These are corrosive times to be a chief executive of a US chemicals company. DuPont and Dow Chemical, the two largest companies in the sector, have been attacked by activist investors calling for them to be broken up. Other groups including Air Products and WR Grace have launched radical restructuring programmes, and all of them have had to re-evaluate their strategies following a profound upheaval in market conditions.

The boardroom headaches are a sign not of an industry that is in crisis, however, but of one that is facing its best prospects for a generation.

US chemicals companies’ fortunes have been transformed by the shale gas boom, which is providing them with a flood of cheap energy and raw materials for their products. The question executives are now grappling with is how best to take advantage of this bonanza.

Contrast this situation with a decade ago, when the outlook was grim for US manufacturing of bulk chemicals such as ethylene, used as a building block for a wide variety of products including plastics. Companies were generally trying to diversify away from such activity into more lucrative speciality chemicals tailor-made for certain industries, such as agriculture and electronics.

“The vogue for strategic statements from companies in the 2000s was to say ‘We want to move from commodity to speciality chemicals, so we can have higher and more stable margins’,” says Andrew Walberer of AT Kearney, the consultancy.

Today that view has been turned on its head. The US has become one of the world’s most competitive locations for bulk chemical manufacturing, and the most successful US-listed chemicals group of the past five years in share price terms has been LyondellBasell, a commodity producer and proud of it.

It was created at the end of 2007 when Basell, controlled by Russian billionaire Len Blavatnik, bought Texas-based Lyondell, and entered Chapter 11 bankruptcy protection not much more than a year later.

The company’s fortunes turned during 2009, though, with the appointment of Jim Gallogly as chief executive. Previously with ConocoPhillips, the oil group, he made himself a star in the chemicals industry by his achievements in improving the operational performance and profitability of LyondellBasell.

Since the company listed in New York in October 2010, its shares have almost quadrupled, while Dow’s are up by 74 per cent and DuPont’s by 50 per cent.

When Mr Gallogly stepped down at the start of this year, he was replaced by Bob Patel, one of his lieutenants.

While the improvement in the company’s performance is genuine, it has been helped by favourable market conditions.

The weak gas prices created by the shale boom have given US-based petrochemical producers a huge cost advantage over their Asian and European rivals, such as Germany’s BASF and Taiwan’s Formosa Petrochemical.

In the US, LyondellBasell mainly uses natural gas liquids produced in shale fields such as ethane, as a feedstock for its products, while its rivals outside the US generally rely on naphtha, a raw material taken from crude oil.

Although oil prices have collapsed since last summer, there have also been steep falls in the US prices of gas and natural gas liquids. LyondellBasell reported record earnings per share for the first quarter of this year.

All US chemicals companies benefit to some degree from lower energy costs and cheaper raw materials, but the scale of the effect varies.

Dow is one of the ones experiencing the most benefit. It has committed to expanding its operations on the US Gulf of Mexico coast, spending $6bn on facilities including a new “cracker” used to produce ethylene.

Mr Patel draws another lesson from LyondellBasell’s success, however: the value of being focused.

“Over cycles, well-run commodity chemical companies have delivered equal or better performance to well-run speciality chemical companies,” he says.

The activist investors — Dan Loeb’s Third Point at Dow and Nelson Peltz’s Trian at DuPont — have made similar arguments when putting the case for dismantling these large chemicals conglomerates, saying the creation of smaller businesses would foster more focused managements and be easier for investors to understand.

Both companies have resisted the activists’ ideas, but the strategic decisions they have been taking have moved them towards a more focused set of businesses.

Dow remains committed to its integrated model, producing both bulk chemicals and specialised products, but it has already exceeded a target it set last year of raising $7bn to $8.5bn from disposals.

DuPont, meanwhile, has pinned its colours to being a research-heavy speciality chemicals business, spinning off its paint pigment and Teflon operations as a new company called Chemours.

Mr Walberer says chemicals companies would be heading towards greater focus and specialisation even if the activists had not been involved.

“It is really hard to be as good as you need to be if you have a portfolio of businesses that are very different,” he says.

For now, the activists are quiescent. Third Point last November reached an agreement with Dow that let it pick two directors to sit on the company’s board. Trian, meanwhile, last month failed in its attempts to have directors voted on to DuPont’s board in a fiercely contested election.

If the activists are to remain quiet, though, the companies will have to keep up their progress in making disposals, cutting costs and returning cash to shareholders, according to Hassan Ahmed, an analyst at Alembic.

“If there are any slip-ups in any of these plans,” he says, “then those investors will become active again.”