Detailed Explanation of PU Foaming Technology
Mold temperature distinction
1. Thermal foaming:
After the casting is completed, the mold is placed in an oven at 220-250 °C (not lower than 180 °C), and after the reaction is completed, it is taken out and demolded.
Advantages: low foam density, good heat aging performance, no need for separate openings. The mold cost is low.
Disadvantages: high energy consumption. The vent hole is easy to produce "mushroom head", resulting in a lot of waste of chemical materials. Later on-site cleaning and equipment maintenance are more troublesome.
Some OEMs in Europe are keen on this method, but there are few in China. As for how the process is designed as a production line, the author has not observed it on the spot. It is speculated that it may be similar to the picture below, a long-shaped large oven, and the seat mold is poured into and out of the oven slowly through the turntable to complete the foaming reaction.
2. Cold foaming
It is generally designed as a multi-station turntable production line. The mold is generally heated to 45-70°C by a mold temperature machine, and then demolded after the foaming reaction is completed by pouring the PU material. After demoulding, the product needs to use a foam breaker to help open the hole.
Advantages: low energy consumption, clean equipment and easy maintenance
Disadvantages: The equipment is more complicated and the equipment cost is high. Foam thermalization performance is average.
Surface adsorption distinction
1. Naked foam:
Named contrary to the concept of adsorption and foaming, the fabric will not be pre-placed in the mold, and the surface of the foamed product is the PU layer. Noodles are all assembled after processing.
Passenger cars mostly use this foaming process.
2. Adsorption foaming
Before pouring, first place the fabric in the mold cavity, make it completely fit by suction and adsorption, and then pour the PU material. After foaming, the surface layer of the molded PU product is tightly attached to the fabric.
Construction machinery seats are more likely to use this foaming process.
Hardness distinction
1. Single hardness foam:
It is the simplest foaming, single formula, single pouring, no other auxiliary means, and the foam products presented have only a single hardness.
2. Double hardness foam:
Double-hardness foam is the selling point of many luxury cars. The ride area is softer, and the support areas on both sides are harder, which can provide more comfort.
The way to achieve this is to use the seating area and the two sides of the area to pour separately, and to achieve the product dual-hardness or multi-hardness distinction by placing the mold at the angle, adding a material gap between the two wings and the seating area, and adding inserts on both sides of the foam. .
This foaming process can also achieve three hardnesses, but generally not more. In the industry, it is also called double-density foaming, which is actually a slip of the tongue. The purpose of the process is to obtain different hardness, not density. And sometimes one density can make two different hardnesses.
Manufacturers who master this foaming process generally need to be equipped with technical personnel who are skilled in adjusting the combination materials, because they need to master the changes and adjustments of multiple formulas.
New technology
At present, new technologies are extended, such as Adient's horizontal foaming DHH and R-comfort technologies.
1. Horizontal foaming DHH
Also known as double-layer foaming technology, the upper and lower layers have different foaming strength and hardness, the upper layer is softer, and the lower layer can ensure an even stress distribution, which can improve the comfort of long-distance driving.
Due to the limited sharing of new technology information, the author speculates that the foaming process is similar to the double-layer sole (as shown in the figure below): design a false cover, first pour the bottom layer and foam and solidify, open the false cover, and then pour through the upper cover and close the mold. Different formulations and different pouring form double-layer foam. If the guess is wrong, please also ask the experts to correct it.
2. R-comfort
The technology presents various textures on the upper surface of the seat foam. On the one hand, it ensures the softness of short-distance driving, and accelerates the flow of gas to help dissipate heat caused by long-term riding, while ensuring the comfort of foam.
Due to limited sharing of new technology information, no further details were available. The author has seen this type of foam and its forming mold on the foaming line of a luxury car seat. I feel that the complex lines and grids on the surface of the foam are more shaped by complex molds. As for the foaming process What minor adjustments have been made, I have not yet learned.
Hyundai will use new material to make car seats
Recently, Hyundai Motor Corporation's Ulsan plant will exclusively use BASF's Elastoflex polyurethane foam combination to produce car seats. This highly elastic polyurethane foam has a low VOC content and is mainly used in the production of car seats and headrests.
Compared to traditional foams, Elastoflex improves comfort, elasticity and load-bearing properties of seats and headrests, for example.
In order to meet the most stringent emission control regulations, BASF has also optimized the production process of polyether polyols. Polyether polyols are used in the production of Elastoflex polyurethane foam, which is used in the production of high-comfort seats. The optimized production process enables BASF to produce specialty polyether polyols with low cost, high performance and low VOC emissions.
In tests conducted by the world's leading testing agency SGSKorea, Elastoflex reduced acetaldehyde and formaldehyde emissions by more than 30%, helping to improve in-vehicle air quality and the health of car drivers. Field tests have also shown that the newly developed polyurethane composition has excellent flow properties and reduced product defect rates, resulting in improved production line productivity.
New materials have strong advantages
In the production of automobiles, car seats occupy a large area, which directly determines the number of materials used. Cars gradually affect people's way of life and make people's travel more and more convenient. Traditional car seats are mostly leather products, and most of them are made of sponge and other materials, which lack a certain degree of comfort. Nowadays, flexible polyurethane foam plastics As one of the production materials of car seats, it is of high quality and low price, and is gradually applied by manufacturers to a large number of car production.
"Polyurethane foam is a kind of relatively soft new material with certain elasticity. It has many pores, density sole, good resilience, sound absorption, breathability, good thermal insulation and other properties. It is used in all aspects of life. Many manufacturers choose High-elastic polyurethane foam is used as a material for car seats, and the performance of this material is gradually accepted by people.
The static comfort of a car seat refers to whether the matching relationship between the car seat and the human body can provide users with comfortable sitting conditions. The static comfort of the seat is related to the size parameters, surface treatment and adjustment characteristics of the seat.
The composition of car seats is mostly foam materials with high elasticity and low density, which can prevent the burning of substances. Today, the Chinese government has stricter requirements on automotive materials, requiring the maximum combustion value to be ≤70mm/min. Such regulations greatly increase the safety of the car itself, and the flexible polyurethane foam with this burning rate standard is used. Doing saddles is also gradually appearing in the field of vision of manufacturers.
The wear resistance of flexible polyurethane foam is used as the raw material of car seats. The fragility of many plastic products makes them unable to be used for a long time, but flexible polyurethane foam has good wear resistance. It has strong tensile strength and tear resistance, which makes it have superior performance. Compared with traditional car seats, it has low cost, long service time and strong plasticity. It can be applied to automobiles and gradually attract automobile production. favored by manufacturers.
The development of the polyurethane foam industry is inseparable from the improvement of production capacity
As one of the six major synthetic materials in the world, the polyurethane industry has expanded rapidly in recent years. According to the "2016-2022 China Polyurethane Industry Market Trend Forecast and Trend Forecast Research Report" released by Booz Data: the global output of polyurethane products has exceeded 21 million tons, of which foam system and non-foam system products each account for half of the country, and its huge growth potential is prepared for attention.
The trend of production scale is obvious In production, the polyurethane industry, like most chemical industries, has an increasingly obvious trend of intensification and scale. As polyurethane production technology becomes more and more mature, products become more popular and application fields continue to expand, manufacturers find that in order to maintain a certain level of profitability, they must have certain economies of scale. As a result, the scale of new enterprises is getting bigger and bigger, and the production capacity is also increasing rapidly.
Consumer acceptance is still unclear, and there are many details to be improved
As mentioned above, high-elastic polyurethane foam is a new type of material, and people do not have a deep understanding of its characteristics, so it has not yet formed a large market awareness.
Since the car is closely related to people's life after being purchased, and because of its high price, many families will not replace the car for a long time after purchasing it. Evaluating its various properties, the seat made of flexible polyurethane foam has gradually become one of the focuses of people's attention. Compared with traditional seats, seats made of new flexible polyurethane foam have many uncertainties. Therefore, it has not yet become a must-have object in the minds of consumers.
First of all, the chemical reaction of the "polyurethane foam" itself. After the flexible polyurethane foam is made into a car seat, due to long-term sunlight exposure, the airtightness of the car is high, and the temperature inside the car will be extremely high. Reaction and release of toxic gas will seriously endanger the life safety of drivers. According to relevant survey results, a large amount of siloxane will enter many finished automobile products during production, and its own components cannot directly produce toxic substances, but in During a certain volatilization process, siloxane will gradually be scattered into the flexible polyurethane foam in the car seat, enhance the volatility of the flexible polyurethane foam, and generate toxic gases. Therefore, it is necessary to actively improve this material and reduce its activity.
In addition, according to ergonomic requirements, the car seat needs to be designed as a product with a certain curved surface, which is difficult to achieve for the box-type foaming process of "polyurethane foam". Therefore, only the molding foaming process can be used at present. , to a certain extent restricts the development of "high elastic polyurethane foam".
As we all know, in summer, the sun shines directly into the interior of the car. Due to the better sealing of the car, it will cause high temperature in the car. If the foam is toxic, the high temperature and airtightness inside the car will cause poisoning of the people in the car. At the same time, If the foam contains a large amount of organic matter, if it melts and volatilizes at high temperature, a large amount of organic matter will volatilize on the glass surface of the car, which will seriously affect the driver's vision and cause traffic accidents. Therefore, a comprehensive understanding of the performance of this kind of foam is required , Only in this way can this material be better used, gradually accepted by drivers and accepted by many consumers.
From the perspective of consumer awareness and education and negative comments, there is still a long way to go before high-elasticity polyurethane foam becomes the standard for future car seats.
But in the long run, although the high-elasticity polyurethane foam itself has certain defects, its advantages are more important. Once overcome, the automobile production technology and the safety factor of the automobile have been further improved. Only then will highly resilient polyurethane foam have a chance to become standard in future car seats.
