HDPE Blow Molding

1. What is small blow molding grade HDPE?

It has a relatively high melt flow rate (MFR), typically 2~10g/10min, resulting in good fluidity and facilitating thin-wall molding. With the density range of 0.941~0.955 g/cm³, the HDPE resin used for small blow molding bottles emphasize toughness and molding stability. It also has an Environmental Stress Cracking Rate (ESCR) ≥500h.

Main applications: Used for processing various small containers, typically with volumes up to 30L, ranging from a few milliliters to 30L, primarily thin-walled products.

2. What is medium blow molding grade HDPE?

With a medium melt flow rate (MFR), typically 1~5 g/10min, it balances flowability and melt strength. With a density range of 0.945~0.955 g/cm³, it can balance rigidity and toughness. The HDPE used for medium blow molding drums has an Environmental Stress Cracking Rate (ESCR) ≥700h, which is capable of withstanding medium loads, suitable for media storage needs in chemical, agricultural, and other fields.

Main applications: Used for producing medium-sized containers with volumes between 30L and 200L, balancing portability and load-bearing capacity. It is commonly used for transitional hollow product in industrial and agricultural fields.

3. What is large blow molding grade HDPE?

The melt flow rate (MFR) is relatively low, typically 0.2~5 g/10 min, while the melt strength is high, effectively preventing preform sagging during blow molding. The density ranges from 0.945~0.965 g/cm³, exhibiting outstanding rigidity, an environmental stress cracking resistance (ESCR) ≥700h, and a tensile yield strength ≥27MPa. Some high-performance models can exceed 1000h ESCR, enabling them to withstand long-term loads and corrosive media.

Main applications: Used for producing large, thick-walled containers with a volume ≥200L. Primarily designed to meet the storage and transportation needs of large quantities of materials, requiring extremely high strength and stability.

4. What is the core difference between hollow-grade HDPE and other HDPEs?

The core difference lies in melt strength and processing adaptability. Hollow-grade HDPE, with its optimized formulation, boasts higher melt strength and better processing stability, making it suitable for the stretching and molding stages of hollow blow molding. Simultaneously, it exhibits superior environmental stress cracking resistance and toughness, specifically designed for the production needs of hollow products. Furthermore, blow molding grade HDPE has a more balanced molecular weight distribution, with some products employing a multi-peak design to balance rigidity and toughness.

5. How does the density of HDPE affect blow molding?

Density directly affects the rigidity and toughness of the product.

Higher density results in greater rigidity and better heat resistance, but a slight decrease in toughness, making it suitable for producing containers requiring load-bearing and pressure resistance, such as chemical drums and IBC containers.

Lower density results in better toughness, making it suitable for producing thin-walled containers requiring impact resistance, such as milk bottles and cosmetic bottles.

6. How does the melt flow rate (MFR) of HDPE resin affect blow molding?

Melt flow rate (MFR) affects blow molding efficiency and product quality.

A low MFR (<0.2g/10min) results in high melt viscosity, poor flowability, difficulty in stretching during blow molding, and a tendency for products to have rough surfaces and uneven wall thickness.

If the melt flow rate (MFR) is too high (>10g/10min), the melt strength will be insufficient, making the blow molding process prone to bubble rupture and product deformation.

The MFR of HDPE used for blow molding is typically controlled between 0.2 and 10g/10min to suit the blow molding requirements of different sizes of hollow products. Small, thin-walled products should use models with a higher MFR, while large, thick-walled containers should use models with a lower MFR.