PET plastic sheet crisp
products crisp was in large part due to internal stress. A lot of reasons that cause products crisp, mainly include:
a equipment of
( 1) Barrel in a corner or obstacles, easy to promote the molten material degradation.
( 2) Machine plasticizing capacity is too small, plastic inside the barrel plasticizing inadequate; Machine plasticizing capacity is too big, plastic is heated and the shearing action in the barrel time is too long, plastic easy to aging, make the products become fragile.
( 3) Ejection device tilt or imbalance, dry area small or poor distribution.
( 1) Gate is too small, should consider to adjust the gate size or adding auxiliary gate.
( 2) Distributary channel is too small or misallocation, should try to arrange reasonable balance or increase the size of distributary channel.
( 3) The mould structure bad cause abnormal injection cycle.
( 1) A barrel, nozzle temperature is too low, raised it. If the material easy degradation, should raise the temperature of barrel, nozzle.
( 2) Reduce the screw plastic back pressure and rotational speed, make the material a little loose, and reducing the plastic degradation caused by shear overheating.
( 3) Mold temperature is too high, demoulding difficulty; Mold temperature is too low, premature plastic cooling, fusion welded seam bad, easy to crack, especially when high melting point, such as polycarbonate plastic.
( 4) Mold core to a proper draft. Core difficult demoulding, to improve the mold temperature, shorten the cooling time. Cavity is difficult to take off, want to lower the temperature in the cavity, extend the cooling time.
( 5) As far as possible with a metal insert, such as polystyrene plastic of this kind of specific volume of brittleness of cold heat is big, can't join the insert molding. Four raw materials
( 1) Raw materials mixed with other impurities or with improper or excessive solvent or other additives.
( 2) Some plastics such as ABS, under the condition of be affected with damp be affected with damp heat and water vapor will happen catalytic cracking reaction, result in large strain of parts.
( 3) Plastic regeneration frequency or reworked material content is too high, or within the barrel heating time is too long, cause embrittlement of fabrication.
( 4) Poor quality plastic itself, such as molecular weight distribution, contains the uneven structure such as molecular chain rigidity is too large in the number of components; Or the other plastic doping pollution, bad additives pollution, dust pollution of impurities is also the cause of brittle.
five products design
( 1) Products with prone to stress cracking of sharp corners, gaps, or thickness vary widely.
( 2) Product design is too thin or hollow out too much.