Viscoelastic polyurethane foams
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Solution Overview
Problem
Viscoelastic polyurethane foams used in comfort applications such as pillows and mattresses suffer from poor airflow, leading to trapped heat and discomfort due to their low resiliency and slow recovery, which results in localized temperature rises.
Innovation Solution
A flexible polyurethane foam is developed using a reaction mixture comprising specific ratios of ethylene oxide, propylene oxide, and liquid polyester polyols, along with water, aromatic polyisocyanate, urethane catalysts, and foam-stabilizing surfactants, which enhances airflow while maintaining low resiliency and slow recovery characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If viscoelastic polyurethane foam is used for comfort applications, then low resiliency and slow recovery are achieved, but heat conduction is poor and air circulation is restricted
Solution Approach 1:
The patent applies porous materials by incorporating a blowing agent (water) that generates gas bubbles during the foam formation process, creating an open-cell structure. This porous architecture enables air circulation pathways through the foam while maintaining the viscoelastic properties, thereby improving heat dissipation and comfort without sacrificing the slow recovery characteristic
2Strength
If foam density is maintained for structural support, then weight bearing capability is preserved, but airflow is reduced
Solution Approach 1:
The patent uses composite materials by combining multiple polyol components (polyether polyol and polyester polyol in specific ratios) with polyisocyanate and blowing agent to create a composite foam structure. This composite formulation achieves optimal balance between density for weight bearing and open-cell structure for airflow, resolving the contradiction between structural support and ventilation
3Reliability
If polyol composition is optimized for viscoelastic properties, then low resiliency is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ratios of polyol components (45-70 wt% polyether polyol with specific equivalent weight, 30-55 wt% polyester polyol with specific equivalent weight) and isocyanate index (80-120) to achieve the desired viscoelastic properties. These parameter specifications ensure consistent low resiliency and slow recovery while providing clear manufacturing guidelines to manage complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modified foam exhibits significantly improved airflow, contributing to greater perceived comfort and supporting human weight without compromising its viscoelastic properties, thus addressing the issue of heat retention in comfort applications.
Implementation Method 1
a reaction mixture that comprises a) a polyol mixture that comprises i) 45 to 80 weight-%, based on the weight of the polyol mixture, of an ethylene oxide copolymer... c) an aromatic polyisocyanate that comprises polymeric MDI
Implementation Method 2
b) water in an amount of 1 to 4 parts by weight per 100 parts by weight of the polyol mixture
Data Source
AI summary
Flexible polyurethane foams having high airflows and excellent viscoelastic properties are made using a polyol mixture that includes a certain liquid polyester, certain ethylene oxide polyols and certain propylene oxide polyols, and a polymeric MDI. When used in applications such as bedding, the high airflows contribute to an improved sense of comfort by the user.