Polyurethanes polyurethane bulk degradation

In dentistry, silicones are primarily used as dental-impression materials where chemical- and bioinertness are critical, and, thus, thoroughly evaluated.546 The development of a method for the detection of antibodies to silicones has been reviewed,547 as the search for novel silicone biomaterials continues. Thus, aromatic polyamide-silicone resins have been reviewed as a new class of biomaterials.548 In a short review, the comparison of silicones with their major competitor in biomaterials, polyurethanes, has been conducted.549 But silicones are also used in the modification of polyurethanes and other polymers via co-polymerization, formation of IPNs, blending, or functionalization by grafting, affecting both bulk and surface characteristics of the materials, as discussed in the recent reviews.550-552 A number of papers deal specifically with surface modification of silicones for medical applications, as described in a recent reference.555 The role of silicones in biodegradable polyurethane co-polymers,554 and in other hydrolytically degradable co-polymers,555 was recently studied. 

Degradation of bulk biocompatible polyurethanes occurs mainly by the hydrolytic mechanism and the stage of cellular degradation is initiated only at later stages when cavities appear as a result of polymer surface erosion (Ref. l5), p. 44). 

There are plenty of examples in the literature where plant-based fibers have been used for reinforcing or filling non-degradable resins such as polypropylene (PP), polyethylene (PE), nylons, polyvinyl chloride (PVC), epoxies and polyurethanes (PU), etc. [6-15]. The bulk of plant-based fiber composites, however, are made using wood flour, a byproduct from saw mills, or wood fiber obtained from waste or used wood products, e.g. packaging pallets, old furniture, and construction wood scraps. These inexpensive... 

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