One cannot simply rely on IOTA-1235A/B being a two-component semi-transparent silicone rubber that is vulcanized using a platinum-rhodium complex or "without the need for a vulcanizing agent" to directly conclude that it is suitable for all extruded silicone tubes, mechanical silicone tubes/strip systems. One must first confirm the extruder and die, screw speed, barrel temperature, A/B mixing ratio, kneading dispersion state, rubber storage time, vertical oven temperature and residence time, product thickness and hardness requirements, before determining whether the problem lies in uneven mixing, mismatched plasticity, insufficient or excessive vulcanization, or poor compatibility with the die and pulling process. The IOTA-1235A/B series can be considered as a candidate direction for platinum-sulfurized extruded solid rubber, but it must be confirmed through small-scale tests, extrusion verification and actual working condition assessment.


Why do A/B two-component extruded silicone rubber often have unstable vulcanization in tube or strip production?


The A and B components were not accurately measured at a ratio of 1000g:1000g, or the kneading was not uniform, resulting in insufficient or excessive crosslinking density in some areas.


The rubber was discharged without being forked at the edge of the kneader, and the platinum catalyst and hydrogen-containing components were not well dispersed. The vulcanization degree fluctuated after extrusion.


The plasticity of the rubber did not match the extruder, die and pulling speed, causing the die to expand, size fluctuations or surface roughness.


The barrel temperature or rubber processing temperature exceeded 65℃, causing partial crosslinking of the rubber to occur prematurely, resulting in dead material or uneven extrusion surface particles.


The safe storage time of the rubber at 25℃ exceeded 2 days, resulting in a decrease in rubber fluidity, an increase in extrusion pressure and a deterioration in vulcanization consistency.


The vertical oven temperature of 400-600℃ did not match the product thickness and extrusion speed, resulting in over-sulfurization at the surface while the interior was under-sulfurized or brittle.


The rubber came into contact with platinum catalyst toxins such as nitrogen, sulfur, phosphorus and heavy metals, resulting in incomplete or non-sulfurization.


The hardness selection was inappropriate, such as choosing a high-rebound soft tube with a high hardness model or a mechanical strip with a low hardness model, resulting in unsatisfactory rebound, support or size.


After changes in product thickness or size, the mold pressing or extrusion vulcanization conditions were not re-tested and the original process was still used.


The A and B components were not stored separately or mixed with vulcanizing agents such as double 25, causing cross-contamination or premature vulcanization.


The storage temperature exceeded 30℃ or the product had a shelf life of more than 6 months, resulting in a decrease in rubber fluidity and vulcanization activity.


Switching from peroxide-cured solid rubber or other platinum-sulfurized extruded rubber, the kneading, extrusion and oven conditions were not adjusted, resulting in performance deviations from the target.


First, determine which stage the extrusion or vulcanization problem occurs.


Failure stage Possible causes Priority inspection direction
The rubber sticks to the roller or does not disperse properly during kneading High or low roller temperature, inaccurate A/B measurement, improper feeding sequence Kneading temperature, A/B ratio, thinning times
The extrusion surface is rough or has particles Unmatched plasticity of the rubber, dead material, improper die temperature Plasticity, barrel temperature, die cleanliness
Extrusion size fluctuations or abnormal die expansion Improper matching of pulling speed and extrusion speed, fluctuation in rubber fluidity screw rotation speed, pulling ratio, die design
Surface vulcanization but internal under-vulcanization High oven temperature or short residence time, thick product Oven temperature curve, line speed, product thickness
Over-sulfurization and brittle or color change High oven temperature, long residence time, overheated rubber Oven temperature, residence time, barrel temperature
Incomplete or non-sulfurization Platinum catalyst poisoning, uneven A/B mixing, expired rubber Environmental cleanliness, mixing uniformity, storage conditions
Hardness or rebound not up to standard Incorrect model selection, insufficient crosslinking density, poor filler dispersion Model selection, vulcanization degree, kneading process
Decreased transparency or surface fogging Contamination of the rubber, moisture, over-sulfurization, improper die temperature Raw material cleanliness, drying, oven conditions
Variations in dimensions or performance between batches Proportion A/B fluctuations, plasticity differences, storage condition changes Incoming inspection, measurement accuracy, storage records
If only "whether IOTA-1235A/B was used" is considered without recording the proportion A/B, the temperature ratio, kneading temperature, extrusion speed, oven temperature and rubber storage time, it is usually difficult to accurately determine whether it is a material issue or a process issue.


Why is merely increasing the oven temperature or increasing the A/B dosage not necessarily effective?


IOTA-1235A/B plays a platinum sulfidation role in the extrusion system, which is affected by the proportion A/B, plasticity, extrusion speed, oven temperature and product thickness. Simply increasing the temperature or dosage may bring side effects.


Increasing the oven temperature may cause surface over-sulfidation and brittleness, while the interior has not reached sufficient sulfidation.


Increasing the total dosage of A/B does not change the ratio A:B = 1:1 requirement. Excessive rubber will not increase the crosslinking density, but may cause waste and storage beyond the expiration date.


Extending the oven residence time may improve deep sulfidation, but it may reduce production efficiency and lead to over-sulfidation of low-hardness products.


Reducing the extrusion speed may improve sulfidation, but it affects output and size stability.


Increasing the barrel temperature may improve fluidity, but exceeding the safe usage temperature of 65°C will increase the risk of dead material.


If the rubber is mixed and used more than 2 days later, only adjusting the oven conditions cannot restore the original fluidity and sulfidation consistency.


After platinum catalyst poisoning, increasing the temperature or extending the residence time cannot normally sulfidate.


Which IOTA-1235A/B models should be selected?


Working conditions IOTA-1235A/B candidate direction IOTA-1240A/B candidate direction IOTA-1250A/B candidate direction IOTA-1260A/B candidate direction IOTA-1270A/B candidate direction Still need verification
High rebound hose Hardness 35A, elongation ≥ 700%, good softening rebound Hardness 40A, elongation ≥ 550% Hardness 50A, elongation ≥ 450% Hardness 60A, elongation ≥ 350% Hardness 70A, elongation ≥ 250% Rebound, compression permanent deformation, low-temperature performance
Mechanical hose/strip Need to evaluate when support is insufficient General medium hardness General mechanical hose Higher support High hardness rubber strip Hardness, tear strength, size stability
Size stability priority High elongation soft, shrinkage needs verification Medium Medium Higher hardness size stability better Higher hardness size stability better Linear shrinkage rate 2.1% actual verification
Transparency requirements Semi-transparent, need verification Translucent Translucent Translucent Translucent Transmittance, haze, surface smoothness
Extrusion speed priority Plasticity 180±50, relatively soft Plasticity 230 Plasticity 250 Plasticity 270 Plasticity 310 Extrusion pressure, die expansion, traction matching
Tear strength priority ≥16kN/m ≥25kN/m ≥25kN/m ≥25kN/m ≥30kN/m Actual tear, crack growth
One cannot only choose based on hardness, as there are differences in plasticity, elongation, tear strength and specific gravity. The final selection depends on the hose application, rebound, support, extrusion process and sulfidation conditions.


What are the differences in selection priorities between the IOTA-1235A/B series and similar extruded solid rubber models?


Comparison of directions: IOTA-1235A/B series (platinum-sulfurized two-component) - over-polymerization curing solid adhesive - ordinary precipitation adhesive - add-on molding adhesive - selection boundary
Sulfurization system: platinum-rhodium complex, A/B two-component - bis-4 or bis-5 - over-polymerization - platinum-based add-on molding - selection depends on extrusion and hygiene requirements
Whether an external sulfurizing agent is needed: no need to add sulfurizing agent - need to add sulfurizing agent - need to add sulfurizing agent - usually already mixed - extrusion process convenience varies
Sulfurization speed: rapid sulfurization in a vertical oven at 400-600℃ - slower - slower - molding faster - continuous extrusion prioritizes platinum-based system
Transparency: semi-transparent - varies depending on the formula - average - good - verification according to appearance requirements
Rebound and elongation: 1235 with elongation ≥ 700%, high rebound - medium - medium - medium - high-rebound hose prioritizes low-hardness model
Platinum toxicity sensitivity: sensitive to N, P, S and heavy metals - not involving platinum - not involving platinum - sensitive to toxins - need to control raw materials and environmental pollution
Storage requirements: A/B separated, mixed and stored safely at 25℃ for 2 days - prone to spoilage after addition of sulfur - prone to spoilage after addition of sulfur - separate storage - management according to system storage time
Applicable scenarios: high-rebound silicone tubes, mechanical silicone tubes/strip - general extrusion products - general products - molding products - selection based on molding method
Why is it still necessary to conduct complete tests when compatibility with extruders and ovens is required?


Our company's public information states that the IOTA-1235A/B series is used for high-rebound silicone tubes, mechanical silicone tubes/strip, with a 1000g:1000g mixture, open rolling, extrusion, and it is recommended to cure in a vertical oven at 400-600℃, and the mold pressing conditions can be determined based on the thickness or size of the product. However, when used in actual systems, there may still be:


Differences in the screw structure, compression ratio, and die design of the extruder.


Differences in the temperature of the barrel segments and the die temperature.


Matching of screw speed, traction speed, and die expansion.


Length and temperature distribution of the vertical oven, and residence time.


Product thickness, structure, and line speed.


Accuracy of A/B metering, open rolling times, and uniformity of the rubber mixture.


Environmental cleanliness and control of platinum catalyst toxins.


Storage time and temperature after mixing of the rubber mixture.


Storage conditions and shelf life.


Acceptance methods for product size, rebound, transparency, and surface quality.


Appearance transparent or normal short-term extrusion does not prove long-term continuous production, size stability, or consistent sulfurization depth. Before use, verification should be conducted using the complete formula, actual extruder and oven conditions.


What parameters should be confirmed when using IOTA-1235A/B series?


Parameter category: information to be confirmed
Application direction: high-rebound silicone tubes, mechanical silicone tubes/strip
Model and hardness: 1235, 1240, 1250, 1260, 1270, and target Shore A hardness
A/B ratio: 1000g:1000g, metering accuracy and mixture uniformity
Open rolling conditions: roller temperature, roller distance, thinning times, edge fork state of the rubber mixture
Safe use temperature: 65℃ below the rubber mixing temperature, including barrel and open rolling machine
Rubber storage: A/B separated storage, safe storage at 25℃ for 2 days after mixing
Extrusion conditions: screw speed, barrel temperature, die temperature, traction speed
Oven conditions: vertical oven at 400-600℃, residence time, temperature distribution
Product specifications: thickness, outer diameter, inner diameter, line speed, size tolerance
Storage conditions: cool, dry, ventilated, environmental temperature less than 30℃, shelf life 6 months
Acceptance indicators: hardness, tensile strength, elongation, tear strength, linear shrinkage rate, transparency, rebound, surface quality
What should be primarily verified when using IOTA-1235A/B series?


A/B metering accuracy and open rolling mixture uniformity.


Viscosity and extrusion fluidity of the rubber compound.


Extrusion surface finish, die swell and dimensional stability.


Sulfurization degree, including consistency between surface and interior.


Hardness, tensile strength, elongation and tear strength.


Linear shrinkage rate within the range of 2.1% ± 0.02%.


Transparency, haze and absence of particles or bubbles on the surface.


Rebound and compression permanent deformation.


Batch-to-batch size and performance fluctuations in continuous production.


Extrusion and vulcanization stability of the rubber compound after storage for 2 days.


The influence of environmental cleanliness on platinum vulcanization.


Changes in viscosity and vulcanization activity within 6 months of storage.


How to design experiments before using the IOTA-1235A/B series?


Establish a reference for the current extruded rubber compound, record the model, A/B ratio, mixing conditions in the pin mill, extrusion speed, oven temperature and failure performance.


Uniform test conditions: extruder, die, barrel temperature, screw rotation speed, traction speed, oven temperature and residence time.


Set candidate samples: current rubber compound, different hardness models of IOTA-1235A/B, different oven conditions gradient.


Complete the full process tests: A/B metering → pin mill → thinning out → extrusion → vertical oven vulcanization → performance testing.


Evaluate the actual results: size, surface, hardness, strength, elongation, tear strength, shrinkage rate, transparency, rebound.


Test items Uniform requirements
Extruder and die Consistent
A/B ratio 1000g:1000g
Mixing conditions Consistent or set gradient according to the test design
Barrel and die temperature Gradient according to the test design, rubber temperature does not exceed 65℃
Screw rotation speed and traction speed Gradient according to the test design
Oven temperature and residence time Gradient according to the test design
Measurement methods Dimension, hardness, strength, elongation, tear strength, shrinkage rate, transparency, rebound consistent
Which situations are not suitable for directly using the IOTA-1235A/B series?


Inability to guarantee A/B metering accuracy or uneven mixing in the pin mill, resulting in unstable vulcanization.


Unable to control the rubber temperature or barrel temperature below 65℃, resulting in easy material clogging.


Unable to use the rubber compound within 25℃ and 2 days after mixing, resulting in decreased fluidity.


Presence of platinum catalyst toxins such as N, P, S and heavy metals in the environment, leading to non-vulcanization.


A and B rubber not stored separately or mixed with double diene vulcanizing agents.


Storage temperature exceeding 30℃ or beyond the 6-month shelf life, resulting in degradation of rubber properties.


Need specific food contact, medical or airworthiness approval, but no corresponding materials have been obtained.


Only know the rubber compound model, but do not have information on the extruder, die, oven and product specifications.


Customer requests to directly mix into the in-use system, but cannot control the A/B ratio and pin mill conditions.


When switching from peroxide-cured rubber, the extrusion and oven conditions are not re-adjusted.


Have strict requirements for transparency, rebound or dimensional tolerance, but no special verification has been conducted.


After changes in product thickness or structure, do not re-test the vulcanization conditions and continue to use the original process.


Our company can provide which selection support?


As a solution provider for the entire organic silicon industry chain, our company can assist in comparing the applicability of different hardness models of the IOTA-1235A/B series in extruded rubber tubes, mechanical rubber strips and continuous vulcanization processes.


For high rebound silicone rubber tubes or mechanical rubber strips/strip projects that need to balance rebound, support, transparency, dimensional stability and continuous extrusion efficiency, before selection, provide:


Application direction and product specifications.


Target hardness, rebound, elongation and tear strength.


Extruder, die and traction conditions.


Barrel temperature, rubber temperature and rubber storage time.


Vertical oven temperature, length and residence time.


A/B measurement and open-mold process.


Current rubber compound model, A/B ratio and failure performance.


Acceptance method and applicable standards.


After receiving complete materials, it can be determined which hardness model of the IOTA-1235A/B series to prioritize for testing, or whether to choose other platinum extrusion rubber or peroxide-curing rubber routes.


Common Misconceptions


There is no need to add a vulcanizing agent to adjust the A/B ratio at will.
The A/B should be measured at a ratio of 1000g:1000g. Deviation in the ratio or uneven mixing will result in insufficient or excessive vulcanization. Do not ignore the proportion just because "no additional vulcanizing agent is required". 


The higher the oven temperature, the better the vulcanization.
A temperature range of 400 to 600℃ should be matched with the thickness of the product, the extrusion speed, and the oven holding time. An excessively high temperature may lead to...