Plastic problem

Just a quick writing. Please help me to write the thesis statement more specific based on the entire essay. Also, the topic sentences and/or the transitioning between paragraphs, especially the sentences that highlight with the red color (see the attached file below). The first sentence (topic sentence) in each paragraph should give some idea of the material to be covered in the whole paragraph. Please write  a specific thesis and revise only the topic sentences in each paragraph, also add the transitiong words before the topic sentences. You do not need to revise other parts only the topic sentences and the thesis.

Transition guideline:
ADDITIONalso, and, besides, furthermore, in addition, indeed, in fact, moreover, so too
EXAMPLEafter all, as an illustration, for example, for instance, specifically, to take a case in point
ELABORATIONactually, by extension, in short, that is, in other words, to put it another way, to put it bluntly, to put it succinctly, ultimately
COMPARISONalong the same lines, in the same way, likewise, similarly
CONTRASTalthough, but, by contrast, conversely, despite the fact that, even though, however, in contrast, nevertheless, on the contrary, on the other hand, regardless, whereas, while yet
CAUSE AND EFFECTaccordingly, as a result, consequently, hence, since, so, then, therefore, thus
CONCESSIONadmittedly, although it is true, granted naturally, of course, to be sure
CONCLUSIONas a result, consequently, hence, in conclusion, in short, in sum, therefore, thus, to sum up, to summarize