Expandable polystyrene without any embedded blowing agent

2020 ◽  
pp. 0021955X2094497
Author(s):  
Habib Haji Avdi ◽  
Morteza Nasiri ◽  
Mohammad Javad Tehrani ◽  
Maryam Alizadeh Aghdam ◽  
Farhang Abbasi
Keyword(s):  
Suspension Polymerization ◽  
Expansion Ratio ◽  
Scanning Calorimetry ◽  
Blowing Agents ◽  
Blowing Agent ◽  
Rate Of Polymerization ◽  
Polystyrene Matrix ◽  
Expandable Polystyrene ◽  
Before And After

In this research, in-situ suspension polymerization of styrene in the presence of graphene, without any blowing agent, was investigated. Steam used in the expansion process of graphene-filled expandable polystyrene (GEPS). The dispersed graphene nano-sheets in the polystyrene matrix may absorb water in high temperatures, which evaporates by lowering the pressure and expansion precedes. The effects of graphene type and loading and steam temperature on the expansion ratio evaluated. Scanning electron microscopy (SEM) used to reveal the cross-section morphologies before and after expansion. The effect of graphene on the polymerization kinetics evaluated by differential scanning calorimetry (DSC). The results showed that by increasing the graphene loading, the rate of polymerization decreased, and the expansion ratio increased. The highest expansion ratio of about 4.8 was for particles containing 0.4% of graphene. Therefore, it was shown that by using graphene as a dispersed phase, polystyrene particles expanded without any organic blowing agents. Here, the idea of expandable polymers without any embedded blowing agent is introduced, which eliminates the release of volatile organic compounds and makes the process environmentally friendly.

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.

Relationships between synthesis parameters and properties of water expandable polystyrene

2012 ◽  
Vol 49 (1) ◽  
pp. 13-31 ◽  
Author(s):  
Sedigheh Mirhoseini Khosrowshahi ◽  
Farhang Abbasi ◽  
Naser Harasi ◽  
Behnaz Memar Maher
Keyword(s):  
Physical Properties ◽  
Water Content ◽  
Suspension Polymerization ◽  
Water Droplets ◽  
Blowing Agent ◽  
Synthesis Parameters ◽  
Expansion Behavior ◽  
Expandable Polystyrene ◽  
Negative Environmental Impact ◽  
Emulsified Water

Because of the negative environmental impact of volatile hydrocarbon-based blowing agents used in expandable polymers, water has been considered a suitable candidate. Water expandable polystyrene is a polystyrene containing water cells, which may be used as blowing agent. Because of different physical properties of water and volatile hydrocarbons, production conditions and physical properties of expandable polystyrene and water expandable polystyrene are completely different. In this work, water expandable polystyrene was prepared via suspension polymerization of the styrene/polystyrene mixture that contained water droplets as blowing agent. An inverse emulsion system was used to incorporate water into the organic phase. An experimental design was created to investigate the effects of variation of pre-polymerization time, surfactant concentration, suspension stabilizer/suspending agent ratio, suspension stabilizer addition time, and the amount of initial emulsified water on the particle size, distribution of water droplets, and the water content of the final beads. The relationships between the synthesis parameters and the properties of water expandable polystyrene were also studied. Regarding to the expansion behavior of water expandable polystyrene beads, the effect of water content and bead size on the expandability and the foam density were investigated.

scholarly journals Expansion Properties and Diffusion of Blowing Agent for Vinylidene Chloride Copolymer Thermally Expandable Microspheres

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3673
Author(s):  
Guiming Xie ◽  
Zhiyang Wang ◽  
Yongzhong Bao
Keyword(s):  
Boiling Point ◽  
Expansion Ratio ◽  
Crosslinking Degree ◽  
Vinylidene Chloride ◽  
Blowing Agent ◽  
Polymer Properties ◽  
And Diffusion ◽  
Expansion Temperature ◽  
Diffusion Properties

Vinylidene chloride copolymer microspheres were synthesized by in situ suspension copolymerization of vinylidene chloride (VDC), methyl methacrylate (MMA), and/or acrylonitrile (AN) in the presence of a paraffin blowing agent. The effects of shell polymer properties including compositions, glass transition temperature (Tg), crosslinking degree, blowing agent type, and encapsulation ratio (Er) on the expansion properties of copolymer microspheres were investigated. Moreover, the diffusion properties of blowing agent in copolymer microspheres were studied. The results show that VDC-MMA-AN copolymer microspheres exhibited excellent expansion properties, and the volume expansion ratio (Ev) and the apparent density were decreased over 40 times, but it was difficult to expand for the VDC-MMA copolymer microspheres. In addition, the moderately crosslinked inside of the polymer shell enhanced the Ev more than 30 and the stable expansion temperature range (Tr) was about 30 °C by adding 0.2–0.4 wt% of divinyl benzene. The Tg of the shell polymer must be higher than the boiling point of the blowing agent as a prerequisite; the lower the boiling point of the blowing agent, the higher the internal gas pressure driven microsphere expansion, and the wider the Tr. By increasing the Er of blowing agent improved the Ev of the microspheres. The diffusion of pentane blowing agent in VDC-MMA-AN copolymer microspheres were divided into Fick diffusion and non-Fick diffusion.

scholarly journals Improving the Continuous Microcellular Extrusion Foaming Ability with Supercritical CO2 of Thermoplastic Polyether Ester Elastomer through In-Situ Fibrillation of Polytetrafluoroethylene

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1983 ◽  
Author(s):  
Rui Jiang ◽  
Tao Liu ◽  
Zhimei Xu ◽  
Chul B. Park ◽  
Ling Zhao
Keyword(s):  
Cell Density ◽  
Supercritical Co2 ◽  
Cell Structure ◽  
Average Diameter ◽  
Extrusion Process ◽  
Expansion Ratio ◽  
Cell Diameter ◽  
Scanning Calorimetry ◽  
Foaming Ability

In-situ fibrillated polytetrafluoroethylene (PTFE) enhanced nanocomposites were successfully prepared by mixing thermoplastic polyether ester elastomer (TPEE) and PTFE using a twin-screw extruder. Well-dispersed, long aspect ratio PTFE nanofibrils with a diameter of less than 200 nm were generated and interwoven into networks. Differential scanning calorimetry and in-situ polarized optical microscopy showed that the PTFE nanofibrils can greatly accelerate and promote crystallization of the TPEE matrix and the crystallization temperature can be increased by 6 °C. Both shearing and elongational rheometry results confirmed that the introduction of PTFE nanofibrils can significantly improve the rheological properties. The remarkable changes in the strain-hardening effect and the melt viscoelastic response, as well as the promoted crystallization, led to substantially improved foaming behavior in the continuous extrusion process using supercritical CO2 as the blowing agent. The existing PTFE nanofibrils dramatically decreased the cell diameter and increased cell density, together with a higher expansion ratio and more uniform cell structure. The sample with 5% PTFE fibrils showed the best foaming ability, with an average diameter of 10.4–14.7 μm, an expansion ratio of 9.5–12.3 and a cell density of 6.6 × 107–8.6 × 107 cells/cm3.

Evaluation of polypropylene/clay nanocomposite foamability based on their morphological and rheological aspects

2018 ◽  
Vol 54 (5) ◽  
pp. 829-850 ◽  
Author(s):  
Anindya Dutta ◽  
Sabapathy Sankarpandi ◽  
Anup K Ghosh
Keyword(s):  
Cell Density ◽  
Thermal Studies ◽  
Expansion Ratio ◽  
Clay Nanocomposites ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Polypropylene Matrix ◽  
Induced Crystallization

To identify the effect of rheological influence on the development of microstructure in polypropylene/clay nanocomposites and thereby the influence of the developed microstructure on the foamability of the nanocomposites, a set of nanocomposites was prepared and batch foamed using supercritical CO2. Polypropylene and nanoclay were selected for preparing nanocomposites. During foaming, the nanocomposites were saturated with CO2 gas for three different time periods and subsequently in-situ heating was done to achieve cell growth. The gas saturation was done at subcritical condition followed by the foaming at critical condition of CO2. Thermal studies of the composites were investigated through differential scanning calorimetry, and clay dispersion morphology was investigated and validated using wide-angle X-ray diffraction, transmission electron microscopy, and parallel plate rheology. The improvement in foam morphology (cell size and cell density) and subsequent reduction in foam density was analyzed. The fingerprint characteristics of nanocomposites have an enormous role on foam structure development. With the increase in clay loading, cell density increased; furthermore, with an increase in saturation time, there was a phenomenal decrease in expansion ratio of neat polypropylene due to CO2-induced crystallization which could be mitigated by the incorporation of nanoclay into the polypropylene matrix. Therefore, nanoclay could be exploited as the inhibitor of CO2-induced crystallization.

Water expandable polystyrene (WEPS): Part 4. Synthesis of the water expandable blend of polystyrene and poly(2,6- dimethyl-1,4-phenylene ether)

e-Polymers ◽  
2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Emile A. Snijders ◽  
Laurent Nelissen ◽  
Piet J. Lemstra
Keyword(s):  
Molar Mass ◽  
Environmentally Benign ◽  
The Novel ◽  
Polystyrene Foam ◽  
Processing Window ◽  
Blowing Agent ◽  
Polystyrene Matrix ◽  
Expandable Polystyrene ◽  
The Difference ◽  
First Time

AbstractIn previous studies, we discussed the use of water as an environmentally benign blowing agent for foaming of polystyrene beads, resulting in so-called WEPS, viz. water expandable polystyrene foam. Several grades of precursors to WEPS have been prepared by varying the water content and the molar mass, to control the melt strength of the polystyrene matrix. Additionally, we have used (endcapped) poly(2,6-dimethyl-1,4-phenylene ether) (PPE) to control both the meltviscosity and the glass transition temperature Tg. The advantage of using the blend PS/PPE is that the processing window for foaming is increased in view of the difference between the Tg and the boiling point of water. Using the novel WEPS route with some adjustments, for the first time a water expandable homogeneous blend of polystyrene and end-capped PPE was successfully obtained.

Injectable in-situ Forming Depot Of Doxycycline Hyclate/α-Cyclodextrin Complex using PLGA for Periodontitis Treatment: Preparation, Charac-terization, and In-Vitro Evaluation

2020 ◽  
Vol 17 ◽  
Author(s):  
Elham Khodaverdi ◽  
Farhad Eisvand ◽  
Mohammad Sina Nezami ◽  
Seyedeh Nesa Rezaeian Shiadeh ◽  
Hossein Kamali ◽  
...  
Keyword(s):  
Complex Form ◽  
Docking Studies ◽  
Morphological Properties ◽  
Burst Release ◽  
Cyclodextrin Complex ◽  
Doxycycline Hyclate ◽  
Scanning Calorimetry ◽  
In Situ Forming

Background:: Doxycycline (DOX) is used in treating a bacterial infection, especially for periodontitis treatment. Objective: To reduce irritation of DOX for subgingival administration and increase the chemical stability and against enzy-matic, the complex of α-cyclodextrin with DOX was prepared and loaded into injectable in situ forming implant based on PLGA. Methods:: FTIR, molecular docking studies, X-ray diffraction, and differential scanning calorimetry was performed to char-acterize the DOX/α-cyclodextrin complex. Finally, the in-vitro drug release and modeling, morphological properties, and cellular cytotoxic effects were also evaluated. Results:: The stability of DOX was improved with complex than pure DOX. The main advantage of the complex is the al-most complete release (96.31 ± 2.56 %) of the drug within 14 days of the implant, whereas in the formulation containing the pure DOX and the physical mixture the DOX with α-cyclodextrin release is reached to 70.18 ± 3.61 % and 77.03 ± 3.56 %, respectively. This trend is due to elevate of DOX stability in the DOX/ α-cyclodextrin complex form within PLGA implant that confirmed by the results of stability. Conclusion:: Our results were indicative that the formulation containing DOX/α-cyclodextrin complex was biocompatible and sustained-release with minimum initial burst release.

Real-life Field Studies of the NOx Removing Properties of Photocatalytic Surfaces in Roskilde and Copenhagen Airport, Denmark

2020 ◽  
Vol 01 ◽  
Author(s):  
Henrik Jensen ◽  
Pernille D. Pedersen
Keyword(s):  
Air Quality ◽  
High Stability ◽  
Reference Site ◽  
Real Life ◽  
Field Studies ◽  
The Real ◽  
Before And After ◽  
Parking Lot ◽  
Photocatalytic Concrete

Aims: To evaluate the real-life effect of photocatalytic surfaces on the air quality at two test-sites in Denmark. Background: Poor air quality is today one of the largest environmental issues, due to the adverse effects on human health associated with high levels of air pollution, including respiratory issues, cardiovascular disease (CVD), and lung cancer. NOx removal by TiO2 based photocatalysis is a tool to improve air quality locally in areas where people are exposed. Methods: Two test sites were constructed in Roskilde and Copenhage airport. In Roskilde, the existing asphalt at two parking lots was treated with TiO2 containing liquid and an in-situ ISO 22197-1 test setup was developed to enable in-situ evaluation of the activity of the asphalt. In CPH airport, photocatalytic concrete tiles were installed at the "kiss and fly" parking lot, and NOx levels were continuously monitored in 0.5 m by CLD at the active site and a comparable reference site before and after installation for a period of 2 years. Results: The Roskilde showed high stability of the photocatalytic coating with the activity being largely unchanged over a period of 2 years. The CPH airport study showed that the average NOx levels were decreased by 12 % comparing the before and after NOx concentrations at the active and reference site. Conclusion: The joined results of the two Danish demonstration projects illustrate a high stability of the photocatalytic coating as well as a high potential for improvements of the real-life air quality in polluted areas.

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