Motorists and trucks aren't the only ones taking it on the chin in the current oil shortage.

The nation's major chemical companies - whose products show up in such diverse applications as film, airline serving trays, garbage bags, plastic party cups and polyester suits - are finding it increasingly difficult to come up with the petroleum-based feed stocks they process and are paying a lot more for what they find.

Like diesel fuel, petroleum jelly and kerosene, basic chemical raw materials such as benzene, toluene, or xylene are refined from crude oil by major petroleum companies, then sold to chemical companies who process them into fibers or plastics.

Between 6 percent and 10 percent of every barrel of crude oil goes to petrochemical production (compared with about 40 percent for gasoline).

Although major companies say they have not faced serious production problem for lack of feed stocks (as raw materials like benzene are called), William W. La Roche, president of U.S.S. Chemicals (a division of U.S. Steel Corp.) predicts the distruptions will get worse as the months wear on.

Although the chemical companies themselves have been grousing about rising prices - and with justification - higher costs have not yet taken a toll in profits.

Merrill Lynch Vice President Bill Williams said the nine major companies that his firm follows had first quarter profict increases averaging 40 percent and will probably do as well in the second quarter.

"But that's about the end of the game," Williams said.

By then, President Carter's price guidelines will begin to smart, the steady increase in oil prices by foreign producers will continue and worldwide hoarding of chemical company products will taper off.

In the United States, the two basic classes of petrochemical feed stocks - the aromatics and the olefins have behaved differently both in terms of price and supplies.

The aromatics, benzene and the like, are in short supply and are high priced because they come from petroleum. The olefins, such as ethylene, come from byproducts of natural gas exploration called natural gas liquids.

As a result, the aromatics have risen in price and have become harder to find, while the olefins are in good supply and their prices have remained stable.

In europe, however, both feed stocks come from naphtha, which is an unrefined gasoline, and are in short supply and high priced.

Because of this, European chemical companies have been at the doorsteps of the Dows and Du Ponts, buying as many finished chemical products as they can.

As a result, antifreeze, an ethylene derivative called ethylene glycol, may be expensive and hard to come by late this year, as motorists discovered it was in 1974 and 1975.

U.S. chemical companies are selling their final products to Europeans at prices substantially higher than they are charging domestic customers. That has helped buoy their profits temporarily, especially on the olefin derivatives where prices have not risen much in recent months.

But supplies of the aromatic feed stocks are both tight and high priced here and worldwide. Not only in refinery production lower, but the refiners themselves are using these chemicals to enhance the octane rating of the unleaded gasoline they are called upon to make in increasing quantities.

James Anderson, director of energy and materials for Monsanto, said his company was paying about 67 cents a gallon for benzene in the first quarter of 1978. Today, benzene bought under contract costs about $1.35 a gallon.

But major petroleum refiners have put chemical companies on allocation just as they have reduced the amount of gasoline or diesel oil they supply service stations and truck stops.

Du Pont's Edward Brightbill, director of energy and hydrocarbons, said that although his company as far is fulfilling most of its needs from its normal contracted suppliers, when and if Du Pont is forced to into the spot market to buy feed stocks, the prices increases will be dramatic.

So far, chemical companies have passed all, or nearly all, of the cost increases on to customers. Their average price increases have been in the range of 2 to 4.5 percent.

Today, for example, Du Pont raised the price of polyester yarns such as those used in tire cords from $1.01 to $1.06 a pound, citing the rising cost of the petro chemical raw materials it uses.

But those price increases will soon run afoul of President Carter's voluntary price standards.

If the profitable export market should moderate later this summer, the currently high flying chemical profits could take a sudden sharp dip.

It will be the worst of all worlds for the companies. Costs will continue to rise, profits will fall and stock prices should tumble as well. Du Pont's stock feel sharply today, for reasons the company said were inexplicable.

As one Wall Street analyst said, "Until the situation sorts itself out, investors would be better off buying antifreeze and holding off any purchases of chemical stocks."