hard polyvinyl chloride (UPVC) of the injection molding process some of the detailed analysis

UPVC known as hard PVC, vinyl chloride monomer which is formed by the polymerization reaction of amorphous thermoplastic resin and certain additives (such as stabilizers, lubricants, fillers, etc.). pvc called hard pvc, vinyl chloride monomer which is formed by the polymerization reaction of amorphous thermoplastic resin and PVC stabilizer for cable  certain additives (eg stabilizers, lubricants, fillers, etc.). In addition to the additive, but also other resins used for blending with the modified approach
upvc called hard pvc, vinyl chloride monomer which is formed by the polymerization reaction of amorphous thermoplastic resin and certain additives (such as stabilizers, lubricants, fillers, etc.).
In addition to the additive, but also other resins used for blending with the modified approach, it has obvious practical value. These resins are cpvc, pe, abs, eva, mbs like.
upvc high melt viscosity, poor mobility, even when the injection pressure and melt temperature fluidity will not change much. In addition, the resin molding temperature and thermal decomposition temperature are very close to the temperature for forming a very narrow range, is a hard molded material.
1, plastic processing
After 24 hours at room temperature, water less than 0.02%, and therefore without drying. If must be dry, can be placed in 60-70 ℃ hot air oven for 3 hours or 80 ℃ 1-1.5 hours in a dryer.
Up to 20% recycled material and new material mixed, the amount of recycled material depends on the end use of the product. Abuse of recycled material injection can fail, not only the composition of recovered much more is due to the material after repeated re-processing. Every once more recycled material decline in the quality recycling more.
2, injection molding machine selection
upvc Since the melt viscosity, easy PVC heat stabilizer for fittings  to decompose, decomposition products have a corrosive effect on iron, which must be dedicated to the plastics injection molding components and temperature control system.
Ramada products covered in each of the clamping force model, has specialized upvc plastics injection system, and with upvc pipe fittings Pulling requirements with a dedicated security gate devices. Under normal circumstances as long as the injection volume to meet the weight requirements, the choice of this series of injection molding device can be molded upvc high-quality products.
3, mold and gate design
Mold temperature can be set to 40 ℃. Flow channel length should be short, will have a large diameter to reduce the pressure loss and the holding pressure can be passed into the mold cavity. Gate as short as possible, cutting surface to be circular, the diameter of the smallest nozzle orifice 6mm,, into a conical angles to 5 °.
Sprue cutting surfaces have circular, with a combination of cold slug well by connecting section sprue and gate radius, diameter of 7mm.
Gate application tangentially connecting radius of the surface shape plastic parts, the shorter the better, cutting surface to be smooth.
Cold slug well to prevent semi-solidified material into the mold cavity, its importance is often overlooked.
Position of the gate to the right, so that the material in the stream flowing smoothly trail, will not stay in sharp corners, debris and metal traces in order to avoid compression or decompression situation, should maintain smooth flow smoothly.
Application of stainless steel casting mold, chromium content of at least 13%, preferably 16%, at least 55 Rockwell hardness, hard chrome-plated steel mold can be processed to form a protective effect.
After production, the application of a mild lye carefully cleaned and then sprayed mold surface quality oil spray or siliceous spray.
4, the melt temperature
Measure of available air-launched by 185-205 ℃ range. Smoothness of the material from the injection can know the exact upvc melt temperature. If the material in the injection after the rough, as evidenced by the material is not homogeneous (plastics insufficient), which means that the temperature set too low; eg, injection newcomer bubble and smoke  low molecular polyethylene a lot of smoke, it means the temperature is too high.
5, the injection speed
Slower rate of fire, or cause excessive shear degradation of materials, the use of upvc produce extremely smooth, thick-walled products should be used multi-stage injection mold filling speed.
6, the screw speed
Should match the molding cycle may be. Screw face velocity shall not exceed 0.15-0.2m / s
7, the back pressure
Up to 150bar, the lower the better, common to 5bar.
8, the retention time
At a temperature of 200 ℃, barrel residence time can not exceed five minutes. When the temperature is 210 ℃, cylinder residence time should not exceed 3 minutes.