Preparation and Properties of Anti-aging Transparent Polypropylene

Polypropylene (PP) is a kind of semi-crystalline polymer, which has excellent mechanical properties and has been widely used. The α crystal form is the most common and stable crystal form in many crystal forms of PP, but the spherulite size of this crystal form is large, which leads to the poor transparency of PP. In addition, the tertiary carbon atoms in the PP chain structure are more sensitive to oxygen and easy to oxidize to form free radicals. The PP products are easy to yellowish under light or hot processing. These defects limit the application of PP in the field of transparent materials. In addition, when PP is used as packaging material, it is necessary to have excellent anti-aging property to ensure the quality of the product. So it's the same thing as improving PP transparency. It is also important to maintain the aging resistance of the materials.

At present, the method for improving the transparency of the PP is mainly to add a nucleating agent. The high-activity nucleating agent mainly comprises the substituted aryl organophosphorus acid and the sorbitol-based organic nucleating agent. Although there are a wide variety of nucleating agents on the market, it is mainly based on the penetration and enhancement of the nucleating agent. The single addition of the nucleating agent PP is not sufficient to meet the increasing demand of the transparent product, and the modified PP with a variety of additional properties has been favored by the researchers.

The effects of compound auxiliaries on the aging resistance, transparency and crystallization behavior of iPP/ nucleating agent NA-11 (NiPP) materials were studied by blending dispersants and antioxidants, and their synergistic effects on PP modification were discussed.

 

Main raw material

IPP:T30S, China Petroleum Lanzhou Petrochemical Company;

Nucleating agent: NA-11, Japan ADEKA Company;

Antioxidants: 1010,168, BASF, Germany;

Compound antioxidant: B215, BASF of Germany;

Dispersant: (EBS), purity > 95%, Suzhou Liansheng Chemical Co., Ltd.

Dispersant: polyethylene (PE) wax (CH-10), Guangzhou Shunde Yayu plastic auxiliaries factory.

 

Preparation

0.2 phr nucleating agent, 0.5 phr antioxidant, 0.1 phr dispersant and 100phr iPP granule were mixed evenly in a high speed mixer. In the twin screw extruder, the screw temperature of extruder is 170 ℃ in zone Ⅰ, 175 ℃ in zone Ⅱ, 180 ℃ in zone Ⅲ, 185 ℃ in region Ⅳ, 190 ℃ in region Ⅴ, 195 ℃ in region Ⅵ, 200 ℃ in zone Ⅶ, 215 ℃ in zone Ⅷ, and 210 ℃ in head temperature. The screw speed is 200 r / min.

The extruded iPP particles were dried in air for 48 hours. The injection process parameters were as follows: injection temperature 200190180 ℃, injection rate 95%, injection pressure 50%, cooling time 20s. The injection process parameters were as follows: injection temperature 200190180 ℃, injection rate 95%, injection pressure 50%, cooling time 20s. Injection molding standard mechanical properties samples for mechanical properties testing, injection molding transparent plate for haze testing, transparent plate size of 50 mm × 50 mm × 1 mm.

 

Properties

(1) When EBS was added as dispersant, the haze of NiPP material increased by 34.8%, which seriously affected the transparency of the material. Compared with EBS, with PE wax as dispersant, the haze of NiPP increased only 7.4%, and the mechanical properties of NiPP remained better.

(2) The three antioxidants have little effect on the crystallization properties of NiPP materials. The effect of adding antioxidant 1010 on the optical properties of NiPP was the most serious, followed by antioxidant 1010, and the composite antioxidant B215 was the least. After 35 days of hot oxygen aging, the anti-aging ability of NiPP material added with antioxidant 1010 was the best, followed by the compound antioxidant B215, and the antioxidant 1010 was the worst.

(3) the composite modifiers composed of dispersant PE wax, antioxidant B215 and organophosphate nucleating agent NA-11 can not only keep the transparent properties of NiPP materials, but also make them more transparent. NPP / PE wax / B215 has only 15.0% haze, 67.2% transmittance and 83.75% tensile strength after 35 days of hot oxygen aging. The retention rate of flexural strength and notched impact strength is 81.36% and 72.32% respectively.