Flexible Phase Change Composition That Prevents Sharp Crystal Formation
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Solution Overview
Problem
Existing phase change materials (PCMs) like Na2SO4·10H2O suffer from loss of flexibility and surface roughness during phase change, which is undesirable in flexible applications such as apparel, and there is a need for a PCM that maintains flexibility and avoids sharp crystalline material formation.
Innovation Solution
A composition comprising 50.0-99.9 wt.% Na2SO4·10H2O, 0.1-5.0 wt.% alginic acid salt, and 0.1-5.0 wt.% fatty acid salt with low water solubility, optionally with additives like NaCl, borax, and sodium carboxymethyl cellulose, to maintain flexibility and prevent crystalline formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Na2SO4·10H2O is used as a phase change material in apparel, then heat storage capacity is improved, but flexibility is lost and surface roughness increases during phase change
Solution Approach 1:
The patent combines Na2SO4·10H2O with hydrogel-forming polymers (polyacrylic acid, polyvinyl alcohol, carboxymethyl cellulose) to create a composite material. The hydrogel matrix encapsulates the phase change material, allowing it to maintain flexibility and softness while undergoing phase transition, thus resolving the contradiction between heat storage capacity and flexibility.
Solution Approach 2:
The patent modifies the physical state and mechanical properties of the PCM by changing its composition parameters - specifically by incorporating hydrogel-forming polymers that alter the material's rheological properties. This enables the PCM to maintain a soft, flexible state during phase change rather than becoming crystalline and rigid.
2Use of energy by moving object
If Na2SO4·10H2O undergoes liquid-solid phase change, then heat storage is achieved, but sharp crystals form that may damage the container
Solution Approach 1:
The hydrogel-forming polymer creates a cushioning matrix before the phase change occurs. This matrix surrounds and protects the PCM, preventing the formation of sharp crystals that could puncture or damage the container during solidification, thus resolving the contradiction between heat storage and container safety.
Solution Approach 2:
The hydrogel polymer acts as an intermediary between the PCM and the container. It mediates the phase change process by providing a protective environment that prevents direct contact between sharp crystals and the container, eliminating the harmful effect while preserving the heat storage function.
3Use of energy by moving object
If water-tight container is used to prevent evaporation, then heat storage capacity is maintained, but flexibility and comfort are reduced
Solution Approach 1:
The patent uses flexible hydrogel films instead of rigid water-tight containers. The hydrogel matrix provides water retention properties while maintaining flexibility and softness, allowing the PCM to be comfortably integrated into apparel without sacrificing heat storage capacity through the formation of a rigid enclosure.
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 composition remains flexible through multiple cycles and avoids crystalline damage to containers, maintaining effective heat storage capacity and phase change temperature.
Implementation Method 1
Phase change materials (PCMs) fulfill an important role herein because of their effective way of storing thermal energy. Being relatively unhazardous and having a sharp phase change at a temperature of 32.4 °C, the compound Na 2 SO 4 ·10H 2 O finds useful application as a PCM in apparel.
Implementation Method 2
Latent heat storage has become increasingly important in recent years. Phase change materials (PCMs) fulfill an important role herein because of their effective way of storing thermal energy.
Implementation Method 3
The phase change on which the heat storage of Na 2 SO 4 ·10H 2 O relies is a liquid-solid phase change, which gives rise to the problems outlined above when it is desired that a flexible pouch of Na 2 SO 4 ·10H 2 O is being applied in apparel.
Data Source
AI summary
The invention relates to a composition comprising 50–99 wt.% of Na2SO4·10H2O and 0.1–5.0 wt.% of an alginic acid salt. Such composition may advantageously be used as a phase change material since the composition (and a pouch comprising the composition) remains flexible during the phase change. This was also the case when subjected to a high number of subsequent cycles of heating and cooling.