Common Low Melting Point Materials: Which One to Choose?

Choosing suitable low melting point materials will benefit your production process and save cost. Let’s figure it out in more detail!

Low melting point materials are popular in many industries. However, each of them has their own advantages and disadvantages.

No matter whether you choose metals or thermoplastics for your products, you should consider factors such as strength, specific application requirements, and environmental impacts.

Let’s get along with our article to understand more about these materials before making an informed decision!

1. Understanding Low Melting Point Materials

The temperature at which a material may coexist in both its liquid and solid states is known as its melting point. At this point, heat raises a solid’s temperature, at which time it transforms into a liquid. The temperature of the liquid is raised by further heat once the material has completely melted. The identification of pure compounds and elements is based on the melting point of crystalline solids.

A solid’s melting temperature and freezing point are usually the same. However, due to variations in crystal structures and impurities, the two may not match each other. Thus, the best way to describe a material is to use its melting point.

In general, low melting point materials melt easily. For example, gallium melts at approximately 30°C. Meanwhile, for plastic, PE has a low melting point (at around 105°C to 135°C).

Using low melting point materials brings many benefits, including:

• Lower processing temperature: Low melting temperatures enable these materials to be easily processed without causing harm to nearby components. Thus, they are suitable for delicate applications.
• Good conductivity: Excellent thermal and electrical conductivity makes many low-melting alloys perfect for electronic applications.
• Casting versatility: Their ease of molding or shaping makes them ideal for complex designs and processes like casting and soldering. It also facilitates their ultrasonic atomization.
• Environmental benefits:  Some low melting point alloys are a more ecological option since they can be made without dangerous substances like lead.

2. Common Types of Low Melting Point Materials

2.1. Metals and Alloys

• Gallium (29.8°C)

One of the low melting point materials is Gallium, a soft, non-toxic metal. It is silvery white in color, which is similar to aluminum.  Its melting point is 29.8°C.

Gallium arsenide is a replacement for silicon and is an essential part of semiconductors and red LEDs. The material can transform power into light and was utilized in the Mars Exploration Rover’s solar panels.

Gallium nitride is a multipurpose semiconductor that is used in touch switch pressure sensors, blue and green LEDs, mobile phones, and Blu-ray technology. Because of its high boiling point and ease of alloying with most metals, particularly in low-melting alloys, it is perfect for recording temperatures that would cause a thermometer to vaporize.

• Wood’s metal (70°C)

Wood’s metal, often called Lipowitz’s alloy, is a metal alloy that is used for customized metal components and soldering. This eutectic, fusible alloy is named after Barnabas Wood.

Its main composition includes 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium. The metal has a modulus of elasticity of 12.7 GPa and a yield strength of 26.2 MPa. It’s one of the low melting point materials, with a melting point of around 70°C.

Like Rose’s metal and other fusible alloys, wood’s metal may be used as a heat-transfer medium in hot baths, enabling the creation of difficult-to-replicate key castings and specially shaped blocks and holes for medical radiation treatment. Although they are not frequently utilized, these hot tubs are used at temperatures higher than 220°C.

Since it contains lead, wood’s metal is toxic. For a non-toxic alternative, let’s have a look at Field’s metal.

• Field’s metal (62°C)

Field’s metal, also known as Field’s alloy, is a fusible alloy made of bismuth, indium, and tin. It’s named after its inventor, Simon Quellen Field.

This metal turns to liquid at 62°C.  Because Field’s metal doesn’t consist of lead or cadmium, it is less harmful than Wood’s metal. Its applications include small-run die casting and rapid prototyping. Besides, many researchers studying nanotechnology are interested in it and have looked at it as a liquid metal coolant in nuclear power plant designs.

• Indium (156.6°C)

When talking about low melting point materials, we can’t skip indium. Indium was discovered in 1863 and is a crucial component of semiconductors, low-melting-point metal alloys, and flat-panel displays. It’s a silvery-white post-transition metal with an atomic number 49 and the symbol In.

The element shares intermediate qualities with thallium and gallium. Sphalerite and zinc sulfide ores are the main sources of indium, which is created as a byproduct of processing other metal ores. Although its components are poorly absorbed after consumption, they are poisonous when breathed or injected into the circulation.

2.2. Polymers

Besides metals, thermoplastics with low melting points are popular in many industries. Here are the most highlighted ones:

• PE

PE (Polyethylene, or polythene) belongs to the renowned group of polyolefin resins and is a versatile material used in many industries. It has a low melting point of around 110°C. 

Polyethylene uses include transparent food wraps, shopping bags, detergent bottles, and automotive fuel tanks. Moreover, it is easily converted into synthetic fibers by spinning or slitting. Alternatively, polyethylene may develop rubber-like elastic properties with the right adjustments.

• LDPE

LDPE (Low-density polyethylene) offers low-density and high-flexibility that are perfect for products like shopping bags and plastic films. Its melting point is from 105 to 115°C, giving it stretchable and moldable properties. 

For example, shrink films are made from LDPE, which is heated to almost its melting point—typically approximately 110°C. This procedure generates a tight, safe package for the products.

After that, the film is quickly cooled to stabilize its structure.  LDPE film shrinks at temperatures between 90°C and 110°C, forming a snug, protected package.

• LLDPE

LLDPE belongs to a group of low melting point materials since it melts at around 120°C – 130°C. This melting point is higher than that of LDPE but lower than HDPE, reflecting LLDPE’s balance between flexibility and strength. 

The linear structure with short branches provides a good compromise, making LLDPE suitable for a wide range of applications where both flexibility and strength are needed. 

• HDPE

High-density polyethylene is widely recognized for its strength, durability, and versatility, making it a remarkable type of plastic. Classified as a thermoplastic polymer in the polyethylene family, HDPE exhibits exceptional resistance to moisture, chemicals, and impact. This resilient and dense material is produced through the process of polymerization, resulting in a robust and durable substance. 

It’s one of the versatile low melting point materials that is used in many industries, including packaging, construction, automotive, and agriculture. It usually melts at the temperature of 120°C – 180°C.

• PP

Polypropylene is a versatile, synthetic plastic that falls within the thermoplastic category. Composed of repeated units of individual propylene monomers joined by a chemical process, polypropylene is a large molecular compound.

The material exhibits superior molecular crystallinity, flexibility, physical toughness, chemical tolerance, and temperature resistance compared to other polymers. It can be liquified for production and recycling since it softens at temperatures close to the melting point. Products made of polypropylene are frequently branded with the #5 resin code and symbol, suggesting that they can be recycled.

PP melting point ranges from 160°C to 170°C. Isotactic PP has a higher melting point than atactic PP. It’s because the former has a regular molecular structure, while the latter features a more disordered molecular arrangement.

3. Factors to Consider When Choosing a Low Melting Point Material

There are numerous low melting point materials, making the decision for a suitable option challenging. However, businesses can consider the following factors:

• Temperature range: The chosen material’s melting point should match the operating temperature range of the application. The best material is the one that melts or softens at the appropriate temperature while staying solid under typical working circumstances.
• Thermal stability: Higher temperatures can cause low-melting materials to lose their mechanical qualities, particularly in situations where the temperature is high for extended periods. Thus, it is essential to select materials with stable attributes, such as mechanical strength and electrical conductivity, within the desired operating temperature range.
• Ease of processing: Depending on your product types and production techniques (injection molding, extrusion, casting, or 3D printing), you need to choose the material that requires less energy and equipment to process. 

• Cost and availability: It’s one of the most important factors when choosing low melting point materials. Expensive options such as indium may not be suitable as they are rare and will increase production costs. 
• Application environment: Businesses should consider the material’s thermal cycles and operational temperature range. Unless their melting point is lower than operational circumstances, low-melting materials could not be appropriate for significant temperature changes. The material’s resilience to heat shock and capacity to retain its integrity are also crucial.
• Environmental and health considerations: As mentioned above, some low-melting alloys may contain hazardous substances like lead that need to be carefully evaluated for their effects on human health and the environment. Besides, there’s a shift in people’s awareness of recyclability and sustainability. Therefore, low melting point materials that are more sustainable and recyclable are preferable in certain industries.

4. Conclusion

There are different types of low melting point materials. Manufacturers should consider their thermal properties, mechanical strength, environmental impact, and cost to make the right decisions.

EuP Egypt is a professional masterbatch manufacturer with 20 years of experience. We provide filler masterbatch, plastic compounds, additives, etc. to businesses in more than 90 countries. With innovative efforts and customer-centric approach, EuP Egypt is a reliable partner in the plastic industry. 

If you choose PE or PP filler masterbatch for your products, EuP Egypt has it all for you. Contact us for more details!