You find expository writing as a chief component of academic writing. In this sense, it is primarily concerned with an analytical effort that finds expression in an argumentative form. By argumentation, it is meant that the piece of writing should convey a position or analytical stance in a convincing and persuasive way. On a professional academic level, this type of writing is often reserved for other individuals working in the same or related field, although not exclusively so. Also important is the fact that this writing is frequently exposed to critique from colleagues in the field, a process usually termed "peer-review."
Technical writing may be seen as having a more clear-cut approach than does expository writing. It is composed of a series, or list, of factual data or informative points that need to be relayed to the intended audience. This form of writing is well-suited to compilation-oriented materials such as industry reports, survey outcomes, medical testing results and like efforts. As nicely stated by Your Dictionary.com., technical writing is an "impersonal" style that dryly, succinctly and matter-of-factly informs the reader.
As technical writing is impersonal and strives for a simple clarity of data, its structuring is perhaps less important than it is in expository writing. An expository piece of writing maintains its need to persuade, and thus the ordering of content should always proceed with maximum effect in mind. The writer wants the piece to flow in such a way that the reader logically arrives at the point she is trying to make and to establish the reader's agreement with that conclusion.
Because of their very different functions, these two forms of writing are likely to read quite differently. The transparency and dryness of technical writing can be accompanied with esoteric vocabulary that suits the jargon of a particular industry or context. The same jargon-based biases can also be found in expository writing. However, the writer of the latter usually needs to employ a more narrative styling, thus enhancing the writing's overall readability. Again, the process of convincing a reader is much different than information sharing.