• Polymer(Korea)
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• v.29 no.6
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• pp.565-570
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• 2005

Melt processing characteristics of nylon 6 (N6) has been investigated by controlling the melt viscosity in melt impregnation process. Calcium stearate (CaST) was introduced as a lubricant for N6 and the melt viscosity of N6 decreased with adding only 1 wt$\%$ of CaST. In addition, reactive blending with polycaprolactone (PCL) was carried out by lowering the melt viscosity in N6. It was found that the melt viscosity of N6 could be controlled and further melt viscosity drop could be obtained by applying phenyl phosphite (PP) and diphenyl phosphite (DPP) to enhance the transesterification between N6 and PCL. Our approaches show that the melt viscosity of N6 could be reduced without loss of thermal stability which is the critical problem in high temperature melt impregnation process of N6.

• Polymer(Korea)
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• v.30 no.2
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• pp.118-123
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• 2006

The effect of transesterification on the rheological properties in the melt reactive blending of poly(butylene terephthalate)(PBT) with poly(ethylene terephthalate)(PET) has been studied. The melt viscosity depression in PBT was found in PBT/PET blends due to the intrinsic low melt viscosity of PET compared to PBT. In addition, the thermal degradation in the melt blending and transesterification between two polyesters were considered as other factors fer the lowering of the melt viscosity in the blends. In the PBT/PET blends, calcium stearate was less effective than in PBT as a lubricant, however it accelerated both the thermal degradation and transesterification during melt blending. As a result, further melt viscosity drop was obtained in the reactive melt blending of PBT/PET.

• Fibers and Polymers
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• v.4 no.3
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• pp.107-113
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• 2003

The branched polypropylene (b-PP) was prepared by melt blending process with initiator, antioxidant, and functional monomers to improve the melt strength through the melt grafting. The melt flow index (MFI) of the b-PP was increased with increasing the initiator content. On the introduction of the alkylamine as the branching agents the MFI of the b-PP was increased, while that of the b-PP with the pentaerythritol triacrylate (PT) was decreased. It may be caused by the chain scission of the i-PP backbone due to the reduced thermal stability of the i-PP on the melt blending. The MFI of the b-PP without the antioxidant was increased due to the chain scission occurred during the melt processing, while on the introduction of the antioxidant, the MFI of the b-PP was decreased. The crystallization temperature of the b-PP was higher than that of PP, which was attributed to the branched chain structure. It was found that the PT was the most effective functional monomers for enhancing the melt properties of the b-PP.

• Fibers and Polymers
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• v.7 no.1
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• pp.36-41
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• 2006

PVC and SAN are often mixed to compensate for the disadvantages of each polymer. Miscibility and thermal stability of PVC/SAN blend were investigated in this study by blending SAN polymer having 20, 24, 28, 32 % of acrylonitrile contents. Two polymers were mixed using a melt blending method with a single screw extruder. DSC thermogram was used to evaluate miscibility of the two polymers. SAN having 24 % of acrylonitrile showed the best miscibility with PVC. In order to evaluate degradation behavior, blended polymer was heat treated in DSC furnace and glass transition temperature was measured consecutively. Glass transition temperature increased continuously with annealing time due to degradation and cross-linking of polymer chains. Melt index of blended polymer was always higher than that of PVC.

• Korea-Australia Rheology Journal
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• v.14 no.3
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• pp.121-128
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• 2002

A series of thermoplastic polymers and their blends were melt-processed with high intensity ultrasonic wave in an intensive mixer. For the effective transfer of ultrasonic energy, an experimental apparatus was specially designed so that polymer melt can directly contact with ultrasonic horn. It was observed that significant variations in the rheological properties of polymers occur due to the unique action of ultrasonic wave without any aid of chemical additives. It was also found that the direct sonication on immiscible polymer blends in melt state reduces the domain sizes considerably and stabilizes the phase morphology of the blends. The degree of compatibilization was strongly affected by viscosity ratio of the components and the morphology was stable after annealing in properly compatibilized blends. It is suggested that ultrasound assisted melt mixing can lead to in-situ copolymer formation between the components and consequently provide an effective route to compatibilize immiscible polymer blends.

• Macromolecular Research
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• v.8 no.1
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• pp.34-43
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• 2000

The melt rheology of four binary blends of ethylene 1-octene copolymers (EOCs) which consist of one component by Ziegler-Natta and another by metallocene catalysts, was studied to elucidate miscibility in the melt by using torsion rheometer at 200$\^{C}$ and different shear rates. The four blend systems, designated into the FA+FM, SF+FM, RF+EN, and RF+PL blend, are divided and interpreted based on the melt index (MI), the density and the comonomer contents. The melt viscosity such asη', η", and η$\^$*/ is weight average value if the comonomer contents are similar, otherwise they show different manner. The experimental resole are analyzed based on the Cole-Cole plot of logη' uersus log η", the logarithmic plots of the dynamic storage modulus (G') versus the dynamic loss modulus (G") for various blend compositions, and the melt viscosity of 11', n", and f" as a function of blend compositions. As a cerise-quence, the FA+FM blend is miscible, but the SF+FM, RF+EN, and RF+PL blends are not in the melt. Thus miscibility of the blends studied in this communication is suggested to strongly influence by the comonomer contents rather than the density or the MI.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1025-1029
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• 2003

We studied the cross-sectional profiles of deformed thermoplastics in hot embossing process and compared with melt flow index for various embossing conditions such as embossing temperature, embossing pressure and initial thickness of the thermoplastics. The fastest embossing times for complete penetration of the cavities were obtained at temperature greater than $60^{\circ}C$ above glass transition temperature (Tg). When the melt flow index of polymer is low, the penetration ratio does not become large even if the embossing pressure increases. The complete occupation of the cavities was easier obtained with high melt flow index polymer than low melt flow index polymer at the same process condition. We believe these results can be very useful for optimizing nanostructured hot embossing also known nanoimprinting process conditions.

• Polymer(Korea)
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• v.38 no.4
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• pp.518-524
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• 2014

Electrospinning has gained interests as a polymer processing technique for nanofiber fabrications. It is well known that both polymer solutions and polymer melts can be electrospun. Among them, melt electrospinning is environmentally friendly technique due to the absence of solvent. However, the diameter of melt-electrospun fibers is typically thicker than solution-electrospun fibers. By using a home-made melt-electrospinning device, micron-sized fibers with smooth and even surfaces were electrospun successfully. We demonstrate that low-density polyethylene fibers can be reduced in diameter with a viscosity-reducing additive such as low molecular weight polyethylene monoalcohol and polyethylene wax. The diameter was further reduced by blending it with oxidized polyethylene wax due to polarity increment. Additionally, parameters affecting the diameter were analyzed such as an applied voltage and a spinning distance.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.65-66
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• 2003

Ternary blend fibers (TBFs) based on melt blends of PEN, PET, and TLCP were prepared by melt blending and spinning to achieve high performance fibers. The reinforcement effect and the TLCP fibrillar structure resulted in the improvement of mechanical properties for TBFs. Molecular orientation was an important factor in determining the tensile strength and modulus of TBFs. Another part of this research is silica nano-particle filled PEN composites were melt-blended to improve mechanical and physicalproperties, and processability. The tensile modulus and strength were improved adding silica nano-particles to the PEN. The decreased melt viscosity by the fumed silica resulted in the improvement of the processability. The fumed silica may act as a nucleating agent in the PEN matrix.

• Polymer(Korea)
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• v.37 no.2
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• pp.204-210
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• 2013

Effects of additives (lubricant and antioxidant) and melt-blending condition (temperature, time and rotor speed) on the mechanical properties of polypropylene-based wood polymer composites (WPCs) were investigated. WPCs were prepared by melt-blending followed by compression molding. To understand melt-blending procedure, torque change of the WPC melt-blend was monitored. Maleic anhydride modified PP and nanoclay were used as a compatibilizer and a reinforcing filler, respectively. UTM and izod impact tester were used to measure the mechanical properties of the WPCs and a color-difference meter was used to measure the discoloration of the WPCs according to melt-blending condition. The mechanical properties showed that the optimized melt-blending condition was $170^{\circ}C$, 15 min, and 60 rpm. The mechanical properties of the WPCs decreased with increasing lubricant and antioxidant content. The two step method, adding wood flour later separately during melt-blending, was more effective than the typical one step method for improving the mechanical properties of the WPCs.