Elastomers Oil Absorption and Surface Texture Improvement Assessment.
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Elastomers Oil Absorption and Surface Texture Improvement Assessment.
Do you have Oil Absorption or related Surface Appearance problems?
Do your pellets have a greasy or sticky surface after compounding?
Do you have agglomeration during packaging?
Do you have to feed free-flowing issues?
After a few days, does the greasy aspect appears again?
Oil absorption occurs by a diffusion-absorption process which is a function of temperature, oil composition, and polymer characteristics. Good porosity is required to absorb oil well in the compounding process. This article summarizes some of the steps to be undertaken during the elastomer manufacturing process or during the compounding formulation and processing process, based on Innventik’s experience performing assessments on this type of issue.
OIL ABSORPTION IMPROVEMENT DURING THE ELASTOMER MANUFACTURING PROCESS.
High molecular weight polymers (i.e. SEBS) are more prone to oil absorption problems and also to exhibit surface appearance issues. The leading causes that influence Oil Absorption and Surface Texture are related to the crumb’s physical form and characteristics, which depend on variables controlled during the Reaction, Polymer Recovery, and/or Drying Processes. An assessment of the process is required to evaluate the root causes, the extent and source of the problem(s), and the measures for improvement. The main goal is to identify the most favorable process synthesis, polymer recovery, and processing conditions to obtain the ideal crumb form, crumb density, particle size, and particle size distribution, for optimum crumb porosity.
OIL ABSORPTION IMPROVEMENT DURING COMPOUNDING FORMULATION AND PROCESSING.
In the case of SEBS, high-viscosity paraffinic oils with viscosities of 70-100 cst (40ºC) can be used. The blending of the elastomer with the polymer (i.e. Polypropylene) can be performed at standard conditions, using high or low-speed blenders, ensuring complete absorption.
FAST METHOD TO EVALUATE OIL ABSORPTION.
Procedure:
- Blend 100-200 g of rubber and 30-60 g of white oil in a container with manual stirring
- Allow to stand for 5 min.
- Blend again manually.
- Allow to stand for 10-15 min.
- If the result is not good, allow standing for 10-15 min.
Observations:
- Excellent Oil Absorption: Crumbs or pellets without any material held to the bottom of the container but with crumbs that stick to the wall. Crumbs held to the wall only.
- Good Oil Absorption: Very few crumbs or pellets without any material held to the bottom of the container.
- Bad Oil Absorption: Most of the crumbs are held to the bottom and to the walls of the container that can be easily separated with stirring
- Worst Oil Absorption: A very oily cluster of crumbs, held to the walls that can be easily separated with stirring.
If you are interested in improving surface appearance, oil absorption (rate of oil absorption or polymer capability of incorporating a higher amount of oil), please share your challenge and contact Innventik.
Author: Walter Ramirez (walter@innventik.com)
Date: 2023-05-21