Banca de QUALIFICAÇÃO: TÚLIO CAETANO GUIMARÃES

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE: TÚLIO CAETANO GUIMARÃES
DATA: 31/03/2026
HORA: 09:00
LOCAL: https://meet.google.com/mzz-skkr-pdr
TÍTULO:

SILANE-MODIFIED CELLULOSE NANOFIBRILS VIA PICKERING EMULSION

PALAVRAS-CHAVES:

Phase change material. Thermal energy storage Cellulose nanofibrils. Pickering
emulsion. Microencapsulation. Surface modification.

PÁGINAS: 100
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
ESPECIALIDADE: Polímeros, Aplicações
RESUMO:

The property of phase change materials (PCMs) to absorb and release large amounts of heat in a controlled manner can be utilized to improve the thermal performance of various end-use products in sectors such as construction, transport, food, packaging, automotive, solar energy installations, and textiles. Encapsulation of PCMs is mainly useful to prevent leakage during the phase change due to the increase in volume. Cellulose, as the most abundant natural polymer on Earth, represents a promising material to substitute petroleum-based polymers typically used as shell materials to encapsulate PCMs. In particular, cellulose-based nanomaterials such as cellulose nanofibrils (CNF) have been gaining interest in this field because of their biodegradability, renewability, recyclability, safety, and relatively low price. Unmodified CNF have been shown to be suitable interfacial stabilizers for the encapsulation of certain PCMs via Pickering emulsion due to their ability to form strong networks, along with their amphiphilic property. However, CNF chemical modifications may be desirable, for example, to lower its surface energy and to enhance its compatibility with hydrophobic PCMs such as paraffin and the thermal durability of the resulting system. The main hypothesis of this work is that it is possible to improve the encapsulation of PCM by CNF via Pickering emulsion by modifying the surface of CNF with a silane grafting, making it more hydrophobic and thus increasing its chemical compatibility with the PCM. Bleached eucalyptus sp. pulp was used as a cellulosic source for the production of CNF via ultrafine grinding, and chemical surface modification of CNF’s surface was done by adding pre-hydrolyzed octyl(triethoxy)silane (OTES) to a CNF suspension at 70°C. Infrared and energy dispersive X-ray spectroscopies confirmed successful grafting of OTES onto CNF, and water contact angle measurements went from 47° to up to 95°, revealing a substantial increase in hydrophobicity,. Pickering emulsions were prepared from CNF suspensions and two PCMs: Rubitherm RT24 (a commercial paraffinic PCM) and coconut oil (as an alterna tive natural PCM). The emulsions were turned into thin composite CNF/PCM films via casting. Thermal properties of the composites were measured through thermogravimetry and differential scanning calorimetry. The thermal regulation performance was evaluated through a double insulated chamber method. Results indicated that the composites may contain up to 82% in mass of PCM while still maintaining its shape and flexibility. In addition, RT24 composites displayed high latent heat of fusion (up to 137 kJ/kg) and expressive thermal regulation ability in comparison to regular CNF films.

MEMBROS DA BANCA:
Presidente - SAULO ROCHA FERREIRA (Membro)
Interno - RAFAEL CARVALHO DO LAGO - UFLA (Suplente)
Externo à Instituição - MATHEUS CORDAZZO DIAS - UFRA (Membro)
Externo à Instituição - MARESSA CARVALHO MENDONÇA - UFLA (Membro)
Externo à Instituição - JESSICA GIRO PALOMA - UNIBARCELONA (Membro)
Interno - GUSTAVO HENRIQUE DENZIN TONOLI (Suplente)