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Access type: UnknownAuthor: search.filters.author.Limthin, Darawan

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    Effects of Annealing Temperature and Time on Properties of Thermoplastic Polyurethane Based on Different Soft Segments/Multi-Walled Carbon Nanotube Nanocomposites
    (2023-01-01)
    Jirakittidul, Kittimon
    ;
    Limthin, Darawan
    ;
    Mahithithummathorn, Sarita
    ;
    Phaewchimphlee, Seenam
    Typically, polymer chains can move under the annealing process, resulting in an ordered structure arrangement. This causes an improvement in nanocomposite properties and in the dispersion of filler. In this research, annealed thermoplastic polyurethane (PU)/multi-walled carbon nanotube (MWCNT) nanocomposites were studied to investigate the effect of annealing on the selective dispersion of MWCNTs. PU matrices were composed of two different soft segments, i.e., polyether (PU-Ether) and polyester (PU-Ester). Nanocomposites were prepared by the melt mixing process and annealed at 80 to 120 °C for 6 to 24 h. The increases in annealing time and temperature resulted in microphase separation in segmented PU and the orientation of crystalline structures in the segregated hard domain. Nanocomposites showed higher electrical conductivity after annealing. This implies that the movement of PU chains during heat treatment encouraged the development of the MWCNT network. However, the increase in ordered structures could obstruct the MWCNT network, resulting in lower electrical conductivity levels. Considering the selective dispersion of MWCNT in PU matrices, it was found that MWCNTs dispersed in soft segments of PU-Ether, leading to a significant decrease in elongation at the break after annealing. On the other hand, a decrease in elasticity of PU-Ester nanocomposites was not observed as a result of MWCNT dispersal in hard segments.
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    Improving Stability of Nanoemulsion Containing Centella asiatica, Lycopersicon Esculentum Mil. And Moringa oleifera Lam. Extract
    (2019-01-01)
    Limthin, Darawan
    ;
    Phromyothin, Darinee
    Natural extracts are interesting because those have bioactive compounds which can be used as antioxidants in pharmacological cosmetics. However, bioactive compounds are unstable to environment. In the present study, formulation and stability of Centella asiatica, Lycopersicon Esculentum Mil. and Moringa oleifera Lam. was performed using high shear homogenization (HSH) technique. Virgin coconut oil was based of oil phase for emulsion. The optimum formulation of the nanoemulsion consisted of 80:10:10 of water, tween 80 and oil, respectively. 1 % of natural extract nanoemulsion was homogenized for 20 minutes at 4,000 rpm. and stored at 4 ºC, 25 ºC and 40 ºC for 7 days. Particles size and electrokinetic potential of emulsion extract was determined by dynamic light scattering method. Single-phase solution and droplet size was observed in the range of 100 to 500 nm. The droplet size and stability of emulsions depends on temperature and times storage, which this study would be approached to develop a natural product in cosmetic market.