Crack plasticity

Ying Huang, Hongxia Yan, and Qiuyu Zhang, Liquid fuel manufactured from waste plastics cracking, Plastics, 31(4), 36-40 (2002). 

Dibutyl phthalate is a plasticizer added to the poly(vinyl chloride) used in vinyl upholstery and garden hoses. Since plasticizers are more volatile than the high molecular weight polymers, they slowly evaporate with time, making the polymer brittle and easily cracked. Plasticizers like dibutyl phthalate that contain hydrolyzable functional groups are also slowly degraded by chemical reactions. 

Steel decking transmits vibrations which have been known to crack plastic monolithic coatings and brickwork. 

Twinning facilitates relaxation of stress by plastic deformation but interaction of twin bands with grain boundaries may initiate cracks. Plasticity of Crl8Re and Cr35Re alloys is sufficient to impeach the formation of such cracks even after 71% deformation at room temperature. 

The described example of solution analysis was shown for the analysis of crude oil vacuum residue, but this method can be successfully applied for different kinds of feed. In our investigation, we used this method for the analysis of mixtures of vacuum residue and plastics, and pure plastics. In the case of the plastic or product of its cracking analysis, one has to consider that what is left behind after soxhlet extraction is the heavy plastic fraction or non-cracked plastic. 

Based on the results shown in table 8.1, it is obvious that during solution analysis of the cracking product of polyethylene and polypropylene, only non-cracked plastics remain completely in the remainder. In contrast to polyethylene and polypropylene, polystyrene and PVC are over 40 wt. % soluble in THF. 

The remainder during this analysis is coke, in the case of thermal treatment of pure vacuum residue, and coke and non-cracked plastics, in the case of the thermal treatment of mixtures of crude oil vacuum residue and plastics. 

Nair and Tien [91] explained the effects of yield strength on Kiscc through hydrogen-induced fracture resulting from the plastic flow on a localized scale in the crack tip plastic zone. The suggested cause of SCC was isolated and unstable local fracture events in the crack plastic zone controlled by the local embrittlement due to adsorbed hydrogen [92]. 

The wear mechanism under diy contact conditions was predominated by micro-cracks, plastic deformation, debonding and detachment of fibers. Under wet contact conditions, the wear mechanism was predominant by debonding, delamination and detachment of fibers associated with loose and tom fibers. 

Finally, many polymers tend to be hard and brittle. When these properties are undesirable, plasticizers are added to increase softness and pliability. Most such polymers are phthalates, and with the advent of mass-produced plastics, they have become ubiquitous. "New-car smell" results from the volatilization of plasticizers from synthetic upholstery and simileir materials when enough of the plasticizer is gone, the material becomes brittle and can crack. Plasticizers have recently been identified for further study as a possible health concern for children, who tend to put soft plastic toys in U eir mouth. 

Figure 15-4-5. Steel braided hose with cracked plastic nut on the end.

Environmental stress cracking plastics may be embrittled by exposure to water, light, temperature and oxygen as well as chemical attack. 

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