Multi-Stage Recycling Induced Morphological Transformations in Solid-State Microcellular Foaming of Polystyrene

2018 ◽  
Vol 37 (3) ◽  
pp. 121-149 ◽  
Author(s):  
Indrajeet Singh ◽  
Abhishek Gandhi ◽  
Manoranjan Biswal ◽  
Smita Mohanty ◽  
S. K. Nayak
Keyword(s):  
Cell Size ◽  
Cell Density ◽  
Saturation Pressure ◽  
Expansion Ratio ◽  
General Purpose ◽  
Microcellular Foam ◽  
Cell Size Distribution ◽  
Microcellular Foaming ◽  
Multi Stage ◽  
Morphological Transformations

In this article, the general-purpose polystyrene was reprocessed four times. The effect of repeated reprocessing of polystyrene on its polymeric properties and on its microcellular, foaming behaviour were investigated. It was observed that reprocessing leads to break of long polymeric chains into short chains, which resulted increment in PDI and MFI. Molecular weight and Glass transition temperature were found to decrease with increasing recycling stages. Reprocessing resulted abruptly decrement in viscosity of neat polystyrene. Effect of reprocessing on foaming behaviour was analysed properly in this report and it was found that reprocessing resulted in improvement in cell sizes and their distribution. A positive effect on expansion ratio was also observed during foaming of reprocessed specimens. Cell density was found to decrease with increasing recycling stages. The effect of saturation pressure and foaming temperature on microcellular foam morphology along with recycling were investigated. Effect of foaming time on cell size, cell size distribution, cell density, expansion ratio and cell wall thickness was investigated.

Advances in Microcellular Foam Processing of PLA

2016 ◽  
Vol 717 ◽  
pp. 68-72 ◽  
Author(s):  
Zhi Zhong Han ◽  
You Cheng Zhang ◽  
Wei Min Yang ◽  
Peng Cheng Xie
Keyword(s):  
Mechanical Properties ◽  
Cell Density ◽  
Cell Morphology ◽  
Expansion Ratio ◽  
Chain Extender ◽  
Microcellular Foam ◽  
Foaming Process ◽  
Microcellular Foaming ◽  
Alternative Materials ◽  
A Chain

PLA is a bio-based biodegradable plastic, which has excellent biocompatibility and biodegradability. Because the mechanical properties of microcellular foaming material is similar to petroleum-based plastics (PS), PLA foams have been considered as ideal alternative materials. However, PLA has several inherent drawbacks such as low melt strength and slow crystallization kinetics, which severely inhibit the PLA foaming process to produce high-density forms and uniform cell morphology. By adding a chain extender or nanoparticles, and blending with other biological materials, these ways could effectively enhance the expansion ratio and the cell density of PLA and improve the mechanical properties of PLA foams. The most current investigations on microcellular foaming of PLA were reviewed in the article, and outlook of PLA foams was raised.

scholarly journals Preparation of Microcellular Foams by Supercritical Carbon Dioxide: A Case Study of Thermoplastic Polyurethane 70A

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1650
Author(s):  
Yu-Ting Hsiao ◽  
Chieh-Ming Hsieh ◽  
Tsung-Mao Yang ◽  
Chie-Shaan Su
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Pore Size ◽  
Cell Density ◽  
Thermoplastic Polyurethane ◽  
Saturation Pressure ◽  
Saturation Temperature ◽  
Expansion Ratio ◽  
Microcellular Foam

In this study, a case study to produce microcellular foam of a commercial thermoplastic polyurethane (TPU) through the supercritical carbon dioxide (CO2) foaming process is presented. To explore the feasibility of TPU in medical device and biomedical application, a soft TPU with Shore hardness value of 70A was selected as the model compound. The effects of saturation temperature and saturation pressure ranging from 90 to 140 °C and 90 to 110 bar on the expansion ratio, cell size and cell density of the TPU foam were compared and discussed. Regarding the expansion ratio, the effect of saturation temperature was considerable and an intermediate saturation temperature of 100 °C was favorable to produce TPU microcellular foam with a high expansion ratio. On the other hand, the mean pore size and cell density of TPU foam can be efficiently manipulated by adjusting the saturation pressure. A high saturation pressure was beneficial to obtain TPU foam with small mean pore size and high cell density. This case study shows that the expansion ratio of TPU microcellular foam could be designed as high as 4.4. The cell size and cell density could be controlled within 12–40 μm and 5.0 × 107–1.3 × 109 cells/cm3, respectively.

Physico-mechanical properties and cell microstructure of cross-linked PVC/organoclay nanocomposite foams prepared at various processing conditions

2020 ◽  
pp. 089270572097869
Author(s):  
Pezhman Rezaei ◽  
Mostafa Rezaei ◽  
Saeid Talebi ◽  
Amin Babaie
Keyword(s):  
Mechanical Properties ◽  
Size Distribution ◽  
Cell Size ◽  
Cell Density ◽  
Expansion Ratio ◽  
Molding Pressure ◽  
Cell Size Distribution ◽  
Gel Content ◽  
Nanocomposite Foams ◽  
Cloisite 30B

Cross-linked polyvinyl chloride (C-PVC) foams and their nanocomposite foams, containing Cloisite 30B nanoclays were prepared. The effects of compression molding pressure and time on the morphology and mechanical properties of different foams were studied. Increment of molding pressure led to higher apparent density, gel content, cell density, and expansion ratio, and wider cell size distribution, which improved the mechanical properties of the foams. Additionally, with the increasing of molding time, lower cell density and final expansion ratio, narrower cell size distribution, and higher gel content and mechanical properties could be obtained. Moreover, incorporation of Cloisite 30B nanoclay in a PVC matrix not only improved cellular microstructure and mechanical properties but also reduced water uptake ratios of nanocomposite foams.

Key Parameters Influencing Microcellular Polystyrene Cell Morphology Blowing with Supercritical CO2

2012 ◽  
Vol 501 ◽  
pp. 237-242 ◽  
Author(s):  
Chang Yun Gao ◽  
Nan Qiao Zhou ◽  
Ti Kun Shan ◽  
Zhen Xiang Xin
Keyword(s):  
Size Distribution ◽  
Cell Size ◽  
Cell Density ◽  
Cell Morphology ◽  
Saturation Pressure ◽  
Processing Temperature ◽  
Polymer Foam ◽  
Cell Size Distribution ◽  
Average Cell ◽  
Foaming Temperature

Polystyrene microcellular foams blowing with supercritical CO2 were prepared with a novel polymer foam processing simulator. Key parameters influencing Polystyrene cell morphology were investigated. The effect of processing temperature and saturation pressure on cell morphology was observed by scanning electron microscope and the average cell diameter and cell size distribution was calculated. The results show that the cell density decrease and cell size increase with the increase of foaming temperature. The cell density increase and cell size decrease with the increase of saturation pressure. And the cell size distribution shows a narrow distribution at lower foaming temperature and higher saturation pressure.

Study on the Foaming Behavior of PS-CO2 by Using Water or Ethanol as Co-Blowing Agent

2013 ◽  
Vol 748 ◽  
pp. 112-116 ◽  
Author(s):  
Yi Wei Luo ◽  
Chun Ling Xin ◽  
Jiao Sun ◽  
Bao Rui Yan ◽  
Ya Dong He
Keyword(s):  
Cell Size ◽  
Cell Density ◽  
Apparent Density ◽  
Expansion Ratio ◽  
Low Density ◽  
Blowing Agents ◽  
Blowing Agent ◽  
Foaming Behavior ◽  
Low Solubility ◽  
Foam Production

Carbon dioxide (CO2) has been reported as an interesting substitute of banned ozone-depleting blowing agents, such as HCFC and HFC etc., for low-density polystyrene (PS) foam production, but it is difficult to industrialize due to its low solubility in PS matrix; therefore, high pressure is always needed in order to obtain the required gas concentrations for low density foam. Mixtures of blowing agents might be a practical way to make foam processing easy to control. In this paper, the foaming behaviors of PS-CO2 by using water or ethanol as co-blowing agent were investigated. The performances of foams obtained by PS-CO2, PS-CO2-water and PS-CO2-ethanol systems were tested respectively. It was found that cell size increased owing to the existence of co-blowing agent; in particular, the expansion ratio of PS foam obtained by CO2-ethanol was 1.3 times greater than that by CO2. At the same time, cell density as well as apparent density decreased with temperature increasing, while cell size showed the opposite. Cell size and apparent density, rather than cell density, decreased with pressure. These results were explained by the solution behavior of each of blowing agent.

Crystallization-induced microcellular foaming behaviors of chain-extended polyethylene terephthalate

2020 ◽  
Vol 39 (6) ◽  
pp. 223-237
Author(s):  
Can Jiang ◽  
Shuo Han ◽  
Shihong Chen ◽  
Hongfu Zhou ◽  
Xiangdong Wang
Keyword(s):  
High Temperature ◽  
Cell Size ◽  
Cell Density ◽  
Polyethylene Terephthalate ◽  
Saturation Temperature ◽  
Crystal Nucleation ◽  
Cellular Structures ◽  
Induction Method ◽  
Microcellular Foaming ◽  
Temperature Melting

The microcellular foaming of chain-extended polyethylene terephthalate (CPET) by crystallization induction method was reported in this article. The crystallization behaviors of various polyethylene terephthalate (PET) samples which were affected by the combined effect of pyromellitic dianhydride, Surlyn, and CO2 were investigated. After Surlyn was added to CPET, the crystal nucleation of various CPET samples was improved, and numerous but small spherulites were generated. Two kinds of CPET samples with the content of 0 phr and 1 phr Surlyn were foamed at various temperature by batch foaming method. Changing the saturation temperature could adjust the appearance of high-temperature melting crystals which would affect the final cellular structures in various CPET foams. With the decrease of saturation temperature, the cell size decreased while cell density increased. At the saturation temperature of 265°C and 250°C, the cell density of CPET foam with Surlyn was one magnitude larger than CPET foam without Surlyn. At the saturation temperature of 247°C, the microcellular PET foams with the cell density of 109 cells cm−3 and the cell size less than 10 µm had been developed successfully.

scholarly journals Production of microcellular foam based on PP/EPDM: The effects of processing parameters and nanoclay using response surface methodology

e-Polymers ◽  
2012 ◽  
Vol 12 (1) ◽  
Author(s):  
Mohsen Keramati ◽  
Ismaeil Ghasemi ◽  
Mohammad Karrabi ◽  
Hamed Azizi
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Cell Density ◽  
Saturation Pressure ◽  
Nucleation Mechanism ◽  
Nucleation Theory ◽  
Microcellular Foam ◽  
Average Cell ◽  
Nanoclay Content ◽  
Foaming Time

AbstractMicrocellular foam is a new class of material with superior properties due to smaller cell size and higher cell density compared to ordinary foams. In this work, microcellular foam of PP/EPDM/Organoclay with supercritical nitrogen as physical blowing agent was prepared via batch process. Experimental design was carried out according to Box-Behnken method and the effects of saturation pressure and foaming times as well as organoclay content on nucleation and final foam morphology were studied using response surface methodology (RSM). Three levels of saturation pressure, nanoclay content, and foaming time were chosen. The mathematical model and response surface graphs have been used to illustrate the relationship between considered parameters and foam properties. The results revealed that cell density and average cell diameter were affected by nanoclay content and pressure. Cell density was in the range of 109-1010 cell/cm3. Larger average cell sizes were observed as a result of increasing foaming time. Classic nucleation theory was used to study the nucleation mechanism. Nanoparticles acted as nucleating agents and changed nucleation mechanism from homogenous to heterogeneous by decreasing nucleating free energy. In order to find out nucleating energy reduction, gas-polymer-nanoparticle contact angle (Ө), was calculated by measuring surface and interfacial free energies of neat polymers and nanoparticle. In addition, nucleation efficiency of organoclay was estimated and the results showed that despite low nucleating efficiency, nucleation is dominated by presence of nanoclay.

Morphological, thermo-mechanical, and thermal conductivity properties of halloysite nanotube-filled polypropylene nanocomposite foam

2016 ◽  
Vol 54 (2) ◽  
pp. 217-233 ◽  
Author(s):  
Renan Demori ◽  
Eveline Bischoff ◽  
Ana P de Azeredo ◽  
Susana A Liberman ◽  
Joao Maia ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cell Size ◽  
Cell Density ◽  
Void Fraction ◽  
Cell Structure ◽  
Cell Size Distribution ◽  
Halloysite Nanotube ◽  
Dynamic Mechanical ◽  
Foaming Behavior ◽  
Homogeneous Cell

Studies about polypropylene nanocomposite foams are receiving attention because nanoparticles can change physical and mechanical properties, as well as improve foaming behavior in terms of homogeneous cell structure, cell density, and void fraction. In this research, the foaming behavior of polypropylene, polypropylene/long-chain branched polypropylene (LCBPP) 100/20 blend, and polypropylene/LCBPP/halloysite nanocomposites with 0.5 and 3 parts per hundred of resin (phr) is studied. The LCBPP was used to improve the rheological properties of polypropylene/LCBPP blend, namely the degree of strain-hardening. Transmission electron microscopy observation indicated that halloysite nanotube particles are well distributed in the matrix by aggregates. Subsequent foaming experiments were conducted using chemical blowing agent in injection-molding processing. Polypropylene foam exhibited high cell density and cell size as well as a collapsing effect, whereas the polypropylene/LCBPP blend showed a reduction of the void fraction and cell density compared to expanded polypropylene. Also, the blend showed reduction of the collapsing effect and increase of homogeneous cell size distribution. The introduction of a small amount of halloysite nanotube in the polypropylene/LCBPP blend improved the foaming behavior of the polypropylene, with a uniform cell structure distribution in the resultant foams. In addition, the cell density of the composite sample was higher than the polypropylene/LCBPP sample, having increased 82% and 136% for 0.5 and 3 phr of loaded halloysite nanotube, respectively. Furthermore, the presence of halloysite nanotube increased crystallization temperature (Tc) and slightly increased dynamic-mechanical properties measured by dynamic-mechanical thermal analysis. By increasing halloysite nanotube content to 3 phr, the insulating effect increased by 13% compared to polypropylene/LCBPP blend. For comparative purposes, the effect on foaming behavior of polypropylene/LCBPP was also investigated using talc microparticles.

The Preparation of Microcellular Foam PP Reflective Film

2012 ◽  
Vol 468-471 ◽  
pp. 1078-1081
Author(s):  
Zhen Jiang Shi ◽  
Sheng Lin Yang ◽  
Jun Hong Jin ◽  
Guang Li
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Chemical Process ◽  
Volume Expansion ◽  
Saturation Pressure ◽  
Expansion Ratio ◽  
Processing Conditions ◽  
Microcellular Foam ◽  
Foaming Agent ◽  
Foaming Temperature

This work was aimed at manufacturing the microcellular foam polypropylene for the applications of reflective film with chemical foaming agent or supercritical carbon dioxide. The effects of processing conditions such as the composition of foaming agent during chemical process, the foaming temperature and saturation pressure in physical process on the microcellular structures and the reflectivity as well as the volume expansion ratio were investigated.

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