Reactively compatibilized Nylon

The interfacial instability of the copolymer was also noticed in the reactively compatibilized Nylon 6/EPM/EPM-g-MA blends [59]. Prolonged mixing at a temperature of 250 °C in the mini-extruder led to shear induced coalescence of the dispersed EPM rubber particles giving rise to coarser domains (see Fig. 3.11). 

Blends that contain no nylon can also be prepared by reactive compatibilization. However, interest in these systems has been limited somewhat by lack of control of the reaction pathways. Eor polyester-based systems, epoxide functionaHty appears to be an effective chemistry, involving reaction of the polyester chain ends (183,184). 

The kinetics of the reactive compatibilization of nylon-6-PP by acrylic acid modified PP was investigated by Dagli et al. [47]. The compatibilization reaction in this system involved the reaction between the acid group of acrylic acid modified PP and the amine group of nylon-6. A typical intensive batch mixer torque (t) vs time (t) trace for a ternary blend showing an increase in mixing torque upon the addition of PP-g-AA to a binary PP-NBR (85 7.5) blend is shown in Fig. 3. The kinetic... 

The influence of maleic anhydride modified styrene-(ethylene-co-butylene)-styrene (SEBS) triblock copolymer as a reactive compatibilizer in a nylon-6-SEBS blend was investigated by Wu et al. [66]. When the ma]e-ated SEBS was incorporated into the PA-6-SEBS biend. 

Reactive compatibilizing agents of the type A-C can also compatibilize an A/B blend as long as C can chemically react with B. Such studied systems include polyethylene (PE)/nylon-6 blends compatibilized with carboxyl functional PE, polypropylene (PP)/poly(ethylene-terephthalate), with PP-g-acrylic acid, nylon-6,6/EPDM with poly(styrene-co-maleic anhydride), and nylon-6/PP with PP-g-maleic anhydride. 

Li et al. reported that immiscible high-density polyethylene (HDPE)/ poly(ethylene terephthalate) (PET) blends, prepared by means of melt extrusion with ethylene-butyl acrylate-glycidyl methacrylate (EBAGMA) terpoly-mer as a reactive compatibilizer, can exhibit shape memory effects [32]. They observed that the compatibilized blends showed improved shape memory effects along with better mechanical properties as compared to the simple binary blends. In the blend, HDPE acts as a reversible phase, and the response temperature in the shape recovery process is determined by of HDPE. The shape-recovery ratio of the 90/10/5 HDPE/PET/EBAGMA blend reached nearly 100%. Similar behavior was observed for immiscible HDPE/ nylon 6 blends [33]. The addition of maleated polyethylene-octene copolymer (POE-g-MAH) increases compatibility and phase-interfacial adhesion between HDPE and nylon 6, and shape memory property was improved. The shape recovery rate of HDPE/nylon 6/POE-g-MAH (80/20/10) blend is 96.5% when the stretch ratio is 75%. 

Dow has prepared a compatibilized blend of PC and linear PE. The compati-bilizer used was EPDM grafted with SAN. The product has high impact strength and good melt processability. Polymer alloys with S-AMS copolymer and PP with styrene-grafted polyolefin copolymer have been reported. Triax 1000 of Monsanto is a blend of nylon and ABS compatibilized with styrene-acrylonitrile and glycidyl methacrylate terpolymer. The compatibilizer often improves the property balance of an immiscible blend. Reactive compatibilization is an emerging technique. 

Various approaches have been undertaken for reactive compatibilization of poly-amide/ABS alloys. Maleic anhydride can be grafted to the ABS. Styrene maleic anhydride (SMA) copolymers have been employed as compatibilizers for polyamide/ABS blends. SMA and SAN copolymers are miscible when the AN and maleic anhydride (MA) contents are equal. The impact strength of these blends has been found to be sensitive to the amount and composition of the SMA copolymer. Addition of SMA to SAN/polyamide blends was found to enhance the tensile and impact properties of these blends. Imidized acrylic polymers have been used as compatibilizers for nylon-6/ABS blends. Glycidyl methacrylate and methyl methacrylate (GMA/MMA) copolymers are used as compatibilizing agents. The epoxide functionality in GMA is capable of reaction with polyamide end groups. GMA/MMA copolymers can be shown to be miscible with SAN over the range of AN content of ABS. Styrene/GMA copolymers have been reported to be used as compatibilizers for polymer pairs such as... 

Polymer alloys are commercial polymer blends with improvanent in property balance with the use of compatibilizers. Texas A M University [1] has patented a com-patibilizer that can result in a product with high impact resistance as well as scratch resistance. The blend is composed of HIPS or polypropylene (PP) and a compati-bilizer made of a triblock copolymer of styrene-ethylene-propylene. Udipi [2] discovered that polymer blends composed of PC, a copolyester of PETG, and nitrile rubber exhibit a superior balance of properties. Reactive compatibilization of PC/ SAN blends at various AN compositions were conducted by Wildes et al. [3] using a SAN-amine compatibilizer. PC and SAN were found to be miscible over a range of AN composition by Mendelson [5]. Nylon/ABS blends can be compatibilized by use of SAN-maleic acid (Lavengood et al. [6]). Styrene-GMA copolymers can be used as compatibilizers for PS/PA, PS/PBT, PS/PET, and PPO/PBT blends. 

The morphology development in the case of EPM/Nylon 6 blends, reactively compatibilized by EPM-g-MA, is reported to be extremely fast [59]. In this study the... 

Figure 3.15 Effect of wt% of EPM rubber on the phase co-continuity of uncompatibilized and reactively compatibilized EPM/Nylon blends [59]...

A Monsanto patent by Lavengood [38] reported on the free radical copolymerization of styrene (S), acrylonitrile (AN) and maleic anhydride (MA) and the use of these terpolymers in the reactive compatibilization of PA6/ABS blends. Indeed, the amine end groups of nylon react with the MA groups of the terpolymer with formation of a graft copolymer at the interface. 

Triacca VJ, Ziaee S, Barlow J-W, Keskkula H, Paul DR. Reactive compatibilization of blends of nylon 6 and ABS materials. Polymer 1991 32 1401-1413. 

Park I, Barlow JW, Paul DR. The in situ reactive compatibilization of nylon-6/polystyrene blends using anhydride functionalized polystyrenes. J Polym Sci B Polym Phys 1992 30(9) 1021-33. 

Datta R J, Polk M B and Kumar S (1995) Reactive compatibilization of polypropylene and nylon, Polym Plast Technol Eng 34 551-560. 

Reactive compatibilization by the formation of in-situ grafting of PBT with EVA-g-MAH takes place competitively and simultaneously with the cross-linking of EVA and the grafting of MAH onto EVA. The maximum formation of the PBT-g-MAH-EVA takes place at a certain MAH content, producing the best reactive compatibilization in the PBT-EVA-g-MAH blend and thus the highest mechanical properties. The reactive compatibilzation of PBT and EVA-g-MAH can be also applied to other PBT-containing blend systems such as PBT/Nylon blend system. 

Els and McGill [48] reported the action of maleic anhydride on polypropylene-polyisoprene blends. A graft copolymer was found in situ through the modifier, which later enhanced the overall performance of the blend. Scott and Macosko [49] studied the reactive and nonreactive compatibilization of nylon-ethylene-propylene rubber blends. The nonreactive polyamide-ethylene propylene blends showed poor interfacial adhesion between the phases. The reactive polyamide-ethylene propylene-maleic anhydride modified blends showed excellent adhesion and much smaller dispersed phase domain size. 

Blends based on polyolefins have been compatibilized by reactive extrusion where functionalized polyolefins are used to form copolymers that bridge the phases. Maleic anhydride modified polyolefins and acrylic acid modified polyolefins are the commonly used modified polymers used as the compatibilizer in polyolefin-polyamide systems. The chemical reaction involved in the formation of block copolymers by the reaction of the amine end group on nylon and anhydride groups or carboxylic groups on modified polyolefins is shown in Scheme 1. 

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