--- title: "How Can We Analyze Problems Using First Principles?" id: "3625" type: "post" slug: "how-can-we-analyze-problems-using-first-principles" published_at: "2026-07-09T03:27:22+00:00" modified_at: "2026-07-09T03:37:56+00:00" url: "https://www.sheenmaterials.com/de/how-can-we-analyze-problems-using-first-principles/" markdown_url: "https://www.sheenmaterials.com/de/how-can-we-analyze-problems-using-first-principles.md" excerpt: "When developing new materials, we cannot remain bound by industry conventions." taxonomy_category: - "Company News" - "Use Guides" --- # How Can We Analyze Problems Using First Principles? ## What exactly is this operation? There are actually only two actions: one is to chase downwards, and the other is to take it up. However, there is a rule in each of these two actions that is easily overlooked. ### The first action is called downward reduction. In other words, when you see any macro-level conclusion, don’t rush to accept it, but keep asking questions: Why is this happening? Keep asking until you can’t push it any further and have to stop at one point. At the most basic level, that’s true. But here’s the key point: you can’t stop at industry conventions. Many people think they are doing first-principles analysis, but It’s just that it stopped too early. For example: - “Everyone chooses this material.” - That’s what it says in the manual. - “That’s how we’ve done projects before.” - “The supplier recommends this brand.” These are not first principles; they are merely industry practices. Experience, engineering practices, and historical paths. They may be useful, but they are not the underlying cause. The true stopping point should be placed at a more fundamental level, such as conservation laws, thermodynamic laws, structure-property relationships, or the actual microscopic phenomena within the material mechanism. Therefore, the dividing line between first principles and ordinary analysis lies not in whether you ask “why,” but in your final floor to stop at. If you stop at “everyone does it this way,” then you’re still just relying on experience points. You only truly understand it when you stop at “this structure determines this performance”. Really getting to the bottom of it. ### The second action is called upward reconstruction. Downward reduction simply breaks the problem down to its lowest level, but that’s still not enough. What truly matters is: can you take these fundamental principles, combine them with the real constraints you have at your disposal, and then launch a plan? Note that this is not a matter of simply applying conclusions that have already been derived by others. Just because someone else uses this brand name doesn’t mean you should use it too. Just because someone else emphasizes this parameter doesn’t mean that parameter is your core contradiction. Just because someone advertises a selling point doesn’t mean the customer will actually buy it. That’s the selling point. Downward reduction simply involves listing the rooms one by one. Rebuilding upwards is the only way to reconnect these rooms into a single line. A walkable corridor. True judgment grows in this “corridor”. This method is particularly useful in polymer materials. Because the vast majority of macroscopic performance can ultimately be attributed to lower performance. Make an appointment on the third floor: ## Chain structure, phase state, molecular motion. - Why is the material strong? - Why is the material soft? - Why do materials absorb water? - Why is the material heat-resistant? - Why do materials age? - Why does the material crack? ### As you follow the trail, most of them eventually come down to these three questions. - Which type of chemical bond is at play? - Which chain structure determines it? - What phase is limiting it? - What scale of molecular motion controls it? Therefore, the first consideration in polymer science, to be more specific… It means tracing any performance metric all the way back to the “link”. The three layers of “structure-phase-molecular motion” are then discussed, and from there… Push back the project plan. The following example of nylon absorbing water will illustrate this point. Why does nylon absorb water? The key isn’t the brand name, but the acyl group. Amine Density. The common analogy approach is: PA6 is absorbent, and its dimensions are unstable, so I’ll find an absorbent… Choose a brand with a lower water content, or add some fiberglass, and adjust the size accordingly. Press down on the change in size. This can certainly solve some problems, but it’s only based on experience. Replacement, not underlying derivation. What we are really asking is: Why does PA6 absorb water? Because nylon molecules contain a large number of amide bonds, that is —CONH— structure. This structure has a strong hydrogen content. The bonding site makes it easy for water molecules to form an interaction. use. Once water enters, it will disrupt the original interchain hydrogen bond network. Network. On the one hand, it reduces the interaction between molecular chains. On the one hand, it is weak and acts as a plasticizer; on the other hand, it stretches… Interchain distance leads to swelling and dimensional changes. ## Go down one more layer: ### What does water absorption capacity essentially depend on? It largely depends on the amide groups per unit chain length density. The denser the amide groups, the more sites water can bind to, and the better the adsorption capacity. The stronger the water absorption tendency, the less water-absorbing the amide group; the rarer the amide group, the stronger the water absorption tendency. The weaker. This is no longer a “brand name issue,” but a “chain structure question”. Therefore, you can determine the general direction without consulting a table: - PA6 has a high amide density; therefore, it has a high water absorption rate; - PA612 has a longer carbon chain, resulting in a lower amide density.The water absorption rate is significantly reduced; - The long methylene chain of PA12 further dilutes the amide group. It is compacted, so its water absorption rate is lower. Under typical conditions, the saturated water absorption rate of PA6 can reach 9%. PA612 decreased to approximately 3%, while PA12 could decrease. It’s in the range of 1% to 2%. This order wasn’t derived by memorizing data, but rather… Deduced from the amide density. This is downward reduction. ## How to rebuild upward? If your ultimate goal is “wet-state dimensional stability”, then positive leverage shouldn’t just be about “finding a low-absorption brand”. Instead of referring to the “number”, we need to return to two directions: - First, reduce the density of the amide adhesive; - Second, it reduces the ability of water molecules to approach amide groups. Following this logic, you would naturally deduce the long carbon chain nylon. For example, PA1010, PA12; or push to a semi-aromatic formula. Nylon, such as PPA and PA6T systems. Why? Because long carbon chains can dilute the density of amides and reduce water absorption driving force. The introduction of the aromatic ring, on the one hand, dilutes the amide group. On the one hand, the group increases the rigidity of the chain segment, and on the other hand, it can also improve… Heat resistance and HDT. At this point, when you choose materials, it’s no longer about “heard this brand absorbs…” It’s not about “low water absorption,” but about understanding why it has low water absorption, understanding its… Which underlying contradiction is being resolved? Conversely, is adding fiberglass useful? It’s useful, but it solves a different problem. Fiberglass can reduce the absolute dimensional changes of materials after absorbing water. Value, because it is equivalent to adding rigidity to the system. The skeleton constrains expansion. However, fiberglass does not eliminate the driving force that drives nylon to absorb water. Water will still get in, and the hydrogen bond network will still be disrupted. The matrix will still be plasticized, so wet strength and modulus… The quantity and fatigue performance may still decline. Therefore, checking the license plate number only stops at this point. Tracing the chain structure backward from the amide density is the real key to solving the problem. Connect the questions. This is the value of first principles: It’s not telling you “PA12 is more water-resistant than PA6”, but rather telling you why it’s more water-resistant; it’s not about making you remember more. It doesn’t just give you a conclusion about the material, but rather empowers you to re-derive the material. 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