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What are long fiber thermoplastics (LFT)?

What are long fiber thermoplastics (LFT)?

Long-fiber-reinforced thermoplastics (LFT) are pioneers and enablers. For new ways of thinking, new designs, new components; for breaking down classic manufacturing thought patterns; for opening up new design freedom and thus ultimately for gaining degrees of freedom. The pivot, or rather the art, for the material developer is to ensure that as many long fibers as possible are incorporated into the injection molded part. From the initial state as granules, through processing in the mold, and into the component. Only then can LFT develop their advantages to the full extent.

LFTs performance spectrum begins where other materials - such as short-fiber-reinforced thermoplastics or metals like steel, aluminum or magnesium alloys - simply reach their performance limits. This is where LFT strengths clearly come into play in a wide variety of components:

  • High strength and stiffness
  • Low creep tendency
  • Better surface quality
  • Lower shrinkage and thus less warpage and higher dimensional stability
  • Extremely high impact strength/energy absorption (especially also in the low-temperature range)

Long-fiber thermoplastics: For components at the highest plastic level.

The first step in achieving optimum material performance in the component is the creation of an intimate bond between the polymer and the fiber, which must not ignore other additives. This is a downright elaborate art form that goes very far beyond "mixing, melting and cutting together." This birthing process - the combination/compounding of polymer and fiber - plays a decisive role in the entire further material development process as well as in the subsequent manufacturing process.

It is then important to transport this fiber length as well as possible into the component.... If this is not successful, the actual "LFT advantage" is lost and the long-fiber thermoplastic partially falls back to the performance of a short-fiber-reinforced material - this is then immediately recognizable, especially in terms of impact strength.

For this purpose, it is necessary to consider the entire process chain and, if possible, to adapt or optimize it. From article and tool design to machine equipment and processing parameters such as temperatures, speeds, pressures and velocities.


Maintaining the length of the LFT into the component is an art in itself.

This consideration and adaptation may sound complex and costly to the ears of one or the other product developer, mold maker or processor - but for a material developer such as LEHVOSS, it is part and parcel of its consulting services. This is the only way to ensure that long-fiber thermoplastics can develop their full performance potential. This applies both to the component itself and to processing, which is often much easier on machines and tools than processing short-fiber-reinforced thermoplastics.


The result of application-specific material development: specially modified, customized high-performance long-fiber thermoplastics.

By formulating the polymer, fiber type, fiber length, additive (such as PTFE) and fiber content to meet specific requirements, LFT achieve a level of performance that is impressive thanks to a number of features. They score particularly well against their "little brothers and sisters", the short fiber thermoplastics (sFT):

  • For example, when high relaxation resistance (creep resistance) is required, LFT can close the technical gap compared to sFT.
  • LFT are less critical when components with thick walls or large wall thickness variations are to be realized. The risk of voids and sink marks is significantly lower compared to sFT.
  • The filling behavior of LFT is generally more favorable compared to sFT, since the filling pressure and the holding pressure can be better directed through the melt.
  • In general, LFT components exhibit lower anisotropy compared to sFT.
  • In addition, LFTs exhibit an impact strength that cannot be achieved with commercially available sFT (exception: LUVOCOM XCF).

In addition, there are other strengths - brought to the point here:

  • Better surface quality
  • Good dyeability
  • Less warpage and higher dimensional stability
  • Isotropy
  • Less shrinkage
  • Better fatigue behavior
  • Better shielding (with carbon or steel fibers)

Conclusion: LFT increase component performance and reduce machine load at the same time

With LFT, technical and economic boundaries can be pushed and redefined. If you have a material developer on your side who has the know-how, the intuition and the experience needed to break new ground constructively. Who is able to raise the topic of long-fiber thermoplastics to a whole new level by means of his consulting services and can thus also design and anchor a whole new perspective for the use of LFT. LEHVOSS material developers can do just that.

Go directly into the subject matter here and find out more in our whitepaper:

Download: Structural applications and  metal replacements (PDF)