Extrusion International 2-2016

Extrusion International 2/2016

www.sp-protec.com

Versatile plant engineering for

high quality LFT compounds

ith the acquisition of PolymersNet GmbH,

Lampertheim, in late June this year, ProTec Polymer Pro-

cessing also took possession of the pultrusion plant installed

there for producing long-fibre-reinforced thermoplastics (LFT).

The plant has now been rebuilt and extended at ProTec's Ben-

sheim process and materials development technology centre

where it can also be used for carrying out specific customer

tests. A new, central component of the plant is a high-perfor-

mance compounding extruder and the plant controller has also

been designed for automated operation of all process steps.

With these new facilities, the LFT plant has restarted operation

with trials commissioned by clients; further development activi-

ties are already in the pipeline. When injection moulded, LFT

compounds with glass, steel or carbon fibre reinforcement along

the length of the pellets result in high-strength, lightweight com-

ponents which simultaneously have very good surface quality.

Any conventional thermoplastics or even biopolymers such as

PLA (polylactic acid) can be used as the matrix. "With focused

know-how along the entire LFT process chain, ProTec has es-

tablished an efficient structure for this high-performance tech-

nology. We are now a one-stop shop for our current and future

clients, offering everything from materials development to test-

ing and commissioning of a tailor-made LFT pultrusion plant. We

design plants for fibre contents of up to 60 wt.% and through-

puts of up to 1,200 kg/h, and all at a fair market price", explains

Managing Director Peter Theobald.

The new compounding extruder installed in the LFT develop-

ment plant at Bensheim with its co-rotating, 26 mm diameter

twin screws is designed for throughputs of up to 150 kg/h. In-

stalled upstream of the extruder is a SOMOS

Gramix S gravi-

metric dosing system for accurately dosing and mixing of up to

nine components. As a result, a very wide range of individual

formulations of the polymer matrix can be produced very flexi-

bly directly in the process. Recycled material and additional fillers

may likewise be included in the material formulation. The LFT

plant's impregnation die, where the fibre strands are spread

apart and enveloped with polymer melt, is designed in such a

way that, even at recycled material contents of up to 10% in

the melt, consistently high quality impregnation of the fibre fil-

aments is achieved. The various different creels required for un-

winding glass and carbon fibres in the pultrusion plant are also

available.

LFT compounds - produced by pultrusion

LFT compounds are produced by pultrusion which involves con-

tinuously drawing fibre strands through a polymer melt, so im-

pregnating the individual fibres with the polymer matrix and,

once the resultant fibre/polymer strands have cooled, pelletising

them. LFT pellets for injection moulding are conventionally

around 10 to 12 mm in length. Pellets 25 mm in length (LFT

compounds with extra-long fibres) are used for compression

mouldings. In the first impregnation process step, the fibre

strands are guided from the creels by a specially designed guide

into the impregnation die.

Downstream from the die, the hot fibre/polymer strands are then

finally shaped, for example into round strands or flat tapes, in a

profiling system. After cooling in a cooling unit appropriate for

the polymer, they pass through a puller before finally being fin-

ished. It is the puller which controls continuous operation of the

plant, the tensile force it applies to the fibre strands extending

right through the impregnation die to the point at which the

strands are unwound from the individual fibre bobbins.

The LFT plant and all its modules are operated from the central

plant controller. Controlled variables include line speed, extruder

throughput, pellet chopping length and, if required for the par-

ticular application, other up- and downstream functions of the

overall plant.

LFT pultrusion

plant at ProTec's

Bensheim

technology

centre –

designed for

developing

high-quality

long-fibre-

reinforced

compounds

with many and

varied polymer

matrices and

reinforcement

fibres (photo:

ProTec Polymer

Processing)