>The assignments of the spectra, the evaluation of triad distribution and the composition were made according to Kakugo (“Carbon-13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-titanium trichloride-diethylaluminum chloride” M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equations:

$\begin{matrix} PPP = 100 T_{ββ} / S & PPE = 100 T_{βδ} / S & EPE = 100 T_{δδ} / S \end{matrix}$

$\begin{matrix} PEP = 100 S_{ββ} / S & PEE = 100 S_{βδ} / S & EEE = 100 (0.25 S_{γδ} + 0.5 S_{δδ}) / S \end{matrix}$

$S = T_{ββ} + T_{βδ} + T_{δδ} + S_{ββ} + S_{βδ} + 0.25 S_{γδ} + 0.5 S_{δδ}$

The molar percentage of ethylene content was evaluated using the following equation:

$E % mol = 100 * [PEP + PEE + EEE]$

The weight percentage of ethylene content was evaluated using the following equation:

$E % wt . = \frac{100 * E % mol * {MW}_{E}}{E % mol * {MW}_{E +} P % mol * {MW}_{P}}$

where P % mol is the molar percentage of propylene content, while MWE and MWp are the molecular weights of ethylene and propylene, respectively.

The product of reactivity ratio r₁r₂was calculated according to Carman (C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977; 10, 536) as:

$r_{1} r_{2} = 1 + (\frac{EEE + PEE}{PEP} + 1) - (\frac{P}{E} + 1) {(\frac{EEE + PEE}{PEP} + 1)}^{0.5}$

The tacticity of Propylene sequences was calculated as mm content from the ratio of the PPP mmT_ββ(28.90-29.65 ppm) and the whole T_ββ(29.80-28.37 ppm).

Melt Flow Rate (MFR)

The melt flow rate MFR of the polymer and the composition were determined according to ISO 1133-2:2011 (230° C., 2.16 kg).

Melt Temperature

The melting Temperatures were determined by differential scanning calorimetry (DSC). A sample, weighing (6±1) mg, was heated to (220±1)° C. at a rate of 10 K/min and kept at (220±1)° C. for 5 minutes in nitrogen stream. The sample was cooled at a rate of 10 K/min to (−30±1)° C. and then kept at this temperature for 10 min, thereby crystallizing the sample. Then, the sample was again fused at a temperature rise rate of 10 K/min up to (220±1)° C. The second melting scan was recorded. A thermogram was obtained. The temperatures corresponding to peaks were read. The differential scanning calorimeter used was DSC 6200 from Seiko. The data were evaluated with the software NETZSCH Proteus Thermal Analysis 6.1.0.

Mechanical Properties: Tensile Modulus, Tensile Strength, and Charpy Impact Strength

Tensile Modulus and tensile strength were measured with tensile specimens DIN EN ISO 527-2 5A according to the procedure DIN EN ISO 527:2012. The tensile test machine used was ZWICK Z005, load cell 2.5 kN, makroXtens extensiometer.

Charpy impact strength was measured with specimens DIN EN ISO 179-1/1eA according to the procedure DIN EN ISO 179-1. The impact test machine used was Zwick 5102.100/00 pendulum impact tester

The test specimens were injection molded or 3D printed.

Specimens for tensile tests according to DIN EN ISO 527-2 5A were prepared with 3D printing, namely:

- i) unidirectional specimens, or
- ii) multidirectional specimens.

Specimens for Charpy impact tests according to DIN EN ISO 179-1/1eA were prepared with 3D printing, namely:

- i) unidirectional specimens, or
- ii) multidirectional specimens.

For the unidirectional specimens i), the 3D printing was carried out with a filling pattern orientation at 0° or 90° relative to the stress (pulling/impact) direction, which corresponds with the length of the test specimens.

For the multidirectional specimens ii), each 3D printed layer was deposited with alternate filling pattern orientation at 0° and 90° as well as +45° and −45° relative to the stress direction.

The injection molded test specimens were cut from an injection molded plate of the polymer material, with the length of each test specimen oriented at 0° or 90° relative to the injection flow.

After determining the cross-sectional area, the tensile test specimens were clamped vertically and stretched to break.

The specific characteristics of the tensile tests were determined from the stress-strain diagrams obtained. The bone sized test specimens were subjected to testing at a pulling speed of up to 50 mm/min. The data were evaluated with the software TESTXPERT II V3.31. The results are listed as the mean of the tested specimen and the sample standard deviation.

After determining the cross-sectional area at the notch, the Charpy impact test specimens were fixed horizontally and impacted.

The specific characteristics of the impact test were determined from the dissipated energy. The results are listed as the mean of the tested specimen and the sample standard deviation.

Warpage

Warpage of printed objects was quantified by printing objects adapted from M. Spoerk et al. Macromol. Mater. Eng. 2017, 302, 1700143. as shown in FIG. 1 using a printing speed of 40 mm/s. The other printing conditions are reported in Table 3. The direction of the linear infill pattern was alternating +45° layer by layer, wherein +45° indicates that the infill strands were oriented in parallel to the diagonal between corner 1 and corner 3 (see FIGS. 1) and −45° indicates that the infill strands were oriented perpendicular to the infill strands of +45°. The first layer that adhered to the build plate had the infill orientation +45°.

After the print finished, the warpage specimens were removed from the build plate and tempered at (80±5)° C. in vacuum for (24÷1) hours.

After cooling the warpage specimen down, the warpage specimen was fixed to the ground at a horizontal distance of 2 mm from corner 1 with a 2 mm diameter rod as illustrated in FIG. 2.

The warpage height h, that is, the distance between the ground and the lower edge of corner 3 (FIG. 2) which was diagonal to the fixed corner 1, was measured for each warpage specimen.

Afterwards, corner 1 and corner 3 were fixed to the ground and the length of the diagonal d between the edges of corner 1 and corner 3 were measured.

The warpage (unit: %) was calculated using the following equation:

$Warpage [%] = \frac{warpage heigth h}{length of diagonal d} \cdot 100 %$

Five specimens were printed and measured for each material composition. The results are listed as the mean of the tested specimen and the sample standard deviation.

Surface Quality

The surface quality was measured using a profilometer μSCAN SELECT from NANOFOCUS. The surface roughness was determined according to DIN EN ISO 4287:2010-07 quantified by the maximum height of the roughness profile R_zand the arithmetic mean deviation of the roughness profile R_aand according to DIN EN ISO 25178 quantified by the maximum height of the roughness profile S_zand the arithmetic mean deviation of the roughness profile S_a. The total measured surface area was 10×10 mm², using a sampling frequency of 300 Hz and a step width of 20 μm.

For each material, the surface of one side wall of a cube of edge length 50 mm was measured. The cube was printed using a printing speed of 40 mm/s. The other printing conditions are reported in Table 3.

The side wall was oriented perpendicular to the build plate.

Propylene Polymer Composition (1)

Propylene composition (1) was prepared by compounding the following materials: 37 wt. % of component A); 14 wt. % of component B); 5 wt. % of component C); 14 wt. % of component D); 26 wt. % of component E); 1 wt. % of component F); and 3 wt. % additives and pigments.

Component A) was HX CA 7201 heterophasic propylene copolymer, containing 52 wt. % of propylene homopolymer; 26 wt. % of ethylene 1-butene copolymer (55:45); and 22 wt. % of propylene ethylene copolymer (46:54), and having a MFR of 12 g/10 min (ASTM D 1238-13 230° C./2.16 Kg, equivalent to ISO 1133). HX CA 7201 heterophasic propylene copolymer was commercially available from LyondellBasell.

Component B) was MC MF650Y propylene homopolymer, having an MFR of 2000 g/10 min and a soluble xylene at 25° C. fraction lower than 5 wt. %. MC MF650Y propylene homopolymer was commercially available from LyondellBasell.

Component C) was KRATON G 1657 styrene-ethylene/butylene-styrene block copolymer, having a polystyrene content of 13 wt. % and a shore A (10 s) measured according to ASTM 2240 of 47. KRATON G 1657 styrene-ethylene/butylene-styrene block copolymer was commercially available from Kraton Polymers U.S. LLC (Houston, Texas).

Component D) was ENGAGE 7467, having density of 0.862 g/cm³according to method ASTM D 792-08, MFR of 1.2 g/10 min (ASTM D 1238-13 190° C./2.16 kg, equivalent to ISO 1133), and hardness Shore A (ASTM D-2240-15) of 52. ENGAGE 7467 was commercially available from The Dow Chemical Co. Ltd.

Component E) was DS 2200-10P glass fibers, having a diameter of 10 μm. DS 2200-10P glass fibers were commercially available from Binani 3B The Fibreglass Company.

Component F) was Polybond 3200 maleic anhydride grafted polypropylene. Polybond 3200 maleic anhydride grafted polypropylene was commercially available from Crompton.

The compounding was carried out on a Leistritz twin-screw extruder with a screw diameter of 50 mm. The parameters used are summarized in Table 1 below.

TABLE 1

Parameters for compounding propylene polymer

composition (I) for further processing

Parameter
Value

T_{Zone 1}/° C.
180

T_{Zone 2-9}/° C.
200

T_{Zone 10}/° C.
210

Revolutions/Number/min
365

Feed Rate/kg/h
80

The resulting composition has a melt flow rate of 11 g/10 min (230° C./2.16 kg) and a melting point of 163° C.

Comparative Composition 1 (CM1)

Comparative composition 1 was MOPLEN 2000HEXP ethylene propylene copolymer, filled with 25% by weight with glass fibers having an average length lower than 200 μm. MOPLEN 2000HEXP ethylene propylene copolymer was commercially available from LyondellBasell. The resulting composition had a melt flow rate of 15 g/10 min (230° C./2.16 kg) and a melting point of 165° C.

Comparative Composition 2 (CM2)

Comparative composition 2 (CM2) was INNOFIL3D PPGF30 filament of diameter 2.85 mm. The filament was commercially available from BASF. Innofil3D polypropylene homopolymer was filled with 30% by weight of glass fibers, having a melt flow rate of 7 g/10 min. (230° C./2.16 kg) and a melting point of 166° C.

Filament Extrusion

The filament for 3D printing from the polypropylene composition (I) and the comparison material (CM 1) was produced from granules on a twin-screw extruder COLLIN TEACH-LINE™ ZK 25T with a round die (3.00 mm diameter;). The extruded polymer strand was withdrawn, water cooled and rolled up on printer coils. The parameters used are listed in Table 2 below.

TABLE 2

propylene polymer composition (I):
CM1:

Parameter
Value
Value

T_{Zone 1}/° C.
190
180

T_{Zone 2}/° C.
190
180

T_{Zone 3}/° C.
180
170

T_{Zone 4}/° C.
175
160

Revolutions/Number/min
38
55

Feed Rate/kg/h
2.0
2.0

Output/mm/s
57
58

FFF (Fused Filament Fabrication) 3D Printing

All FFF printed parts were produced with an Ultimaker S5 FFF printer using 100% infill and a nozzle of 0.5 mm diameter leading to a line width of 0.48 mm. The layer thickness for the analysis of warpage and mechanical properties was 0.2 mm while, for surface quality analysis, the layer thickness was 0.1 mm. For surface quality analysis, a printing speed of 40 mm/s was used for the propylene polymer composition (I) and the comparison materials 1 and 2.

TABLE 3

Polypropylene

Material
composition (I)
CM1
CM2

Build plate
glass + Dimafix
PP adhesive tape
PP adhesive tape

material

(“Scotch Extreme”)
(“Scotch Extreme”)

Nozzle
0.5
0.5
0.5

diameter [mm]

Line width
0.48
0.48
0.48

[mm]

Wall
1.44 (for surface
1.44 (for surface
1.44 (for surface

thickness
quality measurements)
quality measurements)
quality measurements)

[mm]
0.48 (for mechanical
0.48 (for mechanical
0.48 (for mechanical

properties
properties
properties

measurements)
measurements)
measurements)

Layer height
0.2 (0.1 for surface
0.2 (0.1 for surface
0.2 (0.1 for surface

[mm]
analysis)
analysis)
analysis)

Nozzle
220
240
240

temperature

1^stlayer [° C.]

Nozzle
220
240
240

temperature

other layers [° C.]

Build plate
100
100
30

temperature [° C.]

Infill [100]
100
100
100

Printer speed
40 (for surface quality
40 (for surface quality
40 (for surface quality

[mm/s]
measurements)
measurements)
measurements)

25, 40, 100, or 150 (for
40 or 100 (for
40 or 100 (for

mechanical properties
mechanical properties
mechanical properties

measurements)
measurements)
measurements)

Infill pattern
lines
lines
lines

Printed build plate
no
no
no

adhesion

(Raft, Brim, etc.)

Injection Molding

Injection molding of plates for tensile specimen DIN EN ISO 527-2 5A was performed on an injection molding system DEMAG 160 at 220° C., injection speed of 11 mm/s, 90 bar, and 30 s of holding pressure. The mold temperature was 30° C. The tensile specimen DIN EN ISO 527-2 5A were milled from the plates in parallel) (0° or perpendicular) (90° relative to the injection flow.

Injection molding of plates for impact specimen DIN EN ISO 179-1/1eA was performed on an injection molding system KRAUSS MAFFEI 110 at 220° C., injection speed of 13 mm/s, 90 bar, and 15 s of holding pressure. The mold temperature was 40° C. The impact specimen DIN EN ISO 179-1/1eA were milled from the plates parallel) (0° or perpendicular) (90° relative to the injection flow.

Mechanical Characterization Test Results

The filament of propylene composition (I) used for producing sample was compared with injection-molded sample. The results of the tests are reported in Table 4.

TABLE 4

Printing/

injection

orientation

relative
Mechanical properties

Printing
to stress
Tensile
Tensile
Impact

speed
test
Modulus
strength
strength

Example
Process
[mm/s]
direction
[MPa]
[MPa]
[kJ/m²]

1
FFF
25
0°
2460 ± 50
29.4 ± 0.4
36.7 ± 1.0

unidirectional

2
FFF
25
90°
1020 ± 50
15.3 ± 0.2
17.4 ± 1.0

unidirectional

3
FFF
40
0°
2500 ± 40
30.3 ± 0.4
38.9 ± 0.7

unidirectional

4
FFF
40
90°
1010 ± 30
18.3 ± 0.3
18.3 ± 0.9

unidirectional

5
FFF
100
0°
2370 ± 30
29.2 ± 0.2
37.0 ± 1.2

unidirectional

6
FFF
100
90°
940 ± 30
16.3 ± 0.2
17.2 ± 0.4

unidirectional

7
FFF
150
0°
2280 ± 40
26.5 ± 0.3
34.7 ± 1.2

unidirectional

8
FFF
150
90°
890 ± 30
16.1 ± 0.3
16.9 ± 0.4