WPC Total Solution Whole Plant Equipment
WPC is divided into two parts: one being solid and the other being hollow. The inner surface of the hollow structure can produce a smooth and rough inner surface with the mould technology.
According to the plastic substrate, WPC can be divided into PVC, PE, PP, PS, and ABS, and yet products of PBT and PET are in development. Even though PVC is rather inflammable, it still has been a controversial environmental issue. PE plastic wood has a large consumption; however, the oily wax texture of the material has low heat resistance, poor foaming, poor printing performance, and a product shrinkage; PP plastic wood has a wax texture and can withstand high temperature. Although the secondary processing has the risk of cracking, the appearance and texture are identical to a real wood, hence It can very well be done without post-production.
Application of WPC
Application of WPC
According to the foaming agent, WPC products can be divided into foamed and non-foamed WPC. After foaming, WPC can not only reduce weight but also can be processed by ordinary woodworking equipment, with wood cutting, sawing, adhering and nailing, hence easier to thermoform.
WPC Foaming Product
WPC products can be categorized into single-layered and co-extrusion. Traditional single extrusion WPC is lack of climate resilience and wear proof. In fact, a long-term outdoor exposure can cause tarnishing, crumbling, staining, a mold growth, etc. However, the skin layer of a WPC co-extrusion product uses WPC recycling material or foaming to enhance climate resilience and the texture of the WPC products.
Single Extruded and Co-Extruded pictures (http://www.newtechwood.tw/introduce.htm)
Surface treatment technology: sanding, embossing, coating, and thermal transfer. Generally, the surface of WPC floor is quite slick, in order to prevent slipping, the surface of the WPC floor needs to be process through a sanding machine or a wire drawing machine; WPC floor is sanded and then embossed for improvement. Therefore, the wooden floor is non-slip and wear proof.
B. WPC Machine Line:
WPC forming granules on the market can be used to make various types of WPC products. WPC machine line includes extruder, mold, profile calibration table, haul off, cutter, etc. The production line will be slightly adjusted, depending on different plastic substrates which customers own (PVC, PE, PP), the wood powder content (10~70%), and the limitation of factory space. The moisture of wood powder is about 8~12%, and should be controlled under 1.5% after being made into WPC molding pellets. Despite of the WPC molding pellets have no wood powder except water. The treated oil esters and fibers will also affect the stability of the volatile gas during the high temperature extrusion process. Therefore, Everplast has adopted an all-around vacuum degassing extruder to meet the needs of customers. For the extruder part, we provide Single screw extruder, parallel out-of-phase twin-screw extruder, and same-direction modular twin-screw extruder. The single-screw extruder has one vent hole, and a screw L/D ratio>36. The pros of a single-screw machine line are its low cost, low energy consumption, and so on, whereas the cons are its plasticizing and mixing effect slightly inferior to the twin-screw extruder; the parallel out-of-phase twin-screw extruder is equipped with 1-2 vent holes, low shear, low speed of 30-50rpm. The high back pressure extrusion characteristics, enables a production of heat-sensitive plastic wood material and large-scale WPC products; the same-direction building type twin-screw extruder is equipped with 1-2 vent holes, elastic adjustment screw configuration, high shear, mixing and plasticizing, high speed of 200rpm, and the medium back pressure extrusion characteristic enables a production of large PE / PP plastic wood products.
D45mm two-stage exhaust single screw diameter 45mm, screw length 1578mm, screw L / D ratio = 35.07, initial design first section feed pitch and groove depth Pf1 = 45mm, hf1 = 5mm, the first paragraph measurement Pitch and groove depth Pm1=45mm, hm1=2mm, the first stage compression ratio is CR1= Pf1* hf1/ Pm1* hm1=2.5; the second stage feed pitch and groove depth are Pf2=55mm (double mouth), hf2= 5mm, the second section of measuring pitch and groove depth Pm2=40mm, hm2=2.5mm, the second stage compression ratio is CR2= Pf2* hf2/ Pm2* hm2=2.75; the pumping ratio (pump ratio) PR= Pm2* hm2/ Pm1 * hm1=1.1, the simulated melting curve and pressure distribution are shown in the graph below. The PC material is melted at the end of the metering zone of the first zone of the screw. In order to avoid the unmelted ester particles entering the second zone of the screw, there are two sections after the screw design which can force the unmelted particles to undergo the dispersive mixing to enhance the melting and the uniform temperature. The pressure distribution shows that the back pressure of the screw end is up to 2.16 MPa. When the mold resistance is excessively high, the screw volume measuring ability is insufficient. The second feeding zone which caused the material to flow corresponds to the experimental results.
In order to confirm the back pressure of the low mold, the phenomenon of venting of the vent hole can be avoided. The end of the two screws can provide a back pressure of 3.51 MPa without causing the material, and the pressure distribution of the simulated pressure of 1.5 MPa and 3 MPa. As shown in the graph below, under the 1.5MPa back pressure, the plastic under this back pressure only goes back to the second section of the screw metering area, because it has not yet entered the metering area, it can ensure that there will be no accidents; When the back pressure increases to 3 MPa, the plastic traces back to the middle section of the second stage of the screw compression zone, and the risk of the material is higher than the back pressure of 1.5 MPa, but basically ensures that there will be no material. Subsequently, the increase of the second section of the measuring groove depth can effectively improve the maximum back pressure capacity.
The WPC profile mold design can be divided into hot extrusion molding and cold extrusion molding. The hot extrusion molding line speed is approximately 0.3~1 m/min. The special design of a sink insulation system is capable of increasing the production speed; as the high wood powder content reaches 60%, the cold extrusion molding technology can ensure that the center thermoplastic wood material does not penetrate through the skin layer. As a result of a slow production speed (0.3~1m/min), the rear end can be pulled without dragging the whole thing off.
Hot extrusion molding: the average temperature of a plastic mold is greater than the melting point (Tm). For the first sizing mold, the skin temperature (T) must be lower than the curing temperature (Ts), and the skin must have sufficient strength to avoid the central uncured plastic rupture in the cortex. Furthermore, the average temperature of the finalizing mold must be lower than the curing temperature (Ts) to avoid re-melting, and the cross-section temperature difference must be minimized to avoid residual stress. The temperature of the cutting section must be lower than the curing temperature.
Extrusion Mould Extrusion Mould
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