoy X, Gemax , or lupi-ace . For improved modulus and dimensional stability, they are usually reinforced with GF. These alloys are known for excellent processability, high solvent resistance, and dimensional stability. Evolution of these systems is outlined in Table 1.64. 

The polyester-type thermoset polyurethanes were commercialized in 1942, and the linear thermoplastic ones (TPU) 10 years later. Polyester-type TPUs, Texiit resins for extrusion and injection molding, were introduced in 1961, whereas polyether-type, Roylar , in 1971. Owing to great diversity of the ingredients, the TPU performance can be readily modified. For this reason, as well as because of the cost, TPUs are seldom blended. Their use can be divided into three groups (i) blends with POM, (ii) blends in which TPU is used as a compatibilizer and impact modifier, and (iii) others. 

PP and POM are both semicrystalline and immiscible, thus at w s 10 wt.% they should be compatibilized and impact modified. Since POM can develop strong hydrogen bonding with acidic or epoxy groups, usually acidified or epoxidized PO has been used. For example, POM blends with PP were compatibilized by addition of muconic acid-grafted PP. Another system comprised POM, thermoplastic urethane (TPU), 10-30 wt.% of either PP, PA, or polyester, and ethylene-butyl acrylate-GMA copolymer, with (EBA-GMA) as compatibilizer. 

Figure 14.11 Variation of the notched Izod impact strength of PET containing 20 % of an elastomeric toughening system as a function of the ratio of reactive to non-reactive modifier. It can be seen that the 30 70 reactive non-reactive mixture provides the optimum balance. The reactive modifier acts more as a compatibilizer in this system. Note units for impact strength (kJ m 2) can be converted to J nr1 by multiplying by 10...

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). 

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-... 

Polybond . [BP Performance Polymos] Polypropylene or polyethylene compounds thermoplastic for use as chemical coupling agent, compatibilizing agent, metal adhesive and nucleating agent impact modifier additive in polymer aUoys, for adhesion to metals and polar polymers. 

Campbell et al. [1990] have reported properties for compatibilized PA-PPE blends made using anhydride-terminated PPE. A block copolymer may form between PA amine end-groups and PPE-anhydride. For example, a blend containing 49 parts PPE-anhydride, 41 parts PA-6, and 10 parts SEBS impact modifier was extruded using a TSE at 280°C. The copolymer-containing blend was characterized by selective solvent extraction, mechanical properties, SEM, and TEM. Ductile-brittle transition temperatures were determined. Anhydride-terminated PPE was made by capping PPE phenolic end-groups with trimellitic anhydride chloride in solution. 

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