Manit Nithitanakul

Nonisothermal melt-crystallization kinetics for three linear aromatic polyesters

Abstract The kinetics of nonisothermal crystallization of three different types of linear aromatic polyester, namely poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and poly(butylene terephthalate) (PBT), which are different in their number of methylene groups (i.e. 2, 3, and 4 for PET, PTT, and PBT, respectively), was investigated using differential scanning calorimetry (DSC). Analysis of the data was carried out based on the Avrami, Tobin, Ozawa, and Ziabicki models. It was found that the Avrami model provided a more satisfactorily good fit to the experimental data for these polyesters than did the Tobin model. The Ozawa model was found to describe the experimental data fairly well. The Ziabicki’s kinetic crystallizability parameter G for these polyesters was found to be of the following order: PBT>PTT>PET. The effective energy barrier for nonisothermal crystallization process of these polyesters, determined by the Friedman method, was found to be an increase function with the relative degree of crystallinity.

Thermal, crystallization, and rheological characteristics of poly(trimethylene terephthalate)/poly(butylene terephthalate) blends

Abstract Blends of poly(trimethylene terephthalate) (PTT) and poly(butylene terephthalate) (PBT) were miscible in all of the blend compositions studied, as evidenced by an observed single and composition-dependent glass transition temperature for each blend composition. The variation of the glass transition temperature with the blend composition was well predicted by the Gordon–Taylor equation, with fitting parameter being ca. 6.9. The cold crystallization (peak) temperature was found to increase, while the melt crystallization (peak) temperature was found to decrease, with increasing PTT content. The subsequent melting behavior for these blends (after cold crystallization) showed the melting point depression behavior, in that the melting (peak) temperature for each component was lowered with increasing content of the other component. During crystallization, the pure components crystallized simultaneously to form their own crystals. The blend having 60 percent by weight of PTT showed the lowest apparent degree of crystallinity. The steady shear viscosities for the pure components and the blends showed slight decrease with increasing shear rate (within the shear rate range of 0.25–25 s−1), with those of the blends lying in between those of the pure components.

Spinning of fibers from polypropylene/silica composite resins

Isotactic polypropylene (iPP)/silica (SiO2) composites were prepared by solution (toluene) mixing followed by either sonication or autoclaving to disaggregate the silica agglomerates. The obtained composite resins were then spun into monofilament fibers using a ThermoHaakes single screw extruder. The obtained fibers were characterized by morphological analyses (scanning electron microscope, atomic force microscopy (AFM), and Raman), crystallization profile (differential scanning calorimetry), and hot-stage microscopy. AFM images and Raman analysis maps revealed that silica particles of a submicron size range were present on the surface. The inclusion of silica particles into the resins resulted in a higher crystallization temperature (Tc) and shrinkage resistance of the composite fiber when compared to those of the neat or toluene-prepared PP fibers, which were attributed to the nucleating effect of the silica filler with an effective reinforcement. In addition, the silica loadings (0.25–1 wt%) increased the tensile strength attributable to its change in shape from round to elongated and flattened after spinning process, except that the greatest increase (1.4-fold) was seen at 0.25 wt% silica. However, the variances were large, resulting from diameter variation arising from free-fall fibers obtained by gravitational force only. Interestingly, the surface hydrophobicity of the composite fibers was found to be higher than the neat fibers due to the increase in the surface roughness arising from the presence of particles on the surface.

pH-Sensitive PP/Clay Nanocomposites for Beverage Smart Packaging

The modification of clay by ion exchange reaction with cationic surfactants plays an important role in the greater interlayer spacing of Na-bentonite. Four types of quaternary alkyl ammonium ions, DO AM, DOEM, DCEM and DTDM, were introduced into the clay in order to investigate the effects of intercalation of the cationic surfactants. The organobentonites were characterized by XRD, FTIR and TGA. From WAXD patterns, DOEM-B exhibited the largest interlayer spacing, promissing the most suitable choice for producing PP/clay nanocomposites. The nanoclay composites incorporating pH indicator were melt compounding through a twin screw extruder using Surlynreg as a reactive compatibilizer. Subsequently, the nanoclay composites were fabricated into the sample sheet for pH-sensitive test.

High Internal Phase Emulsion Foams (HIPE) Filled with Organo-Bentonite: Hybrid Organic-Inorganic Porous Clay Heterostructures (HPCH) versus Organo-Modified Bentonite (MOD)

Organoclay derived from Na-bentonite can offer an alternative used as an inorganic filler for high internal phase emulsiom foams. Two types of organoclay, hybrid organic–inorganic porous clay heterostructures (HPCH), derived from organo–bentonite which prepared through surfactant–directed assembly of tetraethoxysilane (TEOS)/methyltetraethoxysilane (MTS) into galleries of the clay mineral, and organo-modified bentonite (MOD) treated with quaternary alkyl ammonium cation by ion exchange reaction, were used as a reinforcing agent for poly(divinylbenzene; DVB)polyHIPE foams in this study. Poly(DVB)polyHIPE foams filled with organo-bentonite (MOD and HPCH) loadings of 0, 1, 3, 5, and 10 wt% were successfully prepared using the HIPE technique. To study the effects of the organoclay on morphology, surface area, and mechanical properties of the prepared poly(DVB)polyHIPE foams, SEM, N2 adsorption-desorption, and a Lloyd Universal testing machine were employed. It was demonstrated that the addition of organo-bentonite (both MOD and HPCH) into PolyHIPE foams resulted in the enhancement of physical properties of the poly(DVB)polyHIPE foams. The incorporation of layered silicate in the polymer matrix were supported by SEM images, which shown that the roughness of the polymer wall surfaces appeared to increase due to the presence of organoclay. It was established that the use of organo–bentonite, both HPCH and MOD, as inorganic filler for poly(DVB)polyHIPE, has an effect on improving the surface area of the obtained materials. However, higher improvement in surface properties was achieved with poly(DVB)polyHIPE filled with HPCH when compared with poly(DVB)polyHIPE foams filled with MOD. This is because of the surface charateristic of the HPCH which is a combination of micro– and mesoporosity between each layered of silicates and gas molecules might be able to adsorbed into these porous structures. Mechanical properties of the filled poly(DVB)polyHIPE foams were found to improve when compared to the neat poly(DVB)polyHIPE. Highest Young’s modulus and compressive stress were observed at 5 wt% organoclay loading. It was clearly demonstrated in this study that the suitable content of

High CO2 Adsorption Polymeric Foam from Poly(DVB)PolyHIPE Filled with Maleimide-Terminated Poly(Arylene Ether Sulfone) Oligomers via High Internal Phase Emulsion

Polymerized high internal phase emulsion of poly (DVB) polyHIPE filled with maleimide-terminated poly (arylene ether sulfone) oligomers (M-PSO) has been successfully prepared using high internal phase emulsion technique. Poly (DVB) polyHIPE filled with maleimide-terminated poly (arylene ether sulfone) oligomers (0, 2.5, 5, and 10 wt%) were prepared using SPAN80:DDBSS:CTAB (6.3:0.4:0.3) as mixed surfactant. The obtained polyHIPE foams were characterized for their phase morphology, surface area, thermal behaviour, and mechanical properties using SEM, BET, TG/DTA, and a LLOYD Universal Testing machine, respectively. The prepared polyHIPE foams will be used for adsorbing the CO2 produced during the gasification process to increase the heating value of syn gas. Phase morphology of the obtained polyHIPE foams showed an open cellular structure with small interconnectivity. The mechanical properties and decomposition temperatures (Td) increased with increasing filler content from 0 to 10 wt%. The adsorption of CO2 gas by poly (DVB) polyHIPE foam filled with maleimide-terminated poly (arylene ether sulfone) oligomer was found to increase as well (from 3.125 to 3.459 mmol/g) when compared with neat poly (DVB) polyHIPE foam.

Highly Porous Polymeric Foam of Maleimide-Termiated Poly(arylene ether sulfone) Oligomers via High Internal Phase Emulsions

PolyHIPEs are highly porous polymeric form, prepared through emulsion templating by polymerizing the continuous phase of high internal phase emulsions (HIPEs). A maleimide-terminated aryl ether sulfone oligomer (MAPES) was copolymerized with divinylbenzene (DVB) in the continuous phase, using a mixed surfactants system (sorbitan monooleate (Span80), cetyltrimethylammonium bromide (CTAB), dodecylbenzenesulfonic acid sodium salt (DDBSS)), and peroxide initiator, to improve CO2 adsorption and the mechanical properties of obtained materials. PolyHIPEs were prepared by two different ratios of mixed surfactants; (SPAN80, DDBSS, and CTAB; 6.3, 0.4, and 0.3 wt%, which was denoted as 7s) and (SPAN80, DDBSS, and CTAB; 11.3, 0.4, and 0.3 wt%, which was denoted as 12s). 0, 2.5, 5, 10, 20, and 30 wt% of maleimide-terminated aryl ether sulfone oligomer were copolymerized with DVB. All PolyHIPE nanocomposites foam were characterized for phase morphology, thermal behavior, surface area, mechanical properties and adsorption of CO2 by using SEM, TG-DTA, N2 adsorption-desorption, LLOYD universal testing machine and CO2 adsorption unit, respectively. The obtained PolyHIPEs showed an open cell and a secondary pore structure with surface areas of approximately 400m2/g. CO¬2 adsorption tests were characterized by pilot gasification unit and the obtained materials showed higher adsorption than neat poly(DVB) without MAPES. Compressive modulus test of the materials showed a higher modulus than for poly(DVB) PolyHIPEs.

Magnetite/poly(D,L-lactide-co-glycolide) and hydroxyapatite/poly(D,L-lactide-co-glycolide) prepared by W/O/W emulsion technique for drug carrier: Evaluation of in vitro release of dexamethasone from composite nanoparticles

ABSTRACT Biocompatible polymeric carriers containing inorganic materials for delivering therapeutic agents to a targeted site are promising candidate for drug delivery. Two nanocomposite nanoparticles, magnetite/poly(D,L-lactide-co-glycolide) and hydroxyapatite/poly(D,L-lactide-co-glycolide) (Fe3O4/PLGA and HAp/PLGA, respectively), with different weight ratios of inorganics to polymer and different polymer molecular weights were prepared by water-in-oil-in-water (W/O/W) emulsion technique to determine incorporation and in vitro release profile of the small molecule drugs water-insoluble dexamethasone acetate (DEX-Ac) and water-soluble dexamethasone phosphate (DEX-P). The in vitro release for DEX-Ac nanoparticles showed an initial burst release followed by a continuous slower release, whereas DEX-P nanoparticles showed only rapid initial release behavior. GRAPHICAL ABSTRACT

Material Flow Analysis (MFA) and Life Cycle Assessment Study for Sustainable Management of PVC Wastes in Thailand (Phase III)

Abstract Polyvinyl chloride (PVC) is one of the most commonly used plastics in the worldwide. In Thailand, PVC products are used for domestic consumption more than 400,000 tons annually. After discarded, these products will become wastes which are being accumulated and could cause several environmental problems if they are disposed by inappropriate method. In previous studies, our group investigated the material flow of PVC in Thailand to handle the PVC waste problems systematically and effectively. Material Flow Analysis (MFA) model was developed to estimate the quantity and route of PVC wastes in Thailand using annual production data from 1971-2014 as an input in the model along with an average service life time of each product. In addition, the primary data were collected from recycle shops and landfill sites were used to estimate the amount of PVC wastes that are generated and recycled on yearly basis, and recycling ratio of each PVC product in Thailand. The results indicated that some selected PVC products were effectively recycled such as pipe, cable, and hose but the other products were relatively low portion in recycling. This is the first time that the MFA of PVC wastes and PVC recycling are revealed which could be a potential model for other plastics in Thailand. In this work (phase III), firstly, the MFA model was developed by considering consumer behaviour and economic decisions. Sheet & film product were included in this investigation in order to expand range of PVC products, in which covers about 93% of total PVC products in Thailand. In addition, the existing primary data were revised along with the new data were from other recycle shops and converters. Finally, potential improvements of PVC waste management and suitable data collection system are proposed in order to promote environmentally friendly schemes for PVC production and utilization.

Surface Modification of High Internal Phase Emulsion Foam as a Scaffold for Tissue Engineering Application via Atmospheric Pressure Plasma Treatment

Atmospheric pressure plasma treatment was used to improve hydrophilic properties and scaffold/cell interaction of poly(S/EGDMA)polyHIPE highly porous foam, prepared from poly(styrene/ethylene glycol dimethacrylate) using high internal phase emulsion technique. With our synthesis procedure and surface treatment, this bioactive material, featuring highly porous structure and good mechanical strength, can be applied as a scaffold for tissue engineering applications. The treatment time and external plasma parameters were investigated in regards to the polyHIPE foam surface’s appropriate for fibroblast implantation. The changes in surface properties were characterized by contact angle measurement, showing that the exposure to air-plasma induced polyHIPE foam with hydrophilic surfaces, as observed by a decrease in contact angle degree. Enhancement of the interaction between the polyHIPE foam and the L929 fibroblast-like cells would imply the hydrophilic improvement of the polyHIPE foam surface due to the polar-like property of the biofluid cell medium.