Effect of Ultraviolet Irradiation on Polystyrene Containing Cephalexin Schiff Bases

Abstract

The scale of production of polystyrene has escalated in the recent past in order to meet growing demand. As a result, a large quantity of polystyrene waste continues to be generated along with associated health and environmental problems. One way to tackle such problems is to lengthen the lifetime of polystyrene, especially for outdoor applications. Our approach is the synthesis and application of new ultraviolet photostabilizers for polystyrene and this research is focused on four cephalexin Schiff bases. The reaction of cephalexin and 3-hydroxybenzaldehyde, 4-dimethylaminobenzaldehyde, 4-methoxybenzaldehyde, and 4-bromobanzaldehyde under acidic condition afforded the corresponding Schiff bases in high yields. The Schiff bases were characterized and their surfaces were examined. The Schiff bases were mixed with polystyrene to form homogenous blends and their effectiveness as photostabilizers was explored using different methods. The methods included monitoring the changes in the infrared spectra, weight loss, depression in molecular weight, and surface morphology on irradiation. In the presence of the Schiff bases, the formation of carbonyl group fragments, weight loss, and decrease in molecular weight of polystyrene were lower when compared with pure polystyrene. In addition, undesirable changes in the surface such as the appearance of dark spots, cracks, and roughness were minimal for irradiated polystyrene containing cephalexin Schiff bases. Mechanisms by which cephalexin Schiff bases stabilize polystyrene against photodegradation have also been suggested.

Fabrication of Highly Photostable Polystyrene Films Embedded with Organometallic Complexes

“…It was clear that, at 13.2-fold, the ibuprofen-Mn complex led to the most reduction in the Rq (Table 4). Clearly, the ibuprofen-Mn complex is more effective in stabilizing PS compared with Schiff bases of both biphenyl-3,3 ,4,4 -tetraamine [18] and cephalexin [19], possibly due to the acidic character of the Mn atom that enables the complex to be a better radical scavenger. On the other hand, the 1,2,3,4-triazole-3-thiol Schiff bases [20] showed a better performance than the synthesized metal complexes, due to their high contents of heteroatoms and aromatic moieties.…”

Modifications of Polymers through the Addition of Ultraviolet Absorbers to Reduce the Aging Effect of Accelerated and Natural Irradiation

“…Recently, we synthesized a range of UV stabilizers (e.g., aromatics, heterocycles, Schiff bases, organometallic complexes, and polyphosphates) and tested their efficiency for the stabilization of polymers [ 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 ]. These additives, at a low concentration of 0.5% by weight, led to a significant improvement in the photostability of polymers.…”

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“…Schiff bases resulted in the reduction of photo-degradation and the chain cross-linking levels of the PSB. They are effective due to the fact that they include aromatic rings, azomethine bonds, and heteroatoms [41]. PSB photo-oxidation results in generating radicals of the polymeric chain that may be stabilized via forming stable complexes with the Schiff bases B (1-3) and A (1-3), as depicted in Scheme 3.…”