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Shop Best Cutting Machine for Foam in ALFORU
The reason why cutting machine for foam is highly favored in the market can be summarized into two aspects, namely outstanding performance and unique design. The product is characterized by long-term life cycle, which can be attributed to the high-quality materials it adopts. Sabtech Technology Limited invests a lot to establish a professional design team, which is responsible for developing the stylish appearance for the product.
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We work with our customers to provide innovative and personalized cutting machine for foam that enables the achievement of their current and future sustainability goals. Let us offer you the related products information through Sabtech Technology Limited.
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The stability of polyurethane soft foam sponge foaming refers to whether the foam breaks, closes pores, collapses, and also includes product hardness, density, elasticity, tensile strength, pore size, and other aspects that meet customer requirements. To achieve these, it is necessary to standardize raw materials, formulations, and operating parameters, and to control the complex and diverse chemical reactions in different environments.
Density: Density is measured in kilograms per cubic meter or grams per cubic centimeter. For irregularly shaped small products, it is not easy to measure the cross-sectional area. One can use graph paper with small squares (such as graph paper with 2-millimeter square sides) to draw the cross-sectional area of the product being measured and calculate the density by counting squares. During the production process, the formulation density, flow rate, conveyor belt speed, and foam width have been determined. Measuring the foam height will reveal the foam density. For example, if a sponge reaches a height of 95 centimeters, the density is 20 kilograms per cubic meter. Density is related to the formulation and is also affected by the reaction rate. There is a density difference between the top and bottom of the same foam.
Hardness: Sponge hardness can be divided into two types. One reflects the surface hardness of the product, used for shoe materials, while the other reflects the overall hardness of the product, used for furniture sponges. The hardness of the foam is related to the hard segments, heat, and raw material content during the reaction, corresponding to the materials TDI, MC, and POP. The hardness of the foam is also affected by the degree of cross-linking. As the density of the sponge decreases, it becomes difficult to increase the amount of POP. For low-density, high-hardness foam, the focus is on how to increase POP and TDI in the formulation to reduce MC. For medium-high-density, high-hardness foam, the focus is on maximizing the hardening effect of POP and TDI.
Elasticity: Elasticity is primarily related to the molecular weight of polyether. The higher the molecular weight, the higher the product's resilience. Secondly, it is related to the formation of side chains during the sponge reaction; the fewer the side chains, the better the elasticity. Reducing the TDI index can reduce the formation of side chains, and reducing the heat inside the foam can also reduce the formation of side chains. However, if there are too few side chains, the tolerance of the formulation is not high, and the foam is not stable. Sponge elasticity is also related to the balance of the formulation. When ordinary foam sponge closes its pores, the elasticity drops sharply. High-hardness foam does not have good elasticity, but foam that is too soft also does not have high resilience.
Tensile Strength: Furniture sponges are mainly used for sitting and leaning, so the tensile strength requirements are not too high. The tensile strength of the sponge is related to the NCO content and cross-linking degree in the meridians. Increasing the TDI index and increasing the heat inside the foam can strengthen the NCO content and cross-linking degree. Increasing MC reduces the increase in tensile strength in many cases. The amount of TDI that a formulation can "accommodate" is related to the foaming method, such as high-pressure machines, low-pressure machines, and manual foaming, which are different. A sponge with a high elongation rate does not necessarily have a high tear strength. For products that emphasize tensile strength, adding a small amount of stone powder can greatly reduce the tensile strength without losing the original.
Pores: Foam with very good pores often becomes mid-to-high-end foam, and the price also rises significantly. Pore formation is a comprehensive problem, and to obtain uniform, delicate, and defect-free pores, one must have a deep understanding of the machinery, raw materials, formulations, and parameters. The formation of pinholes and pockmarks is generally caused by excessive air entrainment in the raw materials during stirring at the machine head or during the movement of the raw materials. It may also result from poor raw material quality or contamination. The theory that air leaks in pipes causing pinholes is not tenable. During foaming, the pressure inside the pipe is higher than the atmospheric pressure outside the pipe. Only the raw material flows out of the pipe, and air from the outside cannot enter.
Density: Density is measured in kilograms per cubic meter or grams per cubic centimeter. For irregularly shaped small products, it is not easy to measure the cross-sectional area. One can use graph paper with small squares (such as graph paper with 2-millimeter square sides) to draw the cross-sectional area of the product being measured and calculate the density by counting squares. During the production process, the formulation density, flow rate, conveyor belt speed, and foam width have been determined. Measuring the foam height will reveal the foam density. For example, if a sponge reaches a height of 95 centimeters, the density is 20 kilograms per cubic meter. Density is related to the formulation and is also affected by the reaction rate. There is a density difference between the top and bottom of the same foam.
Hardness: Sponge hardness can be divided into two types. One reflects the surface hardness of the product, used for shoe materials, while the other reflects the overall hardness of the product, used for furniture sponges. The hardness of the foam is related to the hard segments, heat, and raw material content during the reaction, corresponding to the materials TDI, MC, and POP. The hardness of the foam is also affected by the degree of cross-linking. As the density of the sponge decreases, it becomes difficult to increase the amount of POP. For low-density, high-hardness foam, the focus is on how to increase POP and TDI in the formulation to reduce MC. For medium-high-density, high-hardness foam, the focus is on maximizing the hardening effect of POP and TDI.
Elasticity: Elasticity is primarily related to the molecular weight of polyether. The higher the molecular weight, the higher the product's resilience. Secondly, it is related to the formation of side chains during the sponge reaction; the fewer the side chains, the better the elasticity. Reducing the TDI index can reduce the formation of side chains, and reducing the heat inside the foam can also reduce the formation of side chains. However, if there are too few side chains, the tolerance of the formulation is not high, and the foam is not stable. Sponge elasticity is also related to the balance of the formulation. When ordinary foam sponge closes its pores, the elasticity drops sharply. High-hardness foam does not have good elasticity, but foam that is too soft also does not have high resilience.
Tensile Strength: Furniture sponges are mainly used for sitting and leaning, so the tensile strength requirements are not too high. The tensile strength of the sponge is related to the NCO content and cross-linking degree in the meridians. Increasing the TDI index and increasing the heat inside the foam can strengthen the NCO content and cross-linking degree. Increasing MC reduces the increase in tensile strength in many cases. The amount of TDI that a formulation can "accommodate" is related to the foaming method, such as high-pressure machines, low-pressure machines, and manual foaming, which are different. A sponge with a high elongation rate does not necessarily have a high tear strength. For products that emphasize tensile strength, adding a small amount of stone powder can greatly reduce the tensile strength without losing the original.
Pores: Foam with very good pores often becomes mid-to-high-end foam, and the price also rises significantly. Pore formation is a comprehensive problem, and to obtain uniform, delicate, and defect-free pores, one must have a deep understanding of the machinery, raw materials, formulations, and parameters. The formation of pinholes and pockmarks is generally caused by excessive air entrainment in the raw materials during stirring at the machine head or during the movement of the raw materials. It may also result from poor raw material quality or contamination. The theory that air leaks in pipes causing pinholes is not tenable. During foaming, the pressure inside the pipe is higher than the atmospheric pressure outside the pipe. Only the raw material flows out of the pipe, and air from the outside cannot enter.
The compressive resistance of a foam is related to many factors such as the structure of various chain segments composing the foam, the chemical bonds between molecules, the crystallinity of polymers, the degree of phase separation, the structure of isocyanates, and the proportion of isocyanates used.
1. Slow rebound foam is formed by the reaction of high molecular weight polyols and low molecular weight polyols with isocyanates. The soft segments formed by high molecular weight polyols have large volumes, low crosslink densities, and high activity. They are easy to compress and quickly recover after pressure is removed. The hard segments formed by low molecular weight polyols have small volumes, high crosslink densities, and low activity. They are difficult to compress and also difficult to recover after external forces are removed. This characteristic gives foams their slow rebound feature and is the basis for manufacturing slow rebound foams.
Because the properties of the soft and hard segments in slow rebound foams are different, there is a certain degree of phase separation between them. If there is no phase separation between the segments, the foam body is a tightly bound whole on a macro scale, leading to the phenomenon of "move one hair and the whole body moves," meaning it shrinks as a whole when compressed and expands when pressure is released. However, the microstructure of the foam determines that this situation cannot be achieved completely. Especially in slow rebound foams, various chain segments have different molecular structures, uneven molecular weight distributions, and unavoidable phase separation. Slight phase separation causes some hard segments, due to their low activity, to have difficulty recovering during the recovery process after external forces are removed. These "escapees" more or less restrain the recovery of soft segments, ultimately leading to shrinking.
2. The crystallinity of hard segments, which is stronger than that of soft segments, is also a reason for poor recovery. Materials have similar compatibilities, which also apply in slow rebound foams. Because the hard segments have closer cross-linking points and higher crosslink densities, the small molecules formed are more likely to aggregate together. Due to the presence of hydrogen bonds, these aggregated hydrogen-containing substances enhance the crystallinity of the material, leading to greater cohesive forces. After compression, external forces change the aggregation state of the chain segments, making it easier for polar groups to fuse together. When the external force is released, the new aggregation state, due to strong cohesive forces, is difficult to return to the pre-stressed state, resulting in shrinkage of slow rebound foams.
3. The structure of isocyanates is also a factor affecting the compression resistance of slow rebound foams. TDI is usually used to produce slow rebound foams. Because the two NCO groups in the TDI molecule are at the 2,4- and 2,6- positions, they have a certain angle between them, making them prone to deformation under stress. Especially under hot pressing conditions, significant deformation and heat loss occur, particularly evident in bra cup foams, making recovery from these deformations difficult.
4. The low NCO index of isocyanates used in the preparation of slow rebound foams is also a reason for poor recovery. The NCO index of ordinary foams is usually above 100, while in slow rebound foams , the NCO index is generally between 85-95. This means that 5-15% of the hydroxyl groups do not participate in the reaction. Therefore, although the surface of the foam appears to be a single entity, internally there is a considerable portion of chain segments that are independent of each other.
Solutions for Improving Compression Resistance of Slow Rebound Foams:
1.Use high EO polyether (so-called blowing agent polyether) to replace some slow rebound polyether.
A. High EO polyether has a low hydroxyl value and a large molecular weight. After reacting with isocyanates, the segments formed have molecular weights greater than or close to those formed when ordinary polyether reacts with isocyanates, reducing the degree of phase separation and crystallinity.
B. High EO content polyether has soft and smooth segments, which can provide good slow rebound effects. Additionally, the addition of high EO polyether can effectively improve the low-temperature resistance of slow rebound foams.
2.Add a small amount of polyether-modified polyester to increase the material's cohesive force.
The polyester segments, due to the presence of ester groups, have high internal cohesive forces and good tensile and compressive properties, significantly improving the compressive resistance of slow rebound foams.
3.Use a small amount of high-functionality and high molecular weight polyether as a crosslinking agent, and replace some ordinary polyether with high-activity polyether for slow rebound.
This disrupts the distribution of chain segments, reduces the degree of phase separation, and increases the reaction degree, reducing crystallinity.
4.Use MDI or add MDI to TDI.
MDI has a different structure from TDI and produces foams with better compression resistance and less heat loss. If using MDI, it is best to use modified MDI (with high branching and easy closure of cells); liquid MDI can also be used, as it is intramolecular cyclization and more resistant to compression. Slow rebound foams made with all MDI have much better compression resistance than pure TDI, and many manufacturers are already using this.
1. Slow rebound foam is formed by the reaction of high molecular weight polyols and low molecular weight polyols with isocyanates. The soft segments formed by high molecular weight polyols have large volumes, low crosslink densities, and high activity. They are easy to compress and quickly recover after pressure is removed. The hard segments formed by low molecular weight polyols have small volumes, high crosslink densities, and low activity. They are difficult to compress and also difficult to recover after external forces are removed. This characteristic gives foams their slow rebound feature and is the basis for manufacturing slow rebound foams.
Because the properties of the soft and hard segments in slow rebound foams are different, there is a certain degree of phase separation between them. If there is no phase separation between the segments, the foam body is a tightly bound whole on a macro scale, leading to the phenomenon of "move one hair and the whole body moves," meaning it shrinks as a whole when compressed and expands when pressure is released. However, the microstructure of the foam determines that this situation cannot be achieved completely. Especially in slow rebound foams, various chain segments have different molecular structures, uneven molecular weight distributions, and unavoidable phase separation. Slight phase separation causes some hard segments, due to their low activity, to have difficulty recovering during the recovery process after external forces are removed. These "escapees" more or less restrain the recovery of soft segments, ultimately leading to shrinking.
2. The crystallinity of hard segments, which is stronger than that of soft segments, is also a reason for poor recovery. Materials have similar compatibilities, which also apply in slow rebound foams. Because the hard segments have closer cross-linking points and higher crosslink densities, the small molecules formed are more likely to aggregate together. Due to the presence of hydrogen bonds, these aggregated hydrogen-containing substances enhance the crystallinity of the material, leading to greater cohesive forces. After compression, external forces change the aggregation state of the chain segments, making it easier for polar groups to fuse together. When the external force is released, the new aggregation state, due to strong cohesive forces, is difficult to return to the pre-stressed state, resulting in shrinkage of slow rebound foams.
3. The structure of isocyanates is also a factor affecting the compression resistance of slow rebound foams. TDI is usually used to produce slow rebound foams. Because the two NCO groups in the TDI molecule are at the 2,4- and 2,6- positions, they have a certain angle between them, making them prone to deformation under stress. Especially under hot pressing conditions, significant deformation and heat loss occur, particularly evident in bra cup foams, making recovery from these deformations difficult.
4. The low NCO index of isocyanates used in the preparation of slow rebound foams is also a reason for poor recovery. The NCO index of ordinary foams is usually above 100, while in slow rebound foams , the NCO index is generally between 85-95. This means that 5-15% of the hydroxyl groups do not participate in the reaction. Therefore, although the surface of the foam appears to be a single entity, internally there is a considerable portion of chain segments that are independent of each other.
Solutions for Improving Compression Resistance of Slow Rebound Foams:
1.Use high EO polyether (so-called blowing agent polyether) to replace some slow rebound polyether.
A. High EO polyether has a low hydroxyl value and a large molecular weight. After reacting with isocyanates, the segments formed have molecular weights greater than or close to those formed when ordinary polyether reacts with isocyanates, reducing the degree of phase separation and crystallinity.
B. High EO content polyether has soft and smooth segments, which can provide good slow rebound effects. Additionally, the addition of high EO polyether can effectively improve the low-temperature resistance of slow rebound foams.
2.Add a small amount of polyether-modified polyester to increase the material's cohesive force.
The polyester segments, due to the presence of ester groups, have high internal cohesive forces and good tensile and compressive properties, significantly improving the compressive resistance of slow rebound foams.
3.Use a small amount of high-functionality and high molecular weight polyether as a crosslinking agent, and replace some ordinary polyether with high-activity polyether for slow rebound.
This disrupts the distribution of chain segments, reduces the degree of phase separation, and increases the reaction degree, reducing crystallinity.
4.Use MDI or add MDI to TDI.
MDI has a different structure from TDI and produces foams with better compression resistance and less heat loss. If using MDI, it is best to use modified MDI (with high branching and easy closure of cells); liquid MDI can also be used, as it is intramolecular cyclization and more resistant to compression. Slow rebound foams made with all MDI have much better compression resistance than pure TDI, and many manufacturers are already using this.
14. Poor Rebound
A. Raw materials: high activity polyether polyols, low molecular weight, highly active silicone oil.
B. Process formulation: high silicone oil content, excessive tin, high water content with the same tin usage, high TDI index, large amount of white oil and powder.
15. Poor Tensile Strength
A. Raw materials: excessive low molecular weight polyether polyols, low functionality hydroxyl value.
B. Process formulation: insufficient tin, poor gelation reaction, high TDI index with the same tin usage, low water content, low crosslinking.
16. Smoke during Foaming
Excessive amine release a large amount of heat during water and TDI reaction, causing evaporation of low-boiling substances and smoke. If not core scorching, smoke mostly consists of TDI, low-boiling substances, and monomer cycloalkanes in polyether polyols.
17. Foam with White Streaks
Fast foaming and gelation reaction but slow transfer in continuous foaming, resulting in a dense layer due to localized compression, causing white streaks. Increase transfer speed or lower material temperature, reduce catalyst usage.
18. Brittle Foam
Excessive water in the formulation leads to excess biuret formation, which does not dissolve in silicone oil. Poor use of tin catalyst, insufficient cross-linking reaction, high content of low molecular weight polyether polyols, high reaction temperature causing ether bond breakage and decreased foam strength.
19. Foam Density Lower than Set Value
Foam index is too high due to inaccurate measurement, high temperature, low pressure.
20. Foaming with Skin, Edge Skin, and Bottom Air
Excessive tin, insufficient amine, slow foaming rate, fast gelation rate, low temperature during continuous foaming.
21. Elongation Rate Too High
A. Raw materials: high activity polyether polyols, low functionality.
B. Process formulation: low TDI index, insufficient cross-linking, high tin.
22. Uncontrolled Foam (Small bubbles rapidly moving beneath surface)
A. Low-pressure foaming machine: increase mixing head speed, decrease gas injection.
B. High-pressure foaming machine: increase mixing head pressure.
23.Milky Moving Lines
A. Increase conveyor speed
B. Adjust cushion plate inclination.
C. Reduce amine catalyst usage
24.Inserted Material Backflow
A. Increase conveyor speed.
B. Adjust cushion plate inclination.
C. Increase amine catalyst usage.
25.Moon Pits
A. Low-pressure foaming machine: reduce mixing head speed and gas injection.
B. High-pressure foaming machine: increase mixing head pressure.
C. Silicone oil quality issue.
D. Increase amine amount while reducing tin amount to ensure adequate cell opening.
26.Slow Curing,Sticky Surface
Polymer strength increases too slowly, resulting in soft, sticky foam that is difficult to cut.
Foam blocks appear unstable when exiting channels.
Increase catalyst usage, check polyol, water, and TDl measurement accuracy.
A. Raw materials: high activity polyether polyols, low molecular weight, highly active silicone oil.
B. Process formulation: high silicone oil content, excessive tin, high water content with the same tin usage, high TDI index, large amount of white oil and powder.
15. Poor Tensile Strength
A. Raw materials: excessive low molecular weight polyether polyols, low functionality hydroxyl value.
B. Process formulation: insufficient tin, poor gelation reaction, high TDI index with the same tin usage, low water content, low crosslinking.
16. Smoke during Foaming
Excessive amine release a large amount of heat during water and TDI reaction, causing evaporation of low-boiling substances and smoke. If not core scorching, smoke mostly consists of TDI, low-boiling substances, and monomer cycloalkanes in polyether polyols.
17. Foam with White Streaks
Fast foaming and gelation reaction but slow transfer in continuous foaming, resulting in a dense layer due to localized compression, causing white streaks. Increase transfer speed or lower material temperature, reduce catalyst usage.
18. Brittle Foam
Excessive water in the formulation leads to excess biuret formation, which does not dissolve in silicone oil. Poor use of tin catalyst, insufficient cross-linking reaction, high content of low molecular weight polyether polyols, high reaction temperature causing ether bond breakage and decreased foam strength.
19. Foam Density Lower than Set Value
Foam index is too high due to inaccurate measurement, high temperature, low pressure.
20. Foaming with Skin, Edge Skin, and Bottom Air
Excessive tin, insufficient amine, slow foaming rate, fast gelation rate, low temperature during continuous foaming.
21. Elongation Rate Too High
A. Raw materials: high activity polyether polyols, low functionality.
B. Process formulation: low TDI index, insufficient cross-linking, high tin.
22. Uncontrolled Foam (Small bubbles rapidly moving beneath surface)
A. Low-pressure foaming machine: increase mixing head speed, decrease gas injection.
B. High-pressure foaming machine: increase mixing head pressure.
23.Milky Moving Lines
A. Increase conveyor speed
B. Adjust cushion plate inclination.
C. Reduce amine catalyst usage
24.Inserted Material Backflow
A. Increase conveyor speed.
B. Adjust cushion plate inclination.
C. Increase amine catalyst usage.
25.Moon Pits
A. Low-pressure foaming machine: reduce mixing head speed and gas injection.
B. High-pressure foaming machine: increase mixing head pressure.
C. Silicone oil quality issue.
D. Increase amine amount while reducing tin amount to ensure adequate cell opening.
26.Slow Curing,Sticky Surface
Polymer strength increases too slowly, resulting in soft, sticky foam that is difficult to cut.
Foam blocks appear unstable when exiting channels.
Increase catalyst usage, check polyol, water, and TDl measurement accuracy.
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.
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.
The formula for slow rebound sponge is similar to regular sponge with minor differences. Apart from the major difference in the main ingredient polyether, some additives can be interchangeable. However, for the production of high-quality products, careful consideration and selection of additives are still necessary.
1. Choice of Amine
The most classic amine used for slow rebound sponge is Dabco33-LV from the American Air Products. The dosage is generally 0.3-0.8 parts of the total polyether. It is formulated with 33% triethylenediamine and 67% di(propylene glycol) (DPG). The reason for recommending this product is because it uses di(propylene glycol) as a solvent. Some may ask, is a solvent of this kind important? The answer is yes. Looking at the ability to dissolve triethylenediamine, there are many alcohol compounds that can be used as solvents: such as propylene glycol, diethylene glycol, ethylene glycol, 1,4-butanediol, etc. Among these small-molecule alcohols, di(propylene glycol) has the largest molecular weight and the lowest hydroxyl value. As we all know, low molecular weight alcohols can be used as chain extenders or crosslinking agents. This means that these small-molecule alcohols can consume TDI, resulting in: on one hand, it reduces the TDI index, and on the other hand, it easily causes closed-cell sponges.
2. Choice of Tin
Craftsmen who have experienced with regular sponges often like to use stannous octoate (T-9) to create slow rebound, but the author suggests using dibutyltin dilaurate (D22, T-12, also known as K-19 domestically). Stannous octoate is suitable for creating medium to low density sponges. Its characteristic is that it is quick to stick initially but lacks strength later on. It is not good for post-curing when used with high-density sponges. T-9 is prone to hydrolysis, and slow rebound itself has a slow start (generally controlled to start at around 160 seconds), so it is in contact with water for a long time, leading to some hydrolysis, affecting curing. Dibutyltin dilaurate does not hydrolyze, and its initiation, gelation, and curing are stable with good post-curing properties.
Some peers have mentioned that the sponge's tensile strength is not good. The author suggests using dibutyltin dilaurate, and the feedback received was that the tensile strength improved. If using T-9, the dosage is between 0.1-0.4 parts. If using dibutyltin dilaurate, the dosage can be controlled between 0.03-0.05. For slow rebound on assembly lines, the dosage can be reduced to 0.001-0.01 parts. For export orders that restrict the use of tin catalysts, the author suggests using bismuth carboxylate to replace tin.
3. Choice of Silicone Oil
A typical slow rebound silicone oil is B8002, with a dosage between 0.5-2 parts. It is used less for high-density sponges and more for low-density sponges. It is used more for manual foaming and less for machine foaming. In recent years, domestic silicone oil suppliers have developed many silicone oils for slow rebound, and their performance is also good. Some use L-580 for slow rebound, and in this case, the amount of silicone oil should be reduced, as L-580 is more active.
4. Use of Pigments
The use of pigments is basically the same as for regular sponge. Just be cautious when dealing with black sponges because the carbon black used to prepare black pigments is hydrophobic, which can affect the compatibility of various components in the formula and the efficiency of the catalysts. Many colleagues have encountered the phenomenon of easy cracking of black sponges, and the reason lies here. Therefore, when creating black sponges, proper adjustments should be made to the catalyst dosage. These are personal work experiences provided for reference only, and feedback and corrections from colleagues are welcome.
1. Choice of Amine
The most classic amine used for slow rebound sponge is Dabco33-LV from the American Air Products. The dosage is generally 0.3-0.8 parts of the total polyether. It is formulated with 33% triethylenediamine and 67% di(propylene glycol) (DPG). The reason for recommending this product is because it uses di(propylene glycol) as a solvent. Some may ask, is a solvent of this kind important? The answer is yes. Looking at the ability to dissolve triethylenediamine, there are many alcohol compounds that can be used as solvents: such as propylene glycol, diethylene glycol, ethylene glycol, 1,4-butanediol, etc. Among these small-molecule alcohols, di(propylene glycol) has the largest molecular weight and the lowest hydroxyl value. As we all know, low molecular weight alcohols can be used as chain extenders or crosslinking agents. This means that these small-molecule alcohols can consume TDI, resulting in: on one hand, it reduces the TDI index, and on the other hand, it easily causes closed-cell sponges.
2. Choice of Tin
Craftsmen who have experienced with regular sponges often like to use stannous octoate (T-9) to create slow rebound, but the author suggests using dibutyltin dilaurate (D22, T-12, also known as K-19 domestically). Stannous octoate is suitable for creating medium to low density sponges. Its characteristic is that it is quick to stick initially but lacks strength later on. It is not good for post-curing when used with high-density sponges. T-9 is prone to hydrolysis, and slow rebound itself has a slow start (generally controlled to start at around 160 seconds), so it is in contact with water for a long time, leading to some hydrolysis, affecting curing. Dibutyltin dilaurate does not hydrolyze, and its initiation, gelation, and curing are stable with good post-curing properties.
Some peers have mentioned that the sponge's tensile strength is not good. The author suggests using dibutyltin dilaurate, and the feedback received was that the tensile strength improved. If using T-9, the dosage is between 0.1-0.4 parts. If using dibutyltin dilaurate, the dosage can be controlled between 0.03-0.05. For slow rebound on assembly lines, the dosage can be reduced to 0.001-0.01 parts. For export orders that restrict the use of tin catalysts, the author suggests using bismuth carboxylate to replace tin.
3. Choice of Silicone Oil
A typical slow rebound silicone oil is B8002, with a dosage between 0.5-2 parts. It is used less for high-density sponges and more for low-density sponges. It is used more for manual foaming and less for machine foaming. In recent years, domestic silicone oil suppliers have developed many silicone oils for slow rebound, and their performance is also good. Some use L-580 for slow rebound, and in this case, the amount of silicone oil should be reduced, as L-580 is more active.
4. Use of Pigments
The use of pigments is basically the same as for regular sponge. Just be cautious when dealing with black sponges because the carbon black used to prepare black pigments is hydrophobic, which can affect the compatibility of various components in the formula and the efficiency of the catalysts. Many colleagues have encountered the phenomenon of easy cracking of black sponges, and the reason lies here. Therefore, when creating black sponges, proper adjustments should be made to the catalyst dosage. These are personal work experiences provided for reference only, and feedback and corrections from colleagues are welcome.
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