because: as a result of
due to: attributable to, caused by, resulting from
A grammar ‘rule’ is that due to should only be used as an adjective (following the noun), and not as a compound preposition. It should not be used in place of because of:
The colour change was due to a chemical reaction.
not
Due to a chemical reaction, the solution changed colour.
or
The solution changed colour due to a chemical reaction.
Use of due to in a sentence is only correct if these words could be replaced by caused by or attributable to. Due to should not be used as a wordy alternative to because.