Performance Analysis of Common Additives Used in the Development of Polypropylene (PP) Special Materials

Light stabilizer

Mechanism of actionAbsorb or block ultraviolet rays, quench excited molecules, and capture free radicals generated by ultraviolet light.

Main Types：

🔸Ultraviolet AbsorberSuch as benzophenone derivatives (UV-531) and benzotriazole derivatives (UV-326/327). Like "sunscreen," they absorb harmful ultraviolet rays and convert them into harmless heat.

🔸Hindered amine light stabilizersThis is currently the most effective and mainstream type (such as 770, 622, 944). They continuously capture free radicals through a cyclic regeneration mechanism, which is highly efficient and has good long-lasting effects.

Performance Analysis：

🔸Sensitivity of HALSSome alkaline HALS may have antagonistic effects with halogen-based flame retardants and sulfur-based auxiliary antioxidants (such as DLTDP), so careful selection is required.

🔸Thickness dependenceThe effectiveness of UVA is closely related to the thickness of the product and is more effective for thicker products; HALS is effective for both thin and thick products.

🔸 Automotive interior and exterior parts, outdoor furniture, artificial turf, canopy membranes, and other fields with high weather resistance requirements.

2. Additives for Improving Mechanical Properties

These additives directly alter the "strength and structure" of PP, which is key to achieving its high performance.

Toughening agent

Mechanism of actionBy forming "island structures" of elastomer particles in the PP matrix, silver streaks and shear bands are induced, absorbing impact energy and thereby enhancing toughness.

Main Types：POE (Polyolefin Elastomer)、EPDM (Ethylene Propylene Diene Monomer)、SEBS (Hydrogenated Styrene-Ethylene-Butylene-Styrene Block Copolymer)。

Performance Analysis：

🔸POE is mainstream.Due to its good compatibility with PP, high toughening efficiency, minimal impact on fluidity, and no gelation issues, it has become the preferred choice for PP toughening modification.

🔸Core Trade-offsThe addition of toughening agents can improve impact strength (especially low-temperature impact resistance), while...Inevitably leads to a decrease in modulus (stiffness) and thermal deformation temperature.The formulation design needs to find the optimal balance between toughness and rigidity.

🔸 Automotive bumpers, dashboards, door panels, appliance housings, high-impact packaging, etc.

Nucleating agent

Mechanism of actionProvide heterogeneous nucleation for PP melt crystallization, refine spherulite size, and increase crystallization temperature and rate.

Performance Analysis：

🔸Enhance rigidityA finer and more uniform crystal structure directly improves the material's flexural modulus and tensile strength.

🔸Increase heat distortion temperatureAs the crystallinity increases, the HDT rises accordingly.

🔸Improve transparencyWhen the grain size is smaller than the wavelength of visible light, light scattering is reduced and transparency increases.Transparent nucleating agents (such as sorbitol types)It is the key to producing high transparent PP.

🔸Shorten the forming cycle.The crystallization speed increases, allowing products to take shape more quickly and improving production efficiency.

🔸Improve surface glossRefining spherulites makes the surface of the product smoother and more even.

For parts that require rigidity, heat resistance, and appearance (high gloss or transparency), such as microwave oven door frames, transparent food containers, and thin-walled products.

Antistatic agent

Mechanism of actionBy migrating to the surface of the product, it absorbs moisture from the air to form a conductive water film, or discharges charges through its own conductivity.

Main Type：

🔸Inner additive type Glyceryl monostearate、EthoxyaminesGood persistence, but slow to take effect (requires migration time).

🔸Coating typeFast-acting but not durable, easily erased.

Performance analysis：

🔸Humidity dependenceThe effectiveness of internal antistatic agents is greatly affected by environmental humidity, and their effectiveness is reduced in dry environments.

🔸 Electronic components packaging, cleanroom supplies, mining equipment, food packaging films.

Although not exactly "additives," they are often used in conjunction with additives in specialty materials.

Talcum powder：Both as an enhancer and a nucleating agent.Significantly improve the rigidity, heat resistance, and dimensional stability of PP, making it the most common filler for automotive and home appliance applications.

Calcium carbonateMainly asIncrement agentTo reduce costs, it improves rigidity to some extent, but not as much as talc. It can enhance surface gloss.

In actual development, it is by no means simply a matter of mixing various additives. It requires a systematic consideration of the above content.

1. Synergistic and Antagonistic Effects：

Primary/secondary antioxidants, flame retardant synergistic system.

The interaction between alkaline HALS and acidic fillers/flame retardants, and certain lubricants and fillers.

2. Processing AdaptabilityThe additive system must match the processing technology (injection molding, extrusion, blow molding, etc.) to ensure good dispersibility, thermal stability, and fluidity.

3. Regulatory ComplianceFor fields such as food contact, medical use, and children's products, all additives must comply with relevant regulations (such as FDA, RoHS, REACH).

4. Balance of Cost and PerformanceUnder the premise of meeting performance requirements, optimize the formulation design to select the most cost-effective combination of additives.