Recycled polymer blends

The use of recycled urea-formaldehyde (UF) thermosets as fillers for HDPE was noted to offer promise compared to particulate inorganic fillers [1070]. The incorporation of the Zn ionomer of EAA showed modulus and strength improvements for the UF filled HDPE. 

Sheet molding compound (SMC) is comprised of a thermosetting polyester/styrene matrix with fiberglass and CaCOs reinforcement. SMC is a major volume thermoset and comprises a large waste product stream after its intended use cycle. Two methods were evaluated for reinforcement of PP  

The second method gave significantly better properties in PP composites. Reviews of recycled polymer blends can be found in [1088,1089]. 

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Reversible Phase Separation Driven by Photodimerization of Anthracene A Novel Method for Processing and Recycling Polymer Blends... 

To recycle polymer blends it is important to regenerate the morphology and to re-stabUize the ingredients. Thus, it is necessary to ... 

Recyclable polymer blends. Here, the recyclability is conditional on re-generation of morphology, by means of re-compatibilization, re-stabilization, and re-compounding. 

In the following text examples of recycled polymer blends will be given, first for the commodity, then for the engineering and specialty resin blends. Whenever possible, the methods of compatibilization and re-compatibilization should be the same. In particular, when recycling is to reproduce the original blends performance, the same compatibilization method is essential. For this reason, support of the blends manufacturer should be ascertained. 

Chemical re-stabilization of recycled material against the thermal- and light-induced degradation is essential. Addition of 0.1-0.5 wt% of a sterically hindered phenol and a phosphite at a ratio varying from 10 1 to 1 10 is recommended (Pauquet et al. 1994). For outdoor applications, hindered amine light stabilizers with UV absorbers of the benzotriazole type are to be used (Herbst et al. 1995, 1998). Examples of blends used for polymer recycling are listed in Table 1.80. For more details, see Chap. 20, Recycling Polymer Blends in this book. 

To recycle polymer blends it is important to regenerate the morphology and to restabilize the ingredients. Thus, it is necessary to provide adequate mixing, re-compatibilize and restabilize the blend. Frequently, the recycled blends should be impact modified. There are two reasons for this (i) contamination of the composition by other polymers and (ii) degradation of the usually less stable compatibilizers and impact modifiers. 

NEXAFS Microscopy of Mechanically Alloyed Blends. Mechanical alloying of polymers has the potential of becoming an alternative, novel means of prodncing and recycling polymer blends (144,146-148,150,151,158). The efficacy of snch a new method is best assessed by direct visualization of the morphology of the generated materials. 

When the heterogeneous recycled polymer blends are to be used for applications without a downcycling, the materials must show improved mechanical properties. These can be generated ascertaining fine phase dispersion and intensive interactions between the phases. The method that leads to such improvement of properties is known in polymer blends industry as compatibilization. 

Recycled polymer blends Core-shell polymers systems... 

Binary req cled polymer blends, such as recycled polyolefin-polystyrene or polyolefin-polyamides, have poor mechanical properties. It is found in these cases that to introduce styrene-hydrogenated butadiene-styrene block copolymer or maleated polyolefins, respectively, as compatibilizing agents has great benefits. These both produce finer morphologies and enhanced mechanical properties. Other additives [55 to 69] should also be included into recycled polymer blends. We describe this in detail in Section 8.4.3. 

We have previously discussed recycled polymer blends in Section 5.11 and 6.7. We noted that binary (or indeed ternary) blends involving polyethylene, polystyrene, polyvinyl chloride, polyamides, etc., have poor mechanical properties because of a lack of adhesion between the components (Section 5.11). We indicated in Section 6.7 that introducing compatibiHzing agents such as styrene-hydrogenated butadiene-styrene triblock copolymer and maleated polyolefins can enhance the mechanical properties. However, this in itself is not enough. 

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