Pascoe R D, O'Connell B
Camborne School of Mines, University of Exeter, Redruth, Cornwall TR15 3SE, UK.
Waste Manag. 2003;23(9):845-50. doi: 10.1016/S0956-053X(03)00026-6.
Flame treatment has been used for many years to modify the surface of plastics to allow coatings to be added. The effect of the treatment is to produce hydrophilic species on the surface of the plastic making it water-wettable. The production of hydrophilic plastic surfaces is also required in the selective separation of plastics by froth flotation. For the process to be selective one plastic must be rendered hydrophilic while another remains hydrophobic. In this study the potential for separation of PVC and PET has been investigated. Flame treatment was shown to be very effective in producing a hydrophilic surface on both plastics, although the process was not selective under the conditions investigated. Raising the temperature of the plastics above their softening point produced a hydrophobic recovery. As the softening point of PVC was significantly lower than for PET it was possible to produce a significant difference in hydrophobicity, as judged using contact angle measurement. When immersed in water the contact angle of the PVC was found to be strongly dependent on the pH. Good separation efficiency of the two plastics was achieved by froth flotation from pH 4 to 9. One particular advantage of the technique is that no chemical reagents may be required in the flotation stage. The practicalities of designing a flake treatment system however have to be addressed before considering it to be a viable industrial process.
火焰处理已被使用多年，用于改性塑料表面以便能够添加涂层。该处理的效果是在塑料表面产生亲水性物质，使其具有水润湿性。在通过泡沫浮选选择性分离塑料的过程中，也需要制备亲水性塑料表面。为了使该过程具有选择性，必须使一种塑料变为亲水性，而另一种保持疏水性。在本研究中，对聚氯乙烯（PVC）和聚对苯二甲酸乙二酯（PET）的分离潜力进行了研究。结果表明，火焰处理对于在两种塑料上产生亲水性表面非常有效，尽管在所研究的条件下该过程没有选择性。将塑料温度升高到其软化点以上会产生疏水性恢复。由于PVC的软化点明显低于PET，通过接触角测量判断，有可能在疏水性上产生显著差异。当浸入水中时，发现PVC的接触角强烈依赖于pH值。通过在pH值为4至9的条件下进行泡沫浮选，实现了两种塑料的良好分离效率。该技术的一个特别优点是在浮选阶段可能不需要化学试剂。然而，在将其视为可行的工业工艺之前，必须解决设计火焰处理系统的实际问题。
