Composites and nanocomposites
Negin Sadat Jalili; Bahereh T. Marouf; Ali Bakhshi-Zadeh; Reza Bagheri
Abstract
The aim of the current study was to first make two compatibilizers, i.e., maleic anhydride grafted polypropylene (PP-g-MA), based on a homo-and a block copolymer. Then, these custom made compatibilizers were incorporated in PP/nanoclay composites made via direct and two-step masterbatch techniques. The ...
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The aim of the current study was to first make two compatibilizers, i.e., maleic anhydride grafted polypropylene (PP-g-MA), based on a homo-and a block copolymer. Then, these custom made compatibilizers were incorporated in PP/nanoclay composites made via direct and two-step masterbatch techniques. The influence of compatibilizer/nanoclay ratio was examined in the direct method. In the two-step processing technique, the compatibilizer content was divided to two parts such that the first part was used when making the masterbatch and the second part was incorporated in the second step when the masterbatch was diluted by the polymer matrix. The characterizations via titration test and Fourier-transform infrared (FTIR) spectroscopy revealed a higher degree of grafting reaction when homo-polymer was used for synthesizing PP-g-MA. In the next step, nanocomposites containing 3 wt.% nanoclay with three different PP-g-MA (both types)/nanoclay ratios of 1:1, 2:1, and 3:1 were made using a co-rotating twin screw extruder. X-ray diffraction (XRD) analysis was done to evaluate morphology and tensile and impact, and tests were performed to evaluate the mechanical properties of the PP samples. Based on the results, maleic anhydride grafted homo-polypropylene (HPP-g-MA) and the composition containing HPP-g-MA/nanoclay ratio of 2:1 with 7.69% improvement in Young’s modulus was reported as the recommended compatibilizer and ratio for applications. Finally, five nanocomposite samples with identical composition were made in two steps. A masterbatch containing 15 wt.% nanoclay was made first and then, it was diluted with PP to reduce the nanoclay content to 3 wt.%. All samples containing 6 wt.% PP-g-MA, but the method of addition of compatibilizer was different. In one sample, the whole compatibilizer was added into the masterbatch. In another sample, the entire PP-g-MA was added in the second stage of compounding. In the other three samples, the addition of compatibilizer was divided between the two stages of the process. The results of the study showed that the highest improvement of elastic modulus (24.26%) was obtained when the majority of the compatibilizer was added in the second step of production. This was associated with the best dispersion of nanoclay platelets in the PP matrix.
Polymeric foams
Saeed Karimzadeh; Taher Azdast; Rezgar Hasanzadeh; Milad Moradian; Hamidreza Akrami
Abstract
Rotational molding is a process used to produce seamless, one-piece, and hollow polymeric parts. Foam rotational molding has recently become an increasingly important process in the foam industry. However, foam rotational molding is still a challenging process to fabricate polymeric foams. The focus ...
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Rotational molding is a process used to produce seamless, one-piece, and hollow polymeric parts. Foam rotational molding has recently become an increasingly important process in the foam industry. However, foam rotational molding is still a challenging process to fabricate polymeric foams. The focus of this manuscript was to assess the effect of material parameters on the foam properties of samples produced by rotational molding. Rotational molding experiments were performed on a laboratory-scale two-axis rotational machine, designed and manufactured by the authors. The effects of microtalc as nucleating agent, nanoclay as reinforcing agent, and their synergetic effect were investigated on the cell density, cell size, and expansion ratio of hybrid microtalc/nanoclay polyethylene nanocomposites. The cell density was improved by 96% and 89% by addition of 1 wt% of microtalc and nanoclay, respectively, compared to pure polyethylene foams. The cell size was reduced by 20% and 17.5% in 1 wt% of microtalc and nanoclay, respectively. However, the synergetic effect of using both microtalc and nanoclay at 1 wt% was more significant compared to their individual effects. The cell density was enhanced by 313% and the cell size was decreased by 35% compared to pure samples.
Catalysis
Alikhani Ali; Shokoufeh Hakim; Mehdi Nekoomanesh
Abstract
This study presents methods for treating a kind of nanoclay and investigates the effects of methylaluminoxane (MAO) exposure time and or dodecylamine (DDA) reflux time on in-situ polymerization of ethylene in the presence of nanoclay and examines the morphology and properties of the prepared polyethylene/clay ...
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This study presents methods for treating a kind of nanoclay and investigates the effects of methylaluminoxane (MAO) exposure time and or dodecylamine (DDA) reflux time on in-situ polymerization of ethylene in the presence of nanoclay and examines the morphology and properties of the prepared polyethylene/clay nanocomposites. The results revealed that by increasing MAO exposure time productivity decreased. Modification of nanoclay by NH3/MAO led to formation of exfoliated structures. In treatment with NH3/DDA, the change in reflux time resulted in different structures. SEM demonstrated that the morphology of the nanocomposites strongly depended on the modification method and treatment time. Dynamic mechanical analysis indicated that the elastic modulus of the nanocomposites increased by increasing MAO exposure time. The nanocomposites treated with different MAO exposure times showed similar thermal degradation behavior. The nanocomposite modified under the condition of 24 h DDA reflux time indicated the lowest thermal decomposition temperature due to poor dispersion of nanoclay in the synthesized nanocomposite. The nanocomposites modified by NH3/MAO had higher degree of crystallinity compared to those modified by NH3/DDA, which could be attributed to the difference in dispersion level of the modified clays. A relationship between the rheological properties, weight fraction and dispersion of modified nanoclay was observed. The findings showed that the modification condition had a significant influence on the morphology and properties of the synthesized nanocomposites.
