Understanding PP vs. PE Plastics and the Heat Resistance of PET Bottles

In today’s packaging industry, understanding different types of plastics is essential for selecting the most suitable material for your product. Among the most widely used plastics in bottles and packaging are PP (Polypropylene), PE (Polyethylene), and PET (Polyethylene Terephthalate). Although they may look similar from the outside, their chemical properties, durability, and applications vary significantly. Knowing these differences ensures you choose a packaging material that is safe, durable, and truly fit for your product’s needs.

In this article, we explain how PP and PE differ, and take a closer look at the heat-resistance performance of PET bottles—information every manufacturer should know.

What Is Polypropylene (PP)? – Key Features (Plastic No. 5)

PP, or Polypropylene, is widely known as the “king of heat-resistant plastics.” Its outstanding properties make it ideal for applications requiring high thermal stability.

Key Properties of PP

• Excellent heat resistance:
  PP has a high melting point (about 160–170°C), making it suitable for food packaging that requires heat sterilization. It can also be used in microwave-safe containers without deforming. This is one of the major differences between PP and PE.

• High rigidity and shape retention:
  PP is significantly more rigid and form-stable than PE, making it ideal for containers that must retain their shape such as food boxes, bottle caps, and yogurt cups.

• Chemical resistance:
  Highly resistant to oils, fats, and various chemicals.

• Common applications:
  Microwaveable food containers, straws, bottle caps, pharmaceutical packaging, and synthetic fibers for clothing.

What Is Polyethylene (PE)? – Types and Features (Plastic No. 2 and 4)

PE, or Polyethylene, is one of the most widely used plastics in the world. It is well-known for being lightweight and flexible. This flexibility is one of the main differences between PP and PE in terms of user experience and feel.

Two Common Types of PE

1. HDPE (High-Density Polyethylene – No. 2)

• Properties:
  Higher density, stronger and more opaque than other PE types, yet still flexible. Excellent impact and crack resistance.

• Applications:
  Milk bottles, jerry cans, detergent bottles, trash bins.

• Heat resistance:
  Moderate (around 120°C for short periods). Not suitable for very hot liquids like PP.

2. LDPE (Low-Density Polyethylene – No. 4)

• Properties:
  Lowest density among PE types. Very soft, flexible, and slightly transparent.

• Applications:
  Plastic bags, food wrap films, zipper bags, freezer bags.

• Heat resistance:
  Low (around 80°C). It softens quickly when exposed to high heat.

Understanding PET Bottles and Heat Exposure

Aside from PP and PE, PET (No. 1) is another common plastic used in clear beverage bottles.

What Is PET and How Does It Handle Heat?

PET (Polyethylene Terephthalate) is well-known for its clarity and excellent gas-barrier properties, making it ideal for drinking water and carbonated beverages. However, standard PET—also known as Amorphous PET—has limitations when it comes to heat.

Weakness: Poor heat resistance

Standard PET begins to soften and deform at just 60–70°C. Using it for hot beverages or leaving it in a hot car can cause the bottle to warp easily.

Heat-Resistant PET (Hot-Fill PET)

To support beverage industries that require hot-filling (e.g., juices or sterilized tea), manufacturers developed Hot-Fill PET, a special heat-resistant type.

How It Works

• The plastic undergoes a crystallization process during production, strengthening its structure and improving thermal stability.

Heat Resistance

• Hot-Fill PET can withstand 85–90°C without deforming, making it suitable for products that require heat sterilization before sealing.

How to Identify It

• Hot-Fill PET bottles are usually slightly thicker and more rigid than standard PET water bottles.

Safety and Reusability Guidelines

For hot liquids

• PP (No. 5): Safest for hot liquids and microwave use.

• PE (No. 2 and 4): Not recommended for hot liquids (above 80–100°C).

• PET (No. 1): Standard PET should never be used with hot liquids. Only use Hot-Fill PET when specified (typically up to 90°C).

Reusability & Recycling

• All three—PP, PE, and PET—are safe for reuse when cleaned properly.

• PET (No. 1) is the easiest and most widely recycled plastic, followed by HDPE (No. 2) and PP (No. 5).

Choosing the Right Plastic for Your Product

• For hot food or microwavable products → Choose PP

• For room-temperature or cold beverages → Choose PET or HDPE

• For heat-filled beverages → Choose Hot-Fill PET or PP

The Key to Perfect Packaging

Selecting the correct packaging material ensures your product remains safe, high-quality, and aligned with your brand standards. Understanding the differences between PP, PE, and PET—especially in strength, flexibility, and heat resistance—helps you make informed decisions that result in reliable and consumer-safe packaging.

If you're looking for high-quality packaging solutions—whether PP heat-resistant bottles, durable HDPE containers, or Hot-Fill PET bottles for pasteurized products—our team is ready to assist you in selecting the ideal material for your brand.