Comparison of Ether-Based Cast Polyurethane Raw Materials

Comparison of Ether-Based Cast Polyurethane Raw Materials As we all know, the world changed dramatically with the Covid-19 pandemic. When supply chain difficulties in chemical raw materials and logistics problems were added to health sector challenges, prices of chemical raw materials began rising very rapidly. Ether-type polyols, particularly PTMEG-type ether polyols, became one of the chemicals with the fastest and highest price increases. In addition to the general difficulties experienced, certain sectors in an upward trend began drawing high volumes of material from supply chains relevant to PTMEG markets, causing serious supply problems and price increases in the PTMEG (and simultaneously 1,4-butanediol) sector. This graph shows the production stages of PTMEG. PTMEG is a difficult and laborious chemical obtained through 4 production stages after initial base material input. The rapidly developing bioplastics market and 1,4-butanediol, used intensively in bioplastics raw material production, began being sold primarily to this sector. High demand volume and higher profit margins for 1,4-butanediol made the bioplastics sector a priority. Since 1,4-butanediol, obtained through 2 production stages, generates higher profits, PTMEG, obtained through 4 production stages, began being pushed to the background. When insufficient 1,4-butanediol remained for PTMEG production and PTMEG production volumes decreased while production costs increased, limited supply and rising production costs caused PTMEG prices to rise very rapidly. During this period when the pandemic and its problems continued, the lack of sufficient 1,4-butanediol capacity for polyurethane and bioplastics sectors appears likely to push PTMEG prices even higher. This problem creates major difficulties for manufacturers using cast polyurethane raw materials, particularly ether-based materials. Many companies are conducting research on alternatives to PTMEG-based materials, and the most common trends are developing towards using materials produced with PTMEG-PPG polyol mixtures instead of PTMEG or using only PPG-type polyols. Ether-based materials are among the raw material groups most consumed by companies working with hot-cast polyurethane materials. This raw material group typically stands out for its low viscosity properties and long pot life. Due to these characteristics, they are preferred for casting complex and large-scale parts. While ether-based polyurethane cast materials were previously produced using only TDI and MDI-type aromatic isocyanates, they later began being produced using aliphatic isocyanates such as HDI and PpDI. While each isocyanate type has characteristic properties it imparts to these ether-based materials, in this article we will compare ether-based materials produced using TDI-type isocyanates, based on ether polyol types. Generally, two types of ether polyols are used in cast polyurethane material production. The first is PTMEG, a chemical, and cast polyurethane materials produced using this polyol are top-grade materials. They provide much better results than PPG, the other polyol type, in terms of durability, service life and performance. Cast polyurethane materials produced using polypropylene glycol-type polyols, abbreviated as PPG, result in products with very poor tear strength and wear resistance. In the table below, 3 different ether-based cast polyurethane materials produced using TDI-type isocyanate are compared. The common characteristic of these materials is that they are TDI ether group materials and achieve 90 ShA hardness when cast using MOCA-type curing agents. • Material referred to as A is produced with TDI + PTMEG ether-type polyol, • Material referred to as B is produced with a mixture of TDI + PTMEG-PPG ether polyols, • Material referred to as C is produced with TDI + PPG ether-type polyol. As can be seen from the values in the table, as the PTMEG content decreases and PPG content increases, nearly all strength properties of the cast polyurethane material show dramatic decline. For example, while a manufacturer using TDI + PTMEG-based material can operate their scraper for extended periods without wear, a manufacturer using TDI + PPG-based material experiences rapid wear loss as their scraper deteriorates almost like an office eraser at every friction contact. Similarly, the screening surfaces of companies producing mine screens and the wear amounts of those screens in the field show significant variation depending on the polyol type of the raw material. The situation is similar for pallet truck wheels, forklift wheels or heavy-load wheels. Permanent deformation and elasticity values show that PTMEG-based materials are best suited for these applications, while purely PPG-based materials are not suited for them at all. Similar conditions apply to concrete spraying nozzles, impact wedges of rock crushers or internal linings of vibration mills. The yield obtained from materials produced using PTMEG/PPG mixtures will be distant from the PTMEG-based type and close to the PPG-based type. This is because the poor mechanical properties of PPG polyol are sufficient to significantly reduce performance even when a mixture is used. The most important method manufacturers will use to identify these 3 different material types is to compare the NCO levels of the materials. Speaking of materials with the same hardness value; • The more PTMEG content in the material or if there is no PPG in the content, the lowest NCO level is reached with that hardness value. (In the table, the NCO value for 90 ShA hardness is approximately 4.25) • The more PPG content in the material or if there is no PTMEG in the content, the highest NCO level is reached with that hardness value. (In the table, the NCO value for 90 ShA hardness is approximately 5.00) As can be understood from the values in the table and the explanations above, using PPG-based or PTMEG/PPG mixture TDI ether materials provides manufacturers with no additional benefits other than a cost advantage. Therefore, where performance and durability in the working environment are important, if an ether-based material is to be used, the preference should be for PTMEG-based materials.

Serkan İltan Rubber & PU Sales Manager Veser Kimyevi Maddeler A.Ş.