Structures and properties of closed-cell polyimide rigid foams

2013 ◽  
Vol 130 (5) ◽  
pp. 3282-3291 ◽  
Author(s):  
Leilei Wang ◽  
Aijun Hu ◽  
Lin Fan ◽  
Shiyong Yang
Keyword(s):  
Closed Cell ◽  
Structures And Properties ◽  
Rigid Foams

The Synthesis and Application of a Novel Class of Polyols for Preparation of Polyurethane

2013 ◽  
Vol 357-360 ◽  
pp. 1441-1445
Author(s):  
Xiao Lin Li ◽  
Zheng Fang ◽  
Dong Ji ◽  
Zhi Dong Wan ◽  
Kai Guo
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Polyurethane Foams ◽  
Low Density ◽  
Cell Content ◽  
Low Thermal Conductivity ◽  
High Compressive Strength ◽  
Rigid Polyurethane Foams ◽  
Closed Cell ◽  
Rigid Foams

The synthesis of a novel class of diamine-based polyols derivatives and the potentials and the limitations of these polyols were reported. This class of diamine-based polyols with high hydroxyl values and no acid values can be used in rigid polyurethane foams. The prepared rigid foams show the properties of low density, high closed cell content, low thermal conductivity, and high compressive strength.

Preparation and performance of melamine-formaldehyde rigid foams with high closed cell content

2021 ◽  
pp. 026248932110171
Author(s):  
Chunhui Li ◽  
Haihong Ma ◽  
Congqiang Song ◽  
Zhengfa Zhou ◽  
Weibing Xu ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Thermal Insulation ◽  
Apparent Density ◽  
Insulation Material ◽  
Melamine Formaldehyde ◽  
Cell Content ◽  
Closed Cell ◽  
Rigid Foams ◽  
Foaming Temperature

Melamine-formaldehyde (MF)rigid foams with high closed cell content were prepared via oven heating process, using MF prepolymer prepared from melamine and paraformaldehyde as a matrix, cyclohexane as the foaming agent, dimethyl silicon oil as the foam stabilizers, hydrochloric acid as the catalyst. The effect of MF prepolymer viscosity, foaming temperature, amount of catalyst on morphology, closed cell content, apparent density, water absorption and compressive strength of MF rigid foams were systematically studied. The optimized foaming conditions are as follows: the viscosity of MF prepolymer ranges from 35 Pa·s to 45 Pa·s, the foaming temperature is 125°C and the content of the catalyst is 0.65 wt%. The as-prepared MF foams showed the best comprehensive performance with closed cell content of 83.5%, apparent density of 62 kg·m−3, water absorption of 12.0%, compressive strength of 292kPa, thermal conductivity of 0.033 W m−1 K−1 and limiting oxygen index (LOI) of 36%. Compared to conventional organic foams, MF rigid foams possess low water absorption, excellent thermal insulation and flame retardancy due to high closed cell content, and can be expected to be used as thermal insulation material for building exterior walls.

Preparation and properties of melamine-formaldehyde rigid closed-cell foam toughened by ethylene glycol/carbon fiber

2020 ◽  
pp. 026248932092923
Author(s):  
Chunhui Li ◽  
Haihong Ma ◽  
Zhengfa Zhou ◽  
Weibing Xu ◽  
Fengmei Ren ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Stability ◽  
Compressive Strength ◽  
Water Absorption ◽  
Cellular Structure ◽  
Bending Strength ◽  
Melamine Formaldehyde ◽  
Cell Ratio ◽  
Closed Cell ◽  
Rigid Foams

Toughing melamine-formaldehyde (MF) rigid closed-cell foams were prepared by using ethylene glycol (EG) and carbon fiber (CF) as composite toughening agents. The pulverization rate, compressive strength, bending strength, cellular structure, closed-cell ratio, water absorption ratio, thermal conductivity, thermal stability, limiting oxygen index (LOI), and char yield were characterized to study the morphology, mechanical, thermal, and fire-retardant properties of as-prepared toughing MF rigid foams. The pulverization rate result showed that introduction of composite modifier can obviously improve the toughness of MF rigid foams. The cellular structure, closed-cell ratio, and water absorption results showed that the addition of EG/CF can increase the closed-cell ratio and control the cell size of MF rigid foams. The compressive strength and bending strength results showed that the incorporation of composite modifier of MF rigid foams dramatically improved the mechanical properties. The LOI, char yield, and thermal stability results showed that the toughing MF rigid foams remained more intact char skeleton with flame-retardant effect, thus reducing the fire hazards. The as-prepared toughing MF rigid foams showed the best comprehensive performance with pulverization rate of 5.21%, compressive strength of 355.3 kPa, bending strength of 0.44 MPa, closed-cell ratio of 79.1%, water absorption of 9%, thermal conductivity of 0.031 W m−1 K−1, and LOI of 39.6%. Compared with unmodified MF rigid foams, toughing rigid closed-cell MF foams possess excellent pulverization rate, compressive strength, bending strength, cellular structure, thermal insulation, and flame retardancy.

Rigid polyurethane–polyisocyanurate foams modified with grain fraction of fly ashes

2019 ◽  
Vol 56 (1) ◽  
pp. 53-72 ◽  
Author(s):  
Joanna Paciorek-Sadowska ◽  
Bogusław Czupryński ◽  
Marcin Borowicz ◽  
Joanna Liszkowska
Keyword(s):  
Compressive Strength ◽  
Thermal Properties ◽  
Cell Count ◽  
Apparent Density ◽  
Mechanical And Thermal Properties ◽  
Fly Ashes ◽  
Closed Cell ◽  
Rigid Foams

This article describes the results of multidirectional research on producing new polyurethane materials modified with grain fraction of fly ashes. As a result of the conducted research, new polyurethane–polyisocyanurate foams were produced, which contained 5% to 35% of a microsphere in relation to its mass. Examinations on mechanical and thermal properties, as well as flammability, were conducted. The increasing content of aluminosilicate microspheres in rigid polyurethane–polyisocyanurate foams increased the apparent density of these materials. Based on the results, it was determined that the use of the microsphere in the recipe for producing polyurethane–polyisocyanurate foams is very advantageous. The obtained rigid foams are characterized by lower brittleness, higher compressive strength, higher closed cell count, as well as significantly lower flammability in relation to the reference foam (not modified with the filler).

scholarly journals Measurement of thermal expansions of closed-cell polyurethane rigid foams at cryogenic temperatures with an extensometer technique

AIP Advances ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 015353
Author(s):  
Hongyu Dong ◽  
Hengcheng Zhang ◽  
Rongjin Huang ◽  
Zhixiong Wu ◽  
Chuanjun Huang ◽  
...  
Keyword(s):  
Cryogenic Temperatures ◽  
Closed Cell ◽  
Rigid Foams

Effects of Substituting B2O3 for P2O5 on the Structures and Properties of V2O5-P2O5 Glass Systems (II)

2015 ◽  
Vol 53 (3) ◽  
pp. 198-205
Author(s):  
Bong-Ki Ryu ◽  
Su-Yeon Choi ◽  
Young-Seok Kim ◽  
Jong-Hwan Kim ◽  
Jae-Yeop Jung ◽  
...  
Keyword(s):  
Structures And Properties

Seeded Growth of Single-Crystal Two-Dimensional Covalent Organic Frameworks

2017 ◽  
Author(s):  
Austin M. Evans ◽  
Lucas R. Parent ◽  
Nathan C. Flanders ◽  
Ryan P. Bisbey ◽  
Edon Vitaku ◽  
...  
Keyword(s):  
Molecular Transport ◽  
Controlled Synthesis ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Seeded Growth ◽  
Covalent Bonds ◽  
Crystalline Materials ◽  
Step Procedure ◽  
Structures And Properties ◽  
2D Polymer

<div> <div> <div> <p>Polymerizing monomers into periodic two-dimensional (2D) networks provides structurally precise, atomically thin macromolecular sheets linked by robust, covalent bonds. These materials exhibit desirable mechanical, optoelectrotronic, and molecular transport properties derived from their designed structure and permanent porosity. 2D covalent organic frameworks (COFs) offer broad monomer scope, but are generally isolated as polycrystalline, insoluble powders with limited processability. Here we overcome this limitation by controlling 2D COF formation using a two- step procedure. In the first step, 2D COF nanoparticle seeds are prepared with approximate diameters of 30 nm. Next, monomers are slowly added to suppress new nucleation while promoting epitaxial growth on the existing seeds to sizes of several microns. The resulting COF nanoparticles are of exceptional and unprecedented quality, isolated as single crystalline materials with micron-scale domain sizes. These findings advance the controlled synthesis of 2D layered COFs and will enable a broad exploration of synthetic 2D polymer structures and properties. </p> </div> </div> </div>

Seeded Growth of Single-Crystal Two-Dimensional Covalent Organic Frameworks

2017 ◽  
Author(s):  
Austin M. Evans ◽  
Lucas R. Parent ◽  
Nathan C. Flanders ◽  
Ryan P. Bisbey ◽  
Edon Vitaku ◽  
...  
Keyword(s):  
Molecular Transport ◽  
Controlled Synthesis ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Seeded Growth ◽  
Covalent Bonds ◽  
Crystalline Materials ◽  
Step Procedure ◽  
Structures And Properties ◽  
2D Polymer

<div> <div> <div> <p>Polymerizing monomers into periodic two-dimensional (2D) networks provides structurally precise, atomically thin macromolecular sheets linked by robust, covalent bonds. These materials exhibit desirable mechanical, optoelectrotronic, and molecular transport properties derived from their designed structure and permanent porosity. 2D covalent organic frameworks (COFs) offer broad monomer scope, but are generally isolated as polycrystalline, insoluble powders with limited processability. Here we overcome this limitation by controlling 2D COF formation using a two- step procedure. In the first step, 2D COF nanoparticle seeds are prepared with approximate diameters of 30 nm. Next, monomers are slowly added to suppress new nucleation while promoting epitaxial growth on the existing seeds to sizes of several microns. The resulting COF nanoparticles are of exceptional and unprecedented quality, isolated as single crystalline materials with micron-scale domain sizes. These findings advance the controlled synthesis of 2D layered COFs and will enable a broad exploration of synthetic 2D polymer structures and properties. </p> </div> </div> </div>

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