STUDY ON THE RECYCLING OF SOME POLYMERIC MATERIALS: MATERIALS CHARACTERISTICS; EXPERIMENTAL PROCEDURES

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1 ICAMS th International Conference on Advanced Materials and Systems STUDY ON THE RECYCLING OF SOME POLYMERIC MATERIALS: MATERIALS CHARACTERISTICS; EXPERIMENTAL PROCEDURES NICOLETA TEODORESCU 1, VIOLETA DOINA PANDELESCU (STROE) 2 1 Politehnica University of Bucharest, Mechanic and Mechatronics Engineering Faculty, Industrial Process Equipment Department 2 S.C. Rolmira S.R.L The paper presents the general recycling problems of the polymeric materials biodegradable or non-biodegradable. For this reason there were chosen two materials, one is LDPE and the other one is a new biodegradable polymeric material (which is known that can replace HDPE or/and LDPE).This part presents the physical and mechanical properties of the two materials and the experimental procedures. Keywords: recycling, biodegradable, plastics. INTRODUCTION Plastics are more difficult to recycle than metal, paper or glass. The plastics recycling process normally involves cleaning it, shredding it into flakes, than melting the flakes into pellets. The pellets are melted into a final product. Some products work best with only a small percentage of recycled content and other products can be made successfully with 100 percent recycled content. The difficulties of plastics recycling consist of their molecular architecture (molecular weight and molecular weight distribution, degree of branching) and rheological behavior. Plastics are complex rheological materials in that they exhibit both viscous and elastic (usually called viscoelastic) properties under varying conditions of stress, strain and temperature (Ştefănescu et al., 2009). Thermoplastics (at least most of them) are recyclable and reused until their degradation determine poor mechanical properties. The recycling possibilities are: - recycling to obtain new products (when the wastes must be separated in fractions of polymers with similar characteristics); - biological or thermal treatment (if the waste is mixed) in order to obtain biogas (together with other organic waste materials and/or composts) and energy recovery respectively. Mechanical recycling supposes melting and recasting in order to re-use the plastics in new products. The unavoidable quality losses are not too severe and the energy required is low, so the processing costs are reasonable. The collecting of small size parts can be limitative in terms of money. So it is unrealistic to believe that all plastic debris are mechanical recyclable. It is common accepted that ~20% of the used plastics are to be mechanical recycled. Feedstock recycling supposes the breaking down of the plastics into chemical and petrochemical feedstock (in liquid or gaseous form), which can be used in the processing of other chemical products. It is generally agreed as a more efficient procedure than mechanical recycling. About 90% of the used plastics could be recycled in this way but the prices can be limitative. Energy recovery consist in incineration and is the best choice for a number of plastic wastes varieties (including plastics with high proportion of foreign materials even those containing residues) (Teodorescu et al., 2009).

2 Study on the Recycling of Some Polymeric Materials: Materials Characteristics; Experimental Procedures To make an option for the recycling technology one studies the life circle of plastics, which begins with primary resources, continues with extraction and processing, obtained product, use of the product, continues with recycling and disposal which can damage the environment with emissions and waste. (Teodorescu et al., 2009). The recycling process needs recovery logistics from the consumers (including transportations which require on their turn the use of fossil fuels and generate air emissions). So recycling is admitted only if it requires fewer resources than can be gained by this process. There is an increasing demand to develop eco-friendly products (that means material produced from renewable resources and highly biodegradation of the product) (Teodorescu et al., 2009), such as bio-plastics. For producing a bio-plastic product only 65% of the energy consumed by producing a petroleum-based product is needed, which means that by producing only bio-plastic products we will save 35% of the energy we now waste on making traditional plastics. If we take into consideration that annual plastic products used only weights than 50 million tones we will understand why bio-plastic products are so badly needed (Thanate Tan, 2009). The use and the recycling of the polymeric products (both bio and fossil based) cause brutal modifications of the internal structure, of the physical, chemical, electrical properties which determine a significant change in flow properties at reprocessing. The type and the magnitude of the properties changing depend also on the type of chosen recycling technology. (Teodorescu et al., 2009). So it is very important to know precisely how the processing properties as well as in reuse properties are changing, needing each time a thorough experimental research, which is in our intention to pursue. In this paper we will present the main physical and mechanical properties of two polymeric materials, one is LDPE and the other one is a biodegradable polymeric material made of renewable raw materials of agricultural origin and from non genetically modified starch. THE EXPERIMENTS For the experiments a capillary rheometer (Figure 1), a scales and a PC were used. The capillary rheometer characteristics are: inner cylinder diameter D = 9,5 +0,015 mm, heated cylinder length ± mm, capillary dies dimensions L/d [mm/mm] 8/2.272 (capillary 1), 17,4/2,605 (capillary 2), 30/2.401 (capillary 3), temperature regulator scale C, weight masses 2; 2,1; 4,15 and 5,1 kg. The virgin materials were tested at 150 C, 170 C, and 180 C, than nine times recycled, without testing and at the tenth pass the materials were measured at the same temperatures and weight masses. For all recycling experiments the materials were cut approximately at the dimensions of the virgin initial pellets. To obtain the rheograms ( - ), for both materials, from the experimental measurements performed ( the average masses of the samples [kg]; t test time (cutting interval) [s] and G i weight masses [kg]) were used the relations (1) -(4) (Teodorescu et al., 2003).

3 ICAMS th International Conference on Advanced Materials and Systems a b c 1 2 d Figure 1. Capillary rheometer (Ştefănescu et al., 2009): 1 - mechanical device; 2 - automation block; a - weight; b - piston; c - heater; d - cutter p = L 4 d 32 Q d a, p = 3 v (1) (2) p = G i (3) m (4) Q v = t where the symbols are: share stress [Pa], share rate [s -1 ], Δp pressure drop [Pa], L/d capillary dies dimension, L capillary length, d die diameter, Q v flow rate, [m 3 /s]. For the experiments were used: A) a low density polyethylene grade B21/2.0 ( produced by Rompetrol Romania) which has the properties presented in Table 1.

4 Study on the Recycling of Some Polymeric Materials: Materials Characteristics; Experimental Procedures Table 1. LDPE properties (S.C. Rompetrol Petrochemicals S.R.L., 2008) Properties UM Limits Test method Appearance: - Uniform color granules without extraneous matter Visually Contamination (oxidizes and other defects) Physical Melt flow index (3) (190 C, 2,16kg) % m/m Max. 0,01 Visually /Gravimetrically g/10 min 1,8-2,20 ASTM D1238 Density (23 0 C) (1,3) g/cm 3 0,919-0,925 ASTM D792 Thermal Vicat softening temp. (1,2) (A-50 C/h-10N) Mechanical/optical properties for film (4) Tensile strength at brake (2) (23 C, v = 500 mm / min) - machine direction - cross section Elongation at brake (2) (23 C, v = 500mm / min) - machine direction C Min.90 ISO 306/A Min. 13 Min. 11 ISO 527/3 % Min. 200 ISO 527/3 - cross direction Min. 300 Haze (3) % Max. 10 ASTM D1003 Gloss,45 0(3) UL Max. 50 ASTM D2457 Slip agent content Ppm Min. 350 Own method 1) The medium value of the physical/mechanical and thermical properties is measured on the standard samples made by compression proces (ASTM D4703/C) conditioned at room temperature (ISO 291) or unconditioned (performed in one our maximum from specimen output-nominal density). 2) Periodical tests 3) Batch test 4) Film thickness-0,04mm,blow up rate-1:2 Aplications: extrusion, clarity films for packages, with a good transparency. B) a biodegradable polymer Mater-Bi, grade NF803 (produced by Novamont, an Italian research company dedicated to environmental alternatives to polyethylene-based plastics) with the properties presented in table 2. Table 2. Biodegradable material, Mater-Bi NF803, properties (Novamont SpA) Properties UM Limits Method Notes Melting temperature C 110 DSC granules Melt flow index (150 C, 5kg) g/10min 3,5 ASTM D1238 Density (23 C) g/cm 3 1,27 Picnometer granules Tensile strength at MPa 25 ASTM D882 Film thickness- brake Elongation at brake % 300 ASTM D882 0,03mm Film thickness- 0,03mm

5 ICAMS th International Conference on Advanced Materials and Systems Properties UM Limits Method Notes Young module MPa 230 ASTM D882 Film thickness 0,03 mm 45 ASTM D1938 i MD Share strength 45 ASTM D1938 p MD 76 ASTM D1938 i MD 76 ASTM D1938 p MD Haze % 89 ASTM D1003 Water vapour permeability Gx30µm/m 2 x24h 700 ASTM E398 Film of 30µm, 38 0 /90%RH Mater-Bi is the first completely biodegradable and compostable bio-polymer ever invented. The processes are protected by more than 50 patents. It comes from renewable resources of agricultural origin and from non-genetically modified starch, it reduces greenhouse gas emissions, and the consumption of energy and non renewable resources, and it completes a virtuous circle: the raw materials of agricultural origin return to the earth through processes of biodegradation and composting, without releasing polluants. (Novamont SpA). This polymeric material respects the fundamental requirements of EN standard for complete biodegradation under composting conditions which are: - conversion to CO 2, water and biomass via microbial assimilation of the test material; - 90% conversion of the test polymer to CO 2 ; - same rate of biodegradation as natural materials leaves, paper, grass and food scraps; - time of biodegradation 180 days. CONCLUSIONS The NF 803 material has been used in our country since 2009 and was developed as an alternative to polyethylene-based plastics used in packaging industry. Our intention for the next paper is to know if, in the period mentioned above (180 days), the biodegradable material can be recycled and how the recycling process influence the rheological behavior of the two polymeric materials. So it is also tested, to see how rheological properties changes, the LDPE, to have a comparison possibility, to evaluate the recycling properties for both polymers. REFERENCES Novamont SpA, Scheda Tecnica Mater-Bi NF803. S.C. Rompetrol Petrochemicals S.R.L., (2008), SS 59: B21/2.0-Low Density Polyethylene Standard Specification. Ştefănescu, M.F., Teodorescu, N., Jugănaru, M.R. (2009), Ecological use of the solid olymeric wastes-case study: Plastics properties modifications in the recycling process, The second Int. Conference on Polymers Processing in Engineering, Galaţi, Romania, Oct Tan, T. (2009), Bioplastic An Altenative To Petroleum-based Plastic, available at articlesbase.com. Teodorescu, N., Ştefănescu, M.F., (2009), Ecological use of the solid polymeric wastes-quality and economic limitations, The second Int. Conference on Polymers Processing in Engineering, Galaţi, Romania, Oct Teodorescu, N. (2003), Applied Rheology. Laboratory Guidelines (in Romanian), Matrixrom.

6 Study on the Recycling of Some Polymeric Materials: Materials Characteristics; Experimental Procedures