• Macromolecular Research
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• v.10 no.6
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• pp.365-368
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• 2002

Thermoplastic polyurethanes (TPUs) with different hard segment length has been prepared from a fixed molar ratio of poly(tetramethylene ether glycol), 4,4'-diphenylmethane diisocyanate, and 1,4-butanediol by different polymerization procedures. Results reveal that the on-set temperature of endotherms ( $T_{cc}$ ) due to the crystallization of hard segments by cooling the TPUs from melt and the peak temperature of endotherms due to the melting of hard segments ( $T_{mh}$ ) by heating the TPUs increased and levelled off with increasing the hard segment length of TPUs. It has also been observed that soft segment glass transition temperature ( $T_{gs}$ ) of TPU decreased slightly with increasing the hard segment length, which explains less mixing of soft segments and hard segments. In tensile measurement of TPUs, strain hardening is observed with increasing the hard segment length, which is attributed to the strain induced crystallization of soft segments.

• Macromolecular Research
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• v.9 no.3
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• pp.150-156
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• 2001

Polystyrenes(PS) were grafted onto polypropylene(PP) in the PP solution by ultrasonic irradiation-initiated polymerization of styrene. The resulting products consisted of mixtures of homopolymers and PP-PS copolymer because of the homopolymerization of styrene itself and copolymerization with PP. The dependency of the designated polymerization on sonication times was investigated to monitor the evolution lion of the copolymerization. Formation of the PP-PS copolymer was confirmed by FTIR analysis of the reaction products after a proper separation procedure of free PS and PP-PS copolymer. It was found that the tendency for the formation of PP-PS copolymer was closely related with the phase behavior of the PP/styrene mixture which was also influenced by sonication time. In order to verify the effectiveness of the PP-PS copolymer as a compatibilizer for PP/PS blend, melt mixing of PP/PS/PP-PS was performed in a batch mixer. During the mixing, the average torque was higher for the blend containing PP-PS copolymer influencing compatibilization. In accordance with the results from FRIR analysis and torque measurement, the PS domain size remarkably decreased in the PP/PS/PP-PS blend.

• Polymer(Korea)
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• v.34 no.2
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• pp.144-149
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• 2010

Ag/polystyrene(PS) nanocomposites were prepared by in situ reduction of silver 2-ethylhexylcarbamate (Ag-CB) complex and follwing radical polymerization only by heating at 110 $^{\circ}C$. In contrast to this conventional heating method, the microwave irradiation afforded well-dispersed silver nanoparticles(NPs) in styrene monomer without polymerization. The synthesis of Ag NPs proceeded uniformly throughout the reaction vessel only under microwave irradiation, completing the reaction simultaneously in the whole reaction solution. Successive polymerization of the monomer containing the resultant NPs has successfully produced a hybrid of the silver NPs dispersed in PS matrix. Ag/PS (0.1/100) nanocomposites were prepared successfully by melt-mixing process using Ag/PS(4.0/100) as a master-batch. UV-VIS spectroscopy, TEM, and X-ray diffraction techniques were used to investigate the process of formation of Ag/PS nanocomposites.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.336-340
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• 2015

Three different types of polycarbonate (PC)/graphene oxide (GO) composites using diphenyl carbonate as a monomer were fabricated by melt polymerization. Those were the PC/GO composite (PC/GO) using a twin extruder, in-situ PC/GO composite (PC/GO-cat.) using a catalyst, and in-situ PC/GO composite (PC/GO-COCl) using a GO-COCl treated by -COCl, Chemical structures of the composites were confirmed by C-H and C=O stretching peak at $3000cm^{-1}$ and $1750cm^{-1}$, respectively. The slope for the storage (G') versus loss (G") modulus plot decreased with an increase in the heterogeneous property of polymer melts. So we can check the GO dispersion of the PC/GO composites using by the slop for G'-G" plot. According to the G'- G" slopes for three different types of PC/GO composites, GO was well dispersed within PC matrix in case of PC/GO and PC/GO-cat.. It was also confirmed by atomic force microscope (AFM) photos. One of the reasons for the poor GO dispersion of PC/GO-COCl is branching and crosslinking processes occurred during polymerization, which was further confirmed by a plot for the complex modulus versus phase difference.

• Polymer(Korea)
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• v.34 no.4
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• pp.369-375
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• 2010

We used melt polymerization method to prepare a series of aromatic liquid crystals (LCs) based on aromatic ester and amide units with the reactive methyl-maleimide end group, and then the resulting thermally cross-linked LCs to produce LC thermoset films by means of solution casting and the followed heat treatment. The synthesized LCs and LCTs were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomechanical analysis (TMA), X-ray diffractometry (XRD), and polarizing optical microscopy (POM) with a hot stage. All of the LCs prepared by melt polymerization method formed smectic mesophases. The thermal properties of the LC and LCT films were strongly affected by the mesogen units in the main chain structures. The thermal expansion coefficients of samples were in the range of 27.72~50.95 ppm/$^{\circ}C$.

• Journal of the Korean Applied Science and Technology
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• v.24 no.2
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• pp.140-148
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• 2007

As an additional high purification method of p-dioxanone monomer for a high molecular weight polymer, the sweating operation of crystalline layer obtained by layered melt crystallization from p-dioxanone-diethylene glycol system was studied. Purity and yield of p-dioxanone crystal depended mainly on the sweating temperature and sweating time. Increasing sweating time and sweating temperature, the purity of p-dioxanone crystal increase, whereas the yield of that decrease, respectively. Through the optimization of sweating operation, p-dioxanone crystal can be upgraded to very high purity over 99.9 % suited to monomer for polymerization.

• Macromolecular Research
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• v.10 no.4
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• pp.187-193
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• 2002

Several methods have been used to synthesize polymer-clay nanocomposites. In-situ polymerization with clay belongs to a classical way to develop nano-structured materials, while melt intercalation is being recognized as another useful approach due to its versatility and environmentally benign character. In this research, we prepared polymer-clay nanocomposites based on the poly (methyl methacrylate) and organically modified montmorillonite via two-stage sonication process. According to the unique mode of power ultrasonic wave, the sonication during processing led to enhanced breakup of the clay agglomerates and reduction in size of the dispersed phase. Optimum conditions to form stable exfoliated nanocomposites were studied for various compositions and conditions. It was found that a novel attempt carried out in this study yielded further improvement in the mechanical performance of the nanocomposites compared to those produced by the conventional melt mixing process, as revealed by DMA, XRD and TEM. And rheological properties of nanocomposites were measured by ARES. As a result, sonicated PMMA-clay nanocomposites exhibits enhanced properties such as storage modulus and thermal stability than that of neat PMMA.

• Elastomers and Composites
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• v.45 no.3
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• pp.156-164
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• 2010

Thermoplastic elastomers (TPEs) exhibit both elastomeric behaviors at used temperature range and melt processibility. Polyamide based thermoplastic elastomers (TPAEs) are segmented block copolymers with hard blocks consisting of polyamide segments, while the soft blocks usually consist of flexible segments having a low glass transition temperature. The TPAE is one of the engineering TPEs possessing high thermal stability, excellent mechanical performances, chemical resistance and excellent processibility. And they showed wide range of physical and functional properties depending upon the structure of each segment and their relative contents and the hybridization with various inorganic particles. In this review, synthesis, properties, and possible applications of TPAEs are summarized.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.335-336
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• 2003

The synthesis of poly(trimethylene terephthalate) (PTT), whose application is being expanded very rapidly to new apparel and carpet materials, was investigated by melt condensation polymerization using 1,3-propanediol (PDO) and terephthalic acid (TPA). No catalyst was used in the 1st step reaction (esterification), but tetrabutyl titanate(TBT) was used as a polyesterification catalyst ranging from 25 to 75 ppm based on the weight of TPA used in the 2nd step reaction (polyesterification). The molar ratio of PDO to TPA was set as 2.2:1. The effect of reaction conditions on the color and intrinsic viscosity of the final product was investigated. (omitted)

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.219-219
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• 2006

This study focuses on the effects of dispersion method of a nanoparticle in a polymer matrix such as melt mixing, solution blending, and in-situ polymerization on the physical properties of the nanocomposites. Introduction of a nanoparticle to a polymer resulted in some unusual physical properties. In some cases the nanoparticle played a role of a nucleating agent, leading to decreasing induction time to crystallization. In addition, the dispersion state of the nanoparticle in the polymer matrix also had a significant influence on the physical properties of the nanocomposites. Hence the method of introducing the nanoparticle to the polymer made contribution to the rheological properties of the nanocomposite systems.