Reactive blends preparations

II. TECHNOLOGY FOR SOME PROCESS REACTIVE BLENDS PREPARATIONS... 

Moreover, commercially available triblock copolymers designed to be thermoplastic elastomers, not compatihilizers, are often used in Heu of the more appealing diblock materials. Since the mid-1980s, the generation of block or graft copolymers in situ during blend preparation (158,168—176), called reactive compatibilization, has emerged as an alternative approach and has received considerable commercial attention. 

TPEs prepared from rubber-plastic blends usually show poor high-temperature properties. This problem could be solved by using high-melting plastics like polyamides and polyesters. But, often they impart processing problems to the blends. Jha and Bhowmick [49] and Jha et al. [50] have reported the development and properties of novel heat and oil-resistant TPEs from reactive blends of nylon-6 and acrylate rubber (ACM). The properties of various thermoplastic compositions are shown in Table 5.4. In this kind of blend, the plastic phase forms the continuous phase, whereas... 

A remarkable reduction in PA-6 crystallinity was noticed after reactive blending for most of the products. In one particular case the PA-6 crystallinity was reduced from 47% to 7%. For most of the blends prepared, of the PA-6 phase could not be observed. These results suggest that the PA-6... 

DMP head units as oxidation proceeds, molecules with the less reactive MPP head would tend to accumulate. Surprisingly, however, the spectrum of a homopolymer blend, prepared by dissolving the two polymers in warm benzene and precipitating with methanol, showed the same preponderance of MPP phenolic groups although the degree of polymerization of the two polymers was such that more DMP than MPP end groups should have been present. 

Jalali-Arani A, Katbab AA, Nazockdast H (2003) Preparation of thermoplastic elastomers based on silicone rubber and polyethylene by thermomechanical reactive blending Effects of polyethylene structural parameters. J Appl Poly Sci 90(12) 3402-3408... 

In the blends discussed above, the interaction among the components and the compatibilizing agent is purely physical. However, to extend the range of possibilities for optimized blends preparation, reactive processing, where covalent chemical bonds are created between the partners, offers great potential. 

Fixation of dyestuffs and pigments by incorporation in the crosslinked cellulose and in the finish network, also providing better wet fastness for conventional dyeings and printings Cellulosics mainly with direct and acid dyes, cotton/polyester blends with reactive dyes, preparation for dry heat transfer printing of cellulosics ... 

Toughened Polypropylene-Polyamide 6 Blends Prepared by Reactive Blending... 

To toughen PA, 2-5 wt% of either PO, elastomer, ionomer, acidified or epoxidized copolymer may be added. PA/PO blends of type (2) were developed to improve dimensional stability and to reduce water absorbency of PA. Alloying PA with PO reduces the rate of water migration to and from the blend, but not the inherent water absorption of PA [Utracki and Sammut, 1991, 1992]. The alloying is either a two- or three-step reactive process (1°) acidification of PO, (2°) preparation of a compatibilizer, and (3°) compounding PP, PA, and the compatibilizer. Usually, the reactive blending is carried out in a twin screw extruder [Nishio et al., 1990 Hu and Cartier, 1998], Since it may cause reduction of the blend crystallinity (thus performance), the extend must be optimized. The rigid PA/PP blends usually comprise PA PP =... 

Mini-Max The mixer is capable of mixing S 1 g of the resin. Recently, the device was reported to produce similar dispersions of reactive blends as those prepared in industrial mixers, TSE or internal mixer. It was found that Mini-Max makes it possible to pre-evaluate blends, especially those of polymers having low viscosity and elasticity. Maxwell, 1972 Sundararaj et al., 1995... 

Quality control of thermoplastic materials has relied predominantly on viscosity measurements, either in the melt or in solution. This is also the case for polymer blends. For example, QC of PPS/PPE Die PPS) blends (prepared by reactive processing) relies on measurements of density and melt viscosity in a capillary rheometer. Viscosity control before processing allows to assess incoming materials variability and suit-... 

PE-g-SBH copolymer prepared by polycondensation of SBH monomers in the presence of PEox PE-g-SBH copolymers prepared by reactive blending of PEox with SBH... 

In order to confirm the occurrence of reaction, a SEC characterization and comparison between chromatograms of the physical (PB) and reactive blends (RB) was performed for all samples prepared. The zone of low retention time corresponds to high MW, and high retention times correspond to low MW. Then, PB and RB can be differentiated by shift in retention times due to MW changes. Figure 20.1 shows the... 

AVE 02] Avella M., Errico M.E., Rimedio R., et ai, Preparation of biodegradable polyester/high-amylose-starch composites by reactive blending and their characterization , Journal of Applied Polymer Science, vol. 83, no. 7, pp. 1432-1442,2002. 

Imnes, Bedo, D., Domjan, A., Shon, P., Vancso, G. J., Pukanszky B. (2013). Structure, properties and interfacial interactions in polyQactic acid)/ pol3nirethane blends prepared by reactive processing, Bun Po jjJ, 49(10), 3104-3113. 

Fig. 5.9 TEM micrographs for the three PE/PA blends prepared by reactive extrusion [56]...

M.E. Cordova, A.T. Lorenzo, A.J. Miillta-, L. Gani, S. Tence-Girault, L. Leibler, The influenee of blend morphology (co-continuous or sub-micrometer droplets dispersions) on the nucleation and crystallization kinetics of double crystalline polyethylene/polyamide blends prepared by reactive extrusion. Macromol. Chem. Phys. 212, 1335-1350 (2011)... 

Gopakumar et al. [10] reported the in situ compatibilization of poly(phenylene sulfide) (PPS)/wholly aromatic thermotropic liquid crystalline polymer (TLCP) Vectra A950 blends by reactive extrusion. The authors prepared the in situ compatibilized PPS/TLCP blends in a twin-screw extruder by reactive blending of PPS and TLCP in the presence of dicarboxyl-terminated poly(phenylene sulfide) (DCTPPS). Block copolymer was formed during reactive blending, by transesterification reaction between carboxyl... 

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%. 

Reactive blending of 15 wt% maleic anhydride-co-styrene with nylon 6 increased heat distortion temperature by 12 °C and melt viscosity[68], Elis[69] prepared toughened nylons of high stiflhess and toughness by incorporating 10 to 25 wt% ethylene ionomerinto nylon-6, nylon-6,6 or blends of the two nylons. The toughened nylon blends were further characterized by low mold deposit. 

Table 8 lists some representative toughened nylon blends prepared by incorporating acompatibilizer or by reactive blending. 

Numerous nylon blends prepared by compatibilization or reactive blending are commercially successful. The modifiers fiequenfly utilized in commercial nylon blends include polyolefin, thermoplastic polyolefin, thermoplastic polyunethane, ionomer, elastomer, ethylene-propylene rubber, nitrile mbber, polyftetrafluoroethylene), poly (phenylene ether), poly(ether amide), silicone, glass fiber, and carbon fiber. The nonpolar modifiers such as polyolefin, maleic anhydride or a polar vinyl monomer such as acrylic acid, methaciylic acid and fimiaric acid is fiequently incorporated to introduce reactive sites in nylon. 

As seen from this scheme, functionalized POs play an important role as reactive compatibilizers in the preparation of PO nanocomposites and various PO/thermoplastics (s)mthetic and natural polymers) reactive blends and their hybrid nanocomposites in melt by reactive extrusion in situ processing. Therefore, before discussing the results on PO nanocomposites, it is necessary to describe here some types and methods (predominantly extrusion methods) for the synthesis of reactive polymer compatibilizers by the fimction-alization of POs with MA and its isostructural analogs. 

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