Clear distinctions: homopolymer PP, random copolymer PP, and block copolymer PP.

I. Conceptual Distinction

Copolymer polypropylene is a broad category, which is divided into Random copolymer polypropylene (PPR) 、 Block (impact‑resistant) copolymer polypropylene (Block PP, e.g., BI303, PP309) ; The term “copolymerized PP” as used orally generally refers to random copolymerized PP, and the two exhibit significantly different properties; there is also polypropylene produced by pure propylene polymerization. Homopolymer PP (PPH, e.g., 707) 。

1. Random copolymer polypropylene (PPR) : Ethylene randomly inserts into the PP molecular chain, enhancing transparency and toughness, but it disrupts crystallinity, leading to a significant reduction in Vicat softening temperature and heat resistance.
2. Block (impact-modified) copolymer PP : The molecular structure consists of a PP hard‑segment matrix and soft ethylene–propylene rubber particles; ethylene is present only within the rubber particles and does not disrupt the crystallinity of the PP main chain. While retaining high heat resistance and impact toughness. 。
3. Homopolymer PP : Lacks ethylene units; exhibits the highest melting point and Vicat softening temperature, but is highly brittle, with films prone to cracking.

II. Key Physical Properties & Compatibility with Self-Adhesive Films

III. Procurement Traps and Key Identification Points

Raw-material vendor sales pitch trap: They claim “copolymerized PP, heat‑resistant,” but in most cases it’s actually random copolymerized PP. When subjected to baking at 130°C, the film softens, shrinks, and wrinkles, rendering its heat resistance ineffective.

Three key points to identify:

1. Written clarification: Block PP / Impact Copolymer PP ；
2. Physical property index: Vicat VST (A50, 50N) ≥ 128℃ ；
3. Avoid vague descriptions: Simply stating “copolymerized PP” or “transparent copolymerized PP” essentially refers to random‑copolymerized polypropylene.

Mandatory Procurement Requirements (can be copied directly)

Core layer PP: block (impact‑resistant) copolymer polypropylene, designated as Block PP; random copolymer PPR is strictly prohibited as a substitute; acceptance criteria: Vicat softening temperature VST (A50, 50 N) ≥ 128°C.

Selection Logic for High-Temperature-Resistant Self-Adhesive Films on the Fourth and Fifth Floors

1. C Heat-resistant core layer : Use block copolymer PP (BI303), which balances 130°C heat resistance with toughness, ensuring no deformation at high temperatures and no cracking under bending; absolutely prohibit the use of random copolymer PP as a substitute.
2. A adhesive layer : Add PP309 (a block‑type impact‑modified polypropylene), prioritizing compatibility with SEBS and avoiding the need to pursue high heat resistance.

V. Key Knowledge Points on Ethylene Composition

1. Block copolymer PP Contains ethylene However, all the ethylene remains within the EPDM rubber dispersed particles and does not penetrate the PP crystalline backbone, so the matrix crystallinity is unaffected and the heat resistance is not compromised.
2. In random copolymerization, ethylene is directly incorporated into the PP backbone, disrupting crystallinity and leading to a significant reduction in melting point and Vicat softening temperature.
3. When making purchases, don’t just look for “contains ethylene”; focus instead on the resin type and the Vicat softening point.
4. PP309 is a block‑type impact‑modified polypropylene containing an ethylene–propylene rubber phase; it exhibits excellent compatibility with SEBS, resists phase separation in blends, and produces few crystallization points.

VI. Brief Communication Scripts for External Interactions

Copolymerized PP is classified into two types: random copolymer and block (impact‑resistant) copolymer. In random copolymerized PP, ethylene disrupts molecular crystallinity, resulting in poor heat resistance; Block‑impact copolymer PP: Ethylene is concentrated in the rubber particles, while maintaining high crystallinity, resulting in a material that combines excellent heat resistance with superior toughness. It is the designated core‑layer resin for 130°C‑rated high‑temperature self‑adhesive films. . When making purchases, do not rely solely on “copolymer PP”; be sure to confirm that it is block copolymer or impact‑resistant copolymer PP.