Revolutionizing Coating Formulations: The Dynamic Role of IPEMA as a Reactive Diluent

 Sustainability / Natural Coatings    Automotive Coatings    Acrylic Coatings 

This is a sponsored article by Kuraray.

What is a Reactive Diluent? A reactive diluent is a substance added to a coating formulation to alter its viscosity and improve various properties without significantly changing the chemical structure of the final product. Reactive diluents play an essential role in controlling the viscosity, reducing the curing time, and enhancing the characteristics of the material.

IPEMA, which stands for Isoprenyl Methacrylate, is a type of reactive diluent used in various industrial applications, particularly in the field of coatings. To understand what IPEMA is and how it functions as a reactive diluent, let's break down the components of this term:

• Isoprenyl: Isoprenyl is a term that refers to a chemical structure or functional group in chemistry that relates to the isoprene unit, a five-carbon structure that is a fundamental building block in the synthesis of various products and compounds.
• Methacrylate: Methacrylate refers to a chemical group or functional group derived from methacrylic acid, a carboxylic acid with the molecular formula CH₂=C(CH₃)COOH. They have a double bond between the carbon atoms in the ester group (C=O), which gives them distinct properties.

Let's explore how IPEMA functions as a reactive diluent for urethane acrylate formulations along with its key benefits and applications in several industrial sectors.

Functioning of IPEMA as a Reactive Diluent

Isoprenyl Methacrylate (IPEMA) is a multifunctional monomer and a cross-linking agent that proves itself as a remarkable reactive diluent. Let’s understand how IPEMA functions as a reactive diluent:

• Viscosity control: IPEMA is added to coatings for viscosity reduction. Lowering the viscosity is especially important in coatings and adhesives to ensure they can be spread evenly over a surface. Hence, there is ease of handling, mixing, and application assured.
• Faster Curing: IPEMA can influence the cross-linking process by accelerating the curing process, which is crucial in applications like coatings where a quick curing time is needed.
• Better mechanical properties: IPEMA can help improve the mechanical properties of the final product by inducing scratch resistance, durability, and adhesive properties.
• Reduced Volatile Organic Compounds (VOCs): IPEMA can lead to the development of lower-VOC coatings and is a relatively environmentally friendly option compared to its substitutes.
• Compatible: IPEMA blends well with many other resins and is a versatile choice for coating formulators.

Comparative Data with Other Conventional Diluents

The data shared in the table below determines that IPEMA is a much better reactive diluent that renders low viscosity, UV-curing, scratch resistance, low curling, and better flexibility in comparison to HDDA.

Viscosity control for urethane acrylates

This is a very interesting feature of IPEMA. It can decrease the viscosity of urethane acrylate in comparison to the other reactive diluents.

The figure below shows the comparison of viscosity for different diluents with hexa-functional and bi-functional urethane acrylate. It clearly shows that IPEMA has the lowest viscosity level which leads to multiple advantages in the coatings, primarily in easy and even application.



Comparative values of viscosity of each reactive diluent

Properties ↓ / Diluent →	HDDA	THFA	2-EHA	IPEMA
Viscosity @ 40°C, mPa.s	3.37	1.36	0.57	0.18
Chemical Structure

Table 1: Viscosity comparison of each reactive diluent

Improved curing characteristics as a diluent for UV-curable urethane acrylate

IPEMA demonstrates the most rapid curing when combined with hexa-functional urethane acrylate in the low-viscosity spectrum. The image below illustrates the variations in curability among different reactive diluents within the low viscosity range, where oxygen diffuses readily.



The chart below shows the functioning of IPEMA as a diluent in UV-curable urethane acrylate formulations. There is a lesser requirement for IPEMA in comparison to HDDA (conventional diluent) which is clearly depicted in the experimental results in Table 2. Moreover, Figure 5 shows faster curing with a small amount of irradiation and Figure 6 shows better elongation of IPEMA in comparison to HDDA.

Composition	Formulation example	IPEMA	HDDA
Main agent	Bi-functional urethane acrylate (UA-122P, SHIN-NAKAMURA CHEMICAL Co. Ltd., Polyester urethane acrylate)	8g	8g
Diluent	2-EHA	2g	2g
	IPEMA	1.1g (0.6 mmol/g)
	HDDA		1.6g (0.6 mmol/g)
Initiator	1-hydroxycyclohexyl-phenyl ketone (Omnirad® 184)	0.3g	0.3g
Omnirad® is a registered trademark of IGM Group B.V.

Table 2: Lesser requirement for diluent for UV-curing

Figure 5: IPEMA cures faster with a small amount of irradiation
Test conditions: *UV cured in air using a metal halide lamp, Light intensity: 50mW/cm², Conveyor speed: 1m/min

Using IPEMA as a reactive diluent in the right way

1. Low dosage requirement: Achieving low viscosity and rapid curing requires a lower dosage of IPEMA in comparison to the conventional reactive diluents.
2. Oxygen inhibition: IPEMA can enhance curing even during oxygen inhibition.
3. Blending with urethane acrylate: When IPEMA alone doesn't enhance curing performance, it can be improved by blending it with urethane acrylate with a higher number of functional groups.

IPEMA: A Preferable Diluent to Obtain the Finest Resulting Material

IPEMA offers several advantages when used as a diluent in coatings that provide multiple benefits to the resulting material:

➣ Viscosity improvement: IPEMA can significantly reduce the viscosity of the coatings making the application easy and leading to smoother finishes and reduced coating difficulties.

➣ UV-curing: IPEMA promotes quick drying which is good for industrial applications. The fast-curing times can lead to increased productivity and shorten production cycles. It is often used in UV-curable coatings which makes them suitable for applications with UV-light exposure. The figure below reveals that IPEMA cures in air with a small amount of irradiation, in comparison to HDDA.

➣ Improved adhesion: IPEMA as a diluent can enhance better adhesion of the coating to various substrates. It ensures that the coating adheres to the surfaces well and provides long-lasting protection.

➣ Oxygen inhibition: IPEMA can mitigate the issues in which oxygen inhibition can affect the curing process. It can accelerate UV-curing in air that is required in situations where oxygen levels are constrained.

➣ Cost-effectiveness: IPEMA is a cost-effective diluent that requires low dosages in comparison to the other reactive diluents that reduce the potential costs.

➣ Better elongation: IPEMA has a better elongation than the traditional HDDA.

➣ Versatility: IPEMA is compatible with a wide range of coating formulations and can achieve better performance characteristics for different coating systems.

➣ Improved application characteristics: The coatings containing IPEMA as a diluent can exhibit improved flow and leveling properties that give an even and aesthetically finished outlook to surfaces.

Highlights on IPEMA Applications

IPEMA has versatile applications, including its use in automotive coatings and various other industrial sectors.

Automotive coatings

IPEMA plays a significant role in the aesthetics and protection of vehicles for the automotive industry. It is used in UV-curable coatings with a rapid curing process with reduced production time and increased efficiency. IPEMA results in a smoother and uniform finish for the aesthetic appeal of vehicles, making them more attractive and durable.

IPEMA can enhance the adhesion of coatings, including metal, plastic, and glass parts. It provides long-lasting protection against environmental factors and wear and tear. There is effectiveness in reducing the impact of oxygen inhibition for reliable curing. Below are the key features of IPEMA that make it a suitable diluent for interior and exterior automotive coatings:

• Hard coatings
• Low-curling properties
• High scratch resistance
• Low viscosity and UV-curing accelerator
• Flame retardancy without using halogen

Other applications

IPEMA is incorporated as a diluent in many industrial applications, including plastic coatings, printing inks, packaging materials, general industrial coatings, and many other applications. It is a valuable compound serving different purposes across multiple sectors.

Conclusion

Try out IPEMA, a versatile reactive diluent from Kuraray that controls viscosity, improves curing characteristics, and enhances the overall performance of various polymer-based materials. It proves itself as the reactive diluent that offers various benefits, including viscosity control, better properties, cost-effectiveness, and several other benefits!



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