Reactive extrusion of polypropylene

The reactive extrusion of polypropylene-natural rubber blends in the presence of a peroxide (1,3-bis(/-butyl per-oxy benzene) and a coagent (trimethylol propane triacrylate) was reported by Yoon et al. [64]. The effect of the concentration of the peroxide and the coagent was evaiuated in terms of thermal, morphological, melt, and mechanical properties. The low shear viscosity of the blends increased with the increase in peroxide content initially, and beyond 0.02 phr the viscosity decreased with peroxide content (Fig. 9). The melt viscosity increased with coagent concentration at a fixed peroxide content. The morphology of the samples indicated a decrease in domain size of the dispersed NR phase with a lower content of the peroxide, while at a higher content the domain size increases. The reduction in domain size... 

Elucidation of degradation kinetics for the reactive extrusion of polypropylene is constrained by the lack of kinetic data at times less than the minimum residence time in the extruder. The objectives of this work were to develop an experimental technique which could provide samples for short reaction times and to further develop a previously published kinetic model. Two experimental methods were examined the classical "ampoule technique" used for polymerization kinetics and a new method based upon reaction in a static mixer attached to a single screw extruder. The "ampoule technique was found to have too many practical limitations. The "static mixer method" also has some difficult aspects but did provide samples at a reaction time of 18.6 s and is potentially capable of supplying samples at lower times with high reproducibility. Kinetic model improvements were implemented to remove an artificial high molecular weight tail which appeared at high initiator concentrations and to reduce step size sensitivity. 

Dorscht, B. M. and Tzoganakis, C. 2003. Reactive extrusion of polypropylene with supercritical carbon dioxide Free radical grafting of maleic anhydride. Journal of Applied Polymer Science 87 1116-1122. 

R Lew, P Cheung, ST Balke. Reactive extrusion of polypropylene-elucidating degradation kinetics. In Computer Apphcations in Applied Polymer Science. ACS Symposium Series 404, 1989, pp 507-520. 

Mead, D.W. (1995) Evolution of the molecular weight distribution and linear viscoelastic rheological properties during the reactive extrusion of polypropylene. /. Appl. Polymer Sci., 57, 151-173. 

Tke-Yong, H., Sangmook, L, Youngjae, Y, Kwangho, J., Jae-Wook, L. (2012). Reactive extrusion of polypropylene/polystyrene blends with supercritical carbon dioxide, Macrom. Res., 20(6), 559-567. 

Reactive extrusion is the chemical modification of polymer while it is being transported in an extruder. In this work, polypropylene is intentionally degraded by the addition of a free radical initiator (a peroxide) during extrusion. The product has improved flow properties because of the removal of the high molecular weight tail and the narrowing of the molecular weight distribution. 

Wang, Q., Chen, Y.H., Liu, Y., Yin, H., Nico, A., and Kierkels, R. 2004. Performance of an intumescent-flame-retardant master batch synthesized by twin-screw reactive extrusion Effect of the polypropylene carrier resin. Polym. Int. 53 439 148. 

Liu, Y. and Wang, Q. 2008. Reactive extrusion to synthesize intumescent flame retardant with a solid acid as catalyst and the flame retardancy of the products in polypropylene. J. Appl. Polym. Sci. 107 14—20. 

Reactive extrusion takes place when the twin screw system is designed to incorporate one or more chemical reactions during the process, such as grafting or even polymerization. Grafting is the process of attaching pendant molecules onto the backbone of a polymer chain. For example, a small concentration of maleic anhydride can be incorporated into polypropylene to make the... 

We carried out experiments to define the optimal conditions in a reactive extrusion process, and to obtain maleic anhydride grafted polymers of polypropylene copolymers (3050 MN 4 supplied by ATOCHEM). The previous studies were carried out in a batch mixer (HAAKE RHEOCORD), at a temperature of 220° C and a mixing speed of 64 rpm, during 20 minutes. Three different systems were tested i. with pure maleic anhydride ii. in the presence of a solvent (toluene or chorobenzene) iii. by introduction... 

Cheng et al. [316] synthesized the polymer-bound 2-sulfony-l, 3-dienes from the corresponding support-bound suhblene, which upon thermal S02-extrusion gave the highly reactive diene (345), which could be trapped with dienophiles. The synthesis on a polystyrene support begins with polymer-bound lithium phenyl-sulfinate. S-Alkylation with trans-3, 4-dibromosulfolane (343) in the presence of pyridine gave the resin-bound 3-(phenylsulfonyl)-3-sulfolene. Thermal SO2 extrusion had to be performed in xylene under reflux, which restricts the use of this reaction to PS/DVB-resins. Neither the IRORY-Kans [317] nor the Synphase Crowns [199], which are made of polypropylene, are compatible with these reaction conditions, in which polypropylene is dissolved (Scheme 72) ... 

Table 9 Material properties of polypropylene and polyamide 6 blends after reactive extrusion...

The addition of peroxides, R OOR", during reactive processing has become a routine aspect of reactive extrusion technology for polypropylene and polyethylene (Xanthos, 1992). In particular, the dialkyl peroxides at a level ranging Ifom 0.001 to 1 wt.% have been used and have half-lives ranging Ifom 1 to 3 minutes at 180 C, so 99% consumption will occur in 7-20 minutes at that temperature. The reaction steps depend on whether oxygen is present... 

Most reactive extrusion has dealt with polymers that can be difficult to handle by other techniques.68 Polymers can be cross-linked, grafted with other monomers, and so on. Extrusion cross-linking of polyethylene wire coating raises the maximum temperature of use. Polypropylene degrades in this process, but can be cross-linked successfully if mul-... 

CORl s are the prime machines for polymer blending and reactive extrusion [Brown, 1992]. They have been used as reactors for the addition polymerization (polyacrylates, SAN, S-MMA, PA-6, POM, or TPU) and for the polycondensation (PA-66, polyarylates, PEST, PEI). Polymer grafting (polyolefin + silane, maleic anhydride, acetic anhydride, etc.) as well as mechanical and chemical degradation of polypropylene have also been carried out. 

Specifically, PVC blends with polyethylene, polypropylene, or polystyrene could offer significant potential. PVC offers rigidity combined with flammability resistance. In essence, PVC offers the promise to be the lowest cost method to flame retard these polymers. The processing temperatures for the polyolefins and polystyrene are within the critical range for PVC. In fact, addition of the polyolefins to PVC should enhance its ability to be extruded and injected molded. PVC has been utilized in blends with functional styrenics (ABS and styrene-maleic anhydride co-and terpolymers) as well as PMMA offering the key advantage of improved flame resistance. Reactive extrusion concepts applied to PVC blends with polyolefins and polystyrene appear to be a facile method for compatibilization should the proper chemical modifications be found. He et al. [1997] noted the use of solid-state chlorinated polyethylene as a compatibilizer for PVC/LLDPE blends with a significant improvement in mechanical properties. A recent treatise [Datta and Lohse,... 

Poncin-Epaillard, F. (2002). Characterization of C02 plasma and interactions with polypropylene film. Plasmas Polymers, Vol. 7, pp. 1-17, ISSN 1084-0184 Pesetskii, S.S. Jurkowski, B. Krivoguz, Y. M. Kelar, K. (2001). Free-radical grafting of itaconic acid onto LDPE by reactive extrusion I. Efect of initiator solubility. Polymer, Vol. 42, pp. 469-475, ISSN 0032-3861. 

Functionalization of isotactic polypropylene with maleic anhydride by reactive extrusion mechanism of melt grafting. Polymer, Vol. 42, pp. 5549-5557, ISSN 0032-3861. 

Rzaev, Z.MO., Yilmazbayhan, A. and Alper, E. (2007). A one-step Preparation of Compatibilized Polypropylene-Nanocomposites by Reactive Extrusion Processing, Adv. Polym. Tech., 26(1) 41-55. 

In the last decade, considerable progress was observed in the field of PO/compatibil-izer (predominantly on the base of PO-g-MA)/organo-surface-modified clay nanocomposites. Polyethylene (PE), polypropylene (PP), and ethylene-propylene (EP) rubber are one of the most widely used POs as matrix polymers in the preparation of nanocomposites [3,4,6,30-52]. The PO silicate/silica (other clay minerals, metal oxides, carbon nanotubes, or other nanoparticles) nanocomposite and nanohybrid materials, prepared using intercalation/exfoliation of functionalized polymers in situ processing and reactive extrusion systems, have attracted the interest of many academic and industrial researchers because they frequently exhibit unexpected hybrid properties synergisti-cally derived from the two components [9,12,38-43]. One of most promising composite systems are nanocomposites based on organic polymers (thermoplastics and thermosets). 

Giildogan, Y., Egri, S., Rzaev, Z. M. O., and Pi kin, E. 2004. Comparison of MA grafting onto powder and granular polypropylene in the melt by reactive extrusion. Journal of Applied Polymer Science 92 3675-3684. 

Rzayev, Z. M. O., Yilmazbayhan, A., and Alper, E. 2007. Aone step preparation of polypropylene-compatibilizer-clay nanocomposites by reactive extrusion. Advance Polymer Technology 26 41-55. Ho, R. M., Su, A. C., Wu, C. H., and Chen, S. 1993. Functionalization of polypropylene via melt mixing. Polymer 34 3264—3269. 

Three units of ethene/n-octene copolymers (I) were blended with a unit of isotactic polypropylene (II) grafted/crosslinked with mixtures of unsaturated silanes and (PhCMejO)jO under conditions of reactive extrusion at 170-190 °C and studied for mech cal properties, thermal stability and microstmcture. The composite materials consisted of a semicrystal II matrix and dispersed small pertides of cross-linked I. The best mechanical properties were when the II/I mass ratio was 55/45. 

Graft functionalization of polyolefin in a separate processing step (e.g., polyethylene-g-maleic anhydride, polypropylene-g-maleic anhydride, etc.) Graft functionahzation may be performed either by reactive extrusion in the... 

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