How Does LDPE Regranulate Affect the Mechanical Properties of HDPE Film?

Publication date: 2025-03-13

Introduction
The use of LDPE regranulate in HDPE film production is one of the key aspects of the modern circular economy. Recycled film waste, processed into high-quality regranulate, helps reduce raw material costs and the environmental impact of production. At Uniplast Bajer, we successfully use a blend of LDPE regranulate (“słomka”) with virgin HDPE, allowing us to optimize film properties while maintaining high product quality.
However, the addition of LDPE regranulate to HDPE affects the mechanical properties of the film, such as tensile strength, puncture resistance, hardness, and flexibility. What are the main effects of this process, and how can they be controlled? Let's take a closer look.

Impact of LDPE on the Mechanical Strength of HDPE Film
HDPE and LDPE have different molecular structures—HDPE is more crystalline and rigid, while LDPE has more branched polymer chains, making it more flexible. This directly influences the mechanical properties of HDPE/LDPE films:

1. Tensile Strength

• Pure HDPE achieves tensile strength of 25–28 MPa, while LDPE has tensile strength around 9–12 MPa.
• Adding 20% LDPE regranulate to HDPE reduces tensile strength to ~16 MPa, while a 40% LDPE mix lowers it to ~15 MPa.

2. Hardness and Film Stiffness

• HDPE has high hardness (Shore D ~90), while LDPE is softer (Shore D ~80).
• An 80/20 HDPE/LDPE mix retains hardness at ~85 Shore D, which helps maintain sufficient stiffness while improving impact resistance.

3. Elasticity and Tear Resistance

• Pure HDPE has an elongation at break of 200–250%, while LDPE can reach 300–350%.
• An HDPE/LDPE 20/80 blend has an elongation of ~314%, increasing flexibility and mechanical resistance.

4. Puncture Resistance

• LDPE improves the film’s resistance to dynamic loads, making plastic bags less prone to breakage upon impact.
• A higher LDPE content improves impact absorption, but may slightly reduce resistance to static loads.

How to Control the Impact of LDPE Regranulate on Film Quality?
Adding LDPE regranulate in optimal proportions helps achieve the desired film properties. In practice:

• Moderate LDPE content (10–30%) provides a good balance between strength and flexibility, minimizing the impact on extrusion process stability.
• Higher LDPE content (>40%) can reduce film stiffness but improves puncture resistance and impact strength.

At Uniplast Bajer, we precisely adjust HDPE/LDPE ratios and control regranulate quality to ensure production stability and maintain optimal mechanical properties of the film.

Conclusion
Adding LDPE regranulate to HDPE modifies the mechanical properties of the film, making it more flexible and resistant to impact while reducing stiffness and tensile strength. By optimizing proportions and monitoring regranulate quality, manufacturers can produce high-quality films that meet customer requirements while reducing the use of virgin raw materials.

#Recycling #LDPE #HDPE #Extrusion #PlasticProcessing #PlasticFilm #CircularEconomy #SustainableManufacturing #BlownFilm #Regranulate

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