Modulation of cavities and interconnecting pores in manufacturing water blown flexible poly (urethane urea) foams

Abstract

Flexible poly (urethane urea) (PUU) foam based on the polyol and isocyanate with various additional components is synthesized by one shot polymerization. FTIR analysis shows that both urethane and urea formations are closely related to the catalysts, water, and NCO index. Increment of the catalyst concentration increases the initial volume velocity of the flexible PUU foam but decreases the bulk density by the increased number of cavities and pores. Water has strong effects on the initial volume velocity and bulk density, whereas increment of the NCO index has a little influence on the physical properties. The average cavity and pore sizes increase with increasing the equivalents ratio of water to polyol, but there is a limiting equivalents ratio in the PUU foam systems not to form coalesced or collapsed microcellular structure. The foams are also characterized using a scanning electron microscope and a Fourier transformed infrared spectroscopy.

Sound absorption and compressive property of PU foam‐filled composite sandwiches: Effects of needle‐punched fabric structure, porous structure, and fabric‐foam interface

“…Conversely, the thickness of NPUN‐N composite sandwiches was the highest because N‐N composite fabrics had greater fabric density after needle punching, which adversely affected gas release during the foaming process. The cells had difficulty of releasing CO 2 ; thus, the percentage of opening cells and the thickness of interface increased …”

Sound absorption behavior of flexible polyurethane foams including high molecular‐weight copolymer polyol

“…The absorption coefficient is defined as the ratio of the acoustic energy absorbed by the samples to the incident acoustic energy on the surface as a function of frequency. For effective sound absorption, various non‐acoustic parameters such as the strength of the cell walls, sizes of cavity and pores, and an open porosity of flexible polyurethane foams can be optimized . For example, a flexible polyurethane matrix containing an optimum ratio of partially open pores showed the highest sound absorption coefficient by the dissipation of the sound energy through the viscous friction and heat exchange in porous matrix .…”

“…Absorption of a sound wave in porous materials can be mainly achieved by 2 representative mechanisms: frictions with air and dissipation by collision with cell walls . Polyurethane foam, one of the typical materials used in sound absorption applications, has been used as a good candidate to dissipate the sound energy, and also its sound absorption characteristic can be controlled by varying raw materials such as polyol, isocyanate, cross‐linking agent, blowing agent, surfactant, catalysts, and any other additives . Selective uses of raw materials generally influence on the final cell morphology and physical properties of polyurethane foams by controlling the reaction rate, matrix modulus, and gas releases.…”

Characteristics of polyurethane adhesives with various uretonimine contents in isocyanate and average alcohol functionalities

“…Fourier transformed infrared spectroscopy (FTIR Frontier, PerkinElmer Inc.) with an attenuated total reflectance (ATR) accessory was used to qualitative analysis for the polyurethane reactions . The FTIR spectra were obtained from 4 scans with a resolution of 4 , and the conversion of polyurethane reaction was examined with the Time base software.…”