In May 2022, we received an inquiry from Mr. Agus, a customer in Indonesia, regarding a semi-automatic foam machine. Mr. Agus operates a small foam production factory mainly produces rebonded foam and virgin foam, and his products are sold locally. Due to issues related to aging equipment and significant material wastage in his factory, Mr. Agus was interested in upgrading his old machinery. Additionally, the foam he was producing had large pinholes and inside-burn, which he wanted to address.

First, our technical engineers provided Mr. Agus with a new foam production solution. Since foam production can be influenced by local temperature and humidity, after several attempts and improvements to the engineer's formula, the client ultimately achieved the low-density foam he desired, resolving the issues of large pinholes and inside-burn in the foam.

Given that the client's factory equipment was old and had low production efficiency, with frequent machine breakdowns, we proposed a comprehensive equipment upgrade plan based on his budget and specific circumstances.

Our production department customized a machinery solution for the client that reduced the use of molds, and the top-flat device on the machine minimized material wastage during the foam production process. As a result, the client was highly satisfied with the solution provided.

In September 2021, we received an inquiry from Mr. Abdullah in Saudi Arabia regarding a continuous foaming machine. The client was planning to establish a PU foam factory to produce products for the local and Yemeni markets. He had some basic knowledge about machine usage and selection.

The client had no prior experience in foam production before, so he was particularly concerned about after-sales support and technical assistance.

We began by analyzing the client's target market (specific industry) and understanding the local product requirements (such as foam density, hardness, etc.) to confirm the client's production needs.

Through video conferences, we guided the client through our PU foam production process, providing the client with a concrete understanding of foam production and highlighting the convenience and efficiency advantages of our machines compared to those of other manufacturers.

Drawing upon our more than 20 years of experience in foam foaming, we shared insights with the client about using the machine and common challenges in the foam foaming process, addressing any technical concerns the client may have had.

We also provided the client with factory layout plans to expedite the setup of the entire foam production line while maximizing production efficiency.

Due to the client's high level of trust in our professional service, he ultimately chose us as his supplier for foam machinery and later made repeat purchases for a rebonded foam production line and foam cutting machines.

Manufacturing polyurethane filter foam typically involves two key stages. The first stage involves preparing open-cell or partially open-cell polyurethane foam according to the desired porosity. If the foam is closed-cell, it needs to be subjected to roller compression to rupture the cell walls, thereby creating the necessary porous structure. The second stage is to remove all the cell membranes to form a reticulated structure.

To produce polyurethane filter foam, the size of the pores and the structure of the network of the foam are largely determined by the catalyst, foaming agent, and surfactant.

In practical operations, there are two common methods for forming the network:

First is the alkali hydrolysis method. The steps of this method involve immersing the soft polyester-type polyurethane foam obtained from the first stage in a 10% sodium hydroxide solution at 50 degrees Celsius for about 10 minutes. Then it goes through processes such as washing with water, neutralization with acetic acid, another round of water washing, and drying, resulting in the final product of polyurethane filter foam.

Another method is the combustion method, also known as the explosion method. This method requires placing the soft polyether-type or polyester-type polyurethane foam obtained from the first stage into a sealed container. The container is then evacuated to 13.3 Pa, followed by the introduction of oxygen and natural gas (in a volumetric ratio of 2:1), bringing the internal pressure of the container to a certain level (which increases with the porosity). Next, the gas inside the container is ignited using a spark plug. The heat generated from the combustion process will burn off or melt the cell membranes without damaging the cell struts. Finally, the resulting product after combustion is cleared with air, and the filter foam is removed from the container.

Both of these methods are effective ways to prepare polyurethane filter foam, and the specific choice between them depends on the material of the foam and the desired structural characteristics.

Flame-retardant PU flexible foam, also known as fireproof PU flexible foam, is generally a fireproof material synthesized by adding flame retardants to various polyurethane materials.

Function of flame retardants: They can absorb heat and decompose into non-combustible substances at or near the ignition temperature; they can react with the combustion products of the PU flexible foam to produce difficult-to-burn substances, thereby delaying combustion and allowing the ignition point to self-extinguish.

Common flame retardants: Bromine-based flame retardants, chlorine-based flame retardants, phosphorus-based flame retardants, and inorganic flame retardants.

Flame Retardant Grade and Testing for PU flexible foam

Flame retardant grade refers to the obvious property that a substance has or a material exhibits after treatment, which significantly delays the spread of flames.

Flame retardant testing:

HB: The lowest flame retardant grade in the UL94 standard. It requires that for samples 3 to 13 millimeters thick, the burning rate is less than 40 millimeters per minute; for samples less than 3 millimeters thick, the burning rate is less than 70 millimeters per minute; or extinguished before reaching the 100-millimeter mark.

V-2: After two 10-second combustion tests on the sample, the flame is extinguished within 60 seconds. Combustible material may drop.

V-1: After two 10-second combustion tests on the sample, the flame is extinguished within 60 seconds. There should be no combustible material dropping.

V-0: After two 10-second combustion tests on the sample, the flame is extinguished within 30 seconds. There should be no combustible material dropping.

Polyurethane soft foam plastic is one of the important products in the polyurethane industry. Its production necessarily involves the use of organic amine catalysts, especially organic tertiary amine catalysts. This is because organic tertiary amine catalysts play a significant role in the main reactions of polyurethane foam formation: the reactions of carbon dioxide and molecular polymerization, promoting rapid expansion of reaction mixtures, increased viscosity, and sharp increase in polymer molecular weight. These conditions are essential for the formation of foam bodies, ensuring that soft foam plastics have advantages such as low density, high strength-to-weight ratio, high resilience, and comfort for sitting and lying. There are many types of organic amine catalysts that can be used for polyurethane soft foam plastics. Among them, the highly efficient catalysts recognized by various manufacturers are: triethylene diamine (TDEA) and bis(dimethylaminoethyl) ether (referred to as A1). These are also the most widely used organic amine catalysts in the world today, with the highest consumption among various catalysts.

Due to the molecular structural differences between TDEA and A1 catalysts, there are significant differences in their catalytic performance, particularly in their reactions to carbon dioxide gas and molecular polymerization. If the user does not pay attention to these differences in production, not only will they fail to produce qualified foam products, but it will also be difficult for foam bodies to form. Therefore, understanding and mastering the performance differences between these two catalysts in polyurethane foam production is of great significance. TDEA exists in a solid state under normal conditions, making its application less convenient. In actual production, low molecular weight alcohol compounds are commonly used as solvents, formulated into 33% solutions for ease of use, commonly referred to as A33. On the other hand, A1 is a low-viscosity liquid that can be directly applied. Below is a comparison of the catalytic performance differences between A1 and A33 in the production of polyurethane soft foam plastics.

A33 has a 60% catalytic function for the reaction with carbon dioxide gas and a 40% catalytic function for molecular polymerization. It has a low effective utilization rate of carbon dioxide gas, resulting in lower foaming height and higher foam density. Since most of the catalytic function is used for molecular polymerization reactions, it is easy to produce closed-cell foam bodies, which are stiff with low rebound, and the adjustable range of tin catalysts becomes narrower. To achieve the same catalytic function, the amount used is 33% more than A1. Both the bottom skin and outer skin of the foam body are thicker. Increasing the amount can increase the reaction speed, but the amount of tin catalyst must be reduced accordingly, otherwise closed-cell foam bodies will be produced.

A1 has an 80% catalytic function for the reaction with carbon dioxide gas and a 20% catalytic function for molecular polymerization. It has a high effective utilization rate of carbon dioxide gas, resulting in higher foaming height and lower foam density. Since most of the catalytic function is used for gas generation reactions, it is easy to produce open-cell foam bodies, which are soft with high rebound, and the adjustable range of tin catalysts becomes wider. To achieve the same catalytic function, the amount used is less than A33. Both the bottom skin and outer skin of the foam body are thinner. Increasing the amount can increase the reaction speed, but the amount of tin catalyst must be increased accordingly, otherwise over-foaming and cracking may occur.

In terms of overall performance between TDEA and A1, A1 has a higher comprehensive catalytic performance than triethylene diamine. Its actual application effects are also better, although not as convenient as triethylene diamine in terms of transportation and storage. Currently, the vast majority of mechanical continuous foam production facilities almost exclusively use A1, while all box-type foam production facilities use TDEA. However, this is not absolute. With a clear understanding of the differences between the two and appropriate formulation adjustments, they can be interchangeable and both can produce excellent foam products.