Ordinary PP can not foam it? High melt strength PP characteristics, application of large resolution!

In the past 50 years, amorphous polymers such as polyurethane (PU), polystyrene (PS), and polyvinyl chloride (PVC) have been used in the field of foaming. PP is one of the five general-purpose plastics, the amount of which is second only to PE. Material engineers can not help but wonder: Can ordinary PP foam?

the answer is negative. Reasons to look down:

First, why do you need high melt strength PP?

The microstructure of PP is a linear semi-crystalline structure, and the polymer of this structure lacks the stretch rheological properties that should be obtained in a homogeneous, controllable cell structure during the melt foaming process. In other words, the melt viscosity of PP varies with temperature, and a temperature difference of 5 °C may bring about an uncontrollable change in melt viscosity. In addition, the melt strength of PP is small and the expansion ratio is limited.

In the process of plastic foaming, it is required that the cells are not broken and the foaming rate is large; in the hot forming process, the parison is not required to be deformed; in the blown film process, the bubble is required not to sag. PP (polypropylene) is limited in these three application fields due to its low melt strength!

1. How to increase the melt strength of PP?

In this context HMSPP (High Melt Strength PP) came into being. In recent years, Sinopec Zhenhai Refining & Chemical Co., Ltd. has cooperated with the Beijing Chemical Industry Research Institute to develop and produce high melt strength PP grades of HMS20Z and E02ES that can solve the problem of ordinary PP foaming. Here we take HMS20Z as an example to talk about the characteristics and applications of high melt strength PP.

Compared with ordinary PP, the melt strength of HMSPP is obviously improved. How does the material engineer increase the melt strength of PP? From the molecular level, there are three main methods:

1) increase the molecular weight;

2) Widen the molecular weight distribution;

3) Increase the long-chain branch structure.

The melt strength is: Sinopec homopolymeric high melt strength PP (HMS 20Z)> imported HMS PP> common PP.

Comparison of Weight Average Molecular Weight Distribution of Sinopec Homogeneous High Melt Strength PP (HMS 20Z) and Common PP

Compared with ordinary PP, Sinopec's HMS 20Z has a wider molecular weight distribution.

2. What are the preparation methods for HMSPP (High Melt Viscosity PP)?

1) High-energy radiation;

2) reactive extrusion;

3) Blending method;

4) Polymerization method.

3. High Melt Strength PP Domestic Development

At present, the domestic use of radiation grafting, reactive extrusion and blending prepared.

Major research institutes in China: Beijing Chemical Research Institute, Institute of Chemistry, Chinese Academy of Sciences, East China University of Science and Technology, South China University of Technology, Changchun Institute of Applied Chemistry, Qingdao University, Zhejiang University, etc.

Second, the main application areas of HMSPP

1.PP foam

1) Advantages of HMSPP in Foam Plastics

â—† Excellent shock absorption (buffering performance);

â—† Excellent heat resistance, thermal insulation and transportability at low temperatures;

â—† Surface protection (semi-rigid, maintaining a certain strength, toughness and plasticity, can provide better surface protection for transport products);

â—† Good oil resistance and chemical resistance;

â—† recyclable and easily degradable - "green" foams.

2) Application examples

Buffered packaging, food packaging, thermal insulation, automotive, construction, sports leisure and industrial applications.

2.PP thermoforming products

HMSPP thermoforming products include:

Packaging materials: food trays, lunch boxes, cups, microwave containers, etc.;

Large containers and shells: storage tanks, bathtubs, home appliances, etc.

Automotive supplies: car roofs, car dashboards, car supports, seats, etc.

3. Extrusion sheet

HMSPP extruded sheet has the features of light weight, uniform thickness, smooth surface, good heat resistance, high mechanical strength, excellent chemical stability, electrical insulation, non-toxicity, etc. The use temperature can reach 100 °C .

HMSPP board is widely used in chemical containers, machinery, electronics, electrical appliances, food packaging, medicine, decoration and water treatment.

4. Blow blow molding

HMSPP has a higher melt strength and draw ratio. In blow molding, whether it is a film product or a large hollow product, it has a wider processing window, and the product should not be broken during the stretch blow molding process, and the shape is kept good.

5. Blown film

HMSPP blown film has the following advantages:

1) High stiffness;

2) Good temperature resistance;

3) high gloss;

4) Excellent printing performance.

Third, foreign HMSPP

The main commercial grade

Lyondellbasell (Himont, Montell): The main brands are RS1684, ProfaxPF-611, PF-613, SD-613, etc.;

Borealis: Developed PP long-chain branching technology in 1996. The products include Daploy series products such as WB130HMS, WB135HMS, WB140HMS, WB180HMS, WB260HMS and SF203HMS.

Honam Petrochemical: SEP-550, SEP-740, SEP-750;

Chisso, Japan: Newstren series products for large blow molding products, Newfoamer for foam products;

Dow Chemical: Inspire series HMS products for blown film, sheet, profile;

Samsung Chemical Company: HMS200F, HM200S, BM200 and RM200X;

Other companies: ExxonMobil, Rexene, Quantum, AkzoNobel, Hunts-man, etc.

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