Why Does TPE Material Ooze Oil? Solutions to Prevent Customer Returns Due to Oil Oozing
Time of issue:2025-06-09
In the formulation of TPE (Thermoplastic Elastomer) materials, oil is typically added as a plasticizer to reduce the viscosity of SBS (Styrene-Butadiene-Styrene), facilitating easier plasticization and processing. The higher the oil content, the lower the hardness of the TPE material. Due to the good compatibility between SBS and oil, they form a relatively stable mixed system, but this compatibility is physical rather than chemical. Therefore, oil oozing is inevitable over time.
Generally, SBS-modified TPR with a hardness below 50 Shore A is more prone to oil oozing. Selecting high-quality oil varieties and improving the formulation can reduce oil oozing in products. SEBS (Styrene-Ethylene-Butylene-Styrene) has better oil absorption than SBS, so TPE based on SEBS is less likely to ooze oil compared to TPR based on SBS.
The basic component of TPE, SEBS, has good oil absorption properties. When the oil ratio is appropriately controlled, SEBS and oil form a stable system, preventing oil oozing. Some customers, when producing softer TPE products, tend to mix low-hardness TPE with plastics like PP (Polypropylene) and PE (Polyethylene) to reduce raw material costs. However, this practice increases the risk of oil oozing in the final product.
The oil oozing in the aforementioned case is mainly due to the blending of SEBS with newly added plastics like PE, PP, and EVA (Ethylene-Vinyl Acetate), forming a new rubber-plastic blend. Since these plastics do not absorb oil, they weaken the oil absorption capacity of the new blend, leading to oil oozing.
Many TPE products are highly oil-filled, such as adult products, bra pads, and ultra-soft toys. Oil leakage and oozing issues are largely related to material selection (including base material and oil type). In a competitive market, some manufacturers use low-cost materials to reduce production costs. However, achieving both low prices and high quality is rare. Choosing low-cost raw materials often means compromising on quality. Low-end base materials have poor oil absorption (retention) properties, making them prone to oil leakage and easy to break. Additionally, different oil types have varying oil-filling ratios, which is also a significant factor in product oil leakage.
To produce highly oil-filled TPE/TPR materials that do not ooze oil, are odorless, and do not yellow, it is essential to select base materials with high oil absorption (good oil retention) properties and high-quality oils that have undergone multiple hydrogenation processes. Although this increases costs, it ensures superior quality, suitable for high-end consumer markets.
So, how can we produce TPE/TPR materials that are highly oil-filled but do not ooze oil?
A: To achieve a smooth and slippery feel in TPE/TPR products, the following factors should be considered: using paraffin oil, as it provides a better slippery feel than naphthenic oil; selecting star-shaped or high molecular weight SBS/SEBS, as they can absorb more oil compared to linear or low molecular weight SBS/SEBS, resulting in better oil-filling effects at the same oil content; and adding slip agents or anti-sticking agents.
B: During oil filling, it is important to keep the TPE/TPR material rotating or stirring. Static oil filling can easily cause clumping and uneven oil distribution. When the oil-filling amount is high, the rotation speed should be reduced to prevent oil from seeping out of the SEBS/SBS (similar to the principle of a washing machine's spin cycle). After oil filling, it is best to let the material sit for a while to allow the oil to be fully absorbed by SEBS/SBS before production. Otherwise, oil may seep out during production.
C: Oil-filled SBS/SEBS materials are prone to yellowing, mainly due to the presence of unsaturated double bonds in naphthenic oil, which can be oxidized and cause yellowing. Domestic Karamay naphthenic oil, which is hydrogenated, does not have this issue. Therefore, care should be taken when selecting oils.
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