• Macromolecular Research
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• v.16 no.1
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• pp.6-14
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• 2008

Polypropylene (PP)-layered silicate nanocomposites were developed using a new processing method involving a supercritical carbon dioxide ($scCO_2$)-assisted co-rotating twin-screw extrusion process. The nanocomposites were prepared through two step extrusion processes. In the first step, the PP/clay mixture was extruded with $CO_2$ injected into the barrel of the extruder and the resulting foamed extrudate was cooled and pelletized. In the second step, the foamed extrudate was extruded with venting to produce the final PP/clay nanocomposites without $CO_2$. In this study, organophilic-clay and polypropylene matrix were used. Maleic anhydride grafted polypropylene (PP-g-MA) was used as a compatibilizer. This study focused on the effect of $scCO_2$ on the dispersion characteristics of the clays into a PP matrix and the rheological properties of the layered silicate based PP nanocomposites. The dispersion properties of clays in the nanocomposites as well as the rheological properties of the nanocomposites were examined as a function of the PP-g-MA concentration. The degree of dispersion of the clays in the nanocomposites was analyzed by X-ray diffraction and transmission electron microscope. Various rheological properties of the nanocomposites were measured using a rotational rheometer. In the experimental results, the $scCO_2$ assisted continuous manufacturing extrusion system was used to successfully produce the organophilic-clay filled PP nanocomposites. It was found that $scCO_2$ had a measurable effect on the clay dispersion in the polymer matrix and the melt intercalation of a polymer into clay layers.

• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.86-92
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• 1998

Homegeneous feedstock is necessary to make plastic magents with uniform magnetic properties, therefore the optrimized mixing route and the homogeneity evaluation method are demanded. In this paper, method of homogeneity evaluation and effect of homogeneity on the magnetic prperites were investigated using Sr-ferrite /EVA plastic magnets. The feedstocks with different homogeneity were prepared using batch mixer and single screw extruder. The homogeneities of feedstocks were tested by torgue sensor, capilary rheometer, and measurement of magnetic properties. Mixing torque measurement using torque sensor was an effective method to determine the critical powder loading, but it was nor suitable to suitable to determine the feedstock mixing quality. Particle alignment measurement of a plastic magent was very accurate to evaluate the homogeneity, but expensive equipments were required to make and measure the samples. Pressure measurement using capillary rheometer was a very effective and easy method with high accuracy. Homogeneous feedstock increased the particle alignment of plastic magnet. Remanet flux density and maximum energy product increased linearly and quadratically with increasing particle alignment, respectively.

• Elastomers and Composites
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• v.45 no.2
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• pp.129-136
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• 2010

In this work, PLLA/EGMA blends were prepared by melt blending of biodegradable Poly-L-lactic acid(PLLA) with Poly(ethylene-co-glycidyl methacrylate)(EGMA) and Engage as impact modifiers by twin screw extruder. Blend compositions of PLLA/Impact modifier blends were 100/0, 75/25, 50/50, 25/75 and 0/100, respectively. Also, Talc was added to 3 PLLA rich phases on PLLA/EGMA blends. The morphology, viscoelastic/mechanical properties were characterized by FESEM, DMA, UTM and Izod impact tester. DMA and Izod impact test data showed that storage modulus at room temperature with increasing EGMA and Engage contents decreased, and impact strength increased. However, storage modulus at room temperature increased by adding talc. From FESEM image, we observed that domain phase was well dispersed into matrix. Although the tensile strength and flexural modulus were decreased with increasing the content of EGMA and Engage in them, they could be supplemented by adding talc.

• Composites Research
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• v.26 no.3
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• pp.170-174
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• 2013

Atmospheric glow plasma polymerization was applied to wood powder before fabricating polypropylene (PP) matrix composites. Seven different types of monomers (Oxygen, Benzene, CH4, Acrylic-acid, Hexafluoroethane, Trifluorotolune, Hexamethyl-disiloxane) were analyzed to determine the most suitable precursor for plasma polymerization. The surface energy was calculated from measured contact angle about each monomer on PP. Hexamethyl-disiloxane (HMDSO) had a highest surface energy and is selected as the most suitable monomer. Wood powder and polypropylene were mixed as pellets by twin screw extruder and then 50 wt% wood powder/PP composites were produced by an injection machine. Tensile strength and Flexural strength have improved by 7.59% and 12.43% at the maximum respectively. SEM (Scanning Electron Microscope) observation on the fracture surface revealed that the plasma polymerization have improved the interfacial bonding and the mechanical properties of the composites.

• Polymer(Korea)
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• v.37 no.4
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• pp.500-506
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• 2013

The effect of compatibilizer types on the properties of polyphenylene sulfide (PPS)/polyethylene terephthalate (PET) blends was investigated. The blends were extruded by a single screw extruder attached with a Maddock mixing zone and their molded properties were examined. As a basic blend composition, a linear PPS/PET (40/60) blend was selected based on cost efficiency. Three types of compatibilizer, SEBS, modified SEBS, and modified PS were added to the basic blend to improve the properties. The thermal, rheological, mechanical properties and the morphology of the ternary blends were analyzed. The maximum mechanical properties of blends was found at 1 phr of m-SEBS or m-PS content, whose values were almost the same as the theoretical values of miscible blend system. It seemed to by the case that the partial reaction between compatibilizer and the basic blend caused the enhancement of compatibility between linear PPS and PET phases. These ternary blends would be applicable as economic linear PPS alloys.

• Elastomers and Composites
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• v.41 no.3
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• pp.172-181
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• 2006

Flame retardant synergism of phyllite was studied in ABS resins containing brominated flame retardant(tetrabromobisphenol A(TBBA) or brominated epoxy oligomer(BEO)) and antimony trioxide($Sb_2O_3)$. Talc was used for the comparison purpose. ABS compounds were manufactured by a twin-screw co-rotating extruder and subsequently injection molded into several specimen for mechanical and thermal properties. Flame retardancy of ABS compounds measured by UL 94 vertical test with 1.6 mm thick bar specimen was enhanced by the replacement of antimony trioxide into phyllite or talc in the range of 12.5%(0.5 wt%) to 37.5%(1.5 wt%). Phyllite showed better synergistic effect comparing with talc especially for BEO. Only phyllite enhanced the flowability of ABS compounds. Notched Izod impact strength decreased with the proportion of phyllite or talc content. Phyllite could replace the antimony trioxide up to the content of 25%(1 wt%) to give better flame retardancy and flowability without darkening problem.

• Journal of Adhesion and Interface
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• v.2 no.4
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• pp.24-31
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• 2001

Polypropylenes(PP) with different melt index values were mixed with ethylene-propylene rubber(EPR) or ethylene-propylene diene monomer rubber(EPDM) and an ethylene copolymer containing carboxylic acid group in a twin screw extruder. Then test specimens were prepared from the pellets of the blends with an injection molding machine. The mechanical properties and morphology of fractured surfaces were measured. Relative peak intensities of carboxylic acid group on the specimen surface were measured with an attennuated total reflection infrared spectrometer (ATR-IR) and compared with each other. The blend specimens were found to have the gradient morphology of rubber domains in PP matrix in the core region and PP skin layer. The blends containing PP of higher melt index showed greater content of ethylene copolymer containing carboxylic acid on the surface when the relative peak intensities of ATR-IR for carboxylic acid were compared. As the melt index values were increased, the decrease tendency in mechanical propeties such as tensile strength and impact strength was more significant for PP/EPR blends than PP/EPDM blends.

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.78-83
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• 2012

In this study, some experimental results of the peroxide-degradation process of polypropylene(PP) in a co-rotating twin-screw extruder to produce controlled rheology polypropylene(CRPP) are presented. The peroxide was dicumyl peroxide(DCP) and the concentration of DCP was in the range 0-0.3 wt%. It was found that the rheological properties of PP change significantly during reactive extrusion. Melt flow index(MFI) increased with DCP concentration. Intrinsic viscosity decreases with increasing DCP concentration. From dynamic rheological data, number average molecular weight(Mn), weight average molecular weight(Mn) and molecular weight distribution(MWD) were calculated. Results indicated that Mw decreases and MWD becomes narrower with increasing peroxide concentration. Especially, particle size distribution of CRPP decreases with increasing DCP concentration by chemical powdering process, and anti-slip floor paint, CRPP(DCP 0.2 wt%) powder by 10phr was friction coefficient 2.15 ${\mu}$, abrasion resistance 511.18%.

• Polymer(Korea)
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• v.37 no.6
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• pp.770-776
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• 2013

The ENR 50 having the lowest gas permeability was blended with Nylon 6 which exhibits superior gas permeability, excellent wear resistance by using a twin-screw extruder. The blended materials showed the increased gas barrier property and physical properties, but did not yield a great synergistic effect due to low dispersion of Nylon 6 to ENR 50. To improve dispersion of Nylon 6 in the rubber matrix, maleic anhydride (MAH) was grafted to ENR 50. The grafting reaction between MAH and ENR 50 was evidenced using IR spectroscopy. The grafted and blended materials, ENR 50- g-MAH/Nylon 6 compounds, resulted in an enhanced gas barrier property and physical properties compared with compounds without MAH. The compound at 5 phr of MAH showed the highest crosslinking density and the best performances.

• Journal of Adhesion and Interface
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• v.15 no.1
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• pp.14-21
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• 2014

In the present work, PLA/PBS blends with poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) at different contents were processed by using a twin-screw extruder and an injection molding machine, and then their mechanical, thermal and morphological properties were investigated. The mechanical properties such as flexural strength, flexural modulus, tensile strength and tensile modulus and thermal properties such as melting behavior, dynamic mechanical thermal properties and thermal stability significantly depended on the contents of PLA and PBS. However, the heat deflection temperature of the blends was not significantly influenced by the contents of PLA and PBS. Also, the fracture surfaces of PLA/PBS blends were changed from a brittle pattern to a ductile pattern with increasing the PBS contents.