Polypropylene vs Polyethylene: Cost & Strength Guide

Polypropylene and Polyethylene repeatedly show up in a variety of industries and applications (packaging, bulk handling, industrial, etc.), as both are the most dominant materials in the world for all plastics; however, when making these comparisons, they both have their own distinct advantages. When evaluating which type of plastic is best suited for your business, typically the two key determinants will be price and strength.

Selecting the proper type of material is essential for companies that utilize sacks, liners, bags, and industrial packaging. By selecting the improper type of material, companies will incur increased replacement costs, damage to their products, or ineffective operations. To help manufacturers, exporters, and procurement professionals make the right choice, below you will find a detailed breakdown of the physical differences between Polypropylene (PP) and Polyethylene (PE).

Comsyn is a well-known provider of high-performance Polypropylene products and has extensive experience in working with industries that demand high levels of strength, durability, and consistency at large quantities, thus making this an extremely valuable comparison for businesses engaged in heavy-duty applications.

What Is Polypropylene (PP)?

Polypropylene (PP) is a type of thermoplastic polymer composed of propylene monomers. As a result of its low density, PP has exceptional weight-bearing characteristics with a rigid and strain-resistant structure. As a manufactured product, PP appears as a semi-crystalline polymer. 

Key Properties of Polypropylene include:

• High Potential Tensile and Flexural Strength
• Exceptional Stiffness, Shape Retention, and Ruggedness
• Very High Melting Point of (160 to 165 degrees Celsius)
• Outstanding Compatibility with Chemicals
• Very Light Weight, but Extremely Rigid

Due to its unique characteristics, Polypropylene is typically used for Heavy Duty Packaging, Woven Sacks, Containers, Automotive Components, and Industrial Fabrics.

What Is Polyethylene (PE)?

Polyethylene, also referred to as PE, is another highly desired and utilized thermoplastic material that is produced through chemical reactions with ethylene monomers. PE has great value due to its high levels of flexibility, toughness, and impact resistance. 

There are many types of PE which can be categorized into three categories based on their Density and Mechanical Characteristics: 

• LDPE (Low-Density Polyethylene) – Very soft & flexible, Lightweight, 
• HDPE (High-Density Polyethylene) – Provides significantly greater strength and rigidity than LDPE, 
• LLDPE (Linear Low-Density Polyethylene) – A compromise between Flexibility and Strength. 
• PE is often utilized to produce Film. Liners, flexible bags, Pipe, containers, and Chemical Packaging because of their high adaptability, as well as their superior chemical stability.

How Do PP and PE Compare in Strength?

Strength is one of the most significant differences when it comes to comparing Polyethylene and Polypropylene. 

• Polypropylene has a higher tensile strength than most types of polyethylene, making it a better choice for load-bearing applications that require resistance to stretching (e.g., woven sacks and bulk packaging). 
• Polyethylene (particularly LDPE and LLDPE) has superior shock absorption capabilities compared to polypropylene. This characteristic of polyethylene allows products made from polyethylene to survive dropping or sudden impact without becoming damaged or cracked. 
• Polypropylene is a more rigid material than polyethylene; therefore, it better retains its shape; hence, it’s better for items that need to look structured. Polyethylene is much softer than polypropylene and therefore has much greater flexibility. Consequently, polyethylene is better suited for products such as films and bags that need to wrap or conform around more irregularly shaped objects.

Because of these differences, when selecting between Polypropylene versus Polyethylene, the primary factor will depend on whether your intended application requires rigid, high-strength materials versus flexible cushioned materials.

Which Material Is More Cost-Effective?

Cost is not only determined by the price of raw materials; it also reflects the entire value associated with using the raw material over time and includes the total cost of ownership.

• Price of Raw Materials

Globally, the prices for PP and HDPE are typically similar, while the price of LDPE may be somewhat lower. The short-term price differences between PP and PE have historically been small and can fluctuate based on oil prices (predominantly) and supply-demand dynamics.

• Processing Cost

PE typically requires a lower processing temperature compared to PP, which can result in easier and slightly less expensive conversion in some applications. While PP typically is processed at a higher temperature, it provides better dimensional stability and strength (per unit weight).

• Total Life-Cycle Value

PP often wins the Total Life-Cycle Value aspect over PE. When used in durable or reusable applications, PP typically outlasts PE, providing less replacement frequency and therefore providing less overall downtime and failure. 

Thus, even though PP may have a slightly higher initial cost than PE, over time, less downtime, fewer failures, and a lower level of waste counterbalance the marginal difference in upfront cost.

When using polypropylene in heavy-duty applications, it is less about the immediate savings and more about the long-term operational performance.

Applications: When to Choose PP vs PE

Comparing polyethylene vs polypropylene bags/packaging materials requires a clear understanding of each material’s appropriate use case.

• Polypropylene

Polypropylene bags/sacks are used for:

• Heavy-duty sacks of cement, fertilizers, and grains
• Bulk bags or FIBCs
• Industrial bags and woven fabric
• Applications where product rigidity and stacking capability are important
• Reusable packaging cycles
• Use of PP products in an environment that has high weights, heavy loads, and a high Strength-to-Weight ratio. 
• Polyethylene

Polyethylene bags/sacks are used for:

• Flexible liners and films
• Lightweight carrier bags
• Packaging of products with irregular shapes
• Applications with high levels of demand for Impact Resistance
• Short-Term use/disposable applications.

This distinction becomes even clearer in the case of comparing polyethylene bags to polypropylene bags, for use in Industrial Logistics versus use by Retail or End Consumers.

Environmental and Recyclability Comparison

PP and PE are both thermoplastic materials that are recyclable and readily accepted in the recycling stream; however, due to differences in material properties, they behave differently when recycled.

For example, polypropylene is more tolerant of heat than polyethylene; it retains its structure through multiple thermal cycles, which can be an advantage during recycling processes. Conversely, although polyethylene is easier to melt and recycle, the materials lose their rigidity more quickly through repeated use.

For sustainable applications, an important factor to consider is the long-term performance of materials. The durability of a material will determine how often you will have to replace it; therefore, if you want to compare polypropylene and polyethylene in an industrial application, durability will be a crucial element to take into account in order to determine the amount of raw materials you need to manufacture each product.

Comsyn – Experts in High-Strength Polypropylene Solutions

Comsyn produces polypropylene products that are suitable to be used in high-stress areas. We focus on woven fabric and bags, where the material mustn’t fail. The woven bag we manufacture is designed to carry heavy loads and provides reliable bulk packaging and logistics.

Comsyn also provides customized solutions for any requirement. Along with providing laminated structures for moisture-proof options and branding, we can also create custom bags based on reinforcement or special load requirements.

Comsyn’s polypropylene products meet the quality requirements of every country and will provide a dependable and distinct quality product that will provide consistent performance under heavy use.

When comparing polyethylene to polypropylene bags for any type of heavy-duty use, Comsyn provides the best guidance to ensure the customer makes the appropriate choice of material for their specific needs.

Quick Cost & Strength Decision Table

Factor	Polypropylene (PP)	Polyethylene (PE)	Better for Cost/Strength
Tensile Strength	Higher	Lower (except HDPE)	PP
Flexibility	Rigid	Highly flexible	PE
Cost per kg	Similar	Slightly lower (LDPE)	PE (short-term)
Durability in Heavy Use	Excellent	Good	PP
Heat Resistance	Up to 165°C	Up to 120°C	PP

Conclusion

The choice between Polypropylene and Polyethylene is not straightforward, as it is determined by what is most important to you or your company. If you are seeking longevity, durability,y and high-quality strength in your application, then Polypropylene will likely provide a better overall balance than Polyethylene. Polyethylene may be the best option if your primary goal is flexibility or the initial cost savings; however, when it comes to the demands of heavy-duty packaging or industrial applications and your long-term performance requirements, Polypropylene has superior tensile strength as well as chemical resistance.

By collaborating with a company such as Comsyn, which is experienced in engineering Polypropylene products and solutions for use in the real-world environment, you will optimise your company’s performance while maintaining your financial goals.

FAQs

• What effect does temperature have on both PP and PE while stored outdoors?

The performance of PP improved at elevated temperatures; thus, it retains its shape. In contrast, the structure of PE remains pliable but can soften with continued exposure to heat.

• Which material will provide the best printing quality for branded packaging?

Typically, PP provides superior print clarity and ink adhesion due to its ability to create a smoother surface, particularly with woven and laminated products.

• Do PP bags have a longer shelf life than PE bags when used for bulk storage?

Many instances exist in which PP provides better stabilization, moisture barrier properties, and, therefore, increased shelf life than PE when storing in bulk.

• Can you switch from using PE to using PP for your current filling equipment?

Often, yes; however, machine calibration may be necessary due to differences between the stiffness and characteristics of the bags.