Silicone Sealants vs. Hybrid Polymer Sealants

Did you know that silicon or hybrid polymer sealants require moisture to cure? If you put them inside a humidity control chamber, they will never cure! Despite sharing many properties and core purpose of sealing, silicone and hybrid polymer sealants differ in characteristics. Their unique properties make them suitable for varying applications.

Both sealants are incredibly elastic, and their premium grade versions comply with ASTM C920 Class 50 standard or even better. They can move ±50% from their original joint width. It makes them incredibly flexible and allows for a margin for surfaces joined together. So what makes them different, and why did manufacturers have to create two different materials for sealant?

This article will explain both the silicon and hybrid polymer sealants, their ideal use scenarios, and explain their differences in depth. Moreover, it will answer some of the most common questions related to both sealant types and provide a table for selecting the sealant for your project.

1. What are Silicone Sealants

Composition

Silicon sealant is a synthetic polymer. It is created using silicon, oxygen, carbon, and hydrogen. The result is a flexible material that cures when exposed to moisture in the air. The cured material is durable and acts as a barrier against air and water.

Curing Types

The Silicone sealant has two curing types. Each is designed for specific surfaces and has varying curing times.

• Acetoxy (Acid Cure): As an acetoxy-based silicon, it releases a vinegar-like smell due to the presence of acetic acid. It cures fast and offers good adhesion to surfaces like glass and tile. However, it can damage surfaces sensitive to oil or acid.

• Neutral Cure (Non-Acid Cure): Neutral cure type silicon sealant is suitable for acid-sensitive surfaces like some metals and plastics. The curing byproduct is Alcohol or Oxime, which has a milder odor.

Thermal Stability

Silicon-based sealants are exceptional when it comes to performance under high temperatures. It remains stable and exhibits desired sealing properties over the range of -60 and +250 °C.

Weather and UV Resistance

The nature of silicon sealant is hydrophobic. It can resist water and prevent cracking under cyclic loads. Moreover, the inorganic nature and silicon-oxygen bond make it an exceptional performer under UV light.

2. Typical Uses for Silicone Sealants

Silicon is typically utilized in areas where there is a sealing requirement for water-repelling and air sealing. It can handle temperature extremes, movements, and UV exposure while working at its optimal performance. Here are some fields where silicone sealant use is common:

Construction and Weatherproofing

In building structures, ensuring that the structure is resistant to rainwater penetration, silicon sealants are used. They are commonly applied to the gaps between windows, doors, and frames to seal from air and water. Buildings can change dimensions, expand and contract, which puts silicon at an advantage over other fillers due to its ±50% flexibility.

Wet Areas and Sanitation

Silicon is hydrophobic by nature, which makes it excellent for wet environments like kitchens and bathrooms. They are mostly applied in places like between the sink and tile/slab, where sealing is critical. However, to avoid damage to the material, neutral-type silicon is the most favorable sealant.

Extreme Temperature Environments

Places where there is high temperature, like chimneys, stove tops, HVAC ducts, or ovens, silicon sealant works the best. They are often used in refrigerators and freezers for sealing with stability. It can ensure an air-tight enclosure even under sub-zero conditions.

3. What are Hybrid Polymer Sealants

Composition

A hybrid polymer sealant uses a blend of silane-terminated polyethers with silicone and polyurethane chemistries. The presence of these different elements changes the hybrid polymer sealants' properties.

• MS Polymer (Modified Silane) Sealants: These are great for adhesion, strength, and painting over. However, it may become yellow or crack in UV light, and does not contain harmful isocyanates.

• SPUR (Silyl-terminated Polyurethane) Sealants: The silicon variant has excellent flexibility, UV resistance, and temperature stability, but cannot be painted.

Curing Mechanism

It also cures moisture in the air through a process called Room Temperature Vulcanization (RTV). They do not require any solvent for their curation process, which means there is no shrinkage.

Extreme Elasticity

Manufacturers of hybrid polymer sealants claim a 500% elongation. Which means a gap filled with 1inch of sealant can stretch to 5 inches without failing. The property makes the sealant excellent for applications where dynamic forces are expected.

Aesthetics

For a more aesthetic finish, hybrid polymer sealants offer a paintable surface. After initial curing, it is possible to apply paint to create a seamless look. Moreover, MS polymers are color-stable and won't yellow in UV light.

Universal Adhesion

The ability of hybrid polymer sealants to adhere to any surface makes them highly versatile. It does not require any primer. Which means there is no need to prepare the surface or make it wet before the application of the adhesive.

Volatile Organic Compounds (VOCs) Free

For green building standards, hybrid polymer sealants are eco-friendly, odorless, and non-toxic.  They are free from VOCs, which means there is minimal shrinkage during curing. There is no production of gas or evaporation. It leads to precise gap filling.

4. Typical Uses for Hybrid Polymer Sealants

The superior flexibility of the hybrid polymer sealant allows for application where there is a lot of movement and vibration.

High Movement and Infrastructure

The hybrid polymer sealants excel in performance for expansion joints. Especially in high-traffic areas like floors, bridges, and roads. Its UV resistance makes it safe for use in the sun, and it withstands all weather conditions. Particularly applied in marine and automotive repairs due to low-modulus and high-elongation properties.

Versatile Bonding and Structural Sealing

Unlike silicon sealants, hybrid polymer sealants conveniently work on all surfaces. It works with metals, plastics, glass, and wood in paneling, facades, and roofing systems. The sealant, after proper curing, provides excellent structural integrity.

Industrial and Chemical Resistance

It's ideal for plumbing and HVAC-related work. It can seal pipes and ducts while providing resistance against chemicals. It can work in environments that are exposed to cleaners and corrosives without any degradation in its integrity.

5. What are the Key Differences Between MS Polymer and Silicone Sealants?

Now that we know the individual properties and applications of both types of sealants, we can put them head-to-head against each other. Compare their various aspects and see which one comes out superior.

Adhesion and Versatility

Winner: Hybrid Polymer Sealant

MS Polymer takes the spot owing to its adhesion to a variety of surfaces, including metals, wood, glass, and plastics, and in most cases, it does not require a primer. It greatly simplifies construction work. In comparison, silicon requires the use of a primer for surfaces like concrete and metals.

Temperature Resistance

Winner: Silicon Sealant

The ability of silicon sealant to work across a wide range of temperatures makes it an excellent choice where thermal cycling or extreme temperatures are expected. Its inorganic nature gives it the ability to handle up to 250 °C. In comparison, a hybrid can resist up to 150 °C. Silicon also wins at sub-zero conditions with -60 °C tolerance in comparison to -40 °C by hybrids.

Flexibility and Joint Movement

Winner: Hybrid Polymer Sealant

The hybrid polymer sealants offer better elongation, which can go up to 600% for some high-end sealants. However, the difference isn't large as silicon sealants are just behind with 500% elongation in premium materials and a controlled environment. The key difference is the mechanism of absorption, which allows hybrids to absorb the joint movement stress within the material instead of transferring it to the bonding surface. Silicon acts more like rubber, giving it the bouncy feel.

Aesthetics and Finish

Winner: Hybrid Polymer Sealant

The paintability of hybrids makes them ideal for aesthetic applications like kitchen tile or any other location that is visible directly. In comparison, silicon simply resists adhesion to paints.

Environmental and Curing

Winner: Hybrid Polymer Sealant

MS Polymer is an environmentally friendly choice owing to its solvent-free, low VOC, isocyanate-free composition. It does not give off the vinegar-like smell when applied like silicon sealants. Silicon can sometimes bubble or cause corrosion on sensitive material.

6. Questions to Ask When Choosing a Sealant

• What will the sealant be in contact with? Will they be porous as wood, or non-porous like glass? It will help determine whether the user needs a wide-adhesion product, such as a hybrid polymer sealant, or a specialized product, such as silicone, for use with glass.

• Is the place of sealant application under high temperatures, moisture, or chemicals? Pick silicone for high-heat and long-term UV stability, or hybrids for chemical- and primer-free application.

• Does aesthetics involve paintability, or can it be done with a non-paintable, flexible seal?

• What is the anticipated movement or vibration of the joint? Use hybrids in dynamic areas and silicone in areas that do not need to move.

• Have environmental or health limitations? In green building projects, acetic silicones are less suitable than low-VOC, solvent-free hybrids.

• What is the budget and size of the project? Cheap silicone for non-complicated work, and hybrids for more multitasking.

• What is the importance of the time of full cure? Want the shrinkage-free results of fast-skin silicone or patient hybrids?

• Does the location comply with food-grade or sanitary standards? It will assist in making rational decisions about whether neutral-cure alternatives, such as the mildew-resistant sealants provided by Kastar, are safe.

7. Which Sealant Is Best Suited For Your Project Needs?

We can summarize the entire debate of silicon vs. hybrid polymer sealants by simply stating that they are both meant for specific applications. Taking all the parameters like cost, temperature resistance, bonding, elongation, chemical reaction, bubbling, paintability, UV resistance, toxins, VOCs, and priming requirements into consideration, we can conclude that the following are the best choices for the said projects:

If you are looking for a high-quality sealant, either silicon or hybrid polymer, then consider KASTAR. They have a massive 27 years of experience in making adhesives. They specialize in hybrid polymer and silicon sealants with exports to 32 countries and regions worldwide. Their product variety is massive, with suitability for every application. Visit their massive lineup of sealants on their website https://www.kastargrout.com/.

8. FAQs

Q: Is it possible to paint silicone sealants?

No, they are oily, and paint does not stick on them. For paintability, use hybrids. They are excellent at blending the sealant with the material around.

Q: Are indoor polymer sealants that are hybrids safe?

Yes, they are low-VOC, odorless, and non-toxic isocyanates. They are suitable at home and in the office.

Q: What is the time taken by these sealants to dry up?

Silicone skins within 10-30 minutes, yet dries in 24 hours. It takes 24-48 hours before hybrids reach full strength, without shrinkage.

Q: Which one is superior in outdoor weathering?

Silicon is widely claimed to have the highest long-term UV resistance. On the other hand, hybrid polymer sealants are chemically resistant. Silicon is a clear choice for UV and moisture combination.

Q: Does it require a primer to apply?

Hybrids will rarely require a primer. However, for silicone priming a porous surface and preparing some metals, it is vital for strong adhesion.