Efeito do tipo de elemento de rosca na degradação de polipropileno durante múltiplas extrusões

Abstract

A configuração da rosca de uma extrusora de dupla rosca modular pode ser projetada com vários tipos de elementos de condução e mistura, produzindo diferentes níveis de degradação no polímero fundido. Neste trabalho determinou-se o nível de degradação do polipropileno durante múltiplas extrusões em várias configurações de rosca, através de cromatografia por exclusão de tamanho e espectroscopia de infravermelho. Houve decréscimo do peso molecular e estreitamento da sua distribuição em função do número de extrusões e do aumento da agressividade da rosca, assim como, aumento da concentração de carbonilas e insaturações na cadeia polimérica. O elemento de mistura EM90 causou o maior nível de degradação e a adição de elementos de condução esquerdos ECE reduziram o nível de degradação.

Effect of reprocessing cycles on the degradation of polypropylene copolymer filled with talc or montmorillonite during injection molding process

“…2) showed no degradation of the PP by multiple reprocessing cycles. There is no formation of carbonyl groups in the region at 1750 cm -1 [9] attributed this effect to a blocking effect of the filler, which prevents macroradicals from reacting with oxygen [9]. In thermoxidation reaction the oxygen diffusivity plays an important role and is responsible for the degradative extension.…”

Effect of clay amount and reprocessing cycles on thermal, morphological, and mechanical properties of polypropylene/organovermiculite nanocomposites

“…Reprocessing of polypropylene (PP) is used in the manufacturing industry and generally leads to molecular chain scission [1][2][3][4], consequently change in viscosity [5] and loss of properties [4][5][6][7]. With the advent of nanomaterials, new challenges related to PP recovery have been faced such as the understanding of the reprocessing level at which loss of properties due to matrix degradation takes place [8,9] or the role of the nanoclay exfoliation/intercalation taking place more or less intensively would have on properties improvement [10,11].…”

Influence of Reprocessing in the formation of functional groups during low density polyethylene aging

“…Reprocessing is one reasonable alternative to reuse LDPE and other polymers [2] . The most common way to provide it is by extrusion, in a method called mechanical recycling; however, this process subjects the polymer to a set of degradations: mechanical by shear stress, thermal by the action of temperature, and oxidative because of the presence of oxygen [3][4][5][6] . Besides this, all polymeric material is subjected to a set of degradative agents, like electromagnetic radiations, temperature and chemicals, not only in processing step, but during all its life cycle.…”

“…Dontula and Campbell [18] conclude the same effect when HDPE was processed in a twin-screw extruder, following differences in viscosity of the extruded material at different temperature profiles and feeding rate. Canevarolo and Babetto [3] studied the level of …”