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Physical value of dielectric properties among relative permittivity, dielectric loss and loss tangent of mixed melting polymer pellets were measured under temperature variance condition and measurement frequency from 0.5 MHz to 5 MHz in order to develop a real-time non-intrusive measurement technique for high performance waste plastic separation. Various volume fractions of non-polar polyethylene (PE) and polar polyethylene terephthalate (PET) were used as the mixed polymer pellets. As the results, with the volume fractions of PET from 0.05 to 0.22, as the temperature is increased up to melting point temperature and above mold temperature, the relative permittivity is decreased as the temperature is increased. However over melting temperature up to the mold temperature, the relative permittivity is slightly increased as the temperature is increased. On the other hand, the dielectric loss and loss tangent are not affected by the temperature variance, and the dielectric loss and loss tangent are increased as the measurement frequency is increased. As the conclusions, at molding temperature 180 °C (453 K), the highest sensitivity of dielectric property is the relative permittivity. Meanwhile, the highest linearity relationship between PET volume fraction and predicted relative permittivity is achieved at the measurement frequency of 5 MHz. From relative permittivity measurement in these conditions, the performance to distinguish PET volume fraction 0.05 from PE volume fraction 0.95 is achieved in the mixed melting polymer pellets. Therefore, the relative permittivity measurement for waste plastic separation has a possibility to achieve the high purity recycled plastics as compared with conventional methods. [ABSTRACT FROM AUTHOR]

This study involved the incorporation of useful compounds, such as repellents and antibacterial agents, at high concentrations in l-lactide (l-LA) random copolymers. The amount of α-pinene released in gas from the copolymers was also evaluated. Outstanding controlled release properties were developed using random copolymers of l-lactide (l-LA) with γ-valerolactone (VL), ε-caprolactone (CL), tetramethylene carbonate (TEMC) (1,3-dioxepan-2-one), and 1,5-dioxepan-2-one (DXO) using tin 2-ethyl-hexanoate [Sn(oct)2] as a catalyst at 150 °C for 24 h without solvent. Preparation of controlled release materials was accomplished using α-pinene from Japanese cypress oil and synthetic random copolymers of l-LA with cyclic monomers as base materials under supercritical carbon dioxide (scCO2). Poly(l-LA-ran-VL), poly(l-LA-ran-CL), poly(l-LA-ran-TEMC), and poly(l-LA-ran-DXO), which have lower Tm and ΔHm values than poly(l-LA) were used for the impregnation experiments. The oil content of the copolymers was greater than that in poly(l-LA). The content of oil into poly(l-LA-ran-TEMC) (80 : 20) was 8.1%, 2.1-fold greater than that in poly(l-LA) (Lacea H-100) (H-100), and 1.5-fold greater than that in poly(l-LA) (Lacea H-440) (H-440). Although a previous study showed that 3.2% d-limonene could be incorporated into poly(l-LA-ran-CL) (85 : 15) under the same conditions, results of this experiment showed that 5.8% and 6.6% oil could be incorporated into poly(l-LA-ran-CL) (81 : 19 or 91 : 9), respectively. Results from controlled release experiments demonstrated that the oil content in the polymer decreased upon copolymer degradation for all copolymers. In gas release tests, polymers H-440 and poly(l-LA-ran-VL) (85 : 15) released gas upon hydrolysis. Although the weight loss of H-440 was only 9% at 56 days, the calculated loss of oil in H-440 was 28%. [ABSTRACT FROM AUTHOR]

Outstanding controlled release materials were developed using statistically random copolymers of l-lactide ( l-LA) with ε-caprolactone (CL) using Sn(oct)2 as a catalyst at 150 °C for 24 h without solvent. Preparation of novel controlled release materials was carried out using useful organic compounds with low boiling points and synthetic random copolymers composed of l-LA and CL as base materials under supercritical carbon dioxide (scCO2). Low-boiling-point compounds such as d-limonene, hinokitiol, and trans-2-hexenal were used. In impregnation experiments using scCO2, the amounts of low-boiling-point compounds increased with an increase in l-LA content. When enzymatic degradation of poly( l-LA- ran-CL) was performed using lipase PS, copolymers with higher CL contents degraded more rapidly than did copolymers with higher l-LA content. In contrast, enzymatic degradation of copolymers occurred to a higher degree with increased l-LA content in enzymatic degradation by proteinase K. In a controlled release experiment with poly( l-LA- ran-CL) (=73/27), after 400 h of degradation by proteinase K, the remaining weight of the copolymer pellet was 6% and the amount of d-limonene remaining in the pellet was 15%. [ABSTRACT FROM AUTHOR]