Recycling of polypropylene

Although the degradation behavior is common to all polymeric materials, the effects of photooxidative and thermomechanical degradation on PP are dramatic because of the tertiary carbon present in the chain of this polymer. 

The degradation of PP occurs through the following series of reactions describing the oxidative degradation of the polyolefins  

Although this scheme explains, at least qualitatively, the degradation of polyolefins whatever external forces (heat, mechanical stress, ultraviolet radiation, etc.) act on the pol5uner, some of the reactions are more 

As already mentioned, the dramatic reduction of the properties of the recycled PP is due to the easy degradation of this polymer not only during its lifetime, but mostly during the reprocessing operations. By adding suitable stabilizers (re- or post-stabilization) the degradation kinetics can be slowed down and the mechanical properties retained even after many recycling steps [3-5]. 

La Mantia, F.P. (1996) Basic concepts on the recycling of homogeneous and heterogeneous plastics, in Recycling of PVC and Mixed Plastics, (ed. F.P. La Mantia), ChemTec, Toronto, pp. 63-76. 

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A related situation we ll call piggyback markets. By this we mean industries in which extensive recycling exists for some material other than polymers, but in which polymers are easily separated for recycle as well. We earlier mentioned the recycling of polypropylene battery cases. Infrastructure was already in place to recover valuable lead metal from the electrodes. It was easy to also recover the plastic cases when polymer recycling became feasible. Table 9-3 summarizes a few examples. 

S. C. Cardona and A. Corma, Tertiary recycling of polypropylene by catalytic cracking in a semibatch stirred reactor. Use of spent equilibrium FCC commercial catalyst, Appl. Catal. B Env., 25, 151 (2000). 

Recycling of Polypropylene. At its Knapsack site, Hoechst has erected a recycling plant for polypropylene with a capacity of 5 000 t/a of PP recyclate (Fig. 120). Recycling makes it possible to start with pure PP fractions from used parts (such as those from automobiles) and modify them into typeware. The material must be collected, ground, and sorted on a decentralized basis. The ground recycled parts are mixed with virgin PP powder, additives, and reinforcements, processed in an extruder, and thus converted to products that meet the required specifications [253]. 

Pfaflf, R. 1990. Material recycling of polypropylene fi-om automotive batteries—process and... 

PlalF, R. 1990. Material recycling of polypropylene from automotive batteries—process and equipment. In Second International Symposium, J. H. L. Van Linden, ed., pp. 37-36. The Mineral, Metals and Materials Society, Warrendale, PA. 

Some recycling of polypropylene packaging is carried out, most often targeting bottles collected as part of an all plastic bottle collection system. Recycled resin from collected containers has been used in soap bottles. ... 

Recycling of Polypropylene and Its Blends Economic and Technology Aspects... 

R. Pfafif, Material Recycling of Polypropylene from Automotive Batteries - Process and Equipment, II Int. S5unp., Ed. van Linden, The Mineral, Metals Materials Society 1990. 

Once a consumer has purchased a material made of a polymer, the likelihood of it being recycled is dramatically reduced. In the United States there are three resins that are commonly recycled polyethylene, polypropylene, and polyethylene terephthalate, SPI (The Society of the Plastics Industry) recycling codes, found on the bottom of food containers, provide the consumer with information as to the recyclability of the material. Table 17,1 lists these codes. 

Table 7.4 Processing scraps and end-of-life wastes of polypropylene and ABS property retentions versns the recycling conditions...

Polypropylene products can be identified with the recycling symbol containing the number 5 with the letters PP underneath the symbol. Several important characteristics of polypropylene are compared to polyethylene in Table 76.1. 

Particles of polypropylene are continuously formed at low pressure in the reactor (1) in the presence of catalyst. Evaporated monomer is partially condensed and recycled. The liquid monomer with fresh propylene is sprayed onto the stirred powder bed to provide evaporative cooling. The powder is passed through a gas-lock system (2) to a second reactor (3). This acts in a similar manner to the first, except that ethylene as well as propylene is fed to the system for impact co-polymer production. The horizontal reactor makes the powder residence time distribution approach that of plug-flow. The stirred bed is well suited to handling some high ethylene co-polymers that may not flow or fluidize well. 

Application of Polypropylene Fiber and Recycled Glass in Component of Cement-Based Composite... 

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