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    Cleaner Bio-Based Plasticizer Synthesis from Waste Cooking Oil to Substitute Toxic Dioctyl Phthalate in PVC film
    (2025-01-01)
    Chaiyaraksa, Chompoonut
    ;
    Sriprom, Pongsert
    ;
    Boonkaen, Fahana
    ;
    Laemsri, Arthittaya
    ;
    Smingkaew, Arnita
    This research aimed to investigate the possibility of synthesizing a bio-based plasticizer from waste cooking oil using an epoxidation reaction to replace dioctyl phthalate (DOP) in PVC film, which is toxic and hazardous to human health and the environment. This involved synthesizing used household oil through an epoxidation reaction to introduce epoxy groups, followed by isopropyl alcohol to break the epoxy rings and form hydroxyl groups. The chemical structure of the epoxidized waste cooking oil plasticizer was analyzed using Fourier transform infrared spectroscopy (FT-IR), with a focus on confirming the presence of epoxy groups within the 3,500 – 3,000 cm-1 range. Subsequently, this bio-based plasticizer was used in various ratios to DOP to produce PVC films, including ratios of 5:0, 4:1, 3:2, 2:3, 1:4, and 0:5. These PVC films were subject to a comprehensive examination of their physical and chemical properties, including their resistance to tensile stress, elongation ability, the impact on molecular functional groups in the PVC film, and a leaching test. The results showed that the optimal proportion of epoxidized waste cooking oil plasticizer to DOP was 5:0. This ratio demonstrated superior tensile strength, enhanced elongation capacity, increased thermal stability, and exhibited the most robust resistance against solvents compared to other ratios tested.
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    Improving polylactide toughness by plasticizing with low molecular weight polylactide-poly(Butylene succinate) copolymer
    (2021-01-01)
    Srithep, Yottha
    ;
    Veang-In, Onpreeya
    ;
    Pholharn, Dutchanee
    ;
    Turng, Lih Sheng
    ;
    Morris, John
    A low-molecular-weight polylactide-poly(butylene succinate) (PLA-PBS) copolymer was synthesized and incor-porated into polylactide (PLA) as a novel toughening agent by solvent casting. The copolymer had the same chemical structure and function as PLA and it was used as a plasticizer to PLA. The copolymer was blended with PLA at a weight ratio from 2 to 10 wt%. Phase separation between PLA and PLA-PBS was not observed from their scanning electron microscopy (SEM) images and the crystal structure of PLA almost remained unchanged based on the X-ray diffraction (XRD) measurement. The melt flow index (MFI) of the blends was higher as the amount of PLA-PBS increased, indicating that the block copolymer did improve the mobility of the PLA chains. Moreover, tensile tests revealed that PLA with greater PLA-PBS copolymer exhibited higher elongation at break and it reached the maximum at 8 wt% of PLA-PBS in PLA, which was around 6 times higher than that of pure PLA. Furthermore, the glass transition temperature, measured by differential scanning calorimetry (DSC), mark-edly decreased with an increasing amount of the copolymer as it decreased from 61.2°C for pure PLA to 41.3°C when it was blended with 10 wt% PLA-PBS copolymer. Therefore, the PLA-PBS copolymer was shown to be a promising plasticizer for fully biobased and toughened PLA.
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    Durable nitrate sensor by surface modification
    (2016-11-25)
    Chaisriratanakul, W.
    ;
    Bunjongpru, W.
    ;
    Jeamsaksiri, W.
    ;
    Srisuwan, A.
    ;
    Porntheeraphat, S.
    This work presents the development of nitrate sensor based on Ion Sensitive Field Effect Transistor (ISFET) technology to achieve longer device's lifetime. This lifetime depended on the adhesion of PVC ion-selective membrane on the Si<inf>3</inf>N<inf>4</inf> sensing membrane of ISFET. The adhesion level directly affected the leaching of plasticizer. Such improvement utilized surface modification techniques by immersing the sensing membrane in the solution of 5% 3-mercaptopropyl-trimethoxysilane (MPTMS)/methanol. The modified surface was detected through the change of hydrophobicity and thickness of MPTMS using the contact angle measurement and ellipsometry techniques. The appropriate time for immersion was 18 h. The modified surface achieved the optimal hydrophobicity with contact angle of 100.32°. The presence of MPTMS film was confirmed by detecting the thiol-group using Fourier Transform Infrared (FTIR) spectrophotometry and Auger Electron Spectroscopy (AES). The PVC ion-selective membrane was then immobilized on the surface to create nitrate sensors with the following characteristics. The Nitrate-Nitrogen detection limit = 2.44 ppm with linear range from 5 to 60 ppm at sensitivity of 56 mV/dec. (R<sup>2</sup> = 1). The response time was 90 s. Finally, this nitrate sensor could extend the total utilization lifetime from 8 to 17 weeks.