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Combining polypropylene and natural fibre in automotive applications

News International-French

10 Feb 2011

Daimaster is a masterbatch compound that contains 40% polypropylene and 60% natural fibre (hemp). It has to be mixed with pure polypropylene during the injection/extrusion process to reach 20-60% natural fibre content in the final part. Optimum performance levels can be achieved with 30% natural fibre content for injection and 60% for extrusion.

(Published on February-March 2010 – JEC Magazine #55)

 

As an example, 50% Daimaster can be mixed with 50% polypropylene on the injection press to get a part containing 30% natural fibre. The natural fibre content and polypropylene type can be balanced to match the required specifications, and at the same time optimize cost and technical performance.

 

 

Table: Main features: toughened composite assembly adhesive.

Daimaster + Daiflex
Flexural applications

Unit

0% NF

25% NF

40% NF

40-50%
NF

Part density

ISO
1183/A

g/cm3

0,905

0,95-
1,05

0,95-
1,05

0,95-1,05

Bulk density

ISO 1183

g/cm3

     

0,25-0,30

Flexural
modulus

ISO
178

MPa

1,600

2,720

3,913

3,800-
4,800

MFI2

ISO 1133

g/10 min

55

41

31

20-25

Notched
charpy impact

ISO
179/1eA-23°

KJ/m2

3

3,1

3,5

3-5

Unnotched
charpy impact

ISO
179/1eU-23°

KJ/m2

14

13,5

15

13-15

Production
capacity

15,000 T/year

         

QA

ISO 9001

         

 

Daifa manufactures and/or supplies three standard masterbatches and four pure polypropylene materials intended for impact and flexural applications, using natural hemp fibre and polypropylene from TP and LB. This approach makes it possible to control sourcing and performance levels.

 

Customized or specific masterbatches can also be manufactured based on individual customer specifications, using other types of natural fibres such as wood, kenaf, jute, or sisal, and various plastic resins, including polypropylene, polyethylene, and PVC.

 

Main benefits

 

Using natural fibre instead of glass fibre in Daimaster brings the following benefits:

 

  • 10-30% part cost reduction due to the use of a lighter, low-cost material;
  • 10-30% weight saving, as the density of PP/GF is about 1.2 compared to about 1 for PP/NF;
  • improved performance: the flexural modulus of PP/NF is about 3,800 MPa versus 3,600 MPa for PP/GF;
  • improved dimensional stability and faster demoulding of parts;
  • processing/energy cost savings due to lower injection temperatures;
  • reduced environmental impact (lower CO2 emissions, improved eco-balance);
  • marketing arguments.

 

Focus

Located in eastern France, the Daifa group is a consortium of businesses working in the purchase, development, production, processing and marketing of plastics and plant-based raw materials for automotive processors and for the energy sector:

 

- plant-based raw materials: bales, fibres, pellets, powders, nonwoven mats, fabrics, and sandwich materials;

- plant-fibre-reinforced plastics: pellets, compounds, sheets, plates, sandwich and coated materials, thermosets and thermoplastics;

- renewable energies: biofuels and biomass power & cogeneration plants;

- project management, consulting and expertise: plant-based raw materials, automotive plastics processing, biomass plants.

 

Process specifications

Using this masterbatch compound requires adequate process specifications and only minor adaptations:

 

  • because natural fibres contain roughly 10% water, Daimaster has to be oven dried before processing to eliminate any water during the injection/extrusion process, and the user needs to ensure that the exhaust gas pipe on the injection machine is open and/or well calibrated;
  • because the size of natural fibres can vary from 1 to 2 mm, the injection tool should be designed with an injection diameter > 2 mm, and no filter should be used in the injection press;
  • because natural fibres are plant materials, heating/injection temperatures should be set to 190°C to avoid burning or melting; for example, injection temperatures of 210°C will result in more exhaust gas, burning, melt and lower mechanical properties;
  • because the bulk density of the Daimaster compound is twice as low as a pure compound (0.25 g/cm³ versus 0.52 g/cm³), the feed hopper on the injection press has to be equipped with a vibration or gravimetric system to ensure a steady flow.