Zhongsuwang TPE | Technical dry goods: A complete analysis of the essential reasons for the oiling of TPE materials!

In the field of polymer material applications, TPE materials are favored for their excellent elasticity and processing performance, and are widely used in toys, daily necessities, medical devices and other fields. However, the "oiling" phenomenon has become a problem that troubles many users. This phenomenon not only affects the appearance and feel of the product, but may also pose a potential threat to its performance. What exactly causes the oiling of TPE materials? What principles are hidden behind it? Let's take a look with Zhongsuwang editor!

First of all, those who produce TPE and TPR know that the main raw materials of these two are SEBS and SBS, respectively, and oil is used in the production process, but some manufacturers blindly demand to reduce costs, so they desperately fill the raw materials with oil, causing their products to have oil seepage or sticky hands after production or molding. In fact, the biggest role of oil filling is to improve the fluidity of SEBS/SBS, but the fluidity of SEBS/SBS itself is not good, and the processing performance is poor. It is impossible to make 100% SEBS/SBS products. The basic formula of each manufacturer is more or less different, so it is normal for the product parameters tested by different manufacturers to be different.

1. What are the main causes of oil leakage?

1. Formula design problems

Improper selection and content of oil additives. Oil additives are usually added to TPE materials to improve performance. If the content is too high or the compatibility with substrates such as SEBS and SBS is poor, it is easy to cause oil leakage. In addition, affected by other additives, some additives in the formula may promote the migration and seepage of oil.

2. Base material selection problem

Different types of SEBS have different oil absorption properties. If the selected SEBS has low lightness, low soft segment content, easy crystallization, and low molecular weight, the oil absorption is poor and oil is easy to come out; and unhydrogenated or low hydrogenated SBS, due to the residual double bonds in the molecular chain, is easy to be oxidized, which will also cause oil phase separation and a higher risk of oil coming out.

3. Oil filling process problem

If the oil is not fully stirred during oil filling, the oil and materials such as SEBS cannot be evenly mixed, and local oil-rich areas are easy to form, which are easy to precipitate later. If the oil filling ratio is inappropriate, the oil absorption capacity of SEBS is limited, and excessive oil filling will exceed its oil lock threshold, resulting in oil coming out.

4. Processing process problem

If the processing temperature is too high or too low, it will destroy the balance between oil and base material, making it easy for oil components to migrate from the inside to the surface; too fast injection speed, uneven mold temperature, etc., will cause stress or defects inside the material, promoting oil migration and seepage.

5. Environmental factors

Under high temperature, the movement of TPE molecular chains is accelerated, and oil components are more likely to migrate to the surface; while low temperature may cause oil components to crystallize inside, reducing oil lock. In addition, direct sunlight, ultraviolet radiation, oxidation, etc. will also accelerate the aging of TPE materials and cause oil precipitation.

6. Product design issues

If the product design is unreasonable, resulting in excessive pressure or friction on the material during use, it will accelerate the migration and seepage of oil.

2. Is there a solution?

1. Optimize the formula: The amount of oil filling can be appropriately reduced. Under the premise of ensuring material performance, the amount of oil additives added can be reduced as much as possible to reduce the possibility of oil leakage. And choose the right oil, give priority to oils with good compatibility with SEBS, such as cyclohexane oil; if paraffin oil is used, its compatibility, volatility and cost factors need to be considered comprehensively. Then add auxiliary materials appropriately. You can add an appropriate amount of hydrogenated petroleum resin to enhance the oil lock; you can also add surface-treated nano-silicon dioxide, which has a large specific surface area and strong adsorption capacity, and can effectively adsorb free small molecules in the TPE material system to inhibit oil analysis. The addition amount is generally 1%-3%.

2. Reasonable selection of substrate: SEBS with high lightness, high soft segment content, not easy to crystallize and high molecular weight is preferred; for TPE products with high temperature resistance requirements, 10%-20% SEPS can be added to improve temperature resistance.

3. Improve the oil filling process: Use dynamic oil filling method to fully stir oil and SEBS and other materials to ensure that oil molecules penetrate evenly between molecular chains; at the same time, strictly control the oil filling temperature and time to avoid excessively high or low temperature affecting the oil absorption effect of SEBS.

4. Control the processing technology: strictly control the processing temperature to prevent excessively high or low temperature from destroying the balance between oil and substrate; reasonably adjust parameters such as injection speed and mold temperature to avoid stress or defects inside the material.

5. Improve storage conditions: Try to store TPE materials and products in a cool, dry, ventilated and good environment, avoid direct sunlight and adverse conditions such as high temperature and high humidity, so as to slow down the migration and seepage of oil components.

6. Product design optimization: When designing products made of TPE materials, fully consider the stress conditions during use to avoid excessive pressure or friction on the material due to unreasonable design, thereby accelerating oil production.

In summary, the solution to the oil production problem of TPE materials needs to start from the source such as raw material ratio and production process. By scientifically adjusting the formula and optimizing the processing conditions, the oil production phenomenon can be effectively suppressed. If you are still troubled by this problem in actual application, please feel free to communicate with the editor of Zhongsuwang!