1. Outline of EPP Beads Foam
■ What is EPP (expanded polypropylene) ?
“EPP (expanded polypropylene) is an engineered plastic foam material. By combining polypropylene resin with magic dust, and applying heat, pressure and CO2 in an autoclave, the material is foamed into small plastic beads. These small, closed-cell foam beads are injected into a steam chest to create parts custom molded into complex shapes using steam heat & pressure.”
“EPP (expanded polypropylene) is a unique raw material that has many important characteristics making it suitable for a wide range of applications. Some striking selection criteria are: energy absorption, low weight and high thermal stability.”
■ EPP Performance
EPP (expanded polypropylene) is a unique raw material that has many important characteristics making it suitable for a wide range of applications. Some striking selection criteria are: energy absorption, low weight and high thermal stability.
- EPP is in particular used for expensive and vulnerable electronics products or molded parts, such as climate-control and automotive industries parts.
- Despite its low weight, EPP can absorb large amounts of energy and has a remarkable ability to restore its shape after being subjected to static or dynamic loading.
- The deformation is very balanced, independent of the direction of the impact/ load.
- EPP is temperature resistant, absorbs hardly any water and is effectively resistant to chemicals and oils.
■ EPP Character
- High energy absorption and lightweight product
- Excellent repetitive impact performance
- Excellent temperature resistance
- Recycled content
- Low/zero air emissions & hazardous substances
- Easy, non-hazardous maintenance
- End-of-life management keeps materials out of landfills (e.g., reuse, recycling, return to manufacturers)
- Nontoxic and food safety
- Low life cycle cost
- Excellent oil and chemical resistance, weather resistance
- Flexibility makes it easy to handle products
- Remarkable ability to restore its shape after static and dynamic loading
- Possible to recycle by non-crosslink (reduction facility)
- Choice of various expansion ratio (raw material supplier)
- Excellent dimensional accuracy
- It has low water absorption
- Excellent insulation performance
- Environmentally friendly
■ Various Color in Many Different Fields
EPP foam can be produced in many colors. Various colors can be used in various fields such as toys, furniture and many children’s goods etc.. Properties that make the particle foam an ideal material for hobby and recreational applications.
EPP materials are mainly made of black color and are used for automobile parts production. In order to produce colored EPP beads, it is sold at a high price because all production lines must be stopped and cleaned.
By lowering the price through direct production, it is possible to develop EPP color products in many other new fields and significantly expand the market.
■ EPP Impact Performance (Excellent repetitive impact performance)
■ EPP Bead Foaming Ratio
■ EPP Basic Properties
■ Foaming Mechanism (Shape of Beads Cell )
■ DSC Peak Characteristics
Thermal analysis of EPP with Differential Scanning Calorimetry (DSC) reveals that the reactor foam has two peaks (140℃ & 160℃). This was an important patent right for early Japanese companies. The random Polypropylene (R-PP) with a single melting point is kept at a constant temperature and pressure under constant conditions, and when cooled, a melting point of the material is separated into two, and a specific phenomenon can be found.
In the case of EPP, a stable molded article can be obtained at the time of molding by forming appropriate 2 peaks. The region at the lower temperature is used for fusion of the bead, and the region at the higher temperature contributes to maintaining the stable shape without collapsing the bead.
■ Recyclable Material
EPP is extremely recyclable and does not contain CFC or other propellants, it is very environmental friendly.
▶ Polyolefins foam (EPP, EPE) responds to environmental regulations by minimizing the emission of environmental pollutants among plastic materials. (Recycling, incineration)
▶ EPP is responding to the Recycle established by SPI (American Plastic Association)
2. Overview of EPP Business
■ Future EPP Business Trend
“In the future, if EPP beads are produced directly by each EPP molding company, the price of EPP materials will be greatly reduced, and the use of EPP products will be greatly expanded.”
■ Why EPP beads price is so expansive?
First, it sells at a high price through exclusive production based on patents and production know-how held by EPP Beads suppliers. The patent is now extinguished.
Second, it is due to the high profits and fixed costs of current production companies that are multinational companies. And, another reason is the high cost of shipping foamed beads.
Third, the EPP bead production business is suitable for small and medium-sized enterprises. It’s a marginal business that isn’t suitable for multinational companies like today.
■ There is no significant difference in the price of raw materials between EPP and EPS.
The price of EPP raw materials (R-PP Mini Pellets) and the price of EPP Resin are almost the same. However, the reason for the high EPP price is the high cost structure of multinational companies with high fixed costs and the high cost of transportation to each plant.
If the user produces the EPP beads in-house, there is no need to establish a separate factory, the existing utility can be used, and the production can be done with a minimum number of persons (2 person in 1 shift for production). Therefore, the cost can be significantly reduced.
“If EPP beads are produced directly by each EPP molding company, the price of EPP materials will be greatly reduced, "
■ New Paradigm of EPP Bead Production System
“EPP molding companies can purchase mini pellets and produce EPP beads directly in their own factories, which can significantly reduce material and transportation costs. The material cost can be reduced by about 40% ~ 60% compared to the current purchase price.”
3. Autoclave EPP Beads Production System
■ Three Step of EPP Product's Production Process
■ EPP Bead Production Process Outlines
The EPP (expanded polypropylene) is produced in two steps. The first step is to produce mini-pellets from polypropylene granulate. It is only from these mini pellets that it is possible to produce characteristically “foamed” expanded polypropylene, since the grains of the polypropylene granulate would be too large for this purpose.
The manufacturing process is complex, requiring both technical expertise and specialized custom equipment.
Polypropylene resin is combined with other ingredients in a multi-step proprietary process.
Under tightly controlled conditions, extruded pellets expand to become consistently shaped beads of expanded polypropylene foam.
EPP foam beads are then injected into molds. In many cases, cost-effective multi-cavity aluminum molds are used. Pressure and steam heat fuse the beads into a finished shape.
The finished EPP foam part becomes a key component in sub-assemblies incorporated in the original equipment manufacturer’s product.
■ Mini Pellet Extrusion System
To produce EPP beads, use a Single Screw extruder for black and white colors, and a Twin Screw for mini pellets with colored tints. The most important thing of mini pallet is additive know-how, dies and precise cutting machine.
Thus, the production process is effected by melting the granulate in an extruder from which 100 thin fibers, so-called “spaghetti”, emerge. They are cooled in a water bath, dried and chopped to the required mini pellets, which can be imagined as tiny short needles.
The Mini Pallet is made by mixing a masterbatch with R-PP as the main ingredient and a special foaming accelerator.
Functioning of the downstream systems Polymer strands extruded from a die head (01) pass through the cooling trough (02). The air knife 03 ensures effective strand drying prior to cutting. The residual moisture after strand drying evaporates in the evaporation section. The feed tools of the strand pelletizer 04 catch the polymer strands and direct them to the cutting tools where the strands are cut into pellets. The pellets are classiﬁed, cooled, and conveyed in subsequent operations 05. The cut and dried mini pallets are transported to the storage silo by air blower and packed 06. PP resins and the required additives (nucleating agent, compatibilizer, plasticizer, etc.) are compounded in an extruder and are granulated into pellets.
■ Autoclave EPP Beads Expansion System
These Mini Pellets are then put into a stirred autoclave with a dispersion medium (water), dispersing agent, surfactants and a physical blowing agent (CO2) at an elevated pressure and at a temperature above the melting temperature of PP.
After appropriate processing time has elapsed to let the blowing agent impregnate and saturate the pellets, the pressure is released to expand the pellets. Then the expanded beads are cooled, washed and packed.
■ Blowing Agent CO2 Supply System
We use carbon dioxide (CO2) gas as foam material to foam the mini pallet. The pressure injected into the reactor is about 4.8 MPa. We suppling complete set of equipment that are Gas cylinders, Cryogenic cylinders, Storage tanks, Cryogenic pump, Vaporizer, Air separation plant, CO2 Electrical Heater, Cryogenic high-pressure valve, Pressure over protect device, Control panel and High-pressure pipes and skid mounted etc.