Solid-phase forming shows promise for polypropylene - C&EN Global

Nov 6, 2010 - facebook · twitter · Email Alerts ... Shell believes that solid-phase forming, also referred to as cold forming, could account for billi...
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U.S. dye industry will show alarming deficit in world trade as imports of dyes and textiles continue to grow U.S. trade balance for dyes (millions of pounds)

Dyes and intermediates

1953 1957 1961 1965 1966 1967 1972* 1976* 1980*

+7.4 +6.0 +4.5 +7.9 +3.1 + 1-9 -8.5 -32.0 -82.3

Dye content in textiles

+4.5 + 1.3 + 1.9 -0.6 -1.2 -1.5 -7.2 -18.1 -45.1

Total dyes

+ 11.9 +7.3 +6.5 +7.2 + 1.9 +0.5 -15.7 -50.2 -127.4

* Estimates. Source: Trade Relations Council of the U.S., Inc.

lished by the Synthetic Organic Chemicals Manufacturing Association. Dye producers tell C&EN that their profits quickly volatilize in face of more competitive foreign imports, particularly since the German and Swiss dye producers are passing the several-penny tariff savings on to purchasing agents in U.S. textile mills. Without a more realistic U.S. trade policy, Mr. Stewart points out that foreign dye producers will take over the U.S. market by 1980, to the extent that 727c of all dyes in textiles purchased by U.S. consumers will be of foreign origin.

Solid-phase forming shows promise for polypropylene Commercial production of polypropylene parts via solid-phase processes very similar to those used in making metal parts is technically feasible, according to Paul M. Coffman, a research worker for Shell Chemical Co. Speaking at the 26th annual technical conference of the Society of Plastics Engineers in New York City last week, Mr. Coiiman said that forging and rubber pad forming are the two solid-phase approaches showing the most economic promise so far. Shell believes that solid-phase forming, also referred to as cold forming, could account for billions of pounds of polypropylene and other plastics annually within the next 10 years. Much cold-forming development is done in the plastics industry, particularly on acrylonitrile-butadiene-styrene and high-density polyethylene. Today the conventional way of forming thermoplastic parts is by shaping the viscous molten polymer under pressure by extrusion, injection mold16 C&EN MAY 13, 1968

ing, or other techniques. With cold forming the plastic may be heated, but it is kept below its melting point. The major advantages claimed for cold forming include greater production speeds in many cases and ability to form tougher and thicker parts. Another advantage of cold forming, according to Mr. Coffman, is lower equipment costs. He explains that forging tools cost about 35% and rubber pad tools only 10 to 15% as much as their injection molding counterparts. Mr. Coffman told the meeting that pipe, flanges, drive couplings, pump rotors, and other parts with section thicknesses as high as 2.5 inches have been successfully forged from polypropylene at Shell. Cycle time is typically about 20 seconds. In this process a preheated plastic billet is placed on a floating die on top of a punch. The opposing punch then closes to deform the billet into the desired shape. With the polypropylene at 300° F., a force of about 3 tons per square inch is required. Polypropylene melts at about 335° F. Using the rubber-pad forming technique, Shell has made snow shovels, box lids, serving trays, and a host of other objects up to 2 inches deep from polypropylene and other thermoplastic sheets. Production cycle is again about 20 seconds, while pressure requirement is about 1000 to 1500 p.s.i. This method is very similar to matched-die stamping except that one die is replaced by a solid block of rubber. The preheated sheet is placed on this rubber. As the upper die descends, the rubber distorts to conform to the shape of the die and so helps mold the sheet. Diaphragm molding of polypropylene, a further modification of rubberpad forming, is also being investigated at Shell.

AAUP aims resolutions at what ails campus, society All four components of the academic community—faculty, administration, students, and governing board—must share responsibility for preserving that community. They must work together to "establish effective joint mechanisms and processes for continuing examination of the conditions of campus life to ascertain that these conditions are at all times conducive to fulfillment of the academic community's purpose." Thus did the American Association of University Professors—in a resolution on free speech and dissent—call for action on some very immediate problems threatening the tranquility and possibly the very existence of higher education as we know it. Implicit in this resolution and in another on faculty participation and institutional government were pleas by AAUP for negotiated settlement of campus strife. But the professors did not stand still on the subject of campus disruptions, such as the situation at Columbia, which was ebullating just as AAUP was meeting. Deplored as "destructive to the pursuit of learning and a free society" were tactics by individuals or groups which "disrupt educational operations" or "obstruct and restrain by physical force" campus visitors and other members of the academic community. Some of the other resolutions passed by AAUFs 54 th annual meeting dealt with: • Secrecy in research—calling on the academic community to "examine with great care the nature and consequences of research relationships with all outside agencies" to ensure continued academic integrity. • Impact of the draft on colleges and universities—urging adoption either by the President or by Congress of a more equitable system of drafting eligible persons. • Selective Service—condemning punitive use of the draft and stating that "resistance to Selective Service, including refusal of induction by peaceful means . . . should not be a basis for disciplinary action" by a university against either faculty or students. • Racial discrimination and economic equality-recognizing "the special responsibility of educators and scholars in meeting the problems arising from racial discrimination and related inequalities of economic opportunity." • Legislation on drugs—calling on Congress to set up a national commission to investigate all aspects of the problem and then make legislative recommendations.