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    Item type:Publication,
    A concise review on design and control of structured natural rubber latex particles as engineering nanocomposites
    (2021-10-05)
    Wichaita, Waraporn
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    Promlok, Duangkamol
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    Sudjaipraparat, Narissara
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    Sripraphot, Supang
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    In this article, we review the modification of natural rubber (NR) latex into the engineered particles for make use of them in functional nanocomposites. The review focuses on tuning nano-/microstructure and/or composition of NR latex particles by means of surface chemical functionalization, structural modification and incorporation of inorganic nanoparticles (NPs). Due to their polydispersity in size and non-spherical shape with complicated indigenous stabilizers, i.e., proteins and lipids, we first describe the fundamental and common methods for the modification of synthetic polymer latex which become a practical guideline for engineering of NR particles to a variety of designs. Subsequently, the examples of successfully modified NR latex and the involved parameters in the preparation are discussed. The different nature and properties of the modified NR latex compared to the synthetic latex are then depicted. Finally, specific examples of these systems used in a range of applications including nanofillers, controlled releasing materials, textiles, electronics and coatings are demonstrated. The research on modification of NR latex particles would be beneficial to the field of materials science and engineering for the valorization of naturally abundant colloidal polymer to the advanced functional materials in the broader utilization/commercialization in the future.
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    Item type:Publication,
    PMMA-N,N,N-trimethyl chitosan nanoparticles for fabrication of antibacterial natural rubber latex gloves
    (2014-08-30)
    Arpornwichanop, Thanida
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    Polpanich, Duangporn
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    Thiramanas, Raweewan
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    Tangboriboonrat, Pramuan
    This paper presents one-pot synthesis of N,N,N-trimethyl chitosan (TMC) stabilized poly(methyl methacrylate) (PMMA) latex particles via the miniemulsion polymerization technique. From <sup>1</sup>H NMR, synthesized TMC contains 52% degree of quaternization. Compared to native biopolymer chitosan, TMC possesses permanently positive charges as well as provides greater antibacterial activity. Combining properties of PMMA and TMC, PMMA-TMC latex nanoparticles hydrodynamic size.© 2014 Elsevier Ltd. All rights reserved.
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    Item type:Publication,
    Hollow natural rubber latex particles as bio-based alternative white pigment for coating applications
    (2022-11-15)
    Promlok, Duangkamol
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    Sonongbua, Kritayakorn
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    Wilepsuwan, Mutita
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    Tangboriboonrat, Pramuan
    Due to the broad particle size distribution as well as non-spherical shape of natural rubber (NR) latex particles, the non-collapse hollow NR latex particles (HL-NRPs) with well-defined void structure were developed aiming to use as an eco-friendly white pigment/additive for coatings. These hybrid HL-NRPs were prepared via the seeded emulsion polymerization of methyl methacrylate/divinylbenzene/acrylic acid (MMA/DVB/AA) monomers on NR core particles in one-pot. Using cumene hydroperoxide (CHP)/tetraethylene pentamine (TEPA) as a redox initiator, the copolymerization occurred at the particle/water interface. Without seed removal, a single void inside NRP was in situ formed by the phase separation process. Hydrophobic and elastic NR became the inner wall which strengthened the HL particles. Whereas its indigenous stabilizers, i.e., proteins-lipids, allowed the osmosis from the aqueous medium to further expand the void. The proposed mechanism was illustrated using oleic acid (OA) as a model fatty acid for non-rubber substances. Since the multiple light scattering inside the hollow structure could enhance their refractive index, the optical performance of HL-NRPs as a low-density opacifying agent in poly(vinyl alcohol) matrix, was examined using UV-Vis spectroscopy. Results showed that the HL-NRPs-based films exhibited high blocking ability over UV and visible regions. Moreover, the HL-NRPs coated with chitosan (CS) enabled these nanocomposites to adsorb the formaldehyde vapor. For sustainable development, HL-NRPs/CS could potentially be a green alternative white pigment/additive for coatings.
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    Item type:Publication,
    Hollow core-shell particles via NR latex seeded emulsion polymerization
    (2016-09-02)
    Wichaita, Waraporn
    ;
    Polpanich, Duangporn
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    Tangboriboonrat, Pramuan
    Natural rubber (NR)-based hollow latex (HL) particles have been prepared by seeded emulsion polymerization of methyl methacrylate/divinyl benzene/acrylic acid (MMA/DVB/AA) monomers on NR seed. By using tert-butyl hydroperoxide/tetraethylene pentamine (t-BuHP/TEPA) as a redox initiator, the locus of polymerization was localized at the surface of the NR particle. After swelling with monomers, DVB in NR particle gradually moved outward to compensate the co-polymerization. Phase separation between the NR seed and the polymeric shell occurred and a void was subsequently formed at a MMA/DVB molar ratio of 2.7/1. The void cavity was enlarged when the monomer to seed (M/S) weight ratio was increased to 4/1. Without the necessity of any residual core removal, polydisperse NR-based hollow nanocomposites (298 ± 58 nm) possessing NR-P(MMA/DVB/AA) double-layered shell and a single void (155 ± 37 nm) were obtained. SEM images revealed an increase in surface roughness of the HL particle with increasing M/S weight ratios. The large specific surface area of these NR-based hollow nanocomposites (114.6 m<sup>2</sup>/g) with a 3.5 nm pore diameter indicates that the polymeric shell is mesoporous. The presence of carboxyl groups, as indicated by negative zeta potentials, can further facilitate surface functionalization. The large void cavity of these NR-based HL particles makes them particularly suited as delivery vehicle systems.