PP Tube with screw

Polypropylene (PP)

Classification by Crystallinity

• Isotactic PP (crystallinity up to over 95%, molecular weight: 80,000 - 150,000)
• Atactic PP (amorphous at room temperature, molecular weight: 3,000 - 10,000, with limited applications)

Properties and Applications of Polypropylene (PP)

1. Properties of Polypropylene

(1) Physical Properties

• a. Non-toxic, odorless, tasteless, semi-transparent or transparent pellets (milky white powder);
• b. Density: 0.90 - 0.91 g/cm³;
• c. Water stability: Water absorption rate is only 0.01% after 24 hours in water;
• d. Molecular weight: Ranges from 80,000 to 150,000;
• e. Good moldability, high shrinkage rate, and easy depression in thick-walled products;
• f. Good gloss and easy to color.

(2) Mechanical Properties

• a. High crystallinity and regular structure: Higher strength, hardness, and elasticity than HDPE (High-Density Polyethylene);
• b. At room temperature and low temperature: High structural regularity leads to poor impact strength (impact strength increases with the increase of molecular weight);
• c. Flexural fatigue resistance: For example, the one-piece movable hinge injection-molded with PP can withstand 7×10⁷ times of folding and bending without damage marks;
• d. Dry friction coefficient: The dry friction coefficient of PP is comparable to that of PA6 (Polyamide 6), but it is inferior to PA6 under oil lubrication.

(3) Thermal Properties

• a. Melting point: 164 - 170℃;
• b. Heat resistance: It can be sterilized at a temperature above 100℃ and will not deform at 150℃ without external force;
• c. Brittleness temperature: -35℃ (inferior to polyethylene in cold resistance).

(4) Chemical Stability

• a. Chemical stability: It is stable to various chemical reagents except that it can be corroded by concentrated sulfuric acid and concentrated nitric acid;
• b. Softening and swelling: Low-molecular-weight aliphatic hydrocarbons, aromatic hydrocarbons, and chlorinated hydrocarbons can cause PP to soften and swell;
   
  (Note: Chemical stability increases with the increase of crystallinity, which makes it suitable for manufacturing various chemical pipelines and fittings with good corrosion resistance.)

(5) Electrical Properties

• a. High-frequency insulation performance: Excellent (almost non-hygroscopic, so insulation performance is not affected by humidity);
• b. Dielectric constant: 2.0 - 2.5 (for electrical insulation products used under heating);
• c. Dielectric breakdown voltage: 40 KV/mm;
• d. Arc resistance: 130s (high static electricity, easy to age when in contact with copper).

(6) Weather Resistance

• a. Photoaging: PP is sensitive to ultraviolet (UV) rays;
• b. Thermo-oxidative aging: Heat and oxygen will accelerate the aging of PP.

2. Applications of Polypropylene

(1) Film Products: PP film products are transparent and glossy, with low permeability to water vapor and air.

• a. Blown film;
• b. Cast film (CPP - Cast Polypropylene);
• c. Biaxially oriented film (BOPP - Biaxially Oriented Polypropylene).

(2) Injection-Molded Products: Used in engineering parts for automobiles, electrical appliances, machinery, instruments, radio, textiles, national defense, etc., as well as daily necessities, turnover boxes, medical and health equipment, and building materials.

(3) Extruded Products: Can be made into pipes, profiles, monofilaments, fishing ropes, packing belts, binding ropes, woven bags, fibers, composite coatings, sheets, plates, etc. Blow-molded hollow products include various small containers, etc.

(4) Others: Low-foaming products, calcium-plastic boards, synthetic wood, laminates, synthetic paper, and high-foaming products (can be used as structural foams).

Modification of Isotactic PP (Molecular Weight: 80,000 - 150,000)

1. Adding fillers such as calcium carbonate, talc powder, and inorganic minerals can improve rigidity, hardness, heat resistance, and dimensional stability;
2. Adding glass fibers, asbestos fibers, mica, glass beads, etc., can improve tensile strength and enhance creep resistance and low-temperature impact resistance;
3. Adding elastomers and rubbers can improve impact performance, transparency, etc.;
4. Adding carbon fibers (CF) can improve strength, especially flexural modulus.

Materials and Descriptions

Notes

1. For other specifications, please contact Aote Technology Development Center;
2. Except for products with specified colors, all others can be dyed according to requirements;
3. For glass fiber-reinforced products, long fibers or chopped fibers can be selected according to requirements.