Limitation and Improvement of Common Analytical Methods for Foaming

We usually learn the chemical reaction and formulation of polyurethane from the quality, which is called the first level. The unit of mass is kilogram or gram, which is convenient to weigh the formula. For example, if the amine component increases, the reaction will be faster, and if the amine component decreases, the problem will be solved. What's more complicated is that the addition or subtraction of two or three components causes changes to accumulate experience and skills. It can be said that most of the foamers in China, including me, stay at this level. The cruel fact is that only through this level is far from the understanding of polyurethane polymer chemical reaction panorama, in order to accumulate experience, more than a decade later you think you understand, but also by many problems that do not explain the puzzle, in fact, not thoroughly understand. But this level is the most attractive, because "visible", "touchable" and "understandable", and also consistent with logical analysis. So people who stop at this level for several years or even more are everywhere.

Let's look at the limitations of the first level. Foaming is the most important part of the whole process of polyurethane chemical reaction in production. The first level is to find rules and experience by comparing the effect of changes in composition and production parameters (hardness, tension, elasticity and problems) after production. It is precisely not to pay attention to the most important chemical reaction process of foaming. Some people say that it is not very good for me to make bubbles like this for twelve years. First, even if I have made bubbles for more than twenty years, there are many phenomena and problems that can not be divided. Secondly, when it comes to medium and high-end foam production, it will be found that the first level of things is really useless. High-end foam is not necessarily a novel raw material. Even for ordinary foams, if any value of elastic hardness of common physical properties is required in a narrow range, the difficulty of foaming will increase several times. At that time, the difference of fine reaction must be faced, and the chemical reaction must be standardized more finely.

Because of the limitations of the above understanding reaction, some people try to step into the second level to understand: from the quantity of substances and chemical groups to understand the formula changes. The unit of mass of matter is the mole, that is, the number of molecules. The essential difference between the second level and the first level is that it pays attention to the process of foaming chemical reaction, which is qualitative change and the most difficult to leap over. The latter level is only deep in the second level framework. The second level will formally face the basic characteristics of polymer chemical reactions: multidirectionality, reversibility and synergy. None of the above is familiar to our ordinary thinking. Every one of the above is often encountered even at the first level, but we have never discussed the chemical reaction process in depth and avoided it. Multidirectivity is derived from chemical reaction equation and from the consumption and redistribution of active groups by reactants. These are non-linear and complex dynamic changes (e.g. TDI consumption of a formula is a binary quaternary equation model. For example, although the three groups of trihydroxy polyether are theoretically identical in activity, the activity of the first group is very different from that of the second group due to steric hindrance. Big. Reversibility is even more incomprehensible to us: raw material reactions in the past can also be reduced from the decomposition of the product to the state before the reaction, resulting in some side effects. Synergy is simply 1 + 1 > 10 or even more than 100, such as the synergistic catalysis of amine and tin. In this level, there is no distinction between high rebound, slow rebound and common bubble names, but only the difference of base structure, activity and reaction rate. At this level, the freshness of the formulation changes will be lost, and the formulation is only a fragment description of many changes, because he has roughly felt the panorama of the chemical reaction of polyurethane. In this level, the opening and closing are chemical reaction equations, chemical bonds, rate constants, molar concentration, activation energy, gas evolution rate, temperature rise curve, initial temperature and so on, which are not discussed in the first level. At this level, there is a complete loss of interest in the rhetoric of changes in the composition of the formula, which they believe is tantamount to saying nothing. Many of the compositions show oscillation curve distribution, and even the curve shows fracture morphology. (Some people can calculate the inflection point of these oscillations and the interval where the breaking point is located in the recipe, and try to stay away from this area when designing the recipe.)

Although the first level has its limitations, it is the only way we have to go, and whether we enter the second level depends on human efforts and conscientiousness. Without deliberate requirements, it is spontaneous to accumulate to a certain extent. Some people have the ability to step into it but do not step into it.

In the face of complex chemical reactions, we can only be careful to standardize chemical reactions. Some of the factors that we think are unimportant may be the main factors that interfere with production at some time. Do not think that ordinary foam good hair, high rebound slow rebound bad hair, bad handling is a mess. It's just that the general bubble is more tolerant, and the gas response is in harmony with the gel reaction, and the change is close to my usual thinking, and the situation of collapse is less.

The next level is the field of researchers, and there are many things worth learning from our producers. The level of electron transfer makes it possible to unify all the chemical reaction laws. Above all, we can see that the understanding of matter (raw materials and reactions) is: the whole group molecular atoms electrons, is gradually shrinking, which is also the path of in-depth discussion of all technology and knowledge.