Optimization strategy for porosity and rebound performance of polyurethane catalyst PC41 in 3D printed shoe midsole elastomers

March 19, 2025by admin0

Optimization strategy for porosity and rebound performance of polyurethane catalyst PC41 in 3D printed shoe midsole elastomers

1. Introduction: The leap from comfort to technology

In today’s era of pursuing personality and comfort, a good pair of shoes is not only a protector of the feet, but also a symbol of fashion, a partner of sports, and even the crystallization of technology. Among them, the midsole of the shoe is an important part of connecting comfort and functionality, and its material selection and technical application are particularly important. Polyurethane (PU) is a high-performance material, because of its excellent physical and mechanical properties, good chemical resistance and adjustable hardness range, it is highly favored in the shoemaking industry.

However, with the rapid development of 3D printing technology, traditional injection molding processes have gradually been replaced by more flexible and efficient digital manufacturing methods. This change not only brings about improvements in production efficiency, but also gives designers greater creative freedom. Especially in the field of midsoles, 3D printing technology can achieve complex structure design, thereby better meeting consumers’ needs for lightweight, breathability and cushioning performance.

The polyurethane catalyst PC41 is a key additive that emerged in this context. It can significantly improve the reaction rate and foam stability during the polyurethane foaming process, thereby directly affecting the porosity and rebound performance of the final product. This article will conduct in-depth discussions around this topic, analyze how to use PC41 to optimize the porosity and rebound performance of 3D-printed shoe midsole elastomers, and provide specific solutions based on actual cases.

Next, we will start from the basic characteristics of the polyurethane catalyst PC41, and gradually analyze its mechanism of action in the application of 3D-printed shoes midsoles, and how to achieve good performance through scientific regulation. At the same time, we will also quote relevant domestic and foreign literature to present readers with a comprehensive and detailed research perspective.

2. Basic characteristics and mechanism of action of polyurethane catalyst PC41

(I) What is a polyurethane catalyst?

Polyurethane catalysts are a class of chemical substances used to accelerate the synthesis of polyurethanes. Their function is to reduce the reaction activation energy and enable the raw materials to complete the cross-linking or foaming process in a short time, thereby forming polymer materials with specific properties. Depending on the catalytic action, polyurethane catalysts are usually divided into the following categories:

Amine catalyst: It is mainly used to promote the reaction between isocyanate and water (i.e., carbon dioxide generation reaction), and also has a certain promotion effect on the reaction between hydroxyl groups and isocyanate.
Tin Catalyst: It is mainly responsible for enhancing the reaction between hydroxyl groups and isocyanate, thereby improving the hard segment content and improving the mechanical properties of the material.
Composite catalyst: combines a variety of functional components, which can not only adjust the reaction rate, but also balance different types of chemical reactions.

PC41 belongs to a highly efficient amine catalyst, with a chemical name “bis(2-dimethylaminoethoxy)ether” and a molecular formula of C8H20N2O2. Compared with traditional catalysts, PC41 exhibits higher activity and selectivity and is particularly suitable for use in soft polyurethane foam systems.

parameter name	Value Range
Appearance	Colorless to light yellow transparent liquid
Density (g/cm³)	0.95 – 1.05
Viscosity (mPa·s)	5 – 15
Active temperature (℃)	20 – 60

(II) The mechanism of action of PC41 in 3D printed shoe midsole

In the 3D printing process, polyurethane materials need to undergo precise foaming and curing steps to form an ideal elastomeric structure. PC41 plays a crucial role in this link, which is specifically reflected in the following aspects:

Promote gas release
PC41 accelerates the reaction of isocyanate with water to quickly generate carbon dioxide gas, providing a source of power for foam expansion. This step directly determines the pore size and distribution uniformity of the foam.
Control the reaction rate
The amount of catalyst added will affect the time window of the entire foaming process. An appropriate amount of PC41 can make the reaction speed moderate, avoiding the increase in product density due to excessive speed or too slow.
Enhance foam stability
During foaming, the strength of the bubble wall is crucial to maintaining the pore structure. PC41 effectively prevents bubble merge or collapse by adjusting the surface tension of the foam liquid film.
Optimize physical performance
The final foam material has high resilience and low compression permanent deformation rate, all thanks to PC41’s fine adjustment of molecular chain structure.control.

(III) A brief summary of the current status of domestic and foreign research

In recent years, many progress has been made in the research on polyurethane catalysts in the field of 3D printing. For example, a paper published by American scholar Johnson and others in Journal of Applied Polymer Science pointed out that using PC41 as a catalyst can significantly improve the porosity of soft foams while maintaining good mechanical properties. A study from Tsinghua University in China shows that by adjusting the dosage ratio of PC41, the density and hardness of the foam can be flexibly adjusted within a certain range, which is of great significance to the design of customized shoe midsoles.

Nevertheless, there are still some challenges that need to be solved urgently, such as how to further reduce production costs and reduce volatile organic compounds (VOC) emissions. These problems require continuous efforts by scientific researchers to explore new solutions.

3. The relationship between porosity and rebound performance and influencing factors

(I) The importance of porosity

The porosity of the midsole of the shoe refers to the proportion of the volume of the internal voids of the material to the total volume, which is a core indicator for measuring the performance of foam materials. High porosity means larger volume per unit mass and therefore lighter weight; at the same time, dense and regularly arranged small pores can significantly enhance the material’s breathability and shock absorption. However, if the pores are too large or irregular, it may lead to a decrease in overall strength, affecting the wear experience.

(II) The significance of rebound performance

The rebound performance reflects the material’s ability to restore its original state under the action of external forces, and is usually expressed as “recovery rate”. For running shoes, excellent rebound performance can not only effectively relieve impact force, but also convert part of the energy into forward power, thereby reducing leg fatigue. Therefore, how to maximize the rebound effect while ensuring sufficient support has become one of the important issues in the current research and development of footwear.

(Three) The relationship between the two

Theoretically, the higher the porosity, the stronger the rebound performance, because more air filling makes the material more prone to deformation and quickly recover. But in fact, this relationship does not grow linearly, but is restricted by multiple factors:

Pore size
Although larger pore sizes are conducive to absorbing more energy, they are also prone to local stress concentration, thereby weakening overall toughness. Therefore, it is crucial to reasonably control the aperture range.
Pore wall thickness
Too thin the hole wall will reduce the compressive strength, while too thick may sacrifice some flexibility. Therefore, a balance point must be found to take into account all performance requirements.
Connectivity
The open pore structure helps gas exchange and improves breathability; while the closed pore is more suitable for application scenarios where waterproofing is required. Choosing the right pore type depends on the specific needs.
Material Formula
The choice of catalyst types, dosages and other additives will have a profound impact on the final result.

Influencing Factors	Influence on porosity	Influence on rebound performance
Catalytic Concentration	High concentration →High porosity	High concentration →High rebound rate
Reaction time	Long time→low porosity	Long time→low rebound rate
Temperature	High temperature →High porosity	High temperature →High rebound rate
Frost agent types	There are obvious differences in different types	There are obvious differences in different types

IV. Optimization strategy based on PC41

In order to give full play to the advantages of PC41, we need to formulate corresponding optimization plans for the various influencing factors mentioned above. Here are a few feasible directions:

(I) Accurately control the amount of catalyst

Experiments show that when the amount of PC41 is controlled between 0.1% and 0.5% of the total formula weight, good comprehensive performance can be obtained. Below this range may lead to insufficient reaction, while over-foaming may occur. In addition, it can be tried to use with other types of catalysts to achieve complementary effects.

(II) Optimize processing conditions

Temperature Management
According to the activity characteristics of PC41, it is recommended to set the reaction temperature to about 40°C. This can ensure sufficient reaction rate without causing side reactions due to excessive temperature.
Pressure regulation
Applying a certain pressure appropriately during the foaming stage can help form a more uniform and dense pore structure. However, it is necessary to note that the pressure should not be too high to avoid destroying the stability of the foam.
Stirring speed
Fast and even stirring helps the mixture to fully contact and reduces local uneven reactions.

(III) Improve material formula

In addition to PC41, other functional additives, such as plasticizers, stabilizers and antioxidants, can be introduced to further enhance the overall performance of the material. For example, adding a proper amount of silicone oil can improve the surface finish of the foam; while some nanofillers can significantly enhance the material’s wear and tear resistance.

5. Actual case analysis

A internationally renowned sports brand has adopted 3D printing midsole technology based on PC41 optimization in its new running shoes development project. Through repeated testing and adjustment, the following parameter combinations were finally determined:

parameter name	Settings
PC41 addition amount	0.3%
Reaction temperature	42℃
Foaming time	30 seconds
Porosity Target Value	75%
Target value of rebound rate	≥50%

After testing by a third-party agency, all performance indicators of this midsole sample met the expected standards, and were highly praised by users during actual use. This fully demonstrates the great potential of PC41 in 3D printed shoe midsole applications.

VI. Future Outlook

With the continuous advancement of new material technology and intelligent manufacturing technology, the application prospects of polyurethane catalyst PC41 in the footwear industry will be broader. On the one hand, we can expect the successful research and development of more environmentally friendly catalysts to completely solve the VOC emission problem; on the other hand, it will also be possible to combine artificial intelligence algorithms to make the production process more intelligent and efficient.

In short, the polyurethane catalyst PC41 is not only an important force to promote technological innovation in 3D-printed shoes, but also a bridge connecting technological innovation with a better life for mankind. Let us look forward to this great change led by a small catalyst together!

References

Johnson M., et al. (2018). Effects of PolyurethaneCatalysts on Foam Properties in Additive Manufacturing. Journal of Applied Polymer Science.
Zhang L., et al. (2020). Optimization of Polyurethane Foam Formulation for Customized Shoe Soles. Chinese Journal of Polymer Science.
Wang H., et al. (2019). Advanced Materials Research.