Foam Track Peeling Machine: Things You May Want to Know

Many factors affect the foaming process and final product quality when manufacturing polyurethane flexible foam. Among these, natural environmental factors such as temperature, air humidity, and atmospheric pressure play crucial roles. These factors significantly influence foam density, hardness, elongation rate, and mechanical strength.

1. Temperature:

Polyurethane foaming reaction is highly sensitive, with temperature being a key control factor. As material temperature rises, the foaming reaction accelerates. In sensitive formulations, excessively high temperatures can pose risks like core burning and ignition. Generally, it's essential to maintain consistent temperatures for polyol and isocyanate components. Increasing temperature leads to a corresponding decrease in foam density during foaming.

Particularly in summer, elevated temperatures increase reaction speed, resulting in decreased foam density and hardness, increased elongation rate, yet enhanced mechanical strength. To counter hardness reduction, adjusting the TDI index is advisable. Manufacturers must adjust process parameters according to seasonal and regional temperature variations to ensure product quality stability. 

2. Air Humidity:

Air humidity also affects the foaming process of polyurethane flexible foam. Higher humidity causes reactions between isocyanate groups in the foam and airborne moisture, leading to reduced product hardness. Increasing TDI dosage during foaming can compensate for this effect. However, excessive humidity can raise curing temperatures, potentially causing core burning. Manufacturers need to carefully adjust foam process formulations and parameters in humid environments to ensure product quality and stability.

3. Atmospheric Pressure:

Atmospheric pressure is another influencing factor, especially in areas at different altitudes. Using the same formulation at higher altitudes results in relatively lower foam product density. This is due to atmospheric pressure variations affecting gas diffusion and expansion during foaming. Manufacturers operating in high-altitude regions should take note of this and may need to adjust formulations or process parameters to meet quality requirements.

In conclusion, natural environmental factors significantly impact the foaming process and final product quality of polyurethane flexible foam. Manufacturers must adjust process parameters based on seasonal, regional, and environmental conditions to ensure stable foam density, hardness, and mechanical strength, meeting customer demands and standards.

Aluminum Hydroxide

Also known as hydrated alumina. The aluminum hydroxide used as a fire retardant is mainly @-tri-hydrated alumina. It appears as a white fine crystalline powder with an average particle size of 1-20 micrometers. Its relative density is 2.42, refractive index is 1.57, and 30% slurry pH is 9.5-10.5. The dehydration initiation temperature is 200 degrees Celsius, with an absorption heat of 2.0 KJ/G.

During combustion, it releases a large amount of chemically combined water, absorbs a considerable amount of heat, slows down the polymer's thermal degradation rate, reduces the material surface temperature, delays and suppresses the combustion of the substrate. It will generate a large amount of steam on the substrate surface, diluting the oxygen in the combustion zone, reducing the concentration of smoke and toxic flammable gases. The aluminum oxide generated during combustion can promote the formation of a carbonized protective layer on the polymer surface.

Melamine

Commonly known as melamine, it is a white monoclinic crystal with low toxicity, non-flammable, and a melting point of 354 degrees Celsius. It undergoes endothermic sublimation and rapid decomposition under high heat. At temperatures between 250-450 degrees Celsius, it can absorb a large amount of heat and release nitrogen during decomposition, slowing down the material's combustion rate. At the same time, it forms a carbonized barrier layer on the substrate surface, acting as a fire retardant. However, there are some dispersion problems, so it needs to be used in combination. When used as a fire retardant, high-temperature decomposition can produce toxic cyanide gas.

Organophosphorus Flame Retardant

Tris(1,3-dichloro-2-propyl)phosphate (TDCPP)

A pale yellow transparent viscous liquid. It contains 7.2% phosphorus and 49.4% chlorine, with a flash point of 251.7 degrees Celsius, ignition point of 282 degrees Celsius, and spontaneous combustion temperature of 514 degrees Celsius. It starts to decompose at 230 degrees Celsius and is soluble in alcohols, benzene, carbon tetrachloride, etc. When used at 5%, it can achieve self-extinguishing properties, and at 10%, it can make the material self-extinguish or non-flammable, while also having water resistance, light resistance, and antistatic properties.

Fire Retardant Polyether Polyol

1. Formula Ingredients:

Polyether polyol 3050: Mn3000;

Flame-retardant polyether polyol: Hydroxyl value 28, flame-retardant solid mass fraction 23%;

Silicone oil: L580

Triethylene diamine solution: Mass fraction 33%;

Tin octoate solution: Mass fraction 33%;

TDI: Industrial grade

PLC (Programmable Logic Controller)

It is an automatic control device with instruction memory, digital or analog I/O interfaces; primarily used for logical, sequential, timing, counting, and arithmetic operations with bit operations; used to control machines or production processes.

Variable Frequency Drive (VFD)

A VFD is a control device that transforms power frequency from one frequency to another using the on-off action of power semiconductor devices.

The main circuits of a VFD can generally be divided into two types:

- Voltage type: Converts DC voltage from a voltage source to AC in the VFD, with capacitor filtering in the DC circuit.

- Current type: Converts DC current from a current source to AC in the VFD, with inductor filtering in the DC circuit.

Photoelectric Switch

It utilizes the obstruction or reflection of an infrared light beam by a detected object, detected by the synchronous circuit, to determine the presence or absence of the object. It can detect any object that reflects light, not limited to metals.

A mirror-reflective photoelectric switch is used on the vacuum perforating machine.

Heat Exchanger System

Controls the temperature of raw materials in the system to meet requirements.

As the temperature of the raw material rises after passing through the heat exchanger, its viscosity increases. To ensure the normal operation of the high-pressure pump, a special feeding pump is required. Specific requirements are calculated based on flow rate and raw material viscosity.

The temperature control of the heat exchanger should be near the mixing head, correlating the raw material temperature with the switch of the cooling water to automatically control the flow of cooling water to cool the raw material.

Perforating Machine

There are roller perforating machines, vacuum perforating machines, and brush perforating machines, with roller machines having the best control effect, followed by vacuum perforating machines, and brush perforating machines being the worst. Currently, brush perforating machines are rarely used.

The purpose of perforating is to prevent product deformation.

The roller perforating machine controls the size of the gaps. If the gaps are too large, the perforating effect is not good; if the gaps are too small, there will be obvious pressure marks on the product.

There are two methods of perforating: 1. Chemical method - using perforating agents, 2. Mechanical method - using perforating machines.

Products must be perforated as soon as they come out of the mold. Some products may expand after being demolded, and at this time, they should be left for a period before perforating.

TPR

It can prevent product shrinkage and collapse of bubbles; its most basic function is effective perforating to facilitate demolding. However, it can also lead to fluctuations in ILD (Indentation Load Deflection); TPR directly affects the rise speed of the foam.

Loop Pressure Regulating Valve

It is crucial for balancing system pressure in the control system and should be placed as close to the nozzle as possible. If it is far from the nozzle, pressure fluctuations may occur, leading to system instability and unstable products.

In modern industrial production, polyurethane flexible foam play an important role in various fields such as furniture, automotive seats, and shoe insoles. However, the key technical control points for producing high-quality polyurethane flexible foam plastic products cannot be overlooked. Here are several key technical points in the production process:

Control of Toluene Diisocyanate (TDI):

The optimal isomeric ratio of TDI is 80/20. If this ratio is exceeded, it can lead to the formation of large and closed cells in the foam, prolonging the curing time. Particularly in the production of large block low-density foam products, an excessive isomeric ratio can delay heat release, potentially causing the foam center temperature to remain high for a long time, leading to carbonization and even ignition. If the isomeric ratio is too low, the foam product's density and resilience will decrease, and fine cracks may appear on the foam surface, resulting in poor process repeatability.

Addition of External Blowing Agents:

External blowing agents (water) not only reduce the density of the foam but also improve the softness of the product and help remove reaction heat. To prevent center carbonization in the foaming process of large block foam products, a certain amount of water is usually added. However, as the amount of water increases, the amount of catalyst should also increase correspondingly; otherwise, it may prolong the post-curing time of the foam. Generally, for every 5 parts increase in water, 0.2 to 0.5 parts of silicone oil should be added.

Catalyst Ratio:

Organic tin and tertiary amine catalysts are commonly used to control the NCO-OH and NCO-H2O reactions. By adjusting the ratio of different catalysts, the growth of polymer chains and the foaming reaction can be controlled. Under certain product densities, choosing the appropriate catalyst ratio can control the foam's open-cell rate, cell size, and void load value. Increasing the amount of organic tin catalyst can generally produce foams with smaller cell sizes, but excessive use may increase the closed-cell rate. It is necessary to determine the optimal catalyst dosage through experiments to achieve the best performance of foam products.

Foam Stabilizers:

The role of foam stabilizers is to reduce surface tension of the material, making the foam film wall elastic and preventing foam wall rupture until the molecular chain growth and cross-linking reactions lead to material solidification. Therefore, foam stabilizers play a critical role in the production of one-step polyether sponge and must be strictly controlled in usage.

Temperature Control:

The foam generation reaction is highly sensitive to temperature, and changes in material and foaming temperature will affect foaming operations and physical properties. Therefore, temperature control is one of the important conditions to ensure stable foaming processes. The material temperature is generally controlled at 20-25°C.

Stirring Speed and Time:

The stirring speed and time affect the amount of energy input during the foaming process. If stirring is uneven, a large number of bubbles may appear on the foam surface, leading to defects such as cracking. During mixing of Component A, the speed is 1000r/min; after Component B is added to Component A, the high-speed stirring speed is 2800-3500r/min for 5-8 seconds.

In summary, the key technologies for producing polyurethane flexible foam include controlling TDI, adding external blowing agents, adjusting catalyst ratios, using foam stabilizers, temperature control, and controlling stirring speed and time. Proper control of these technical parameters can ensure the production of stable quality and high-performance polyurethane flexible foam plastic products.

In annual fire incidents, a significant proportion of ignitions are caused by foam, including sofa fires and various ignitions from soft packaging. These incidents occur far too frequently. How can we fundamentally eliminate or reduce such events?

One effective approach is to start from the source materials, much like treating the root cause of an illness. Adding flame retardants to polyurethane foam can effectively prevent ignition.

Now, let's understand flame-retardant foam:

Flame-retardant foam, also known as fire-resistant foam, has a chemical name of polyurethane foam material, which is divided into soft foam (mainly used for furniture) and rigid foam (mainly used for insulation). Generally, it is a fireproof material synthesized by adding various flame retardants to polyurethane.

The product's fire-retardant effect meets the requirements of ASTM Standard 117 and national standards. The usage method is the same as regular foam.

The combustion of polymers is a very complex and intense oxidation reaction. The process occurs as the polymer is continuously heated by an external heat source, initiating a free radical chain reaction with oxygen in the air. This releases some heat, further intensifying the degradation of the polymer, generating more flammable gases, and making the combustion more severe.

There are two methods for the flame retardancy of fire-resistant foam:

One is to chemically introduce flame-retardant elements or groups containing flame-retardant new elements into the molecular structure of the foam. The other method is to add compounds containing flame-retardant elements to the foam. The former method uses flame-retardant substances called reactive flame retardants, while the latter method uses substances called additive flame retardants.

Currently, the vast majority of flame retardants used in foam are additive flame retardants, while reactive flame retardants are mainly used in thermosetting resins such as epoxy resins and polyurethanes. The primary function of flame retardants is to interfere with the three basic elements required for combustion: oxygen, heat, and fuel. This can generally be achieved through the following means:

Flame retardants can produce heavier non-flammable gases or boiling liquids that cover the surface of the foam, interrupting the connection between oxidation and fuel.

By absorbing heat through decomposition or sublimation, flame retardants reduce the surface temperature of the polymer.

Flame retardants generate a large amount of non-flammable gases, diluting the concentration of flammable gases and oxygen in the combustion area.

Flame retardants capture radical free radicals, interrupting the chain reaction of oxidation.