Wheat Straw Fiber Biocomposite

Wheat straw is a biocomposite: wheat straw fiber compounded into a polypropylene matrix, typically at 20-40% fiber loading. The fiber replaces a portion of the virgin polymer and produces a matte surface with visible fiber speckle.

It is not compostable or biodegradable. The polypropylene matrix is neither, and the fiber content does not change that. Its mechanical properties also differ enough from neat PP that it is not a drop-in substitute in existing tooling.

• Composition: 20-40% of the part by weight is agricultural fiber rather than fossil-derived polymer.
• Appearance: Matte finish with visible fiber speckle.
• Mechanical properties: Lower impact strength and stiffness than neat PP.
• Color range: Limited. The fiber tints all colors warm; cool tones and true whites are not achievable.
• Thermal ceiling: The fiber scorches above approximately 200°C melt temperature.
• Moisture: Hygroscopic. Requires drying before processing.

Cosmetic jars and closures. Refillable system components. Programs specifying reduced virgin resin content.

Process: Injection molding.

Shrinkage: 1.0-1.8%, lower than neat PP because the fiber restrains the matrix.

Melt temperature: Must stay below approximately 200°C. Above that the fiber scorches, producing dark speckle and odor in the finished part.

Drying: Required. The fiber absorbs moisture in a way the PP matrix does not.

Wall thickness: Increase 10-15% over the neat PP equivalent to compensate for reduced impact strength.