Recycling of Plastic Materials Part 9 ppsx

To develop this concept Himont and CSI have divided their research project into two main tasks: • to develop new advanced polypropylene materials • to promote new technologies. Although many different polymers are used in cars today, the industry tends to favor more and more polypropylene use due to a large range of properties available. Polypropylenes became standard of reference where aesthetic quality, structural properties, easy processing, and recyclability must blend harmoni- ously into the requirements of every individual item. These phenomena are il- lustrated by data in Table 5 and Figure 5. The table shows polymers employed in a car respectively in 1980 and 1990, clearly demonstrating the rapid growth of the polypropylene materials. Figure 5 shows the trend for polypropylene in various parts of a car: from 1990 to 1995, analysts predict an increase from about 22.4 kg per car to around 38.0. 130 Processing of Mixed Plastic Waste Table 5 Plastic consumption by car industry in Western Europe Material 1980 1990 Difference PP 18.0 28.2 10.2 PC 1.0 3.1 2.1 UP 4.3 6.3 2.0 PE 2.9 4.7 1.8 PA 4.6 5.5 0.9 POM/PBT 1.5 2.0 0.5 PPO 1.0 1.0 0.0 PMMA 2.9 2.4 -0.5 Others 6.9 4.9 -2.0 PU 24.5 21.2 -3.3 ABS 10.8 7.4 -3.4 PVC 21.6 13.3 -8.3 Total 100 100 Although there is an increasing interest in the use of these materials for body- work elements, the largest contribution to this growth (9.1 kg) will be from car interior components as a result of large-scale replacement of more traditional materials. CONCEPTS FOR CAR INTERIORS New developments in polyolefin-based materials have created a family of polypropylene products with a wide range of physical properties, including the abil- ity to be easily recycled. When utilized by automotive and product designers as a part of a “design for disassembly” strategy, these compatible materials will yield large sub-assemblies that can be reclaimed with a minimum of handling. 1-5 In each project, the design incorporates readily identifiable hard point connec- tions between the polypropylene components and the metal automobile subframe. This will allow personnel in recycling centers to remove these parts quickly, and in large pieces that can be completely reground and recycled. The concept presented here has been applied to car dashboards and such interior vehicle components, like floor covering,trim,anddoorpanelsaswellasbumpers. A. Vezzoli, C. A. Beretta, and M. Lamperti 131 Figure 5. Advanced materials used for vehicles. TPO BASED MATERIALS Thermoplastic Elastomers (TPE) are classes of heterophasic polymers, charac- terized by thermo-reversible interaction among the polymeric chains. The new polymeric materials that are considered to produce easy recyclable automotive systems, can be defined as a sort of a new generation of Olefinic Thermoplastic Elastomers (TPO), belonging to a broad family of polyolefinic alloys that can now be produced directly during the polymerization phase. These completely new materials, resulting from advanced research and development carried out by HIMONT, can be tailored in order to meet different requirements of most of car applications. The basic partly finished components suitable for the construc- tions of the main automotive composite structures will be described. Synthetic leather The TPO synthetic leather was produced from a resin studied to have a good processability both by extrusion, the traditionally utilized for polyolefins manufacturing, and calendering, the most employed technology in producing PVC and PVC/ABS synthetic leathers. 1 The embossing, as well as the coupling with a large variety of different layers (e.g. films, woven and non-woven structures, foams sheets) can be easily obtained in line, using traditional technologies. The thermoformability of the TPO based synthetic leather is excellent as well as the graining. Tensile strength, flexural modulus, puncture strength, scratch, and marking resistance at low, as well as at elevated temperatures, are better than those of synthetic leathers present in the market. Outdoor ageing and accelerated UV tests indicate that this material can well overcome the severe conditions produced by the tendency to increase the oblique angle of car windshield. Same characteristics of the TPO based synthetic leather are reported in the Tables 6-8. Foam sheets The technology used for the production of TPO based foam sheets cannot be fully disclosed here. The research guidelines were principally oriented to overcome some limitations in physical foaming of polypropylene, related to intrinsic rheology and kinetics of crystallization. 2 These materials present a loss of stiff- ness quite abrupt near the melting point, due to the melting of a crystalline 132 Processing of Mixed Plastic Waste dition for expansion that could be obtained only in a narrow temperature range. Hence the problem is to improve dramaticallythe strength-temperature properties near the melting point. The rate at which polymer crystallizes from melted state is the other important physical property in the foaming process. For instance, polypropylene crystallizes much slower than polyethylene. This means an increasing of the time required to build up sufficient modulus to avoid cell-wall rupture and cell-coalescence during the expansion which is a serious process limitation to overcome. The cushioning and soft-feeling propertiesrequired for some car interior applications were achieved by matrix modification as well as by the structural pa- rameters affecting the compression-deflection of the foamed material 2 (i.e. density, open cell content, cell size). A. Vezzoli, C. A. Beretta, and M. Lamperti 133 Table 6 Properties of TPO material Specific gravity Melt flow rate Flexural modulus Vicat 1 kg Hardness Shore D Elongation at break ASTM method D-1505 D-1238 D-790 D-1525 D-2240 D-639 Units g/cm 3 g/10’ MPa o C point % HIFAX CA12A 0.89 0.9 350 64 35 >350 HIFAX CA10A 0.89 0.6 70 5.5 30 >350 Table 7 UV resistance of HIFax CA12A (UV exposure in Xenotest 1200 according to ISO-4892) UV package ∆ E after aging 500 kJ 1750 kJ 2750 kJ 1 0.19 0.34 1.63 2 0.45 0.50 0.69 structure. The consequence of a rapid change in modulus is an unfavorable con- Technologies In order to obtain all TPO recyclable applications described below, different assembling techniques have been specifically studied toobtainthebasic composite structures. 3,4 The most interesting technique is one that allows to obtain simul- taneously thermoforming, embossing, and coupling in onestage operation yield- 134 Processing of Mixed Plastic Waste Figure 6. Dashboard sketch. Figure 7 Sketch of floor covering. Table 8 Fogging test for HIFax CA12A skin (transmittance measured according to DIN 75201-C) Transmittance (%) Stabilization package 1 2 HIFax CA12A black 98 97 dark grey 99 99 light gray 99 99 Plastified PVC 65-80 Plastified PVC/ABS 80-95 ing a foamed-synthetic leather bilayer on a rigid support (all TPO based) without adhesives. This process can eliminate problems of embossing distortion present in thermoforming of an embossed synthetic leather. AUTOMOTIVE APPLICATIONS Dashboard Figure 6 shows a sketch of the dashboard designed for recycling and obtained with a process based onthe previously described assembling technique. The system has three basic components, that, in the past were made of different materials; in a new design this system has been molded from TPO based polymers to provide rigidity, comfort, safety, and aesthetics. Some prototypes have been recycled following the traditional procedures for the scrap recovery of thermoplastic materials. The mechanical characteristics of the obtained materials are reported in Table 9. Floor covering The structure proposed does include a lower high density TPO based sheet, an intermediate polypropylene felt layer, and a polypropylene fiber carpet ( loop pile or cut pile ) on the top. A sketch of this component is shown in Figure 7. The recovery possibilities of the scraps from the sandwich production (about 20%) and material coming from the whole structure are the following: after passing through a mechanical mill, the material can be calendered and then processed by injection molding as well as mixed with virgin polypropylene and afterwards A. Vezzoli, C. A. Beretta, and M. Lamperti 135 Table 9 Properties of PP recycled from dashboard Method Units Recycled material Standard PP Tensile strength ASTM D638 MPa 18 22 Elongation ASTM D638 % 520 580 Flexural modulus ASTM D790 MPa 1130 2080 Charpy impact ASTM D256 MPa 3.13 3.68 cussed above, have been usefully utilized to produce the lower layer of the floor covering and have met the required specifications. The characteristics of the recycled materials are reported in Table 10. Other components All the other interior components are now being designed following this approach procedure: 136 Processing of Mixed Plastic Waste Table 10 Properties of PP recycled from floor covering Property Method Units Recycled material Tensile strength ASTM D638 MPa 8.4 Elongation ASTM D638 % 141 Hardness Shore D 6 mm/3 sec points 54 Charpy impact ASTM D256 MPa 1.84 Figure 8. Door panel prototype. extruded. Materials, obtained from sandwich samples and processed as dis- Door-panels - Polypropylene materials allow the production of integral structures of aesthetic and functional elements produced within the same family of materials. The frame and the arm-rest are obtained by injection molding of glass filled PP. Trim parts are produced in lightweight panels of thermoformed sheets which are laminated with fabrics, calendered film materials and/or carpeting. PP air ducts are also included. Figure 8 shows a prototype of a door-panel. Pillar Trim & Rear Shelf - Blow molding has been used for the pillar trim to provide the double functions of air ducting and aesthetic trimming. Finishing is provided during the molding process with an application of fabric or textured film. The support structure may be filled or unfilled types, depending on the mechanical properties required. For the rear shelf, the design presented is a vac- uum formed laminate of extruded PP and woven fabric. CONCLUSIONS • The general solution to the problem of plastic recycling at the life-end cannot be unique and some suitable approaches have been studied, depending on application sectors. • Although mixed plastics can be processed and recycled through some technologies, the use of homogeneous or compatible plastics seems to be the most suitable way to allow a direct and more profitable recycling. • Recent technological advances have made available thermoplastic families of materials that can be tailored in order to meet different requirements of each application sector. • It is possible to design automotive structures, for instance, made of the same chemical material and provide an important aid to the recycling of plastic. REFERENCES 1. J. C. Haylock, A. Addeo, and A. J. Hogan, Thermoplastic Olefins for Automotive Soft Interior Trim, SAE International Congress and Exposition, Detroit, Michigan, February 26 - March 2, 1990. 2. A. Addeo, Mechanical Energy Absorption by Plastic Foam, Sitev Forum, Geneve 15-18 May 1990. 3. A. Addeo, Novel TPE for Car Interior Trim : a PVC Replacement, TPE 90 Deaborn, Michigan, March 28-29,1990. 4. A. Addeo, New Materials for Automotive Interiors, 22nd ISATA Florence, Italy 14-18 May, 1990. 5. F. Forcucci, D. Tompkins, and D. Romanini, Automotive Interiors Design for A. Vezzoli, C. A. Beretta, and M. Lamperti 137 Recyclability, 22nd ISATA Florence, Italy 14-18 May, 1990. The Use of Recyclable Plastics in Motor Vehicles Michael E. Henstock and Klaus Seidl* The University of Nottingham, Nottingham NG7 2RD, England *BMW, Section EG-554, München, Germany INTRODUCTION In market economies recovery operations are judged on financial criteria. Thus, whether or not a discarded waste is exploited for the materials it contains depends, among other things, on the technical ease of recovery of a saleable sec- ondary product. Since industry must also consider the environmentally-sound disposal of its residuals theeaseofresiduals disposal is financially important. 1 RECOVERABLE MATERIALS IN THE MOTOR VEHICLE Discarded vehicles yield ferrous metals, aluminium, copper, lead, and zinc. However, as currently processed by shredding, they also generate a valueless fraction, containing the non-metallic detritus of seats, carpets, tyres, and other components. The historical position of steel in the automotive scrap industry emerges from data for the composite car described in the pioneering work of Dean and Sterner. 2 The recovered steel, even when contaminated with the re- sidual copper in the car, would have generated 43% of gross revenue in 1969, 60% in 1976, and 56% in 1986 at prevailing metal prices for those years. 3 PRESENT RECOVERY PRACTICE A discarded vehicle may first be stripped of resaleable parts by a salvager (wrecker) or dismantler, or it may go directly to a scrap processor, who may or may not strip such parts before processing the hulk. Until some twenty years ago processing usually took the form of compression into a cuboid or rectangular bale, known in the USA as a No. 2 bundle, and in the United Kingdom as a No. 5 bale. Sometimes, where air pollution regulations permitted, the hulk was incin- erated to remove non-metallic items, but since this step involved cost it was of- M. E. Henstock and K. Seidl 139 ten omitted. The bale, containing all the non-ferrous and non-metallic materials that it had not been worthwhile to remove, was then charged to a steelmaking furnace. Because it is impossible to inspect the interior of bales their purity is unknown and their desirability limited. Hence, this procedure is now much less common. Early in the 1960s the market was considerably disturbed by the introduction of the scrap shredder, which comminutes feed, including whole vehicles, to frag- ments some 5-20 cm in diameter. For physical and chemical reasons steel mills usually prefer shredded scrap to bales. Hence, shredded steel scrap enjoyed a rapid rise in popularity and market. The shredder generates, however, a non-metallic residue, currently worthless, whose disposal involves cost. In 1991 there is, however, increasing realization that shredding, though offer- ing financial advantages over baling so far as materials recovery is concerned, is nevertheless a noisy, energy-intensive, and self-destructive process. There is, at last, some interest in designing road vehicles to make them easier to dismantle. Ironically, far from being pleased by this prospect, some sectors of the scrap industry view with disquiet the setting up, by certain vehicle manufacturers, of in-house recycling plants. 4 CHANGES IN THE MATERIALS USED IN VEHICLES Changes in vehicle materials are made for a variety of reasons, including cost, absolute performance, lightness, (to improve fuel economy), and longevity. The magnitude of fuel savings over an estimated 174,000 km vehicle road life has been computed as 15-25 l/kg of weight saved. 5,6 Though improved engineering design may achieve weight reductions, a point is reached where further improvements may be made only through the use of light materials. Considerable effort has therefore been devoted to substitution of steel and cast iron by lighter materials, such as aluminium and polymers. Polymers are used in manufacturing for financial and technical reasons. In transport they can provide reductions in the first cost. 7 Such cost reductions are not necessarily permanent, since technological improvements and shifts in the raw materials prices continually give one material a cost advantage relative to another. Such a case isthe substitution of plated ABS for zinc-based die castings in trim. However, plastics also offer other advantages: their use can achieve sig- nificant weight savings relative to metals and, whether for this reason or for others, they may offer substantial lifetime energy savings. For example, it has been 140 The Use of Recyclable Plastics in Motor Vehicles [...]... -233 -12.11 -460 -23 .92 -565 - 29. 38 58 5.22 - 19 -1.71 -102 -9. 18 22 11 .97 58 31.55 113 61.47 0.5 0.33 -3 -1 .95 -8 -5.2 Zinc -11 -3.01 - 19 -5.21 -21 -5.76 Lead - - - - -1 -0.06 Material Steel Cast iron aluminium Red metals e Net change relative to 196 0* 2.4 -1.24 11. 89 Net change relative to 196 0** -0.86 -11. 19 -9. 55 a b c d e * ** data for 197 5 vehicle and projections for 198 0 and 199 0 from Ref.10 reference... values of materials recoverable from cars between the model years 196 0 and 199 0 Scrap values recalculated at December 197 6 prices show that probable revenues for the 198 0 and 199 0 model years exhibit a drop of around 10% compared with the 196 0 model year What is clear is that, at any reasonable set of metal prices, revenues have not kept pace with inflation Since metal prices can change significantly, particularly... improvements in its efficiency 144 The Use of Recyclable Plastics in Motor Vehicles Figure 1 Changes in recoverable metal values and labour costs for vehicles of 196 0 - 199 0 model year at April 197 6 and December 198 6 metal prices DISPOSAL OF RESIDUALS An important financial element in recycling is residue disposal, whose costs are part of the overall economics of the recovery operation Four general methods... applications By 198 5 the plastics contents of automobiles produced in various countries were 8% (Japan), 9% (USA), and 10.5% (Federal Republic of Germany) It is estimated that these figures will, by 199 5, have risen to 13%, 14.5%, and 15%, respectively, with a corresponding increase in the quantities of non-metallic waste during scrap9 ping THE EFFECTS OF MATERIALS SUBSTITUTION ON VEHICLE RECYCLING The... risen from $31 to $54, a rise of 74% on the 197 6 costs in the same period No realistic data are available for the changes in the costs of disposal of the non-metallic residues, but they are known to be rising rapidly M E Henstock and K Seidl 143 Table 1 Changes in scrap values for the 197 5 composite car and the 196 0 composite car ( 197 6 and 198 6 metal prices) 197 5 198 0 199 0 a,b c,d a,b c,d a,b c,d change... those of 2 Dean and Sterner for the 196 0 composite car However, the nominal composi10 tions derived by Roig may be used, with appropriate scrap metal values, to determine the relative value of the recoverable materials contained in 196 0, 197 5, 198 0, and 199 0 model year vehicles These changes are given in Table 1, which shows scrap value changes at metal prices obtaining in April 197 6 and December 198 6... which offer potential for reclamation as well-characterised individual polymers Some particularly complex components, such as vehicle front- and rear-end systems, exhibit special suitability for manufacture in plastics instead of metals, because of their ease of production and assembly Plastic fuel tanks are now in common use, and an investigation has been made of some possibilities for the recycling of. .. any, of fluorine on the properties of the recycled material • The results of Stage 2 were then compared with those obtained by recycling of used fuel tanks, again on a labouratory-scale, to assess the effects of ageing and exposure to and absorption of fuel; the tanks were some ten years old and had been taken from cars which had covered some 150,000 km • Stage 4 will involve the recycling of used plastic. .. has been estimated that, in the period 198 5- 199 0, only about 25% of the total quantity of plastics waste is likely to be diverted from the municipal waste stream and recycled Of this, some 27%, i.e approximately 7% of the total is likely to come from the transport sector in the United States M E Henstock and K Seidl 145 A step lower in the hierarchical use of polymers, attempts have been made to separate... of which PVC has given particular cause for concern, which release corrosive and polluting fumes Some 80 -90 % of these can be removed by suitable techniques, but the need for scrubbers may so increase the cost as to minimise any financial gain from incineration 146 The Use of Recyclable Plastics in Motor Vehicles RECYCLABLE PLASTICS COMPONENTS An alternative approach to the recovery of automotive plastics . respectively in 198 0 and 199 0, clearly demonstrating the rapid growth of the polypropylene materials. Figure 5 shows the trend for polypropylene in various parts of a car: from 199 0 to 199 5, analysts. 75201-C) Transmittance (%) Stabilization package 1 2 HIFax CA12A black 98 97 dark grey 99 99 light gray 99 99 Plastified PVC 65-80 Plastified PVC/ABS 80 -95 ing a foamed-synthetic leather bilayer on a rigid support. -5.76 Lead 1-0.06 Net change relative to 196 0* 2.4 -1.24 11. 89 Net change relative to 196 0** -0.86 -11. 19 -9. 55 a data for 197 5 vehicle and projections for 198 0 and 199 0 from Ref. 10 b reference points

Định dạng
Số trang	17
Dung lượng	546,29 KB