Plastic Material: PP Resin

Basic Information

Polypropylene(PP): The chemical formula of Polyoxymethylene is (C3H6)nLow density (approx. 0.89~0.91g/cm3), original color is white and translucent, lower cost than other plastic materials, recycleable, resin identification code: 5. 

PP and PE has many features in common, but PP is much easier to degraded by UV rays and heat, there are many similarities in the material properties of PE, but PP is more likely to be oxidized and degraded under the action of ultraviolet rays and heat, resulting in reduced chemical resistance. PP can be classified into 3 different kinds, PP-H, PP-R, and PP-B:

  • PP-H (Isotactic PP Homopolymeride): Also known as "Polyoxymethylene Homopolymeride", which is made with polymerization of propylene alone. It was produced earlier, and has been widely applied in daily life. There's no vinyl monomer exist in its molecular chain, thus it has higher regularity and crystallinity, yet result in brittleness, easier to break, and poorer impact resistance. PP-H has the highest crystallinity and therefore the highest hardness, tensile strength and stiffness. PP-R has a very good long-term creep strength at higher temperatures.
    Advantage: Good long-term creep strength at higher temperatures, better strength than the other two kinds.
    Disadvantage: Poorer impact resistance (more brittle), less stiffness, poor dimensional stability, and age-sensitive.
    Application:extrusion molding, blow molding, injection molding. Products such as plastic bottle, packaging strap, brush, cord/rope/lanyard, plastic woven bag, toy, microwave meal box, document folder, electronic equipment, packaging film, etc.
    How to classify: When it is burned with fire, the stretched filament is flat, because the extension is not very good, so the stretch is not long.
  • PP-R (PP Random Co-polymeride): Also known as "Polypropylene Random", which has the best characteristic among these three kinds of PP. Produced by adding in 1~4% of vinyl, heaten, pressurized, and use of catalyst. Vinyl monomer distributes randomly among the molecular chain, so it decreases the crystallinity and lower the melting point of polymer, enhance the impact resistance, aging resistance, and heat resistance. From this we can see, adding suitable amount of vinyl is able to affect the heat resistance, mechanical properties, and machining performance. In particular, the more irregular the distribution in molecular chain, the better the improvement of polypropylene properties.
    Advantage: Good comprehensive performance. The appropriate amount of vinyl monomer increases hardness, stiffness, nice heat resistance, dimensional stability, outstanding stiffness at low temperature, transparancy, glossiness, and fine appearance.
    Application: extrusion moulding, blow molding, film-grade, injection molding. Products such as tubing, infusion bottle, transparent container / housewares, one time syringe, film packaging, etc.
    How to classify: It will not turn black after burning, and because the material has better toughness, it can draw a long round wire.
  • PP-B (PP Block Co-polymeride): The vinyl content is higher than PP-R, it has 7~15% vinyl monomer generally, however, because the probability that two vinyl monomers and three monomers are connected together in PP-B is very high, the vinyl monomer only exists in the block, and the regularity of PP-H is not reduced, so it cannot improve the melting point, long-term heat resistance, and oxidation resistance by adding vinyl.
    Advantage: At room temperature and low temperature, it has great impact resistance, suitable hardness; compare with PP-R, it has less transparency and glossiness.
    Application: extrusion molding, injection molding. Products such as baby stroller, sport equipment, luggage/suitcase, paint barrel, battery box, etc.
    How to classify: After burning, it will not turn black and can pull out a long round wire.

  • Common feature of above three kinds: non-hygroscopic (only adherent moisture on the surface, not absorbed), resistant to chemical, acidity, and alkalinity, poor resistance to oxidation under high temperature.



1. Tough yet flexible, resistant to fatigue


2. Heat resistance


3. Chemical, acidity, and alkalinity resistant


4. Nice electric insulativity


5. The surface is printable, which available for wide applications, such as LOGO printing or marking warning message/sign.


6. Low density, has the lightest weight among all kinds of resins, so we can use Buoyancy Test Method to classify it with other materials.


7. Smooth surface and glossy


8. Except PP, plastic is generlly not suitable to be used for producing microwave meal box because toxic substances release.




1. Not resistant to UV rays, long-time exposure to UV rays may result in decrease of mechanical property, fading of color, cracking surface, or chalking

2. Ageing after contacted with copper

3. High shrinkage rate, approx. 1.8%-2.5%




  • Suitable molding method: extrusion molding, injection molding, blow molding, etc.
  • To improve poor resistance to UV rays: add DLTP (Dilauryl Thiodipropionate), Zinc Oxide
  • Drying before production is not necessary unless the humidity is too high, and it doesn't need too much time for drying (1~2 hours will be quite enough)


auto parts, PP fiber for industrial usages, food container (available for microwave), dining ware, water bottle/cup, bucket, trach can, paint barrel, bottle of alcohol, syringe (injector), outer case of electronic equipment, rope/lanyard/cord/webbing, paper coin of UK, Australia, and Canada, etc.


**Ji-Horng Plastic is a leading plastic injection molding manufacturer since 1986, for more information, please contact us!**