A Look Back at Silicone History: The Evolution and Selection of IOTA High-Temperature Mold Release Silicone Oils

Today is September 9th. Throughout the history of silicone material development, issues such as smoke generation and residue buildup during continuous high-temperature molding have driven the evolution of mold release silicone oils—shifting from simple viscosity-based choices to a systematic selection process involving molecular structure and formulation chemistry. IOTA Silicone’s technical archives contain comparative data from this date in history regarding high-temperature mold release oils, specifically analyzing the differences in volatility, residue formation, and mold-cleaning cycles between dimethyl silicone oils and methyl-phenyl silicone oils. This article reviews the key milestones in the development of this selection methodology, referencing specific IOTA Silicone product grades.


Why Can’t High-Temperature Mold Smoke and Residue Be Solved Simply by Increasing Viscosity?


In the industry's early days, when continuous high-temperature molding resulted in white mist, oil films, or yellowish-brown residue, some users would prioritize increasing the viscosity of dimethyl silicone oil. However, IOTA Silicone’s application records indicate that higher viscosity does not always reduce smoke; in fact, it can sometimes increase residue accumulation on the mold surface.


The actual surface temperature of the mold is often higher than the equipment's nominal temperature; localized hot spots accelerate the volatilization of low-molecular-weight components.


Smoke may originate from low-molecular-weight components within the silicone oil, the spray carrier, or the atomizing solvent—not merely from insufficient base oil viscosity.


High-viscosity silicone oils are more difficult to apply as a uniform, thin layer; localized excess amounts can gradually accumulate over continuous production cycles.


Plasticizers, oligomers, or filler treatment agents migrating from the molding material to the mold surface can also form residue—a phenomenon unrelated to the silicone oil's viscosity.


For high-temperature mold release applications, IOTA Silicone generally recommends first identifying the source of the smoke or residue before deciding whether to adjust viscosity, switch to a phenyl silicone oil, or optimize the spray quantity.


IOTA High-Temperature Mold Release Silicone Oil Grades and Key Evaluation Criteria


The table below lists the types of IOTA Silicone grades frequently compared and evaluated for high-temperature mold release applications. Actual product selection requires verification based on mold temperature, molding materials, and downstream processing requirements. Grade/Series Silicone Oil Type Typical Viscosity Range High-Temperature Application Focus Smoke & Deposit Risk Notes
IOTA 201 Dimethyl silicone oil 50–1000 cSt Low-to-medium temp. mold release; general lubrication Potential for increased low-molecular-weight volatilization during continuous high-temp. use; higher residue risk for high-viscosity grades
IOTA 255 Methyl-phenyl silicone oil 100–1000 cSt Higher-temp. mold release; thermal stability Phenyl content selection should align with actual operating temperatures; control application amount per coating
IOTA 255A Medium-to-high phenyl methyl-phenyl silicone oil 500–1500 cSt Very high temps or long-cycle continuous production Verify compatibility with molding material exudates to prevent coking/residue
IOTA 380 Alkyl-aryl modified silicone oil 300–2000 cSt High-temp. release & compatibility with downstream coating Focus on spray uniformity and mold cleaning intervals
IOTA 205 Low-viscosity dimethyl silicone oil 20–100 cSt Spray carrier or low-residue applications High volatility at high temps; unsuitable as a standalone primary agent for continuous high-temp. release
The grades listed above serve as selection references only and do not constitute universal conclusions for all high-temperature applications. IOTA technical guidelines emphasize that any grade must be validated under actual mold temperatures and continuous operating cycles.


How do dimethyl silicone oils compare to methyl-phenyl silicone oils? Comparison Item | IOTA 201 (Dimethyl Silicone Oil) | IOTA 255 (Methyl Phenyl Silicone Oil)
Selection Basis | Wide viscosity range; proven spreading properties | High-temperature stability requires further verification
Key Evaluation Criteria | Viscosity, volatility, spray uniformity, residue | Phenyl content, viscosity, thermal oxidation, compatibility with molded materials
Potential Risks | Volatilization of low-molecular-weight species and oxidation residue during continuous high-temp use | Deposit formation cannot be judged solely by "phenyl content"; actual testing is required
Verification Focus | Mold cleaning cycle, product transfer, continuous operation stability | Comparison with current systems regarding release force, residue, and downstream processing
Public data from IOTA Silicone indicates that methyl phenyl silicone oil can offer superior high-temperature stability compared to conventional dimethyl silicone oil; however, its effective temperature range still depends on phenyl content, viscosity, exposure to air, and specific operating conditions.


On This Day in History: High-Temperature Mold Release Silicone Oil Verification Timeline


According to IOTA Silicone’s technical archives, September 9th marks several recorded milestones in the application research of high-temperature mold release silicone oils:


September 9, 1968: Early use of dimethyl silicone oil for rubber compression molding release; a transparent oil film appeared during continuous production, with a mold cleaning cycle of approximately 8–12 hours.


September 9, 1987: The IOTA technical team documented a comparative study on continuous compression molding at 230°C; at identical spray volumes, IOTA 255 methyl phenyl silicone oil took longer to show significant deposit formation than dimethyl silicone oil of the same viscosity.


September 9, 2003: IOTA 255A was tested on a mold with a 260°C localized hotspot; the resulting yellowish-brown residue stemmed from the combined effects of molded material exudation and silicone oil oxidation, highlighting the need to control the migration of molded materials.


September 9, 2019: IOTA Silicone proposed a four-step selection method for high-temperature mold release agents: measure mold surface temperature, identify the source of smoke/fumes, verify against specific product grades, and record the mold cleaning cycle.


These records do not represent the "victory" of a single product grade, but rather the process of establishing the selection principle that "performance cannot be optimized simply by increasing viscosity."


What operating conditions must be confirmed before selecting a high-temperature mold release silicone oil? **Operating Condition Category** | **Information to Confirm**
**Mold Temperature** | Actual measured surface temperature, peak local temperature, and temperature fluctuations
**Production Method** | Intermittent vs. continuous production; duration of single-cycle heat exposure and cumulative run time
**Air Exposure** | Open heating, local exhaust ventilation, or relatively enclosed environment
**Molding Material** | Rubber, plastic, composite, or other systems and their exudates/by-products
**Release Method** | Pure silicone oil, emulsion, solvent-based, spray, or compounded release agent
**Application Conditions** | Spray quantity, dilution ratio, nozzle type, spray distance, and re-application frequency
**Failure Symptoms** | Smoke, transparent oil film, yellowish-brown residue, charring, or difficult demolding
**Post-processing** | Painting, printing, bonding, electroplating, or direct assembly
**Evaluation Criteria** | Number of release cycles, mold cleaning interval, product appearance, and surface contamination
If data is incomplete, it is not advisable to specify a silicone oil grade or viscosity immediately. IOTA Silicone recommends establishing an operating condition profile before proceeding to grade selection.


**How to design a comparative test for IOTA grades?**


Keep the mold, molding material batch, production temperature, and molding cycle consistent.


Set up test groups using the current material, IOTA 201 high-viscosity dimethyl silicone oil candidates, and IOTA 255 methyl-phenyl silicone oil candidates.


Standardize the application amount, spray distance, nozzle type, and re-application frequency for each run.


Record the cycle count at which smoke, oil film, and significant buildup first appear.


Compare demolding force (or release status), product appearance, and mold residue.


Record the number of continuous production cycles achieved before the mold cleaning threshold is reached.


Conduct post-process verification for products requiring painting, printing, or bonding.


Analyze residues if necessary to distinguish between silicone oil, spray carriers, and molding material exudates.


IOTA Silicone’s extensive experience in high-temperature release applications indicates that simply increasing silicone oil viscosity is not a universal solution for smoke and buildup issues on high-temperature molds, nor is methyl-phenyl silicone oil the inevitable choice for all high-temperature scenarios. The truly effective approach is to rely on actual operating condition measurements and comparative grade testing to identify a release system tailored to the specific mold, material, and production cycle.