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

Abstract

Noise pollution is an important issue for automotive industries. In this article, the high molecularweight copolymer polyol is blended in the polyol mixtures for fabricating flexible polyurethane foams to improve sound absorption efficiency. Changes of cavity size and material density of the foams are negligible by inclusion of copolymer polyol in the polyol mixture, but the closed pore ratio and specific airflow resistance increase for the copolymer polyol content higher than 20 wt% because of changes of phase separation behavior from drainage flow rate reduction that occurs with increased viscosity. Sound absorption efficiency increases with increasing copolymer polyol content up to 20 wt%, but it decreases beyond this point. The sound absorption property mainly results from the closed pore ratio, not from the cavity size. The compression strength increases with increasing copolymer polyol contents by increased amount of hard segments.Therefore, an optimum amount of high molecular-weight polyol is recommended for enhanced sound absorption property.

The study of palm‐oil‐based bio‐polyol on the morphological, acoustic and mechanical properties of flexible polyurethane foams

“…Interestingly, all the bio‐based PU foams possessed a high content of closed pores except for the reference foam (PU‐P 0 ). Therefore, the closed pore ratio was calculated using the following equation: where N c , N o and N p represent the number of closed, open and partially open pores, respectively.…”

“…The air‐flow resistivity σ is defined as the resistance per unit thickness, and the value was determined by a specific apparatus in accordance with standard ASTM C522‐03 (2009). The samples (100 mm diameter and 30 mm thickness) were placed in this apparatus, which provided an air flux to form an air pressure difference as through the examples . The air‐flow resistivity was calculated using the equation where Δ P (Pa), A (m 2 ), U (m 3 s –1 ) and d (m) denote pressure difference, cross‐sectional area, volumetric air‐flow rate and thickness, respectively.…”

Flexible polyurethane foam‐based sandwich composites: Preparation and evaluation of thermal, acoustic, and electromagnetic properties

“…At the FR contents below 40 wt %, increased drainage flow rate and reduced phase separation with the high-molecular weight FR can compensate each other, and thus, the opened pore ratio did not show considerable change. 15,16 However, when the FR content reaches to 50 wt %, a dramatic increase in pore diameter is shown, indicating an excessive amount of FR agent will significantly change the morphology of open pores.…”

Acoustic damping flexible polyurethane foams: Effect of isocyanate index and water content on the soundproofing

“…Noise pollution is one of the most critical quality‐of‐life issues and continues to get dire due to the rapid population growth and fast expansion of modern industries and transportations . Several types of industrial and domestic equipment and also vehicles, especially the automobiles, are the sources of both structural and air‐borne noises .…”

“…The sound absorption performance can be assessed by the sound absorption coefficient (α) which depends on the both solid‐phase attributes and cellular morphology of foams including macroscopic density, tortuosity, thickness of cell walls and struts, airflow resistivity, porosity, average cell size, and cell size distribution …”