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Chemical modification of polypropylene with peroxide/pentaerythritol triacrylate by reactive extrusion
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1996
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EngineeringChemical ModificationResinsTwin-screw ExtruderPolymer NanocompositesPolymersChemical EngineeringPolymer MaterialPolymer TechnologyPolymer ProcessingPolymer ChemistryMaterials SciencePolymer BlendPolymer EngineeringIsotactic PpPolymer AnalysisPolymer ScienceReactive ExtrusionPolymer CharacterizationPolymer Additive
The study investigates producing branched polypropylene via reactive extrusion of isotactic PP with pentaerythritol triacrylate and a peroxide initiator. Reactive extrusion was performed in a twin‑screw extruder at 200 °C using varying peroxide (200–1000 ppm) and PETA (0.64–5.0 wt %) levels, and the resulting xylene‑soluble fractions were analyzed by FTIR and DSC. Increasing PETA raised shear viscosity and MFI, while higher peroxide lowered them; macrogel formation appeared only above 1.8 wt % PETA and increased with peroxide, suggesting low PETA/peroxide to avoid macrogels; FTIR intensity ratios rose with PETA, and DSC showed two melting peaks and higher crystallization temperatures, indicating branched or lightly cross‑linked structures. © 1996 John Wiley & Sons, Inc.
To explore the possibility of producing branched polypropylene (PP) by a reactive extrusion (REX) process, isotactic PP was reacted with a polyfunctional monomer, pentaerythritol triacrylate (PETA), in the presence of 2,5-dimethyl-2,5(t-butylperoxy) hexane peroxide (Lupersol 101). Experiments were carried out in an intermeshing, corotating twin-screw extruder at 200°C using three concentrations of peroxide (200, 600, and 1000 ppm) and four concentrations of PETA (0.64, 1.8, 2.8, and 5.0%, by weight). Shear viscosity and MFI of the whole polymers was found to increase with PETA concentration and decrease with increasing the peroxide concentration at a given PETA concentration. The macrogel amount in the materials produced was determined in refluxing xylene using Soxhlet extraction and at PETA concentrations higher than 1.8wt % the macrogel content increased with increasing peroxide concentration. No macrogel was detected at low PETA concentrations (<0.64%) at all three peroxide levels, suggesting that low concentrations of PETA and peroxide should be used in order to minimize the formation of macrogels. The xylene soluble portions (sols) of the modified materials were characterized by FTIR and DSC. Generally, the relative intensities A1740/A841 in the FTIR spectra increased with increasing PETA incorporated into PP. Two melting peaks (Tm1 and Tm2) were observed in the DSC traces of some of the sols, and the crystallization temperatures (Tc) were higher than those of the virgin and degraded polypropylenes. The DSC behavior of the sols suggests that the modified PPs contain branched and/or lightly crosslinked chain structures. © 1996 John Wiley & Sons, Inc.