scholarly journals In-situ aging of roof systems containing polyisocyanurate roof insulation foamed with alternative blowing agents

1993 ◽  
Author(s):  
A.O. Desjarlais ◽  
J.E. Christian ◽  
R.S. Graves
Keyword(s):  
Blowing Agents

scholarly journals High Performance Attapulgite/Polypyrrole Nanocomposite Reinforced Polystyrene (PS) Foam Based on Supercritical CO2 Foaming

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 985 ◽  
Author(s):  
Yidong Liu ◽  
Lingfeng Jian ◽  
Tianhua Xiao ◽  
Rongtao Liu ◽  
Shun Yi ◽  
...  
Keyword(s):  
Supercritical Co2 ◽  
High Performance ◽  
In Situ Polymerization ◽  
Compression Modulus ◽  
Blowing Agents ◽  
Foaming Process ◽  
Potential Applications ◽  
Polymerization Method ◽  
Low Solubility

CO2 has been regarded as one of the most promising blowing agents for polystyrene (PS) foam due to its non-flammability, low price, nontoxicity, and eco-friendliness. However, the low solubility and fast diffusivity of CO2 in PS hinder its potential applications. In this study, an attapulgite (ATP)/polypyrrole (PPy) nanocomposite was developed using the in situ polymerization method to generate the hierarchical cell texture for the PS foam based on the supercritical CO2 foaming. The results demonstrated that the nanocomposite could act as an efficient CO2 capturer enabling the random release of it during the foaming process. In contrast to the pure PS foam, the ATP/PPy nanocomposite reinforced PS foam is endowed with high cell density (up to 1.9 × 106) and similar thermal conductivity as the neat PS foam, as well as high compression modulus. Therefore, the in situ polymerized ATP/PPy nanocomposite makes supercritical CO2 foaming desired candidate to replace the widely used fluorocarbons and chlorofluorocarbons as PS blowing agents.

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.

In situ synthesis of CO2 adducts of modified polyethylenimines in polyether polyols for polyurethane foaming

2021 ◽  
pp. 0021955X2098715
Author(s):  
Shuai Yuan ◽  
Yuanzhu Long ◽  
Xingyi Xie
Keyword(s):  
Propylene Glycol ◽  
Monomethyl Ether ◽  
Universal Method ◽  
Molecular Weights ◽  
Blowing Agents ◽  
Hydrophobically Modified ◽  
The Matrix ◽  
Poly Propylene ◽  
Polyurethane Foaming

CO2 adducts from hydrophobically-modified polyethylenimines (PEIs) in powder form are newly-developed environment-friendly blowing agents for polyurethanes (PUs). However, they are difficult to disperse into foaming systems that usually contain polyether polyols as the PU soft segments. Herein, we employ mixtures of di(propylene glycol) monomethyl ether-grafted polyethylenimines (DPG-PEIs) and poly(propylene glycol) (PPG) polyols to absorb CO2, with in situ formation of the CO2 adduct particles as PU blowing agents. Their CO2 saturation degrees, revealed by thermogravimetry, scatter in the range of 93–98%. The DPG side chains tend to be exposed at the particle–matrix interface to stabilize the particles. In addition, some PPG oligomers in the matrix might entangle with the CO2 adduct macromolecules during the in situ particle formation. The entangled PPG chains could further stabilize the suspending particles. The high grafting rate and high molecular weight of the PEI backbones could result in small particles, which largely thicken the foaming systems. The optimized blowing agents, with grafting rates between 5% and 8% and PEI backbone molecular weights not higher than 10k Da, show particle sizes from several hundreds of nanometers to ∼1 μm. The resultant foams demonstrate densities below 50 kg/m3 and compressive strengths over 200 kPa, comparable to the values from industrial foams. This in situ CO2 adduction has potential as a universal method suitable for PU foaming at an industrial scale.

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

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