Nanocompósitos de Blendas HDPE/LLDPE e OMMT Parte II: Avaliação das Propriedades Térmica, Óticas e de Transporte a Gases

Abstract

Resumo: Nanocompósitos de blendas de polietileno de alta densidade (HDPE) com polietileno linear de baixa densidade (LLDPE) e OMMT (montmorilonita organofílica) foram preparados sob fusão em extrusora de duplarosca, utilizando HDPE-g-MA como agente compatibilizante. Os nanocompósitos foram caracterizados através das propriedades térmicas, óticas e de transporte de gases. A blenda HDPE/LLDPE e os nanocompósitos das blendas HDPE/LLDPE como esperado comportam-se como barreira ao vapor de água e são permeáveis ao CO 2 e O 2 . A adição de nanoargila modificou o grau de cristalinidade da matriz polimérica dos nanocompósitos e a diminuição do coeficiente de permeabilidade foi atribuída ao aumento do grau de cristalinidade e do aumento ao caminho difusional para as moléculas do gás passarem pelo filme polimérico. O caminho difusional mais longo devido ao aumento da tortuosidade está relacionado a uma boa dispersão da carga inorgânica, boa molhabilidade desta pela matriz e forte interações na interface. Modelos teóricos de permeabilidade propostos por Nielsen e Bharadwaj foram utilizados para estimar a razão de aspecto da nanoargila nos nanocompósitos e forneceram resultados que se correlacionam bem com as morfologias observadas por microscopia eletrônica de transmissão. HDPE/LLDPE Blend-based Nanocomposites -Part II: Evaluation of Thermal, Optical and Transport PropertiesAbstract: High density polyethylene/ linear low density polyethylene (HDPE/LLDPE) blend-based nanocomposites were prepared in a twin-screw, using HDPE-g-MA as compatibilizer agent. The nanocomposites were characterized through thermal, optical and transport properties. The HDPE/LLDPE blend and the nanocomposites behave as a barrier to water vapor but are permeable to CO 2 e O 2 . The addition of organoclay modified the crystallinity degree of the polymer matrix of the nanocomposites. The reduction of the permeability coefficient of the nanocomposites was correlated to the increase in the crystallinity of the polymer matrix and to the increase in diffusional path of the gas due to the increase in the tortuosity related to a good dispersion of the clay platelets in the matrix. These effects are related also to a good wettability of the filler by the polymeric matrix and strong interactions at the interface. Theorical permeability models proposed by Nielsen and Bharadwaj were used to estimate the aspect ratio of the organoclay in the nanocomposites with correlate well with the images observed through transmission electron microscopy.

Nanocomposites of Polyethylene Blends Using Organomica

“…Polymer blends have significant industrial importance, since their properties can be altered allowing encompass a wide variety of applications. Polymer blends can be obtained by physical blending of two polymers in an extruder or by in situ polymerization employing catalytic mixtures or reactors in series. The mixture of high‐density polyethylene with linear low‐density polyethylene (HDPE/LLDPE) allows obtaining a material easier to process due to the high melt flow rate of LLDPE.…”

Antistatic packaging based on PTT/PTT‐g‐MA/ABS/MWCNT nanocomposites: Effect of the chemical functionalization of MWCNTs

“…The optical properties of polymers are related to the passage of light through the material. Haze is characterized by the transmitted light, when passes through the sample, deviated from incident radius, scattering at an angle greater than 2.5° 38 . Clarity is characterized by the transmitted light that, when passes through the sample, deviated from incident radius scattering at an angle less than 2.5°.…”

“…Haze is characterized by the transmitted light, when passes through the sample, deviated from incident radius, scattering at an angle greater than 2.5 . 38 Clarity is characterized by the transmitted light that, when passes through the sample, deviated from incident radius scattering at an angle less than 2.5 . Transmittance is the total of incident light that is transmitted through the sample without being scattered.…”

“…Transmittance is the total of incident light that is transmitted through the sample without being scattered. 38 Usually, these properties are measured in percentage (%).…”

“…Optical properties are related to the degree of crystallinity and the structure of the polymer. 38 Amorphous materials have better optical transparency than semicrystalline ones, and a decrease in the crystallinity of a semicrystalline polymer increases clarity. 39 It was not possible to measure the opacity of nanocomposites with a higher concentration of nanofiller (nanocomposites with 1.0 wt% of MWCNT and MWCNTf ), because higher content of filler made the nanocomposite very dark.…”