Search results for "Chain scission"

showing 3 items of 13 documents

Recycling of high density polyethylene containers

1997

The recycling of homogeneous high density polyethylene from containers for liquids gives rise to materials having mechanical properties that are strongly dependent on the reprocessing apparatus and the processing conditions. The thermomechanical degradation during processing gives rise to different modifications of the structure depending on the temperature, residence time and applied stress. In general, it is possible to say that if the reprocessing operations are carried out in apparatus with low residence time, the mechanical and rheological properties of the raw materials are only slightly influenced by the recycling operations. Significant degradation phenomena and reduction of some me…

chemistry.chemical_classificationMaterials sciencePolymers and PlasticsChain scissionPolymerRaw materialCondensed Matter PhysicsBranching (polymer chemistry)chemistryRheologyMechanics of MaterialsHomogeneousMaterials ChemistryHigh-density polyethyleneComposite materialPolymer Degradation and Stability
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Melt stabilization of wet polyamide 6

2002

Abstract Melt processing of polycondensate polymers must be carried out after careful drying in order to avoid any hydrolytic chain scission caused by the presence of water or other small molecules. In this work, the effect of two different antioxidants on the processing and flow properties of a polyamide 6 sample not dried before processing operations has been studied. One of these stabilizers seems to protect the wet polymer from hydrolytic chain scission. This action has been interpreted considering that the stabilizer hydrolyses instead of the polyamide macromolecules.

chemistry.chemical_classificationPolymers and PlasticsChain scissionPolymerCondensed Matter PhysicsHydrolysisMolten stateSettore ING-IND/22 - Scienza E Tecnologia Dei MaterialichemistryMechanics of MaterialsPolyamidePolymer chemistryMaterials ChemistryFlow propertiesmelt stabilization polyamide recycling processing stabilizationMacromoleculeStabilizer (chemistry)
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Competition between chain scission and branching formation in the processing of high-density polyethylene: effect of processing parameters and of sta…

2009

Two samples of high-density polyethylene with different molecular weight were processed in a batch mixer and the rheological and structural properties were investigated. In particular, the effect of different processing parameters and the eventual presence of different stabilizers were evaluated. Actually, two reactions may occur during processing: branching/crosslinking or chain scission. The results indicate that when the processing conditions promote a scarce mobility of the macromolecular chains (lower temperatures, lower mixing speed, and higher molecular weight), branching is more favored than chain scission. On increasing the mobility of the chain (higher temperature, higher mixing s…

polyethyleneMaterials sciencePolymers and PlasticsIntrinsic viscositychain scissionConcentration effectmacromolecular substancesGeneral ChemistryPolyethyleneBranching (polymer chemistry)stabilizationchemistry.chemical_compoundSettore ING-IND/22 - Scienza E Tecnologia Dei MaterialiChemical engineeringchemistryRheologyPolymer chemistrybranchingMaterials ChemistrypolyehtyleneThermal stabilityHigh-density polyethyleneMelt flow indexdegradation
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