If you’re unsure about the parts that go into a wood plastic composite machine, read on. We’ll discuss the Extruders, Secondary side-feeders, Capstock layer, and more. You’ll learn what they all do and why they’re important for your business. And, as always, if you have questions, feel free to ask our expert team. We’ll be happy to answer your questions!
Processing zones of a wood plastic composite machine
A wood plastic composite is a composite material with several key advantages. Wood flour and plastic constituents improve stability, impact strength, and tensile strength. Combining 50% wood flour and plastic constituents enhances interfacial compatibility. These two constituents also provide enhanced bending strength and impact resistance. Several types of wood flour are available in the market today. These composites are used to manufacture products ranging from boat hulls to automobile parts.
The tensile strength of WPC varies depending on the proportion of wood flour. The optimal wood flour proportion is 50 percent. In other words, an increasing proportion of wood flour reduces the tensile strength of the composite. The reason behind this is that wood fibres have a large volume and poor plastic surface. Wood flour proportions should not exceed 50 percent to increase tensile strength.
Heat transfer between the two zones of a wood plastic composite machine is a key element of process optimization. In addition to the nozzle, the press unit needs to be properly insulated to keep the composite material cool. Heat transfer can be reduced by using resistor heaters and insulators. To reduce heat loss at the start of processing, infrared heaters with thermostats are an excellent choice. They are highly efficient in cooling WPC parts.
Mixing and finishing are important components for the durability of a wood plastic composite. The right mixture will reduce MSW and improve composite properties. Wood fibre and thermoplastics can be mixed together to increase flexural strength and stiffness, compared to virgin plastic waste. A wood plastic composite can be either thermoplastic or thermosetting. The main differences between these two materials are the degree of polymer mixing and the type of additives used.
A wood plastic composite has a relatively good interface between the wood fibre and the plastic matrix, indicating that the wood powder has a good mechanical interface. The wood powder pulls out of the plastic matrix when smashed. The coupling agent enhances the mechanical properties. As the wood powder is mixed, it is not completely blended with the plastic matrix. It is possible to mix different types of wood powder with the same coupling agent.
When it comes to wood-plastic composites (WPC) production, extruders play an important role in the entire process. The wood powder must be screened from residual moisture. The fines that pass through the screen are difficult to disperse into the plastic matrix. Consequently, these materials become “wood spots,” or wood fibers that don’t evenly disperse into the plastic matrix.
Co-rotating and counter-rotating extruders can process wood fiber with a high moisture content if the fibers are dried to about 1% moisture content. However, this will reduce throughput and increase the maximum residence time in the extruder. This will result in an increased percentage of water removed from the extrudate. The recommended moisture content for wood fiber is 2% to 4% by weight.
Wood fiber is not the only natural fiber used for WPC production. Polyolefin is another common material, but polyethylene and polypropylene are the most commonly used plastics for WPC production. These materials are ground, screened, and dried before they are extruded. Some applications call for a rough surface texture for the wood fiber, such as decking and fence profiles. Screening the fibers to 40-60 mesh ensures even dispersion and mixing into the plastic matrix.
The material used in WPC production is typically recycled. However, a significant fraction of this material is virgin material. This material is not tightly controlled and is subject to significant variations in its properties over time. These variations affect the maximum throughput, yield, and scrap rate of the WPC machine. For this reason, it is vital to choose the plastic with the highest melt flow index (MWI), since high melting temperatures are more likely to cause the wood to degrade.
The secondary side-feeders in a wood plastics composite machine feed the product from a side of the line to the main body of the machine. These side-feeders are essentially the same as the main feed, but are used in different configurations. Wood-based products have varying physical and mechanical properties. They can have low dimensional stability and exhibit defects due to the differences in the moisture content and drying process.
A side-injection extruder works like a twin-screw extruder, but has a much smaller feed opening. The resulting material is mixed with a polymer that is injected at a controlled rate. Secondary side-feeders allow the machine to process several different materials at the same time, allowing for increased productivity. Secondary side-feeders also help prevent the re-composition of materials that are low in bulk density. They also help to reduce the overall heat history and energy consumption of the machine.
A third common issue involving secondary side-feeders is that the first side-feeder may not be suitable for the type of material being processed. In this case, a longer-extruder with degassing zones near the feeding zone is necessary. This option may make more sense for your company’s manufacturing process. The wood fiber composite produced in this way can then be packaged in tote bins or gaylord containers and brought to the profile extrusion line.
One method of pre-drying wood is the addition of molten polymer before feeding the wood. Pre-drying wood is a process that requires mixing wood and polymer separately in separate zones. A secondary side-feeder in a wood plastic composite machine is used to do this. The pre-drying wood allows better control of the residence time of the wood filler. High capacity twin-screw extruders are ideal for this type of processing, as they allow for the distribution mixing and degassing zones required to prepare the composite.
The ZSFE extruder includes a ZSFE side-feeder. This side-feeder has special Ultra Feed vacuum technology that enhances the bulk density of the light filler materials. Its addition to a WPC machine increases the total output rate by about 2.5 times. This is an extremely useful feature that allows the company to maximize its profits. If you need additional feedstock, secondary side-feeders are worth considering.
This invention relates to a method of manufacturing products using a thin capstock layer, typically about 4 mil or less, containing polyvinylidene fluoride (“PVDF”) resin. Moreover, the capstock layer is useful in creating stone or wood-like appearances, as well as a variety of other appearance characteristics. For example, the capstock layer can produce surfaces that have the appearance of metamorphic rocks, while the top layers may feature variegated printing.
In addition to this feature, the present invention also applies to all types of PVC-based products. These materials generally require a capstock layer to protect them from long-term weathering. However, many of the existing capstock materials are incompatible with the present invention, including those made from ASA and other acrylic resinous compositions, since their processing windows are too small and their coefficients of linear thermal expansion are not well-controlled.
WPC is made from a mixture of wood fibres and polymers. To make it durable, it undergoes various physical and chemical processes. It must be treated to withstand thermal expansion during installation, and this requires additional cost. However, this cost is offset by the complexity of the material. With the growing popularity of WPC, the use of wood-based plastic has expanded rapidly. The advantages of wood plastic composite in these applications include durability, aesthetic appeal, and ease of fabrication.
While polyethylene is one of the most recyclable materials in the world, its recycling capacity diminishes after it has been combined with wood flour. German WPC manufacturers also recycle their materials, but no U.S. manufacturer does so. While recycled polyethylene is a popular material for capstock boards, many manufacturers prefer to use poly-vinyl chloride as a cap material, because it’s more resistant to UV exposure and wear. UV light is a common problem for wood-based decks, but it’s also important to include a UV-absorbing additive in the composite mix to help prevent premature degradation.
In terms of geography, the North American market for wood plastic composite is anticipated to hold the largest revenue share in 2020, followed by Asia Pacific and Europe. The demand for WPC in North America is projected to continue growing, with the materials used in porches, decking, and window frames. The rising demand for bio-based plastics and growing environmental concerns are expected to spur market growth. Additionally, the presence of leading manufacturers and the growing online sales will further boost the market.