Morphology and physical properties of closed cell microcellular ethylene-octene copolymer: Effect of precipitated silica filler and blowing agent

2001 ◽  
Vol 83 (2) ◽  
pp. 357-366 ◽  
Author(s):  
N. C. Nayak ◽  
D. K. Tripathy
Keyword(s):  
Physical Properties ◽  
Blowing Agent ◽  
Precipitated Silica ◽  
Silica Filler ◽  
Closed Cell ◽  
Ethylene Octene Copolymer

Interaction between Carboxylated Nitrile Rubber and Precipitated Silica: Role of (3-Aminopropyl)Triethoxysilane

1996 ◽  
Vol 69 (4) ◽  
pp. 637-647 ◽  
Author(s):  
Sumanda Bandyopadhyay ◽  
P. P. De ◽  
D. K. Tripathy ◽  
S. K. De
Keyword(s):  
Physical Properties ◽  
Coupling Agent ◽  
Spectroscopic Studies ◽  
Nitrile Rubber ◽  
Dynamic Mechanical ◽  
Precipitated Silica ◽  
Silica Filler ◽  
Bound Rubber ◽  
Rubber Filler

Abstract On the basis of measurements of bound rubber and physical properties and the results of Monsanto rheometer, dynamic mechanical and infrared spectroscopic studies, it is observed that strong rubber-filler interaction occurs between XNBR and precipitated silica filler. During molding, XNBR was found to be crosslinked by the filler surface through the formation of primary bonds. The coupling agent, namely (3-aminopropyl)triethoxysilane facilitates the formation of rubber-filler bonds at the expense of filler-filler networks, leading to improved dispersion and enhanced degree of crosslinking.

Failure Properties of Silica-Filled Ethylene Vinyl Acetate Microcellular Rubber

1993 ◽  
Vol 66 (1) ◽  
pp. 38-47 ◽  
Author(s):  
Kinkar Mukhopadhyaa ◽  
D. K. Tripathy ◽  
S. K. De
Keyword(s):  
Physical Properties ◽  
Vinyl Acetate ◽  
Reasonable Agreement ◽  
Pore Diameter ◽  
Ethylene Vinyl Acetate ◽  
Foam Rubber ◽  
Blowing Agent ◽  
Silica Filler ◽  
Failure Properties

Abstract The concentrations of the blowing agent and silica filler alter the microstructure of ethylene vinyl acetate rubber foam which in turn is responsible for changes in the physical properties of the foam vulcanizates. The theoretically predicted flaw sizes were found to be in reasonable agreement with the largest pore diameter observed from SEM photomicrographs. The results support the theory that the tensile rupture of foam rubber occurs by the catastrophic tearing from a flaw present in the form of the largest pore in the microstructure of the foam.

Temperature dependency of the long-term thermal conductivity of spray polyurethane foam

2021 ◽  
pp. 174425912110454
Author(s):  
Neal Holcroft
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Cellular Structure ◽  
Gas Diffusion ◽  
Temperature Dependent ◽  
Blowing Agent ◽  
Closed Cell ◽  
Wall Assembly ◽  
Cell Foam

The thermal properties of closed-cell foam insulation display a more complex behaviour than other construction materials due to the properties of the blowing agent captured in their cellular structure. Over time, blowing agent diffuses out from and air into the cellular structure resulting in an increase in thermal conductivity, a process that is temperature dependent. Some blowing agents also condense at temperatures within the in-service range of the insulation, resulting in non-linear temperature dependent relationships. Moreover, diffusion of moisture into the cellular structure increases thermal conductivity. Standards exist to quantify the effect of gas diffusion on thermal conductivity, however only at standard laboratory conditions. In this paper a new test procedure is described that includes calculation methods to determine Temperature Dependent Long-Term Thermal Conductivity (LTTC(T)) functions for closed-cell foam insulation using as a test material, a Medium-Density Spray Polyurethane Foam (MDSPF). Tests results are provided to show the validity of the method and to investigate the effects of both conditioning and mean test temperature on change in thermal conductivity. In addition, testing was conducted to produce a moisture dependent thermal conductivity function. The resulting functions were used in hygrothermal simulations to assess the effect of foam aging, in-service temperature and moisture content on the performance of a typical wall assembly incorporating MDSPF located in four Canadian climate zones. Results show that after 1 year, mean thermal conductivity increased 15%–16% and after 5 years 23%–24%, depending on climate zone. Furthermore, the use of the LTTC(T) function to calculate the wall assembly U-value improved accuracy between 3% and 5%.

scholarly journals Microstructural and Chemical Analysis of Polyurethane and Polyisocyanurate Foam Insulations

2021 ◽  
Author(s):  
Umberto Berardi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Performance ◽  
Cell Structure ◽  
Polymer Degradation ◽  
Chemical Characterization ◽  
Aging Behavior ◽  
Blowing Agent ◽  
Closed Cell ◽  
Physical Attributes ◽  
Cell Foam

For some closed cell foam insulation products, the thermal conductivity increases at low temperatures, contrary to single thermal resistance values provided by manufacturers. This phenomenon has been demonstrated in various polyurethane and polyisocyanurate insulations. The reduction in thermal performance has been attributed to the diffusion of air and blowing agent through the foam and to the condensation of blowing agent. Aging processes such as freeze-thaw cycling, moisture accumulation, and polymer degradation further increase thermal conductivity. The initial cell structure plays a role in dictating the thermal performance. To further understand the loss of thermal performance in closed cell foams, microstructure and chemical characterization was performed in this study. The aging behavior of foam insulations was analyzed by imaging foams with SEM and by measuring foam. Changes in the polymer physical attributes were identified and compared to increases in thermal conductivity. This project also used gas chromatography and quantified changes in pentane concentration in polyisocyanurate foams that have undergone aging

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