comma or semicolon in list: to achieve higher...; even better...; and

[Lola Lola]

What is the general rule for the use of semi-colons?

I tend to use them in lists where the listed "items" are longer phrases, using commas in a list of single words, for example.

I have tried to make the following (very long) sentence easier to read by using punctuation to make the meaning and the relation between the various clauses more explicit. Is it grammatically accurate and, more importantly, legible?

With the objectives being to achieve even higher mechanical strength properties, with a particular focus on reducing the mass of prefabricated components while retaining the same strength, and thereby conserving resources; to achieve higher finish quality; even better processability; and wider application as substitute materials (in place of PVC, for example): the processes, nuclear technology and catalysts have been modified in a way that facilitates the production of a polymer powder with a broad bi- or multimodal molecular weight distribution.

 

[xqby]

I think I would keep the first semicolon but change the next two to commas so that it's clear "to achieve" applies to those as well. I had to read the sentence a couple of times, so not easily legible, but yeah, probably about as good as you're going to get.

 

[Cenzontle]

One of the general rules for semicolons is to use them to divide between items that contain commas of their own. You seem to be on the right track with that.
But a bigger legibility problem I see in your sentence is that the items divided by semicolons are not parallel in structure.
"With the objectives being (1) to achieve [...]; (2) to achieve [...]; (3) even better processability; and (4) wider application [...]."
(Infinitive verb; infinitive verb; noun phrase; noun phrase.)
You could insert "to achieve" at the beginning of (3) and (4)—but saying "to achieve" four times would be "echo-y".
Probably it would be better to say "to achieve" just once before the series of four items:
"With the objectives being to achieve (1) even higher [...]; (2) higher finish quality; (3) even better processability; and (4) wider application [...]."
If you keep this series of four items, some of which are long, I suggest you enumerate them with "(1)...; (2)..." as I have done above, or "(A)...; (B)..."
That's parallelism.
After the four objectives have been listed, we begin the subject and predicate of the sentence ("the processes, [...]"),
and you rightly sense the need for a pause stronger than a comma.
But (for reasons I won't elaborate here) I think a colon is not appropriate, and that it should be replaced with a dash, what a printer calls an "em dash".
All that said,
if it were my sentence, I would try to find a way to break it into two or three separate sentences.

 

[Lola Lola]

Thanks, Cenzontle. Yes, I'd be very tempted to take your approach too. However, it's a translation, and since the original uses only one sentence, I'm very weary about splitting it up.

Having said that, the original text is from German, and, as they're known for their ridiculously long and meandering sentences, I might have a decent case for dividing it up in English!

 

[Keith Bradford]

... However, it's a translation, and since the original uses only one sentence, I'm very weary about splitting it up...

Don't be wary (or even weary). Sentence-length is as much a part of a language as its punctuation or vocabulary, and if you're putting a foreign text into English you should follow good English style. And that is to use shorter sentences than many other languages. I've very often had to translate a 120-word French sentence, and I have no compunction in splitting them up into four or five sentences in English. This is simply the way we do things.

I would no more hesitate in breaking down a German Sentence, than I would in replacing capital Letters on Nouns into lower Case.

 

[Lola Lola]

Thanks for the advice, Keith- that has saved me a lot of hassle!