Form-Stable PCM Pellets via HDPE Mixing and Extrusion
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Solution Overview
Problem
Current methods for manufacturing form-stable phase change materials (PCMs) are costly and inefficient, primarily due to the use of toxic monomers and labor-intensive encapsulation processes, limiting their widespread adoption in energy-efficient building applications.
Innovation Solution
A low-cost, continuous method for producing PCM pellets involves mixing paraffin with high-density polyethylene (HDPE) and forming them into small pellets using an underwater or strand pelletizer, with optional additives like flame retardants, to create a form-stable PCM suitable for building insulation and other applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If encapsulation process is used to manufacture form-stable PCM, then leakage prevention is improved, but manufacturing cost increases and process complexity increases
Solution Approach 1:
The patent combines the PCM and binder materials into a single homogeneous mixture that is then extruded directly into pellet form. This eliminates the need for separate encapsulation steps, reducing manufacturing complexity and cost while maintaining form stability through the binder matrix that prevents leakage.
Solution Approach 2:
The patent changes the physical state and composition parameters by creating a specific mixture ratio of PCM to binder materials, then controlling the extrusion and cooling parameters to produce solid pellets. This parameter optimization achieves form stability without requiring complex encapsulation processes.
2Reliability
If encapsulation process is used to manufacture form-stable PCM, then leakage prevention is improved, but manufacturing efficiency decreases
Solution Approach 1:
The patent implements a continuous extrusion process where PCM and binder materials are continuously mixed and extruded into pellets. This continuous operation eliminates the batch processing nature of encapsulation methods, significantly improving manufacturing efficiency and productivity while maintaining product quality.
3Ease of manufacture
If mixing with polymer is used to create form-stable PCM, then manufacturing cost decreases, but heat transfer rate may be reduced
Solution Approach 1:
The patent uses small pellet sizes (1-5 mm diameter) to increase the surface area to volume ratio. This local geometric optimization compensates for the lower thermal conductivity of polymer binders by reducing the heat transfer path length, thereby maintaining efficient heat transfer rates despite the cost-effective polymer mixing approach.
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
This method enables the production of cost-effective, high-volume PCM pellets with enhanced heat transfer rates, suitable for energy-efficient building materials, clothing, and footwear, addressing the limitations of existing PCM manufacturing processes.
Implementation Method 1
the paraffins of interest for building envelopes are those that undergo solid-liquid phase change (melting and freezing) at indoor comfort temperatures
Implementation Method 2
Relatively large amounts of energy are stored during paraffin phase change (about 100 to about 240 J/g)
Implementation Method 3
forming the melt composition into PCM pellets in a pelletizer
Data Source
AI summary
The present technology generally relates to phase change material (PCM) pellets consisting essentially of a mixture of paraffin, a polymer, and optionally a thermal conductivity improver, a nucleating agent, an anti-oxidant, or a combination of any two or more thereof; wherein the paraffin is at least about 60 wt % of the PCM pellet; and the polymer is uncrosslinked high density polyethylene (HDPE) that has a melt flow index between about 0.1 g/10 min and about 50 g/10 min.