Matters Needing Attention of PPSU in the Process of Injection Molding

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PPSU, the scientific name of polyphenylene sulfone resin, is an amorphous thermoplastic with high transparency and hydrolytic stability, and the products can withstand repeated steam disinfection.

PPSU is more common than polysulfone (PSU), polyethersulfone (PES) and polyetherimide (PEI).

 

The application of PPSU

 

1. Household appliances and food containers: can be used to manufacture microwave oven equipment, coffee heaters, humidifiers, hair dryers, food containers, baby bottles, etc.

 

2. Digital products: instead of copper, zinc, aluminum and other metal materials, the manufacture of watch cases, interior decoration materials and photocopiers, camera parts and other precision structural parts.

 

3. Mechanical industry: mainly use glass fiber reinforced specifications, the products have the characteristics of creep resistance, hardness, dimensional stability, etc., suitable for the production of bearing brackets and mechanical parts shell and so on.

4. Medical and health field: very suitable for dental and surgical instruments, disinfection boxes (plates) and a variety of non-human implantable medical instruments.

 

PPSU appearance

 

Natural yellowish semi-transparent particles or opaque particles.

 

Physical performance requirements of PPSU

 

Density (g/cm³)

1.29

Mold Shrinkage

0.7%

Melting temperature (℃)

370

Water absorption

0.37%

Drying temperature (℃)

150

Drying time (h)

5

Mold temperature (℃)

163

Injection temperature  (℃)

370~390

Several points should be paid attention to when designing PPSU products and moulds

 

1. The fluidity of PSU melt is poor, and the ratio of melt flow length to wall thickness is only about 80. Therefore, the wall thickness of PSU products should not be less than 1.5mm, and most of them are above 2mm.

PSU products are sensitive to notches, so arc transition should be used at right or acute angles. The molding shrinkage of PSU is relatively stable, which is 0.4%-0.8%, and the melt flow direction is basically the same as that in the vertical direction. The demoulding angle should be 50:1. In order to obtain bright and clean products, the surface roughness of the mold cavity is required to be more than Ra0.4. In order to facilitate the melt flow, the sprue of the mold is required to be short and thick, its diameter is at least 1 / 2 of the thickness of the product, and has a slope of 3 °~ 5 °. The cross section of the shunt channel should be arc or trapezoid to avoid the existence of bends.

 

2. The form of the gate can be determined by the product. But the size should be as large as possible, the straight part of the gate should be as short as possible, and its length can be controlled between 0.5~1.0mm. The position of the feed port should be set at the thick wall.

 

3. Set enough cold holes at the end of the sprue. Because PSU products, especially thin-walled products, need higher injection pressure and faster injection rate, good exhaust holes or grooves should be set up in order to exhaust the air in the mold in time. The depth of these vents or grooves should be controlled below 0.08mm.

 

4. The setting of mold temperature should be beneficial to improve the fluidity of PSU melt during film filling. The mold temperature can be as high as 140 ℃ (at least 120 ℃).


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