evaluation of properties of injected polymer composite filled with talc ...

Transfer inovácií 32 /2015

2015

EVALUATION OF PROPERTIES OF INJECTED POLYMER COMPOSITE FILLED WITH TALC MINERAL FILLER Ing. Ľudmila Dulebová, PhD. Technical University of Kosice Faculty of Mechanical Engineering Department of Mechanical Technologies and Materials, 74 Mäsiarska St. 040 01 Košice, Slovakia e-mail: [email protected] Ing. Ph.D. Volodymyr Moravskyi National University Lviv Polytechnic Department of Plastics Engineering 12 Bandera St., 79013 Lviv, Ukraine, e-mail: [email protected] Abstract

Polymer composites are most common used among all types of composite materials. As the polymer matrix is used a wide variety of polymer materials from common types such as thermosets and thermoplastics to special engineering polymers. This paper deals about influence of talc mineral filler on final properties of composite material. Based on previous research and studies this paper summarizes the change of mechanical properties. For comparison of blends and evaluation of dispersion, Raman spectrum and SEM images were obtained. Keywords: injection moulding, talc, polypropylene, tensile test, Raman spectrometry 1. INTRODUCTION Polymeric materials due to their unique properties have been used in many industries. The products resulting from the processes of data are used in the packaging industry, automotive, pharmaceutical, construction, agriculture, technology, radio and television, chemical, aerospace, and cable and textile industries. Due to the very good processing and utility to the most commonly used materials include polyethylene (PE) of high and low density polypropylene (PP), and poly (vinyl chloride). The emergence of new fields of applications, forcing the market to improve the properties by modifying materials. In the injection moulding process, products modification can be obtained by changing the process conditions, the processing tool, but also by adding to the plastics additives. Additives include, among others, fillers, plasticizers, stabilizers, etc. The great importance in the modification of polymeric materials have fillers. Added to polymers, improve the mechanical properties, dielectric, thermal, or chemical processing. The fillers in the form of a powder, short fibers and the sections are used to obtain a moulding, and in the form of long fibers to obtain laminates.

2. FILLERS CHARACTERISTIC Fillers are called auxiliaries natural or synthetic origin, which are added to polymers to form suitable polymeric composites, typically with improved performance characteristics. Fillers according to the origin can be divided into: 

natural organic fillers ( e.g. wood flour, cellulose fibers, flax, sisal),



inorganic ( e.g. chalk, kaolin, talc, quartz, silica),



synthetic (e.g. glass fibers, carbon, graphite, glass beads). Due to the form in which fillers are divided into: 

powder fillers ( e.g. calcium carbonate, talc, barites),



fibrous fillers ( e.g. glass fibers, boron fibers). As a result of a combination of different fillers (e.g. the fibrous with powders) can be obtained further improve certain properties of the polymer composites. The biggest problem related to composite materials is connected with the processing, since due to the presence of fillers same viscosity and the elastic reaction are significantly increased, which deteriorates the processability in comparison with the processing of the polymer matrix. Reinforcing fibers are bound to crack under the influence of stress occurring during the processing of composites. Another problem is the high hardness of fillers, as a result of wear significantly increased wear of the processing machines. However, this disadvantage can be prevented by the use of liquid crystal polymers, which have an impact on the tribological nature of the processes taking place during processing. 2.1 Talc mineral filler Talc is a phyllosilicate mineral with a trioctahedral layered structure, Mg3Si4O10(OH)2. The idealized crystal structure contains a layered structure of a ‘sandwich’ of magnesium oxide (brucite-like) octahedral between tetrahedral of silica, as seen on Figure 1. This leads to a neutrally charged system, with all vacancies satisfied with no net surface charge. As a result, the lamellar platelets are only held together by Van der Waals forces, which lead to talc being the softest mineral, defined as 1 on Mohs scale. Furthermore, the main sites for chemical attack or amphiphilic reaction on the talc surface are mineralogical defects and platelet edges. Theoretical chemical composition of talc is 31.88 % MgO, 63.37 % SiO2 and 4.75 % H2O. In nature talc does not exist in its theoretical form and purity. A small fraction of the Mg and Si atoms in the

19


talc mineral can be replaced by iron (Fe), aluminum (Al), nickel (Ni) and other similar sized cations. Further when the talc ore is mined it can also include other minerals such as magnesite, dolomite, chlorite, calcite, quartz and tremolite.

2015

stabilized. Pelletized and additivated PP Moplen HF501N is suitable for injection molding. The main applications for PP Moplen HF501N are mineral filled compounds, color and additives master batches, furniture. Material PP Moplen HF501N has a wide range of approval for contact with food. The selected properties reported in Table 1 are measured on the pelletized and additivated resin. Table 1 Mechanical properties of PP Moplen HF501N Mechanical property Value 1550 MPa Tensile Modulus 35 MPa Tensile Stress at Yield >50 % Tensile Strain at Break 9% Tensile Strain at Yield 3.0 kJ/m² (23 °C) Charpy impact strength

Fig. 1 Structure of fine lamellar talc Pure talc is colorless or white, but may have a glow gray, greens or yellows. It is not irritable to the skin or eyes, and do not cause allergies. Due to the hydrophobic talc epitome easily dissolved in the polymer, e.g. PP, PE. It is a very soft mineral, prone to splitting. Can with stand temperatures up to 900ºC. Has the lowest hardness in the Mohs hardness scale greasy, soapy to the touch, running anti- static and having release. The filler is commonly used to reinforce polypropylene, which is produced by injection moulding automotive parts. In contrast, talc mixed with glass fiber is used to reinforce polyamides which are produced various parts in the automotive industry. Introduced into the thermoplastic polymers reduces their susceptibility to creep under load. The PP significantly increases the rigidity and heat resistance. The introduction of talc for floor coverings made of PVC increases the abrasion resistance.

Mechanical properties were verified by tensile test machine TiraTest 2300 according to STN ISO EN 527-1. Values σM and εM of material PP with various percentages of filler are displayed on Figure 2 and Figure 3.

Fig. 2 Values σM of material PP/talc filler

3. EXPERIMENTAL PROCEDURE 3.1 Properties of talc filled PP Influence of filler added into the basic material to the change of the mechanical properties of composite was determined by various tests performed on the samples molded on injection molding machine Demag 25-80. Polymer blends were prepared on laboratory extruder with the auger speed control system: 0 - 100 rpm and temperature in zones (4 zones of heating); screw L / D = 28. The material PP Moplen HF501N was used for the experiments with different percentages of filler in basic matrix of material 10%, 20%, 30%, 40% and 50%. Filler used in the production of the samples was Imeris Talc Luzenac A20 - Highly pure, very white talc with a high aspect ratio. With its fine grind, it is recommended for PP dashboard, interior trim and aesthetic applications. PP Moplen HF501N is a nonpelletized homopolymer powder. The product is non-

20

Fig. 3 Values εM of material PP/ talc filler For obtaining spectrum of samples, Raman spectrometer DeltaNu RapidID with NuSpec software was used. Raman scattering depends upon the polarizability of the molecules. For polarizable molecules, the incident photon energy can excite vibrational modes of the molecules, yielding scattered photons which are diminished in energy by the


amount of the vibrational transition energies. A spectral analysis of the scattered light under these circumstances will reveal spectral satellite lines below the Rayleigh scattering peak at the incident frequency. Such lines are called "Stokes lines". If there is significant excitation of vibrational excited states of the scattering molecules, then it is also possible to observe scattering at frequencies above the incident frequency as the vibrational energy is added to the incident photon energy. These lines, generally weaker, are called anti-Stokes lines. Raman scattering can also involve rotational transitions of the molecules from which the scattering occurs. Thornton and Rex picture a photon of energy slightly than the energy separation of two levels being scattered, with the excess energy released in the form of a photon of lower energy. Since this is a twophoton process, the selection rule is DJ = +/-2 for rotational Raman transitions. The Figure 4 is an idealized depiction of a Raman line produced by interaction of a photon with a diatomic molecule for which the rotational energy levels depend upon one moment of inertia. The upper electronic state of such a molecule can have different levels of rotational and vibrational energy. In this case the upper state is shown as being in rotational state J with scattering associated with an incoming photon at energy matching the J+2 state.

2015

Using Raman spectrometer DeltaNu RapidID, spectrum of pure PP Moplen HF501N was obtained. After transmission and processing at NuSpec software, spectrum curve was acquired, shown on Figure 5. For comparison, spectrum of samples PP/T10, PP/T20, PP/T30 was obtained. For processing these spectra, Baseline was set to 600. Figure 6 shows comparison of Moplen HF501N spectrum (lower line) with Moplen HF501N + 10% of Imeris Luzenac A20 - Highly pure Talc. As it is apparently, the peaks of PP and sample with addition of 10% of talc have same wavenumber, but the intensity of addition spectrum of PP/T10 sample is placed higher. Figure 7 shows comparison of PP Moplen HF501N spectrum with samples PP/T10 (addition of 10% of Imeris Luzenac A20 pure talc), PP/T20 (addition of 20% of Imeris Luzenac A20 pure talc), and PP/T30 (addition of 300% of Imeris Luzenac A20 pure talc). Structures of tested materials after tensile test were observed at SEM microscope type TESLA BS 340. Figure 8 ( magnification 250x) and Figure 9 ( magnification 1000x) shows structure of material PP/T10, while Figure 10 (magnification 250x) and Figure 11 (magnification 1000x) shows structure of material PP/T40. It is noticeable; that breach at material PP/T10 was more ductile, while at material PP/T40 was observed brittle fracture. Structures also show that dispersion of filler was at required quality, observed on SEM images.

Fig. 4 Idealized depiction of a Raman line produced by interaction of a photon with a diatomic molecule

Fig. 5 Obtained Raman spectrum of material PP Moplen HF501N with no baseline

21


2015

Fig. 6 Comparison of Moplen HF501N spectrum (lower line) with PP Moplen HF501N + 10% of Imeris Luzenac A20 - Highly pure Talc

Fig. 7 Comparison of Moplen HF501N spectrum with samples T10, T20, T30

Fig. 7 Comparison of PP Moplen HF501N spectrum with samples PP/T10, PP/T20 and PP/T30

Fig. 8 Structure of material PP/T10

22

Fig. 9 Structure of material PP/T10


2015

References

Fig. 10 Structure of material PP/ T40

Fig. 11 Structure of material PP/ T40 CONCLUSIONS Based on this research, we can conclude that talc is attractive as filler for polypropylene for several reasons. For example, it has a positive nucleation effect on PP crystallization and offers relatively high strength and stiffness. In addition, talc is an abundant, low-cost source of laminar particles. However, delamination, dispersion, and distribution of talc within the polymer and matrix-particle interface all have a significant effect on the performance of PP/talc composites. Samples filled witch talc prepared at injection molding machine Demag 25-80 showed minimum differences at tensile strength but great difference at elongation values.

1. Tor - Swiatek, A., Krasinskyi, V., Markovičová, L., Characteristic of selected physical properties of injected polimer composites. In: Technological and design aspects of extrusion and injection moulding of thermoplastic polymer composites and nanocomposites : Volume III.. Lublin 2015 p.141155. ISBN 978-83-89263-37-7. 2. Rotzinger B., Talc-filled PP: A new concept to maintain long term heat stability. Polymer Degradation and Stability. 2006, 91, 2884-2887. 3. Dobránsky J., Baron P. Kočiško M., Běhálek L., Vojnová E., Solving depressions formed during production of plastic molding, Metalurgija 2015, 3, 496-498. 4. Zweifel, H., Maier, R.D., Schiller, M., Plastics Additives Handbook. Hanser Publishing, Arnoldstein, Austria, 2009. p. 1248. ISBN 978-3466-40801-2. 5. Shammya, A. et al., Physical, optical and thermal properties of graphite and talc filler reinforced polypropylene (PP) composites. Imternational Journal of Advanced Scientific and Technical Research 2012, 5, 2, 40-49. 6. Smit, I. et al., Structuring of polypropylene matrix in composites. Polimeri 2009, 30, 4,183-192. 7. Krzyzak, A., Bondyra R.,Dulebova L.,Moravsky V., Wskażnik szybkości płynięcia kompozytów na osnowie polipropylenowej z dodatkiem ciętego włókna szklanego oraz talku. Postępy nauki i techniki. 2012, 13, 78-85. 8. Hahna T., Suena W., Kanga S, Hsu S.L., An analysis of the Raman spectrum of syndiotactic polypropylene. Polymer, 2001, 42, 13. 9. Gen D. E., Prokhorov K. A., Raman spectra of various polymorphs of isotactic polypropylene. Laser Physics 2011, 21, 1 Acknowledgment This contribution is the result of the project implementation VEGA No.1/0600/13.

23