Polypropylene Homopolymer (PP Homopolymer): Properties, Grades and Supply

PP Homopolymer as an Industrial Raw Material Category

Polypropylene homopolymer (PP homopolymer) is a thermoplastic polymer of propylene produced by stereospecific polymerisation. Unlike copolymers, the homopolymer consists only of propylene units, providing maximum stiffness, heat resistance, and chemical resistance among all PP types. It forms the basis for packaging, automotive parts, household appliances, electrical products, medical devices, and textile fibres.

The category specificity is determined by high isotacticity (up to 95-99%), providing crystallinity up to 75%. Unlike polyethylene, PP homopolymer has a higher melting point (160-170 degrees Celsius) and service heat resistance (up to 100-120 degrees Celsius), but inferior impact strength at sub-zero temperatures. This combination makes it indispensable where stiffness and heat resistance are critical.

Chemical Identification and Classification

PP homopolymer is identified by CAS number 9003-07-0 and classified under HS code 3902.10. Its density typically ranges from 0.900 to 0.910 g/cm3, lower than polyethylene. In terms of macromolecular structure, it is a linear stereoregular polymer with an isotactic configuration. By purpose, injection, extrusion, film, fibre, and pipe grades are distinguished. In Russian practice, grades are designated by numeric indices according to GOST (Russian national standard) 26996-86, such as 21020 or 21030, where the digits indicate the polymerisation method, material type, and melt flow index (MFI).

Physico-Chemical Properties

Key parameters determine PP homopolymer behaviour during processing. The crystalline melting point is 160-170 degrees Celsius, and the Vicat softening point is 150-155 degrees Celsius. The melt flow index varies widely from 0.3 to 40+ g/10 min at 230 degrees Celsius, allowing grade selection for specific methods: low MFI for extrusion, high MFI for thin-wall injection moulding.

Mechanical properties include tensile strength of 30-40 MPa and flexural modulus of 1400-1700 MPa. PP homopolymer has high chemical resistance to water, acids, alkalis, and most organic solvents, but limited resistance to strong oxidisers at elevated temperatures. Prolonged UV exposure causes photodegradation, so light stabilisers and antioxidants are added for outdoor articles. In granular form, the polymer is low-hazard and non-toxic.

Technical Grades and Supply Forms

PP homopolymer is supplied as granules 2-5 mm in size. Grades differ in MFI, additives, and purpose. Typical groups include injection grades for caps, crates, and household goods; extrusion grades for pipes, sheets, and films; fibre grades for nonwovens (spunbond); and specialty grades. Standard supply forms include 25 kg bags, 500-1000 kg big bags, octabins, containers, and bulk tankers. Food-contact and medical grades comply with strict sanitary requirements.

Regulatory Framework

Circulation of PP homopolymer in the EAEU is regulated by TR CU 005/2011 for packaging and TR CU 021/2011 for food contact. GOST 26996-86 applies to polypropylene and propylene copolymers, establishing base grades and test methods. International standards used for control include ISO 1183 (density), ISO 1133 (MFI), ISO 306 (Vicat), and ASTM D256 (impact strength). For export supplies, quality is confirmed by certificates of conformity with the importing country requirements.

Mechanism of Action and Functional Role

In processing, PP homopolymer acts as a thermoplastic matrix that solidifies on cooling. High stereoregularity provides a crystalline structure that gives articles stiffness and heat resistance. In compounds, it acts as a carrier for antioxidants, light stabilisers, antistatics, and fillers (chalk, talc, glass fibre) to modify rigidity and cost. Impact modifiers (rubbers) are added to increase impact strength at low temperatures.

Applications by Industry

The packaging industry is the largest consumer, using PP for containers, caps, crates, pallets, and films. High heat resistance allows hot filling and sterilisation. In automotive, PP is used for bumpers, instrument panels, and battery housings. In electronics, it is used for insulation and appliance housings. In medicine, for syringes and single-use devices. In textiles, for nonwovens (spunbond) used in hygiene products.

Comparison with Alternative Materials

Compared to polyethylene, PP homopolymer offers higher stiffness and heat resistance, but lower impact strength at sub-zero temperatures. Compared to polystyrene, it is more heat-resistant but less transparent. Compared to polycarbonate, it is cheaper and lighter, but inferior in impact strength and optical clarity. Compared to ABS, it is more heat-resistant and chemically resistant, but less impact-resistant.

Common Processing Challenges and Solutions

The most frequent problems in PP processing are:

• Insufficient drying. Surface moisture causes micro-bubbles. Drying at 80-100 degrees Celsius for 2-4 hours is recommended.
• Incorrect temperature profile. Too high a temperature causes degradation; too low results in incomplete melting. Recommended melt temperature: 200-250 degrees Celsius for injection.
• Warpage and shrinkage. PP has high shrinkage (1.5-2.5%). Optimising mould temperature (60-80 degrees Celsius) and holding pressure is required.
• Extrusion instability. Grades with a narrower molecular weight distribution are recommended for pipes and sheets.

Quality Control and Laboratory Methods

Quality control includes incoming granule inspection (MFI by ISO 1133, density by ISO 1183, moisture, ash content) and mechanical testing (impact strength by ISO 180, flexural modulus by ISO 178, Vicat softening point). For food contact, sanitary-chemical testing is mandatory. Laboratory confirmation is a critical element of supply that reduces processor risks.

Storage, Safety, and Recycling

PP homopolymer is stored in dry rooms protected from sunlight at temperatures not exceeding 30 degrees Celsius. Shelf life is 12 months. During processing, volatile degradation products may be released, requiring ventilation. PP is recyclable and assigned recycling code 5 (PP). However, it is sensitive to thermo-oxidative degradation during repeated processing, so stabilisers should be added.

Analogue Selection and Interchangeability

The portal assists in replacing imported PP grades with technically equivalent alternatives. The algorithm includes analysing the current grade (MFI, density, impact strength), verifying certificates, and organising trial batches for testing on the customer equipment. For food contact and medical devices, supporting documents are mandatory.

Supply Scheme and Logistics

The portal organises worldwide PP homopolymer supplies. Each supply is a separate project covering grade selection, quality verification, logistics, and customs clearance. Customs clearance is supported by the portal broker, including HS code classification (3902.10) and certification.

FAQ

How does PP homopolymer differ from block copolymer?

PP homopolymer consists only of propylene units, offering maximum stiffness and heat resistance. Block copolymer contains ethylene, which improves impact strength at low temperatures but reduces stiffness.

How to choose a PP grade for injection moulding?

Focus on MFI: for thin-wall articles, 20-40 g/10 min; for thick-wall, 5-15 g/10 min. Impact strength and heat resistance are also critical.

Can an imported PP grade be replaced with an analogue?

Yes, provided key parameters match and testing confirms it. The process includes rheology analysis and trial batches.

What documents accompany a supply?

Conformity certificates, quality certificates, sanitary documents for food contact, and origin documents.

What is the recycling code for PP?

PP is assigned recycling code 5 and is recyclable.

Conclusion

PP homopolymer remains a base polymer for packaging, automotive, and medical applications. Success depends on the correct choice of grade, confirmed quality, and stable supply. The portal helps select analogues, organise logistics, and ensure transparency worldwide.

Contact Us

If you are looking for PP homopolymer granules or need advice on grade selection, analogue search and worldwide supply organisation, please contact our team at info@apptrade.ru. We will help you find the right product, verify documentation and organise supply.