Thermoset recyclate fillers

Examples of filled polymer compositions are discussed, where the role of the preparation method has been clearly identified in relation to compound structure and end properties. Particular attention is also given to recent developments in the field of natural fibre-filled composites, supercritical fluid assisted processing of filled polymers, re-use of thermoset recyclate fillers and silicate layer polymer nanocomposites. 

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. 

Although it would be desirable to recycle laminate scrap, this has been difficult because of its thermoset nature. However, a 1993 patent (18) suggested a means whereby scrap consisting of cellulose, thermoset resins, and partially reacted resins can be ground to a powder which is used as a filler in a thermoplastic resin. The filled thermoplastic resin is then used for mol ding of various articles. 

Research on the pyrolysis of thermoset plastics is less common than thermoplastic pyrolysis research. Thermosets are most often used in composite materials which contain many different components, mainly fibre reinforcement, fillers and the thermoset or polymer, which is the matrix or continuous phase. There has been interest in the application of the technology of pyrolysis to recycle composite plastics [25, 26]. Product yields of gas, oil/wax and char are complicated and misleading because of the wide variety of formulations used in the production of the composite. For example, a high amount of filler and fibre reinforcement results in a high solid residue and inevitably a reduced gas and oiFwax yield. Similarly, in many cases, the polymeric resin is a mixture of different thermosets and thermoplastics and for real-world samples, the formulation is proprietary information. Table 11.4 shows the product yield for the pyrolysis of polyurethane, polyester, polyamide and polycarbonate in a fluidized-bed pyrolysis reactor [9]. 

Unlike thermoplastics, which are simply melted, thermoset resins chemically react from low-viscosity liquids to solid materials during processing, a process termed curing. Structurally, thermosets differ from thermoplastics because of the presence of cross-links in the former, which means that thermosets cannot be reshaped or recycled once the chemical reaction occurs. One advantage of thermosets vs. thermoplastics is that wetting the filler becomes much easier with a low-viscosity material. By far the most common thermoset composite is automobile tires, which consist of a polymer made from styrene and butadiene monomers and carbon-black filler. The actual recipe used is much more complicated, and can include other monomers or polymers, as well as other fillers. In the absence of filler, the cured resin is rubbery at room temperature, which makes tires a... 

Plastics make up only about 8 percent of the volume in the average landfill but represent a huge investment of energy and raw materials. Most plastics produced from petroleum materials by polymerization of monomers such as ethylene or vinyl chloride are thermoplastic materials and can be cleaned, melted, and re-formed. Thermosetting plastics can also be cut into pieces that are mixed with other plastics or used as fillers. High-density polyethylene (HDPE) and polyethylene terephthalate (PETE) are the most widely reused plastic materials, but polyvinyl chloride (PVC), polypropylene, and polystyrene account for 5 percent of the recycled plastics. In 2001 80 million pounds (36 milfion kilograms) of plastics were recycled in the United States. Recycled plastic materials are used in the production of bottles, fabrics, flowerpots, furniture, plastic lumber, injection molded crates, and automobile parts. 

Thermosets Particle recycling 1. Use of the finely ground mass as filler 2. Use of glass fibers in reinforced masses (SMC/BMC) in new material... 

Multilayer packages are more difficult to recycle, unless reworked and reused as an iimer layer in new multilayer films. The thermosets are in principle nonrecyclable, but in some cases technology exists for depolymerization or pyrolysis. In principle they may be reground into fillers (incorporating fiber-... 

The primary advantage of TPE over conventional rubber is the ease (and therefore low cost) of processing, the wide variety of properties available, and the possibility of recycling and reuse. Besides the obvious environmental benefits of a recyclable raw material, TPE scrap material can be reprocessed. The disadvantage of these materials relative to thermosets is the relatively high cost of raw materials, the general inability to load TPEs with low cost fillers... 

Phenolic thermosets can be recycled using a mechanical recycling system such as milling or crushing, and the obtained powder material can be used as a filler or additive for new thermosets (Goto and Santorelli, 2010). 

These two major classifications of thermoplastics (TPs) and thermosets (TSs) in turn have different classifications such as virgin or recycled plastics. Virgin plastics have not been subjected to any fabricating process. NEAT plastics identify plastics with Nothing Else Added To. They are true virgin polymers since they do not contain additives, fillers, etc. However they are rarely used since they do not provide the best performances. Thus the technically correct term to identify the materials is plastics. Of the 35,000 types available worldwide there are about 200 basic types or famihes that are commercially recognized with less than 20 that are popularly used. Examples of these plastics are shown in Table 1.2. 

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