- Email: [email protected]
film structure poly (ethylene-co-octene) foam materials and its sound absorption properties
Materials Letters 139 (2015) 275–278
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Preparation of a new foam/film structure poly (ethylene-co-octene) foam materials and its sound absorption properties Tianbao Zhao a, Mingtao Yang a, Hong Wu a,n, Shaoyun Guo a,nn, Xiaojie Sun b, Wenbin Liang b a b
The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China National Institute of Clean-and-Low-Carbon Energy, Beijing, People’s Republic of China
art ic l e i nf o
a b s t r a c t
Article history: Received 10 May 2014 Accepted 11 October 2014 Available online 22 October 2014
Poly (ethylene-co-octene) foaming materials with alternating multilayered structure were successfully prepared through multilayer co-extrusion. Poly (ethylene-co-octene) was micro-crosslinked and fully cured before and after the foaming process with co-extrusion. The effects of the layer number on foam morphology and density of poly (ethylene-co-octene) foaming materials were investigated. It was found that with increasing the layer number, the cell size was reduced while the density was not obviously changed. Meanwhile, this technique provided the new idea to obtain the poly (ethylene-co-octene) foaming material with excellent sound absorption. The results indicated that the foam/film alternating multilayered structure could improve the sound absorption efficiency of the foaming sheet, which was increased with increasing the layer number and decreasing of cell size. & 2014 Elsevier B.V. All rights reserved.
Keywords: Multilayer structure Porosity Polymers POE Foam Sound absorption
1. Introduction Polymer foams were comprised of gas pore surrounded by a continuous solid phase so that the sound waves could be absorbed. It was widely used as sound absorbing materials in noise control engineering due to the good sound absorption performance [1–3]. Meanwhile, researches show that the sound absorption efficiency was dependent on the foam density, cell microstructure such as cell size, shape and type (open or close) and solid polymer properties [4–6]. Moreover, Olek reported that four factors were related to the sound absorption and the followings were included: (1) the porosity of surface layer, (2) airflow resistance of surface layer, (3) the curvature of the pore connectivity, and (4) the thickness of the porous layer [7]. The foam structure among these factors was most important to the sound absorption efficiency. In other words, the polymer foams with the small cell size, more uniform cell distribution had better sound absorption efficiency. It was well known that the foam structure was strongly dependent on the preparation methods and foaming techniques [8–11]. Generally, the most of polymer foams were prepared through injection molding and extrusion [12,13]. However, the most cells in polymer foams were uneven and disordered in the two-dimensional or three-dimensional
space. As our understanding of foams advances, the foam structure became one of increasingly important control parameters. Excellent control for the foam structure was provided by using cell designing and ordered foams. These foams were special due to their tendency to self-order into periodic structures under gravity or confinement, resulting in excellent properties such as mechanical properties, thermal insulation, sound absorption, etc. [14–16]. At present, ordered foams could be generated by the bubbling technique or self-assembly methods [2,17–19]. However, it was limited to the foaming liquid or block polymer and could not be applied in the injection molding and extrusion foaming. We found the multilayer co-extrusion technology provided a new method for preparing ordered foaming materials by the introduction of foam layer/film layer alternating multilayered structure and this foam structure could improve the sound absorption efficiency of the foaming sheet. In this paper, the poly (ethylene-co-octene) (POE) foaming sheet with the alternating multilayered structure was prepared through multilayer coextrusion technology. The foam structure and sound absorption for POE foaming sheets were investigated.
2. Material and methods n
Corresponding author. Tel.: þ 86 28 85466077. nn Corresponding author. Tel.: þ 86 28 85405135. E-mail addresses: [email protected] (H. Wu), [email protected] (S. Guo). http://dx.doi.org/10.1016/j.matlet.2014.10.061 0167-577X/& 2014 Elsevier B.V. All rights reserved.
POE (ENGAGETM 8150) containing 25 wt% co-monomer was supplied by Dow Chemical Company (USA). Talc was purchased from Guangxi Longguang Talc Development Co., Ltd. (China).
276
T. Zhao et al. / Materials Letters 139 (2015) 275–278
Azodicarbonamide (AC) and dicumyl peroxide (DCP) was purchased from Chengdu Kelong Chemical Reagent Factory (China). 100 phr POE, 0.3 phr DCP, 0.5 phr AC, 1 phr Talc and 0.5 phr white oil was mixed by a high-speed mixer. Then, the composites were mixed through twin screw extrusion at 150 1C as the foaming layers materials. Meanwhile, the composite with 100 phr POE, 0.2 phr DCP and 0.5 phr white oil was also prepared through process as the film layers materials. A multilayer co-extrusion system (as Fig. 1) contained two extruders, feed block, multiplying elements, water chill block, and haulage dram. An assembly of n multiplying elements produced 2(n þ 1) layers [20] and was used to co-extrude the POE foaming sheets with alternating multilayered structure (as Fig. 2). Two extruders contained POE foaming materials and POE film materials, respectively. After merging in the two-component feedblock, two kinds of the melts were formed into multiplying element by using the 0, 2, 3 multipliers. The temperatures from the hopper to the exit of the extruder were set at 120, 190, 200 and 190 1C, respectively. The temperature of multiplying element was 180 1C. Exit die was maintained at a colder temperature (160 1C) in order to create a pressure drop. A nip roll set-up was used as a sheet take-off. The prepared foaming sheets were measured and weighed to calculate densities. Scanning electron microscope (SEM) was used to examine the foam structure. It is a Hitachi S3400 þEDY SEM (Japan) at an accelerating voltage of 20 kV. All specimens were sputtered with gold.
Fig. 1. Schematic of alternate multilayer co-extrusion system (A, B-extruder, C-connector, D-co-extrusion block, E-multiplying elements, F-die).
3. Results and discussion The foaming process of multilayered co-extrusion could be divided into three stages; nucleation, bubble growth and stabilization stages [21]. As the chemical blowing agent decomposes in the extruder, the gas was released and mixed with POE melt. If the amount of the released gas was below the estimated solubility limit, then the released gas was totally dissolved in the POE melt, indicating that no nucleation took place in the extruder or in the multiplying element. The alternating multilayered sheet experienced a pressure drop when it exited the die. Therefore, the dissolved gas started to nucleate in the form of bubbles. The bubbles grew as more gas diffused into the bubbles. Then, a nip roll set-up at room temperature was used to cool the foaming sheet. Meanwhile, the bubbles growth was stabilized. The morphology of monolayer foaming sheet was shown in Fig. 3a. The cell is too large and have plenty perforation. It was ascribed to the free growth of the cell during the extrusion and a lot of bubble coalescence. The morphology of the foam/film foaming sheet with 8 layers and 16 layers was shown in Fig. 3b and c. By foaming process of multilayered co-extrusion, the foaming space in each layer was reduced with increasing the layer number since the thickness of the sheet is constant. The growth of the cell was confined due to the decreased thickness of each layer. The cell size was reduced considerably (as Fig. 4). The isotropic cell morphology was observed. The cell distribution was changed from disorder to order by increasing the layer number. Meanwhile, the reduction of the cell size was attributed to the enhanced nucleation and/or the suppressed cell coalescence under the confinement of alternating multilayered structure. It has been observed that the cells with small size were obtained when the foaming took place under geometrical confinement between two impermeable plates. The density of monolayer foaming sheets and the foam/film foaming sheet with 8 layers and 16 layers were 0.624 g/cm3, 0.630 g/cm3, 0.634 g/cm3, respectively. The density of foaming sheet was not obviously changed with increasing the layer number, since the density of foaming sheet was governed by the total amount of gas released in the system. However, the foaming materials with small cell size had the greater surface area for gas and resin. This phenomenon and alternating multilayered structure were beneficial to sound absorption. Generally, the sound wave was reflected by the interface and absorbed by the foaming materials. The effect of alternating multilayered structure on sound absorption efficiency of the
Fig. 2. Schematic of monolayer foaming sheet, 8 layers foam/film foaming sheet and 16 layers foam/film foaming sheet.
T. Zhao et al. / Materials Letters 139 (2015) 275–278
277
Fig. 3. The cell morphology of monolayer POE foaming sheet (a), 8 layers foam/film POE foaming sheet (b) and 16 layers foam/film POE foaming sheet (c).
The absorption mechanism can be summed up in the resonance absorption and the interface dissipation. When the sound wave propagates in the foaming sheet with alternating multilayered structure, more reflection and friction loss happened due to more interfaces with increasing the layer number and the acoustic impedance of adjacent layers, and then the sound absorption performance could be improved. Meanwhile, the high frequency wave, which had lower wavelength, was easily dissipated by more interfaces and the cells with small size. Therefore, the sound absorption peaks appeared in the high frequency with increasing the layer number.
4. Conclusions
Fig. 4. The cell distribution of POE foaming sheets with various layers.
The POE foam/film foaming sheet with high sound absorption coefficient in alternating multilayered structure was successfully prepared through multilayer co-extrusion system. The foam morphology with alternating multilayered structure was better than with the monolayer. This technique provided the new idea to obtain structure–foaming material with high sound absorption. The foam/film alternating multilayered structure could be improved the sound absorption efficiency due to more reflection and friction loss of sound in layer interface and the wall of cells. Meanwhile, the sound absorption efficiency of the foam/film foaming sheet with alternating multilayered structure increased with increasing of layer number and decreasing of cell size.
Acknowledgements
Fig. 5. Effect of layer number on sound absorption efficiency of POE foaming sheets with various layers.
Financial supports of the National Natural Science Foundation of China (51273132, 51227802 and 51121001), Program for New Century Excellent Talents in University (NCET-13-0392) and National Institute of Clean-and-Low-Carbon Energy are gratefully acknowledged. References
foaming sheet and the foam/film foaming sheets was investigated (as Fig. 5). The sound absorption efficiency of POE foaming sheet should be influenced by the acoustic impedance of adjacent layers and cell size. As excitated by sound wave, the air molecule in hole of foaming layer would be vibrated intensively. The vibration produced a strong energy exchange results in more sound energies were consumed. Furthermore, the sound absorption efficiency of the POE foaming sheet with alternating multilayered structure increased with increasing of layer number and decreasing of cell size. The small size cells have more surface area and the more layers have more interface, this factors could dissipate the sound wave and improved the sound adsorption efficiency of materials.
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Arenas JP, Crocker MJ. Sound Vib 2010;44:12–8. Drenckhan W, Langevin D. Curr Opin Colloid Interface Sci 2010;15:341–58. Rey RD, Alba J, Arenas JP, Sanchis VJ. Appl Acoust 2012;73:604–9. Najib NN, Ariff ZM, Bakar AA, Sipaut CS. Mater Des 2011;32:505–11. Zhai W, Yu J, He J. Polymer 2008;49:2430–4. Attenborough KJ. Acoust Soc Am 1983;73:785–99. Olek J, Weiss WJ, Neithalath N. Final Report; 2004. SQDH2004-2. Lin JH, Lin CM, Huang CC, Lin CC, Hsieh CT, Liao YC. J Compos Mater 2011;45:1355–62. Reverchon E, Cardea S. J Supercrit Fluids 2007;40:144–52. Stafford CM, Russell TP, McCarthy TJ. Macromolecules 1999;32:7610–6. Liao R, Yu W, Zhou C. Polymer 2010;51:6334–45. Kaewmesri W, Lee PC, Park CB, Pumchusak J. J Cell Plast 2006;42:405–28. Chang YW, Lee D, Bae SY. Polym Int 2006;55:184–9.
278
[14] [15] [16] [17] [18]
T. Zhao et al. / Materials Letters 139 (2015) 275–278
Ranade AP, Hiltner A, Baer E, Bland DG. J Cell Plast 2004;40:497–507. Gupta N. Mater Lett 2007;61:979–82. Song L, Lu A, Feng P, Lu Z. Mater Lett 2014;121:126–8. Olson DA, Chen L, Hillmyer MA. Chem Mater 2007;20:869–90. Zavala-Rivera P, Channon K, Nguyen V, Sivaniah E, Kabra D, Friend RH. Nat Mater 2012;11:53–7.
[19] Theato P, Ungar G. Nat Mater 2012;11:16–7. [20] Xu S, Wen M, Li J, Gao SY. Polymer 2008;49:4861–70. [21] Lee ST. Foam extrusion: principles and practice. Boca Raton, Florida: CRC Press; 2002.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Preparation of a new foam/film structure poly (ethylene-co-octene) foam materials and its sound absorption properties Tianbao Zhao a, Mingtao Yang a, Hong Wu a,n, Shaoyun Guo a,nn, Xiaojie Sun b, Wenbin Liang b a b
The State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China National Institute of Clean-and-Low-Carbon Energy, Beijing, People’s Republic of China
art ic l e i nf o
a b s t r a c t
Article history: Received 10 May 2014 Accepted 11 October 2014 Available online 22 October 2014
Poly (ethylene-co-octene) foaming materials with alternating multilayered structure were successfully prepared through multilayer co-extrusion. Poly (ethylene-co-octene) was micro-crosslinked and fully cured before and after the foaming process with co-extrusion. The effects of the layer number on foam morphology and density of poly (ethylene-co-octene) foaming materials were investigated. It was found that with increasing the layer number, the cell size was reduced while the density was not obviously changed. Meanwhile, this technique provided the new idea to obtain the poly (ethylene-co-octene) foaming material with excellent sound absorption. The results indicated that the foam/film alternating multilayered structure could improve the sound absorption efficiency of the foaming sheet, which was increased with increasing the layer number and decreasing of cell size. & 2014 Elsevier B.V. All rights reserved.
Keywords: Multilayer structure Porosity Polymers POE Foam Sound absorption
1. Introduction Polymer foams were comprised of gas pore surrounded by a continuous solid phase so that the sound waves could be absorbed. It was widely used as sound absorbing materials in noise control engineering due to the good sound absorption performance [1–3]. Meanwhile, researches show that the sound absorption efficiency was dependent on the foam density, cell microstructure such as cell size, shape and type (open or close) and solid polymer properties [4–6]. Moreover, Olek reported that four factors were related to the sound absorption and the followings were included: (1) the porosity of surface layer, (2) airflow resistance of surface layer, (3) the curvature of the pore connectivity, and (4) the thickness of the porous layer [7]. The foam structure among these factors was most important to the sound absorption efficiency. In other words, the polymer foams with the small cell size, more uniform cell distribution had better sound absorption efficiency. It was well known that the foam structure was strongly dependent on the preparation methods and foaming techniques [8–11]. Generally, the most of polymer foams were prepared through injection molding and extrusion [12,13]. However, the most cells in polymer foams were uneven and disordered in the two-dimensional or three-dimensional
space. As our understanding of foams advances, the foam structure became one of increasingly important control parameters. Excellent control for the foam structure was provided by using cell designing and ordered foams. These foams were special due to their tendency to self-order into periodic structures under gravity or confinement, resulting in excellent properties such as mechanical properties, thermal insulation, sound absorption, etc. [14–16]. At present, ordered foams could be generated by the bubbling technique or self-assembly methods [2,17–19]. However, it was limited to the foaming liquid or block polymer and could not be applied in the injection molding and extrusion foaming. We found the multilayer co-extrusion technology provided a new method for preparing ordered foaming materials by the introduction of foam layer/film layer alternating multilayered structure and this foam structure could improve the sound absorption efficiency of the foaming sheet. In this paper, the poly (ethylene-co-octene) (POE) foaming sheet with the alternating multilayered structure was prepared through multilayer coextrusion technology. The foam structure and sound absorption for POE foaming sheets were investigated.
2. Material and methods n
Corresponding author. Tel.: þ 86 28 85466077. nn Corresponding author. Tel.: þ 86 28 85405135. E-mail addresses: [email protected] (H. Wu), [email protected] (S. Guo). http://dx.doi.org/10.1016/j.matlet.2014.10.061 0167-577X/& 2014 Elsevier B.V. All rights reserved.
POE (ENGAGETM 8150) containing 25 wt% co-monomer was supplied by Dow Chemical Company (USA). Talc was purchased from Guangxi Longguang Talc Development Co., Ltd. (China).
276
T. Zhao et al. / Materials Letters 139 (2015) 275–278
Azodicarbonamide (AC) and dicumyl peroxide (DCP) was purchased from Chengdu Kelong Chemical Reagent Factory (China). 100 phr POE, 0.3 phr DCP, 0.5 phr AC, 1 phr Talc and 0.5 phr white oil was mixed by a high-speed mixer. Then, the composites were mixed through twin screw extrusion at 150 1C as the foaming layers materials. Meanwhile, the composite with 100 phr POE, 0.2 phr DCP and 0.5 phr white oil was also prepared through process as the film layers materials. A multilayer co-extrusion system (as Fig. 1) contained two extruders, feed block, multiplying elements, water chill block, and haulage dram. An assembly of n multiplying elements produced 2(n þ 1) layers [20] and was used to co-extrude the POE foaming sheets with alternating multilayered structure (as Fig. 2). Two extruders contained POE foaming materials and POE film materials, respectively. After merging in the two-component feedblock, two kinds of the melts were formed into multiplying element by using the 0, 2, 3 multipliers. The temperatures from the hopper to the exit of the extruder were set at 120, 190, 200 and 190 1C, respectively. The temperature of multiplying element was 180 1C. Exit die was maintained at a colder temperature (160 1C) in order to create a pressure drop. A nip roll set-up was used as a sheet take-off. The prepared foaming sheets were measured and weighed to calculate densities. Scanning electron microscope (SEM) was used to examine the foam structure. It is a Hitachi S3400 þEDY SEM (Japan) at an accelerating voltage of 20 kV. All specimens were sputtered with gold.
Fig. 1. Schematic of alternate multilayer co-extrusion system (A, B-extruder, C-connector, D-co-extrusion block, E-multiplying elements, F-die).
3. Results and discussion The foaming process of multilayered co-extrusion could be divided into three stages; nucleation, bubble growth and stabilization stages [21]. As the chemical blowing agent decomposes in the extruder, the gas was released and mixed with POE melt. If the amount of the released gas was below the estimated solubility limit, then the released gas was totally dissolved in the POE melt, indicating that no nucleation took place in the extruder or in the multiplying element. The alternating multilayered sheet experienced a pressure drop when it exited the die. Therefore, the dissolved gas started to nucleate in the form of bubbles. The bubbles grew as more gas diffused into the bubbles. Then, a nip roll set-up at room temperature was used to cool the foaming sheet. Meanwhile, the bubbles growth was stabilized. The morphology of monolayer foaming sheet was shown in Fig. 3a. The cell is too large and have plenty perforation. It was ascribed to the free growth of the cell during the extrusion and a lot of bubble coalescence. The morphology of the foam/film foaming sheet with 8 layers and 16 layers was shown in Fig. 3b and c. By foaming process of multilayered co-extrusion, the foaming space in each layer was reduced with increasing the layer number since the thickness of the sheet is constant. The growth of the cell was confined due to the decreased thickness of each layer. The cell size was reduced considerably (as Fig. 4). The isotropic cell morphology was observed. The cell distribution was changed from disorder to order by increasing the layer number. Meanwhile, the reduction of the cell size was attributed to the enhanced nucleation and/or the suppressed cell coalescence under the confinement of alternating multilayered structure. It has been observed that the cells with small size were obtained when the foaming took place under geometrical confinement between two impermeable plates. The density of monolayer foaming sheets and the foam/film foaming sheet with 8 layers and 16 layers were 0.624 g/cm3, 0.630 g/cm3, 0.634 g/cm3, respectively. The density of foaming sheet was not obviously changed with increasing the layer number, since the density of foaming sheet was governed by the total amount of gas released in the system. However, the foaming materials with small cell size had the greater surface area for gas and resin. This phenomenon and alternating multilayered structure were beneficial to sound absorption. Generally, the sound wave was reflected by the interface and absorbed by the foaming materials. The effect of alternating multilayered structure on sound absorption efficiency of the
Fig. 2. Schematic of monolayer foaming sheet, 8 layers foam/film foaming sheet and 16 layers foam/film foaming sheet.
T. Zhao et al. / Materials Letters 139 (2015) 275–278
277
Fig. 3. The cell morphology of monolayer POE foaming sheet (a), 8 layers foam/film POE foaming sheet (b) and 16 layers foam/film POE foaming sheet (c).
The absorption mechanism can be summed up in the resonance absorption and the interface dissipation. When the sound wave propagates in the foaming sheet with alternating multilayered structure, more reflection and friction loss happened due to more interfaces with increasing the layer number and the acoustic impedance of adjacent layers, and then the sound absorption performance could be improved. Meanwhile, the high frequency wave, which had lower wavelength, was easily dissipated by more interfaces and the cells with small size. Therefore, the sound absorption peaks appeared in the high frequency with increasing the layer number.
4. Conclusions
Fig. 4. The cell distribution of POE foaming sheets with various layers.
The POE foam/film foaming sheet with high sound absorption coefficient in alternating multilayered structure was successfully prepared through multilayer co-extrusion system. The foam morphology with alternating multilayered structure was better than with the monolayer. This technique provided the new idea to obtain structure–foaming material with high sound absorption. The foam/film alternating multilayered structure could be improved the sound absorption efficiency due to more reflection and friction loss of sound in layer interface and the wall of cells. Meanwhile, the sound absorption efficiency of the foam/film foaming sheet with alternating multilayered structure increased with increasing of layer number and decreasing of cell size.
Acknowledgements
Fig. 5. Effect of layer number on sound absorption efficiency of POE foaming sheets with various layers.
Financial supports of the National Natural Science Foundation of China (51273132, 51227802 and 51121001), Program for New Century Excellent Talents in University (NCET-13-0392) and National Institute of Clean-and-Low-Carbon Energy are gratefully acknowledged. References
foaming sheet and the foam/film foaming sheets was investigated (as Fig. 5). The sound absorption efficiency of POE foaming sheet should be influenced by the acoustic impedance of adjacent layers and cell size. As excitated by sound wave, the air molecule in hole of foaming layer would be vibrated intensively. The vibration produced a strong energy exchange results in more sound energies were consumed. Furthermore, the sound absorption efficiency of the POE foaming sheet with alternating multilayered structure increased with increasing of layer number and decreasing of cell size. The small size cells have more surface area and the more layers have more interface, this factors could dissipate the sound wave and improved the sound adsorption efficiency of materials.
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Arenas JP, Crocker MJ. Sound Vib 2010;44:12–8. Drenckhan W, Langevin D. Curr Opin Colloid Interface Sci 2010;15:341–58. Rey RD, Alba J, Arenas JP, Sanchis VJ. Appl Acoust 2012;73:604–9. Najib NN, Ariff ZM, Bakar AA, Sipaut CS. Mater Des 2011;32:505–11. Zhai W, Yu J, He J. Polymer 2008;49:2430–4. Attenborough KJ. Acoust Soc Am 1983;73:785–99. Olek J, Weiss WJ, Neithalath N. Final Report; 2004. SQDH2004-2. Lin JH, Lin CM, Huang CC, Lin CC, Hsieh CT, Liao YC. J Compos Mater 2011;45:1355–62. Reverchon E, Cardea S. J Supercrit Fluids 2007;40:144–52. Stafford CM, Russell TP, McCarthy TJ. Macromolecules 1999;32:7610–6. Liao R, Yu W, Zhou C. Polymer 2010;51:6334–45. Kaewmesri W, Lee PC, Park CB, Pumchusak J. J Cell Plast 2006;42:405–28. Chang YW, Lee D, Bae SY. Polym Int 2006;55:184–9.
278
[14] [15] [16] [17] [18]
T. Zhao et al. / Materials Letters 139 (2015) 275–278
Ranade AP, Hiltner A, Baer E, Bland DG. J Cell Plast 2004;40:497–507. Gupta N. Mater Lett 2007;61:979–82. Song L, Lu A, Feng P, Lu Z. Mater Lett 2014;121:126–8. Olson DA, Chen L, Hillmyer MA. Chem Mater 2007;20:869–90. Zavala-Rivera P, Channon K, Nguyen V, Sivaniah E, Kabra D, Friend RH. Nat Mater 2012;11:53–7.
[19] Theato P, Ungar G. Nat Mater 2012;11:16–7. [20] Xu S, Wen M, Li J, Gao SY. Polymer 2008;49:4861–70. [21] Lee ST. Foam extrusion: principles and practice. Boca Raton, Florida: CRC Press; 2002.