Biomedical Engineering Reference
In-Depth Information
The admixture of lyocell fibers as a force elongation modifier for kenaf fiber rein-
forced PLA composites as well as the optimization of the processing parameters and
the use of lignin as a kind of natural additive for improved fiber/matrix interactions
will be described in the present chapter. The study is focused on compression molded
lyocell and kenaf fiber reinforced PLA composites.
materials aNd methods
Fibers and matrix
For the composite production regenerated cellulose fibers (lyocell) provided by the
Lenzing AG (Lenzing, Austria) with different fineness values (1.3, 3.3, 6.7, and 15.0
dtex) and yield retted kenaf fibers (Holstein Flachs, Mielsdorf, Germany) were used
as reinforcements. As matrix PLA fibers (Ingeo fibers, type SLN 2660D (Far Eastern
Textile Ltd., Taipai, Taiwan)) with a fiber fineness of 6.7 dtex and a density of 1.24 g/
cm³ (produced from a Nature Works PLA type 6202D; Cargill Dow LLC, Minnetonka,
Minnesota, USA) were used. The PLA and cellulose fibers were mixed during the
carding process with 20 and 40 mass% reinforcing fibers.
Fiber Characteristics
Fibers and fiber bundles were tested for their tensile characteristics and width values.
Prior to the investigations the fibers were conditioned for at least 24 hr in a standard
climate at 20°C and 65% relative humidity according to DIN EN ISO 139.
The tensile characteristics of single elements (single lyocell fibers and single
kenaf fiber bundles) were tested by a testing instrument Fafegraph M (Textechno,
Mönchengladbach, Germany) working with a load cell of 100 cN (lyocell fibers) and
10,000 cN (kenaf fiber bundles), respectively. Fibers and bundles were clamped into
clamps covered with PVC under a pressure of approximate 3-4 bar under a preload of
200 mg. They were tested at a gauge length of 3.2 mm with a testing speed of 2 mm/
min. At least 80 single elements were tested per sample.
For the investigation of the fiber width the Fiber shape image analyzing system
was choosen. The elements were distributed on a slide frame (40 x 40 mm², glass
width of 2 mm; company Gepe, Zug, Switzerland). Four slide frames were prepared
per sample and scanned with a Canoscan scanner FS 2710 (Canon, New York, USA) at
a resolution of 4,000 dpi. The images were analyzed with the image analysis software
Fiber shape 4.1 (IST AG, Vilters, Switzerland). The evaluation was done with an IW-
TO-wool calibrated measuring mask based on a standard long-fiber measuring mask.
Composite Production
To investigate the influence of the kind of semi finished product composites were pro-
duced from multilayer webs or needle felts. Multilayer webs were produced by using
a lab roller card (company Anton Guillot, Aachen, Germany) with a working width
of 30 cm. The fibers were oriented predominantly in length direction to the machine
direction (MD). The area weight per unit of the multilayer webs used for composite
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