1.Understand the three main types of PE raw materials
| Raw material type | Density range (g/cm3) | Core features | Typical applications |
| Low-density polyethylene (LDPE) | 0.91 - 0.925 | Excellent softness, extensibility, transparency and processability. | Requires flexible sheets, protective films, packaging liners, etc. |
| High-density polyethylene (HDPE) | 0.92 - 0.965 | Hardness, tensile strength, heat resistance (service temperature up to 100°C) and creep resistance are superior to LDPE. | Sheets requiring certain rigidity, containers, chemical pallets, decorative panels, etc. |
| Linear low-density polyethylene (LLDPE) | Between LDPE and HDPE | Its performance (tear strength, impact resistance, environmental cracking resistance) is significantly better than LDPE, while also possessing flexibility and heat resistance. | For high-strength sheets, heavy-duty packaging bag liners, and blending with LDPE to improve performance. |
2.Clarify the core indicators of high-quality raw materials
Melt Flow Rate: This is the most important processing parameter. It determines the flowability of the resin in the molten state. You should select grades with stable MFR based on the characteristics of the extruder screw and the sheet thickness to ensure stable extrusion output and melt pressure.
Mechanical Properties: Check data such as tensile strength and elongation at break according to the end-use application. For example, sheets that require frequent bending need raw materials with high elongation at break.
Density: Density is directly related to the rigidity and flexibility of the sheet.
Optical Properties: LLDPE may not be the best choice if high transparency is required (its transparency and gloss are generally poor), while specific grades of LDPE or modified blends may be more suitable.
3.Strictly control the form and cleanliness of raw materials
Use only original granular raw materials: For extrusion production lines with strict requirements, the use of powder or re‑granulated materials with unknown composition is strictly prohibited. Such materials may contain impurities, excessive moisture, or unstable melting behavior, which can cause fish eyes (gels), bubbles, uneven color, and even screen clogging in the sheet, seriously affecting production efficiency and product quality.
Check raw material consistency: High‑quality raw materials should have uniform color and particle size from batch to batch, with no color difference or foreign matter. This ensures stability in the color and performance of the final product.
4.Emphasize the Additive System
Functional additives: such as antioxidants (to prevent thermal degradation during processing), UV absorbers (to improve weather resistance), slip/anti-blocking agents (to prevent sheet adhesion), etc. These are usually added in the form of masterbatches.
Filler masterbatch: To reduce costs or improve specific properties (such as whiteness and rigidity), filler masterbatches such as calcium carbonate may be added. The key is to ensure good dispersion of the filler masterbatch in the resin; otherwise, it will lead to reduced mechanical properties or surface particles on the sheet. Dispersion can be initially judged by observing whether there are "color spots or streaks" on the blown film or sample sheet.
Color masterbatch: If coloring is required, color masterbatches with good compatibility with the PE carrier should be selected, and their heat resistance must meet the processing temperature requirements.
5.Establish a Reliable Supply Chain and Verification Process
Choose reputable suppliers: Prioritize internationally renowned brands such as SABIC, Dow, ExxonMobil, or large, credible domestic petrochemical enterprises and masterbatch manufacturers. They can provide more stable product quality and detailed technical documentation.
Request and understand technical data: Ask suppliers for the Material Safety Data Sheet (MSDS) and technical data sheet (TDS) of the product, and verify whether they meet your process requirements or relevant industry standards (such as food contact, medical grade, etc.).
Conduct machine trials: Before mass purchasing, be sure to request samples for small‑batch machine testing. Observe melt stability, sheet appearance (fish eyes, streaks), and dimensional stability under actual production conditions.