(1) molding method.
End batching and mixing. the great of percent sheet manufacturing immediately impacts the extrusion velocity, procedure parameters and product excellent of the extruder, so this process have to be strictly controlled.
The material of every thing within the method ought to be measured as it should be to prevent the change of the real formulation as a result of the big mistakes inside the measurement, accordingly growing the difficulty of pleasant analysis and nice control. this factor in the actual production technique is frequently clean to ignore, should reason enough attention.
A. mixing temperature. mixing generally takes region in a high-pace mixer. material inside the mixer in excessive velocity friction heat, within the blending procedure, the temperature manipulate is very crucial. points have to be cited for temperature manipulate: first, after % resin and components are placed into the mixer, they will be stirred at once, and the temperature can be raised with the aid of friction. when the temperature reaches about 120t, it will likely be discharged into the mixer. 2nd, warm blend in the cold mix in a sure time frame, whilst the temperature of the fabric is lower than 45 can open the bloodless mixer sluice discharge.
B. blending time. in the procedure of blending, materials undergo such tactics as density exchange, uniformity and partial gelation, and on the equal time take away the moisture and risky count in materials, which takes a sure time to complete. if the combination time is just too brief, it'll be hard to extrude. if the combination time is simply too long, the temperature will upward thrust too excessive, as a way to effortlessly motive the discoloration and decomposition of substances.
C. feeding collection. there are numerous components of rpvc sheet, so it's far very important to pick out reasonable feeding collection. the choice of feeding collection need to be conducive to the effect of additives, avoid hostile effect among components, and additionally be conducive to enhance dispersion velocity.
Usual warm and bloodless blending approaches are as follows.
(a) warmness up the p.c resin to 60 in high pace mixer.
(b) installed stabilizers and preserve to warmness up to ninety euros.
(c) in-situ lubricants, processing aids, effect modifiers, fillers, colorants, etc.
(d) out of doors lubricant, continue to warmth as much as 115~ 120t.
(e) at a low velocity, substances are discharged into a rotating bloodless mixer with cooling water.
Refrigerate until forty~45
The main advantage of powder is brief heating method, low requirement for device and short production cycle. its essential shortcoming is terrible fabric uniformity and forming system overall performance, high compression price. the powder can be directly used for extrusion (typically through twin screw extruder), or may be plasticized into granule for unmarried screw extruder.
Extrusion molding method. extrusion molding is one of the maximum crucial steps inside the whole manufacturing method of extruded sheet.
A. molding temperature. the forming temperature of rpvc sheet is decided consistent with the formula, thickness of the sheet and other factors. the barrel temperature of the single-screw extruder is, in turn, the mouth. ? ^. ^ ^. ? 140 yi, a hundred and fifty ~ 160 t, a hundred and seventy ~ a hundred and eighty ^. the temperature of the feeding segment of the twin screw extruder is barely higher. the reason is to make the cloth melt at the cease of the feeding segment, a good way to cover the ferrite bar and save you the cloth from being eliminated when passing via the exhaust phase, ensuing in waste of substances. see desk five-20 for connector temperature and head temperature
B. extrusion speed. the extrusion speed is determined via the screw speed, the screw velocity increases, the extrusion amount increases, the extrusion pace increases, below the same molding temperature condition, the plastic fine of the material will drop down, the willpower of affordable extrusion pace (screw velocity) may be very vital to assure the product nice and enhance the monetary performance.
C. traction pace. the linear velocity of the traction roller must be slightly faster than that of the three rollers of the calender, with the intention to maintain a sure tension, in order that the plate within the cooling system will not produce deformation, warping and other defects. but, if the rate is too speedy, the plate will produce extra internal pressure, a good way to affect the excellent of the secondary processed products.
D. cooling molding manner. the principle function of three - roll calender is calendering and cooling. see desk 5-2 for the temperature of the cylinder of the calender. the gap among the 3 rolls and the die lip of the device head should be as small as viable, usually 5 ~10cm. if it's miles too large, the plate extruded by way of the gadget head may be vulnerable to stoop, wrinkle and surface roughness, and on the same time, it is simple to burn up heat and funky. the period of the curler must be barely large than the width of the top. increasing the diameter of the roller can boom the roll time, growth the extrusion pace and make the % sheet gloss excellent. the operating distance among the higher and center rolls of the 3-roll calender can be barely large than the thickness of the plate. the traction velocity of the 0.33 figure must be regular with the extrusion velocity of the extruder to keep away from stretching.
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