Direct Answer

IOTA LSR 3420-40T is a low-viscosity addition-cure silicone rubber specially designed for high-strength fire-resistant fabric. Its main features include excellent flowability, the ability to fill flame-retardant materials, good adhesion to fiberglass fabric, and high strength. Components A and B are mixed at a 1:10 weight ratio. Typical viscosity after stirring at 23°C is 1,000 mPa·s for Component A, 25,000 mPa·s for Component B, and 18,000 mPa·s for the A+B mixture. Typical cured properties are translucent appearance, Shore A 40 hardness, 3.5 MPa tensile strength, 250% elongation, and 13 kN/m tear strength.

Selection should not rely only on “low viscosity” or “high strength.” First confirm the fiberglass fabric type and pretreatment, application method—knife coating or dip coating—whether flame-retardant fillers are used and at what ratio, the metering accuracy for A:B = 1:10, the coloring sequence, curing conditions, and the project acceptance criteria for flame retardancy, adhesion, strength, and fire rating. This article does not equate typical mechanical data with a specific fire rating or service life. IOTA can provide addition-cure silicone rubber raw materials and corresponding product data; the company does not provide complete formulations or formulation development services.

1. First Ask What LSR 3420-40T Is Expected to Solve

Typical applications are adhesives for fire-resistant fabric and other knife-coating or dip-coating products. Different projects focus on different points: some on low viscosity and flowability for filler loading, some on adhesion to fiberglass fabric, some on cured strength, elongation, and tear resistance, and others on flame-retardant or fire-test results. Selection should start with the target defect, application method, and whether fillers are used, not just “adhesive for fire-resistant fabric.”

2. What to Specify in an Inquiry or Sample Request

If the customer already has a test specification, obtain the original document first. When criteria are missing, confirm them with the project owner and test laboratory before making samples, so that both sides do not discover different interpretations of “pass” after testing.

3. Check the Mixing Ratio and Catalyst System Before Discussing Cured Properties

IOTA LSR 3420-40T is a platinum-catalyzed addition-cure silicone rubber, with the platinum catalyst in Component A. Strict care is required during use to avoid catalyst poisoning. If coloring is needed, the color must first be added to Component B and stirred evenly before mixing with the measured amount of Component A. Colorants should not be added directly to Component A or to the mixed compound without confirming compatibility.

The mixing ratio is A:B = 1:10 by weight, which differs from 1:1 systems. Metering deviation has a greater impact on curing and properties and requires particular attention. Typical viscosity is 1,000 mPa·s for Component A, 25,000 mPa·s for Component B, and 18,000 mPa·s for the mixture. Before application, confirm metering accuracy, mixing uniformity, and workable time; the difference between manual and equipment mixing should be verified with representative samples.

4. Evaluate Low Viscosity and Flowability Together with Filler Loading and Application

The product features excellent flowability and the ability to fill flame-retardant materials. After flame-retardant fillers are added, viscosity, flow, wetting, adhesion, and cured mechanical properties may all change. Typical data for the unfilled product cannot be directly used for filled formulations. Knife coating and dip coating have different requirements for flow and pick-up, so the same application parameters cannot simply be transferred from one to the other.

When comparing candidate solutions, keep the fiberglass fabric batch, pretreatment, mixing ratio, filler ratio, and curing conditions as consistent as possible. If film thickness, number of passes, or additional layers are changed, record them separately. Adhesion should be evaluated on the actual fabric and at the target film thickness using the agreed method.

5. Typical Properties Are Cured Data, Not a Fire Rating

Typical cured properties are translucent appearance, Shore A 40 hardness, 3.5 MPa tensile strength, 250% elongation, and 13 kN/m tear strength. These data come from the corresponding test methods and should be understood together with sample preparation, filler ratio, and curing conditions. The product is used as an adhesive for fire-resistant fabric, but typical mechanical data are not the same as having passed a specific fire standard or fire rating. Fire rating, smoke toxicity, heat resistance, and durability requirements for fire-resistant fabric projects must be verified separately according to the project specification.

6. Prepare Samples in This Order Before Sending

1. Obtain the customer’s service conditions and acceptance criteria; confirm whether flame retardancy, adhesion, strength, elongation, tear strength, and fire rating are targets or existing results.

2. Specify fiberglass fabric type, surface treatment, application method, target film thickness, A:B = 1:10 mixing ratio, filler type and ratio, coloring method, and curing conditions.

3. Check the current IOTA LSR 3420-40T data, then have the user make representative samples and keep records of mixing, coloring, filling, coating, and curing.

4. Arrange tests as agreed; keep sample identity, test conditions, observation photos, and evaluation results in the report. Before expanding use, confirm whether the samples represent actual workpieces.

IOTA/Anhui Iota Silicone Oil Co., Ltd. positions itself as a solution provider across the organosilicon industry chain and can provide addition-cure silicone rubber raw materials and corresponding product data. When communicating, provide the fiberglass fabric type, existing application method, target defects, filler materials, and equipment together to facilitate candidate screening; the company does not provide complete formulations or formulation development services.

FAQ

1. Can you directly recommend an LSR 3420-40T formulation that passes a specific fire rating?

First define the fiberglass fabric, coating system, film thickness, filler ratio, curing conditions, and fire criteria, and then obtain the corresponding test evidence. The product is used as an adhesive for fire-resistant fabric, but this is not the same as having passed a specific fire rating.

2. How is A:B = 1:10 different from a 1:1 system?

This product is mixed at A:B = 1:10 by weight. Component B accounts for a larger proportion, so metering deviation has a greater impact on curing and properties. Confirm metering equipment and mixing uniformity, and verify with representative samples.

3. How can platinum catalyst poisoning be avoided?

The platinum catalyst is in Component A. Strict care is required during use to avoid contact with substances known to poison platinum catalysts. Specific material compatibility should be included in the customer’s raw-material approval and site management requirements.

4. Why should color be added to Component B?

The data explicitly require that if coloring is needed, color must be added to Component B, stirred evenly, and then mixed with the measured amount of Component A. This helps color dispersion and reduces effects on the catalyst system and mixing ratio.

5. The product can be filled with flame-retardant materials—can typical data be used directly after filling?

No. Filler type and ratio change viscosity, flow, adhesion, and cured mechanical properties. Samples must be made and evaluated with the filled formulation.

6. Does 3.5 MPa tensile strength represent the strength of the finished fire-resistant fabric?

Not directly. This is a typical cured property. Finished strength also depends on the fabric, coating weight, film thickness, filler ratio, composite structure, and curing conditions, and must be evaluated on the actual workpiece.