Polymeric foams
Mohammad Nourmohammadi; Reza Jahanmardi; Hamid Moeenfard; Gholamhossein Zohuri; Saeed Bazgir
Abstract
Novel EPDM-based polymer foams were prepared using a combination of nanomaterials, namely nano silica, nano clay, and graphene nanoplatelets. In order to achieve optimal acoustic performance, the Taguchi design (TD) technique was applied to reduce the number of experiments and optimize the formulation. ...
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Novel EPDM-based polymer foams were prepared using a combination of nanomaterials, namely nano silica, nano clay, and graphene nanoplatelets. In order to achieve optimal acoustic performance, the Taguchi design (TD) technique was applied to reduce the number of experiments and optimize the formulation. By employing an orthogonal array of L9(34), four controlled factors, including content of the three nanomaterials and the blowing agent (Unicell D200A), were chosen. In practice, the acoustic properties of the nine suggested experiments with TD were examined with an impedance tube, and the signal-to-noise ratio analysis revealed two more optimal formulations for foam composites. Further experiments for the last two formulations compared to the nine Taguchi tests, showed an improvement of 13.04 and 19.68%, respectively, for noise reduction coefficient (NRC) and average transmission loss (ATL). It seemed that the idea of using multiple nanomaterials simultaneously is to be an effective way. Besides, the SEM images of nine samples proved that the smaller cell size of the foam were achieved using the higher concentration of nanoparticles. These findings are in accordance with the acoustic results, as the sample with larger cell size and more open cells (C3) showed higher NRC and the sample with larger cell size and closed cells (B2) showed higher ATL values. To complete the study, some blank samples with zero level or only one type of the nanomaterial were also investigated. Interestingly, the obtained results indicated that the formula should contain more than one type of nanoparticle to achieve a better acoustic performance. Comparing the result obtained in this study for EPDM foam with the same EVA foam in our previous work, it can be seen that EPDM showed an increase of 15.56% in NRC and a slight decrease of 2.5% in ATL. This behavior could be due to the difference in their morphology, in which the EPDM has probably more open cells and thinner cell walls.
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.
Polymeric foams
Hossein Hazrati; Nader Jahanbakhshi; Mohammad Rostamizadeh
Abstract
In this study, the response surface methodology (RSM) based on the central composite design (CCD) was used to optimize the preparation condition of polypropylene-grafted maleic anhydride (PP-g-MA) microporous membrane by thermally-induced phase separation (TIPS) method. A mixture of dibutyl phthalate ...
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In this study, the response surface methodology (RSM) based on the central composite design (CCD) was used to optimize the preparation condition of polypropylene-grafted maleic anhydride (PP-g-MA) microporous membrane by thermally-induced phase separation (TIPS) method. A mixture of dibutyl phthalate (DBP) and dioctyl phthalate (DOP) was used as diluent. The effect of polymer composition and quenching bath temperature on the morphology and performance of the fabricated microporous membranes was investigated by using RSM. Analysis of variance (ANOVA) was used to determine which variables and interactions between variables had a significant effect on our responses. The ANOVA revealed that the bath temperature was the most significant variable associated with porosity and pure water flux responses and the polymer concentration was the most significant variable associated with tensile response. The obtained results also showed that with increasing the polymer concentration and decreasing the quenching bath temperature, the membrane porosity and pure water flux decreased, whereas the membrane tensile increased. The regression equations were reasonably validated and used to predict and optimize the performance of PP-g-MA membranes within the limits of the variables. Finally, the maximum responses (flux of 115.6 L/m2h, porosity of 62% and tensile of 1.6 MPa) were obtained under the following conditions: polymer concentration of 28.5 wt% and temperature of 329 K. Further, comparison of laboratory-made and commercial membranes in a membrane bioreactor (MBR) system showed that the rate of membrane fouling was decreased by 4.2 times.
Polymeric foams
Christophe Daniel; Simona Longo; Gaetano Guerra
Abstract
Monolithic aerogels of high molecular weight polyethylene (Mw= 3x106- 6x106 g/mol) have been prepared by solvent extraction with supercritical carbon dioxide from thermoreversible gels prepared in decalin. These low density and highly porous aerogels present an apparent porosity up to 90%. The aerogel ...
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Monolithic aerogels of high molecular weight polyethylene (Mw= 3x106- 6x106 g/mol) have been prepared by solvent extraction with supercritical carbon dioxide from thermoreversible gels prepared in decalin. These low density and highly porous aerogels present an apparent porosity up to 90%. The aerogel morphology observed by scanning electron microscopy (SEM) is characterized by spherulitic structures being interconnected by fibers. X-ray diffraction experiments show that PE aerogels are highly crystalline with a degree of crystallinity of c.a. 80% and PE chains being packed into the typical orthorombic unit cell. Combined SEM and N2 sorption investigations show that PE aerogels are essentially macroporous with a small amount of mesopores. The oil-sorption performance of polyethylene aerogels has been also evaluated in this study in order to assess a possible use of these materials for oil spillage recovery and results show that aerogel macropores allow a very fast sorption kinetics with a 100% oil weight uptake obtained in less than 1 minute.
Characterization
Ning Zhao; Ruihua Cheng; Qi Dong; Xuelian He; Zhen Liu; Shiliang Zhang; Minoru Terano; Boping Liu
Abstract
SiO2-supported silyl chromate catalyst is an important industrial catalyst for production of high grade HDPE pipe materials. The control of the short chain branch (SCB) distribution using this catalyst system is still a great challenge. In this work, ethylene and 1-hexene copolymers were synthesized ...
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SiO2-supported silyl chromate catalyst is an important industrial catalyst for production of high grade HDPE pipe materials. The control of the short chain branch (SCB) distribution using this catalyst system is still a great challenge. In this work, ethylene and 1-hexene copolymers were synthesized using SiO2-supported silyl chromate catalyst combined with triisobutylaluminium (TIBA), triethylaluminium (TEA) and mixed TIBA/TEA at molar ratio 1:1 (TIBA/TEA/1:1) as three different Al-alkyl co-catalysts.The temperature rising elution fractionation (TREF) and successive self-nucleation and annealing (SSA, by DSC) methods were combined to analyze the short chain branch distribution (SCBD) of these ethylene/1-hexene copolymers. The results showed that different types of co-catalyst had a great influence on SCBD of ethylene/1-hexene copolymers. The copolymer produced with TIBA showed better SCBD than the copolymer produced with TEA, and the copolymer produced with TIBA/ TEA/1:1 showed a SCBD in between those with TIBA and TEA.
