Polyether Polyol: Hydroxyl Value 36, Primary Hydroxyl > 65%, 60%.

Polymeric Polyol: Hydroxyl Value 28, Copolymer 20%, 40%.

Water: 3%.

80TDI and Polymeric MDI (Viscosity 300mpa): 80:20.

T12: 0.025%.

A33: 0.4%.

HR-3 Silicone Oil: 1%.

HA-1 Crosslinker: 6%.

Di(b-dimethylaminoethyl) Ether: 0.15%.

Cold Cure

A process for seat foam production, which produces high resilience foam (referred to as HR foam).

During this process, the mold temperature is generally between 50-70 degrees Celsius; the polyether molecular weight is typically between 2500-6500, and the ISO can be TDI/TM/MDI.

This process has high production efficiency, low energy consumption, and is currently widely used.



Pump Capacity

Used to check the stability of the metering pump flow output.

The current method for verifying pump capacity is as follows: at the set flow rate, shoot continuously 35 times, weigh each shot, then calculate the capacity. Based on the pump capacity, determine whether the metering pump needs repair or replacement. Generally, pump capacity is checked every three months.



Pump Linearity

A characterization of the correlation between the metering pump's speed and output.

Usually, five different speeds are selected for flow testing. The output of the metering pump at each speed is then obtained. If these five points align on a straight line, it indicates good linearity between the metering pump's speed and output.



NBT (New Blending Technology)

NBT stands for New Blending Technology.

The previous blending technology involved spraying and mixing one ISO with one POL to react and produce polyurethane foam. When adjusting process parameters with this method, only the POL/ISO mixing ratio and the casting weight could be adjusted, with no other adjustments possible.

NBT involves spraying and mixing one ISO with 2 or 3 groups of POLY materials to react and produce polyurethane foam. (Equipment requires a frequency converter)

NBT can adjust the following variables: formula moisture, formula solids content, formula index, casting weight, and other variables. This allows for greater process tolerance when manufacturing foams of different densities and hardnesses.



TPR (Timed Pressure Release)

TPR stands for Timed Pressure Release, also known as venting or pre-venting.

Typical TPR parameters are: venting starts around 90-120 seconds after mold closure, with the bag dropping down, venting for about 2 seconds, then the bag rising back up.

Common phenomena: Venting too early can result in tender products prone to tearing. Venting too late can lead to stiff products prone to shrinkage after demolding.



Initial Spray

At the start of normal pouring, the ISO and POLY nozzles are opened simultaneously, allowing the materials to mix in the mixing chamber and react to produce polyurethane foam.

If during pouring the ISO and POLY nozzles do not open simultaneously, the one that opens first will cause the material to flow out of the mixing chamber without reacting, resulting in unreacted material at the beginning of the foam. If polyether comes out first, the foam will be sticky and wet at the top (mild initial spraying), while if ISO comes out first, the foam will be crispy, locally thin (mild initial spraying), or have ISO spots (severe initial spraying).

Common phenomena: Another special case is when there is softness at the initially poured area, which could also be a form of initial spraying. This might be due to the component coming out first, causing the foam at the initial pour point to be soft.



Foaming Index

When ISO and POL react, if they react in the exact theoretical amounts, it's called stoichiometric reaction, and the foaming index is defined as 100.

Foaming Index = Actual ISO usage/Theoretical ISO usage * 100. Currently, the foaming index for seat foaming is generally between 90-105.

As the foaming index increases, the foam gradually becomes harder.

Index > 105, the product is prone to being brittle; Index < 85, the product is prone to closed-cell shrinkage.

Foam scorching is a common phenomenon encountered in actual foam production. Below are the reasons behind this issue along with potential solutions:



(1) Issues with the quality of polyether polyols: During production and transportation, the product's water content exceeds the standard, there is an excess of peroxides and low-boiling-point impurities, the concentration of metal ions is too high, and there is improper selection and concentration of antioxidants.



(2) Formulation: In low-density formulations, the TDI index is too high, the proportion of water to physical blowing agents in the foaming agent is improper, the amount of physical blowing agent is insufficient, and there is excessive water content.



(3) Climate impact: In summer, high temperatures lead to slow heat dissipation, high material temperatures, high air humidity, and the temperature at the reaction center exceeds the antioxidant temperature.



(4) Improper storage: When the TDI index increases, the accumulated heat energy during post-maturation causes an increase in internal temperature, leading to scorching.

1. Adjust Formulation:

Control the amount of water to not exceed 4.5 parts, and if necessary, use low-boiling-point liquid compounds as auxiliary foaming agents to replace some water. Pay attention to the amount of water in the formulation, which must not exceed 5 parts. The highest safe temperature rise point for low-density foam is 160°C, and it must not exceed 170°C.



2. Strictly Control the Accuracy of Component Measurement:

During continuous block foam production, adjust the discharge speed of the mixing head material and the conveyor belt speed to coordinate them. Avoid phenomena such as under-foaming materials flowing into the bottom of already foaming materials due to slow conveyor belt speed or excessive discharge, which can prevent normal foaming, resulting in collapse. Collapsed materials are not easily able to produce localized "gas species," leading to localized heat accumulation and increased risk of scorching. In actual production, poor process parameters may result in small yellow scorching lines appearing at the bottom of foam blocks.



3. Avoid Compressing the Newly Produced Foam:

This is because compressing the foam before it is fully cured affects the foam network and structure. It also prevents heat accumulation due to compression, increasing the risk of self-ignition of new foam. Especially during the most sensitive stage of foam rising, any operational errors and vibrations, such as sudden movements caused by tight conveyor belt chains or excessive folding of isolation paper and belt shaking, can cause compression of immature foam, leading to scorching.



4. Strictly Observe the Curing and Storage Process of Foam:

For the production of polyurethane soft block foam, the curing process of new foam is a high-risk period for fire accidents. Due to the high internal temperature and long duration of heat dissipation in large block foams, the time to reach the highest internal temperature is usually about 30 to 60 minutes, and it takes 3 to 4 hours or longer for it to slowly decrease. During this time, the new foams have left the production line and entered the curing and storage phase, which is easily overlooked. Without proper monitoring measures, it can easily lead to fires. There have been reports that when producing block soft foam with a density of 22kg/? using a polyol with a molecular weight of over 5000, 4.7 parts of water, and 8 parts of F-11 with a TDI index of 1.07, a small amount of light yellow smoke was observed 2 hours later. Although the external temperature of the foam was not high, the interior was in a very dangerous initial stage of decomposition, with a temperature of around 200-250°C, already beginning to self-ignite.



5. To Prevent Self-Ignition of Foam:

Newly produced foam should be cured and stored, not exceeding 3 layers when stacked, with a spacing of more than 100mm between layers, preferably placed separately. The curing and storage phase should have dedicated personnel for enhanced monitoring, such as measuring the internal temperature of the foam every 15 minutes for at least 12 hours, or even longer, before normal storage. For foams that may generate high temperatures, large foam blocks should be cut horizontally (e.g., with a thickness of 200mm) to facilitate heat dissipation. When smoke or self-ignition is detected, use water spray or fire extinguishers, and do not move the foam or open doors and windows indiscriminately to prevent increasing airflow and exacerbating the fire.

What is Polyurethane Rigid Foam?



Polyurethane rigid foam, often abbreviated as PU rigid foam, is one of the most commonly used polyurethane products, second only to polyurethane soft foam, in polyurethane applications. Polyurethane rigid foam is mostly a closed-cell structure, known for its excellent insulation, lightweight, high strength-to-weight ratio, ease of construction, as well as soundproofing, shock absorption, electrical insulation, heat resistance, cold resistance, solvent resistance, and more. It is widely used in the insulation layers of refrigerator and freezer boxes, cold storage rooms, refrigerated trucks, as well as insulation materials for buildings, tanks, and pipelines. A small amount is used in non-insulation applications such as wood imitation and packaging materials. Generally, lower-density polyurethane rigid foam is primarily used as thermal insulation material, while higher-density polyurethane rigid foam can be used as structural material (wood imitation).



Polyurethane rigid foam is typically foamed at room temperature, with a relatively simple molding process. It can be categorized into manual foaming and mechanical foaming based on the degree of construction mechanization; high-pressure foaming and low-pressure foaming based on the foaming pressure; and casting foaming and spraying foaming based on the molding method.



What is Polyurethane Soft Foam?



Polyurethane soft foam, also known as PU soft foam, is a type of flexible polyurethane foam with a certain degree of elasticity. It is the most extensively used polyurethane product among all polyurethane products.



Polyurethane soft foam is mostly an open-cell structure, characterized by low density, good elastic recovery, sound absorption, breathability, and insulation properties. It is primarily used as cushioning materials for furniture, mattresses, vehicle seat cushions, and also finds industrial and domestic applications as filter materials, soundproofing materials, shock absorption materials, decorative materials, packaging materials, and insulation materials. Based on the degree of softness and load-bearing capacity, polyurethane soft foam can be divided into ordinary soft foam, super soft foam, high load-bearing soft foam, high resilience soft foam, etc. High resilience and high load-bearing soft foams are generally used for manufacturing seat cushions and mattresses. According to the production process, polyurethane soft foam can be divided into block foam and molded foam. Block foam is produced by continuous process to form large volume foam which is then cut into required shapes, while molded foam is produced by direct injection of the mixture into molds to form foam products of desired shapes.



After understanding polyurethane rigid foam and polyurethane soft foam, the question arises: how do we differentiate between the two?



In fact, the classification can be based on the degree of hardness, dividing them into soft foam plastics and hard plastics. Soft foam plastics have a matrix polymer component above the crystalline melting point, or, if it is an amorphous polymer, it is above the glass transition temperature; hard foam, on the other hand, has its matrix polymer in a crystalline state or an amorphous state but below the glass transition temperature. Semi-rigid foam is a foam plastic between soft and hard foam. It is similar to soft foam, with an open cell rate above 90℃, but semi-rigid foam has higher density and higher compression strength. After compression deformation, semi-rigid foam takes much longer to recover, and its crosslinking density is much higher than soft foam but lower than hard foam.



Based on this classification of softness and hardness, most polyolefin foams, unplasticized polyvinyl chloride (PVC) foams, phenolic foams, polycarbonate foams, and polyphenylene ether foams are all classified as hard foams, while elastic polyurethane foams and some polyolefin foams and plasticized PVC foams are classified as soft foams.



According to the national standard, soft foam plastics are those that are flexible, have low compression hardness, return to their original state after stress is relieved, and have minimal residual deformation. On the other hand, hard foam plastics are inflexible, have high compression hardness, deform when stress reaches a certain level, and do not return to their original state after stress is relieved.



The American Society for Testing and Materials (ASTM) specifies that to differentiate between soft and hard foam plastics, at a temperature of 18-29℃, a rod with a diameter of 2.5 cm is rotated around it for one full rotation within 5 seconds. If it does not fracture, it is classified as soft foam plastic; otherwise, it is classified as hard foam plastic.



According to ISO standards, when the compression deformation reaches 50% and is then released, if the thickness decreases by no more than 2% compared to the original thickness, it is classified as soft foam plastic. If it decreases by more than 10%, it is classified as hard foam plastic. If the decrease is between 2-10%, it is classified as semi-rigid foam plastic.



If we use elastic modulus as the criterion, in a standard environment of 23℃ and 50% relative humidity, a foam plastic with an elastic modulus greater than 686 MPa is classified as hard foam, less than 68.6 MPa is classified as soft foam, and between 68.6-686 MPa is classified as semi-rigid foam. Although the elastic modulus of semi-rigid foam is higher than that of soft foam, its stress-strain behavior is closer to soft foam and significantly different from hard foam. Generally, soft foam plastics mostly have an open-cell structure, while hard foam plastics mostly have a closed-cell structure, but there are exceptions.