In the production of PE (polyethylene) rotomolding drums, plastic mill is the key pretreatment equipment, its role is to process PE raw materials into fine powder suitable for rotomolding process.
PE rotomolding usually uses powdered raw materials (particle size of about 30-500 microns), while most of the PE on the market is in the form of granules. The mill crushes and grinds the granules into a uniform powder to ensure good fluidity and uniform melting.
It can handle PE with different densities (e.g. LLDPE, HDPE), and adjust the grinding parameters (e.g. rotational speed, screen size) to control the fineness of the powder, to meet the rotomolding requirements for powder flowability and melting effect.
Powder with large specific surface area is heated more evenly in the rotomolding mold, avoiding uneven wall thickness or air bubbles caused by uneven melting of particles.
Accurately controlled powder particle size reduces material dispersion during processing and reduces wastage.
Fine powder makes the wall of rotomolded drums smoother, reduces internal stress and improves mechanical strength (e.g. impact resistance, weather resistance).
Focus on capacity (matching with rotomolding line), energy consumption, dust control (explosion-proof design) and accuracy of screening system.
Usually need to be matched with dust removal and cooling devices to prevent PE powder from overheating and sticking or the risk of dust explosion.
Closed milling design with dust collection system to reduce PE dust pollution.
PE powder is flammable, the equipment needs to be equipped with anti-static, inert gas protection and other safety features.
In the production of PE rotomolded drums, plastic mill as the key equipment for raw material pretreatment has the following significant advantages:
Compatible with a variety of PE materials: it can process polyethylene raw materials with different densities such as HDPE, LLDPE, etc., adapting to the requirements of rotomolding process on the fluidity and melting characteristics of the materials.
Recycling material reuse: it can crush and grind the edge material and inferior products into powder, realizing the recycling of waste material and reducing the cost of raw material (it can save 15-30% of the cost of purchasing new material).
Optimize rotomolding fluidity: By adjusting the parameters of the grinding machine (e.g. cutter speed, screen mesh), powder in the range of 80-500 mesh can be obtained, and the uniform fine powder ensures a more even flow of the melt in the mold, reducing the problems of air bubbles and uneven wall thickness.
Concentrated particle size distribution: The advanced grading system reduces the proportion of coarse particles or excessively fine powders and improves the packing density of the powder, making the heating and melting more efficient.
Continuous production: Modern mill with automatic conveying system can realize seamless connection with rotomolding machine, reduce downtime waiting time and increase production capacity up to 20% or more.
Quick material change design: Modularized structure facilitates cleaning and material change to avoid cross contamination.
Low energy consumption design: Compared with traditional crushing equipment, the unit energy consumption of high-efficiency turbine mill can be reduced by 30%, which is especially suitable for large-scale production.
Reduction of raw material waste: precise particle size control can reduce the loss of material flying during the rotomolding process and increase the yield by about 5-8%.
Improvement of surface finish: The fine powder melts more fully, reducing the “orange peel” defects on the barrel surface.
Optimization of mechanical properties: Uniform powder distribution makes the wall thickness of the product more consistent, and the impact resistance and weather resistance more stable.
Enclosed design: Equipped with dust removal system and noise suppression device to meet the working environment dust emission standards (e.g. below 10mg/m³).
VOC control: Low temperature grinding process reduces thermal degradation of PE materials and reduces the generation of volatile organic compounds (VOCs) during subsequent rotomolding heating.
The type of mill should be selected according to the melting index (MI) of PE - liquid nitrogen freezing grinding is recommended for high MI materials to prevent sticking of knives; low MI PE can be ground at room temperature and supplemented with air-cooling to reduce the temperature.
With the above advantages, plastic grinding machine becomes the key link to improve the economy and quality of PE rotomolded drum production, especially suitable for small and medium-sized container manufacturing fields which are sensitive to cost and require light weight.
