Properties of water blown rigid polyurethane foams with different functionality

Abstract

Water blown rigid polyurethane foams with different functionality were prepared. The physical properties of rigid foams were measured with rotational viscometer (NDJ-1), universal testing machine (Instron3365), scanning electron microscope (SEM) and differential scanning calorimeter (DSC). The results show that the viscosity of polyether polyol increases exponentially from 62 mPa•s to 6 000 mPa•s with the increase of functionality from 2 to 5.6, respectively. The overall density of foam increases slightly from 31.7 kg/m 3 to 37.4 kg/m 3 with increasing functionality while core density exhibited little difference. Compressive strength of foam shows the similar behavior with density except for 2-functional sample. At the same time, dimensional stability becomes better with increasing functionality except for 5.6-functional foam that has worse stability than 4.8-functional foam. From the SEM results, the functionality is not an important factor in determining distribution of cell size of foam. According to the results of thermal analysis, the glass transition temperature (T g ) shifts to a higher temperature from 128.9 ℃ to 166.3 ℃ for the 2 to 5.6 functional foam, respectively.

Water‐blown polyurethane/polyisocyanurate foams made from recycled polyethylene terephthalate and liquefied wood‐based polyester polyol

“…A higher functionality means a greater amount of OH groups per molecule and a consequently larger amount of intermolecular bonding. The latter results in molecular mobility being reduced which increases the viscosity of the polyol …”

“…A large amount of intermolecular bonding is formed with the increase of functionality. As more OH groups occur per molecule, molecular mobility and foaming efficiency are reduced, resulting in longer reaction times . With the composition of the liquefaction reagent, the cream time and tack free time in the PUR/PIR foam preparation can be tailored so that they satisfy the industrial production requirements.…”

“…The glass transition temperature ( T g ) shifted to a higher temperature ranging from 58.9°C to 66.1°C, with an increase of glycerol in the liquefaction reagent from 10% to 70%. This could be due to the higher crosslink density of the foam when a greater amount of glycerol is present in LW‐PES and consequently in the polyol . In highly branched or crosslinked structures, the mobility of the molecules is reduced and more thermal energy is required to initiate chain movements.…”

“…Polyesters were made due to the lower number of hydroxyl groups in comparison to LW and depolymerized PET, which means reduced isocyanate consumption. As a blowing agent, we used water, which is non‐ozone depleting, non‐toxic, and cheap …”

Preparation of polyester polyols from unsaturated fatty acid

“…The particles have a honeycomb structure, with a size distribution of 200–400 μm in diameter, and a uniform and smooth surface texture. The cell size of the rigid foam has an important effect on thermal conductivity and mechanical properties 19. The excellent honeycomb structure obtained during foam formation made it possible for a considerable amount of still air to be trapped, thus, leading to an increased passive insulation.…”