Effect of isocyanate index on the properties of rigid polyurethane foams blown by HFC 365mfc

Abstract

Rigid polyurethane foams (RPUFs) were fabricated from crude MDI (CMDI) and polypropylene glycols (PPGs) of various isocyanate indices with a physical blowing agent (HFC 365mfc). There was a tendency for the gel time to decrease and the tack-free time to increase with increasing index value. With increasing index value the foam density and compression strength decreased and the glass transition temperature, dimension stability and thermal insulation increased, while the cell size and closed cell content were virtually unchanged. Allophanate crosslinks and condensation reactions between the isocyanate groups, which are favored with a high index value, exerted significant effects on the properties of RPUFs.

Effect of Natural Oil Based Polyols on the Properties of Flexible Polyurethane Foams Blown by Distilled Water

“…In this particular case low molecular weight of polymers will be obtained. Sung Hee Kim et al [11] has explained that the PUF containing low molecular weight polymer would resulted in low free surface energy and hence stickiness on the surface was persisted. This could increase tack free time.…”

A Comparison of Two Sampling Methods for the Detection of Airborne Methylene Bisphenyl Diisocyanate

“…(8) As a result, repeat units of NHCOO groups are generated, which are characteristic of polyurethane (PUR) products that can be produced with varying degrees of mechanical strength, rigidity, or flexibility. (6)(7)(8)(11)(12)(13) The functionality, moiety, and isomeric species of both the isocyanate and polyol help determine these properties to meet the needs for specific applications and emerging technologies. (6)(7)(8) One industrial process involving a two-component spray application of isocyanate-containing materials is spray-on truck bed liners (STBLs), and the primary isocyanate used in this process is 4,4 -diphenylmethane diisocyanate, or monomeric MDI.…”

“…(14,15) MDI is also used extensively in the synthesis of other rigid polyurethanes, which includes protective coatings for walls, decks, boats, as well as insulation materials for construction and industrial applications, such as refrigerators, freezers, piping, tanks, and shipbuilding. (13,16,17) The morphology of these foams typically exhibits a closed cell structure with superior mechanical properties (e.g., high compression strength, high strength-to-weight ratio, and low moisture permeability) and thermal stability (e.g., low thermal conductivity).…”

Rigid polyurethane foams incorporated with phase change materials: A state-of-the-art review and future research pathways

“…Being an excellent thermal insulating material, rigid polyurethane foam (RPUF) has been widely used in the field of thermal insulation in building envelopes to save energy due to their M a n u s c r i p t low thermal conductivity, superior specific mechanical properties and low density [3][4]. As traditional blowing agents, CFCs and HCFCs have been phased out in developed countries and will be totally banned by 2020 in developing countries according to the Montreal protocol, which led to an important research focus on foam synthesis modification using HFC-245fa, HFC-365mfc, cyclopentane and water as new generation of blowing agents [5][6][7][8]. Owing to the inherent drawbacks in these environmentally friendly blowing agents, the mechanical and thermal performance of the new generation of foam products are not as good as traditional foams.…”