Virgin resin

These lower prices make it more difficult for recycled plastics to compete with virgin resins in the absence of legislation mandating plastics recycling. 

Scrap and Recycle. Acetal resins can be processed with very Htde waste. Spmes, mimers, and out-of-tolerance parts can, in general, be ground and the resins reused. Up to about 25% of regrind can usually be safely recycled into virgin resin. However, the amount of regrind that can be used in a particular circumstance varies. The appropriate Hterature from the suppHer should be consulted. 

The process can be used to recover scrap or low quaUty resins by using them as the core layer, and using outer layers of virgin resins designed for the specific functional needs of the product such as sHp or gloss and appearance. The inner core may be a foamed resin with surface layers of supedor finish resins. Coextmded films often eliminate the need for cosdy lamination processes. 

The melting point of commercial Teflon PEA is 305°C, ie, between those of PTEE and EEP. Second-order transitions are at —100, —30, and 90°C, as determined by a torsion pendulum (21). The crystallinity of the virgin resin is 65—75%. Specific gravity and crystallinity increase as the cooling rate is reduced. An ice-quenched sample with 48% crystallinity has a specific gravity of 2.123, whereas the press-cooled sample has a crystallinity of 58% and a specific gravity of 2.157. 

Recycling of HDPE. Polyolefins, including HDPE, are the second most widely recycled thermoplastic materials after PET (110). A significant fraction of articles made from HDPE (mostly bottles, containers, and film) are collected from consumers, sorted, cleaned, and reprocessed (110—113). Processing of post-consumer HDPE includes the same operations as those used for virgin resins blow mol ding, injection molding, and extmsion. 

Total energy use for production virgin resin (feedstock -i- other) ... 

Khait, K., Reconstituted polymeric materials derived from post-consumer waste, industrial scrap and virgin resins made by solid state pulverization, US patent, 5,814,673, 1998. 

Contaminants in recycled plastic packaging waste (HDPE, PP) were identified by MAE followed by GC-MS analysis [290]. Fragrance and flavour constituents from first usage were detected. Recycled material also contained aliphatic hydrocarbons, branched alkanes and alkenes, which are also found in virgin resins at similar concentration levels. Moreover, aromatic hydrocarbons, probably derived from additives, were found. Postconsumer PET was also analysed by Soxhlet extraction and GC-MS most of the extracted compounds (30) were thermally degraded products of additives and polymers, whereas only a few derived from the original contents... 

Increasing costs of virgin resins and viable end-use markets are currently making the recycling business attractive, and more and more... 

Epoxy resin was cured with polyamine, polyamide, or anhydride ground to pass a 0.5-mm screen and 20 was recycled into the next batch of virgin resin, either directly or after pre-soaking in the liquid ingredients. When these "filled" resins were cured, hardness was generally higher than for virgin resins. 

The quality and properties of recyclate should be comparable to those of virgin resins. Therefore, upgrade of recycled materials might be necessary in order to improve their properties. Clearly the effect of polymeric contaminants on the end-use performance of recyclate is an important issue, and the amount of contaminants that can be tolerated depends on the final application. Polymeric contaminants do not only pose a threat for environmental impact but also impact the ultimate tensile elongation behaviour [12, 13]. 

Whereas no expansion is observed for the virgin resin, the four coatings show maximum expansion between 300°C and 350°C. The expansion is attributed to the evolution of volatile degradation products of the resin as well of the intumescent additives, which are trapped in the structure. 

Virgin resin in pellet form contains emulsifiers that give the pellet surface a thin, oily coating that acts to collect dust, preventing it from becoming airborne. Colorant and additive products also contain emulsifiers and/or lubricating waxes (especially when powdered resins are used) that also impart this property to the final product pellet. 

Phenolic products, especially sterically hindered phenols, are widely used throughout the PVC industry - for instance, as chain-stoppers and antioxidants in PVC polymerisation, to terminate the reaction and prevent degradation of the virgin resin in the stripper and dryer. Methyl methacrylate butadiene-styrene (MBS), a frequently used impact modifier for rigid PVC, needs highly efficient protection against oxidative degradation... 

Pressure sintering and cooling is more often used for compounds than for virgin resins. In this process the preform is either sintered and cooled in a confined mold or placed into a special self-supporting frame. The frame is placed into an oven with the pressure cylinder outside, actuating the piston to compress the preform in the mold. Different sinter/cooling/pressure cycles can minimize certain physical properties for each different compound. The disadvantage of this method is that the product has a... 

---