Characteristics of medical PP plastics and processing conditions

Medical PP plastic features

PP plastic is non-toxic, tasteless and colorless. It looks like polyethylene but is more transparent and lighter than polyethylene. PP is a kind of thermoplastic with excellent performance, which has the advantages of small specific gravity (0.9g/cm3), non-toxicity, easy processing, impact resistance and flex resistance.

Main properties of medical PP plastics

High temperature disinfection:

PP plastic is a semi-crystalline material with high melting point, good heat resistance and can be sterilized at temperatures above 100 °C. Yield strength, tensile strength, compressive strength, hardness and elasticity are higher than polyethylene (PE).

Low temperature resistance and impact resistance:

The homopolymer PP has a high brittleness, and the random copolymer PP synthesized with ethylene has better toughness and stronger impact strength. Generally, products used under low temperature conditions should be modified with PP as much as possible, or by adding thermoplastic rubber to increase the flexibility and low temperature impact resistance.

The Non-PVC large infusion bag is made of copolymerized PP and elastomer blended modified material.

insufficient:

It is easily depolymerized and aged under the action of oxygen, heat and light, so it is necessary to add an anti-aging agent. PP products are not easy to bond, need to be treated before bonding, and special adhesives are used. The cyclohexanone used in the equipment factory cannot meet the requirements. The coloring property is poor, the shrinkage rate is large (generally 1.6-2.5%), the burn resistance is poor, and it is easy to catch fire. PP is a non-polar material and has a low adsorption capacity for drugs.

Processing conditions

Processing technology:

It can be injection molded, extruded, blow molded or made into a film. The PP film is usually welded into a bag by heat sealing, and the processing process is more complicated than the process of welding the PVC bag with high frequency. Non-PVC large infusion bags are produced using fully automated equipment to ensure process stability and reliable quality.

Injection pressure:

Can be as large as 1800bar.

Drying treatment:

Low water absorption, no need for drying treatment.

Melting temperature:

220-270 ° C, be careful not to exceed 275 ° C. Mold temperature: 40-80 ° C, 50 ° C is recommended.

Injection speed:

High-speed injection molding minimizes internal pressure. If defects appear on the surface of the product, low speed injection at higher temperatures should be used.

Runners and gates:

For cold runners, typical runner diameters range from 4-7 mm. It is recommended to use a round inlet and flow path. All types of gates can be used. Typical gate diameters range from 1 to 1.5 mm, but gates as small as 0.7 mm can also be used. For edge gates, the minimum gate depth should be half the wall thickness; the minimum gate width should be at least twice the wall thickness, and the PP material can be fully used with the hot runner system.