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

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.

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Expandable polystyrene without any embedded blowing agent

Journal of Cellular Plastics ◽

10.1177/0021955x20944971 ◽

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.

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936117 In-situ determination of air permeability and diffusion properties of helium in sedimentary iron ore

International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts ◽

10.1016/0148-9062(93)91345-j ◽

1993 ◽

Vol 30 (6) ◽

pp. 347

Keyword(s):

Iron Ore ◽

Air Permeability ◽

And Diffusion ◽

Diffusion Properties

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A New Image Encryption Scheme Using Dual Chaotic Map Synchronization

The International Arab Journal of Information Technology ◽

10.34028/iajit/18/1/11 ◽

2020 ◽

Vol 18 (1) ◽

Keyword(s):

Image Encryption ◽

Chaotic Systems ◽

Initial Conditions ◽

Chaotic Map ◽

Security Applications ◽

The Common ◽

And Diffusion ◽

Confusion And Diffusion ◽

Sensitivity To Initial Conditions ◽

Diffusion Properties

Chaotic systems behavior attracts many researchers in the field of image encryption. The major advantage of using chaos as the basis for developing a crypto-system is due to its sensitivity to initial conditions and parameter tunning as well as the random-like behavior which resembles the main ingredients of a good cipher namely the confusion and diffusion properties. In this article, we present a new scheme based on the synchronization of dual chaotic systems namely Lorenz and Chen chaotic systems and prove that those chaotic maps can be completely synchronized with other under suitable conditions and specific parameters that make a new addition to the chaotic based encryption systems. This addition provides a master-slave configuration that is utilized to construct the proposed dual synchronized chaos-based cipher scheme. The common security analyses are performed to validate the effectiveness of the proposed scheme. Based on all experiments and analyses, we can conclude that this scheme is secure, efficient, robust, reliable, and can be directly applied successfully for many practical security applications in insecure network channels such as the Internet

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