Banca de DEFESA: CARLA LAIZE DOS SANTOS CRUZ COSTA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : CARLA LAIZE DOS SANTOS CRUZ COSTA
DATE: 21/03/2022
TIME: 08:00
LOCAL: meet.google.com/duv-qyjk-afx
TITLE:

DEVELOPMENT OF A POLYETHYLENE FILAMENT YARNS WITH THERMOCHROMIC PROPERTY FOR TEXTILE APPLICATIONS

KEY WORDS:

HDPE, Thermochromic pigments, aditives, extrusion mixing, filament yarns.

PAGES: 90
BIG AREA: Engenharias
AREA: Engenharia Química
SUBÁREA: Tecnologia Química
SPECIALTY: Têxteis
SUMMARY:

The aim of this work was to develop a continuous filament of high density polyethylene (HDPE) with thermochromic property, for applications in textile materials. For this, two types of thermochromic pigments, in orange and purple, both with color change at a temperature of 31°C, were mixed with HDPE during extrusion processing to obtain a filament at melt state, and the proportions used of 0.5, 1.0 and 2.0 wt.% of pigments. The photomicrographs obtained from the pigment powders showed that the materials had a spherical morphology. To identify the activation temperature of the pigments, the powders were subjected to heating, where the thermochromic transition temperature could be identified and the images were obtained in a digital camera, showing the differences in colors at 21°C and 45°C. After the mixing process by extrusion and granulation of all samples, part of the granules was used to mold specimens by injection molding, these specimens were used in the preliminary characterizations to evaluate the incorporation of pigments in HDPE before the production of filamento yarns continuous. The rest of the granules were used for the production of continuous filamento yarns, keeping the screw rotation speed and the filament pulling speed constant in all samples. Flow index measurements (MFI) were performed on pure HDPE granules and on mixtures of HDPE with pigments for the three proportions used. The results of the melt flow index (MFI) analysis had increasing values, unlike the results of the Shore D hardness analysis, which decreased, such behavior was an indication that the proportions of thermochromic pigments used promoted an increase in the mobility of the HDPE polymer chains, which which may have influenced a change in viscosity and an increase in MFI values. The photomicrographs obtained by scanning electron microscopy (SEM) of the injection molded specimens showed that the pigments maintained the spherical structure preserved within the polymer, maintaining its protected function. The images obtained from the specimens by digital camera showed the color change of pure HDPE from beige to orange and purple, as well as the color change to yellow and blue, respectively, when the samples were submitted to thermochromic activation temperature, the color change is reversible. The yarns obtained from the granules also acquired the thermochromic property and, through images taken with a digital camera, it was possible to identify the difference in color when the samples were exposed to 21°C and 45°C. The spectrophotometric analysis showed the change in reflectance spectra when these materials were exposed to these two temperatures, evidencing the color alteration caused by the structural alterations of the pigments. The uniaxial tensile results showed that the addition of the two types of thermochromic pigments, at the concentrations used, did not interfere in the mechanical properties of the HDPE polymer matrix, even as a result of the difference in size observed in the two types of pigments used. The atomic force microscopy (AFM) test showed that despite a slight difference in the surface roughness of the HDPE additives, the thermochromic pigment particles were incorporated into the matrix. It was concluded in this work that the optimal thermochromic addition composition is less than 0.5 wt.% and that these characteristics are not lost during melt processing and due to the high shear rate in injection molding processing.

BANKING MEMBERS:
Presidente - 1639676 - EDSON NORIYUKI ITO
Interno - 2239386 - JOSE IVAN DE MEDEIROS
Externo à Instituição - ERIK DOS SANTOS SILVA - UNIFEI
Externa à Instituição - JUCIKLÉCIA DA SILVA REINALDO - UFRN