1. Properties of hot compacted sheets from polypropylene films or fabrics
We would like to thank our colleague Mrs. P.Bartaskova for the DSC measurements.
We acknowledge the Czech ministry of Trade & Industry and CHEMOPETROL for financial support of the project 1H-PK/39.
Conclusions:
It was found that the temperature window where the improved strength properties of oriented PP tapes (films) are still partially preserved and where the structure of PP changes only in some extend to permit the hot compacting process of such elements exists slightly above 160°C.
It was shown that the dissipation of impact energy is much higher in the hot compacted sheet than in the homogeneous PP plate of the same thickness.
Objective:
Drawn oriented fibres, tapes or films have significantly higher modulus of elasticity, strength and tensile toughness. The usual technique to produce the self-reinforced sheets is hot pressing. It is necessary to orient the reinforcing layers perpendicular each other or in more complicated schema. The main problem is to preserve the excellent properties of oriented elements and to reach a sufficient cohesion between reinforcing elements and matrix that is necessary to prevent buckling and shearing of reinforcing elements in a sheet under the transverse or compression stress. It was found that a narrow temperature window for the hot pressing exists.
Properties of hot compacted sheets from polypropylene films or fabrics
J. Kučera*, J. Sadílek
POLYMER INSTITUTE BRNO, Ltd., Tkalcovska 36/2, CZ Brno, Czech Republic,
Experimental:
PP homopolymer Mosten TB 002 (MFR = 2 g/10 min) (Unipetrol, Czech Republic)
drawn film (thickness of 200 μm, draw ratio  = 5) and drawn tapes (width of 8 mm,  = from 5 till 11) were tested
sheets were pressed by the Fontijne 400 press using a special mould at chosen temperatures near below 170°C
measured properties: tensile modulus, tensile strength, nominal tensile deformation at break, DSC scans, puncture properties
Properties of PP tapes and the effect of their annealing
Properties of self-reinforced PP sheets
Figure 2: Tensile modulus of annealed PP tapes with different draw ratio .
Figure 3: DSC scans of annealed PP tapes with the draw ratio  = 8.
Figure 4: Effect of press temperature on the energy at maximal impact force during puncture test compared with unoriented PP Mosten plate. Test temperature: 23°C.
Figure 5: Effect of press temperature on the energy at maximal impact force during puncture test compared with unoriented PP Mosten plate. Test temperature: -20°C.
Figure 6: Comparison of break of hot compacted self-reinforced PP sheet of 12 layers (on the left side) with unoriented PP Mosten plate (on the right side). Test temperature was -20°C.
Figure 1: Tensile strength and elongation at break of annealed tapes.