Materials.

Although numerous engineering-resin grades were introduced at NPE, two entirely new resin lines were announced by DuPont Engineering Polymers, Wilmington, Del. One was the Zytel HTN line of high-heat aromatic nylon. The other major launch was DuPont's Zenite line of melt-processable liquid-crystal polymers (LCPs).

Polyolefin entries were similarly numerous, including products for thin-wall injection, blow molding, and sheet extrusion/thermoforming.

NEW LCP LINE

DuPont is commercializing the Zenite 6000 and 7000 series LCPs, which previously were available only in small lots or as developmental grades. DuPont plans construction of a new LCP resin production facility by mid-1995 in Chattanooga, Tenn., where it currently has a pilot plant. Capacity of the new plant was not revealed. DuPont's recommitment to the LCP market comes after putting the program on hold for two years.

PROPERTIES OF DUPONT'S ZENITE LCP

                                  6130         6330           7130
                                  30% Glass    30% Mineral    30% Glass

Tensile Strength, kpsi            21.8         23.9           21.0
Flexural Strength, kpsi           24.6         18.5           25.3
Flexural Modulus, Mpsi            1.7          1.4            1.8
Elong.
Notched Izod Impact, ft-lb/in.    2.3          3.0            4.2
Compressive Strength, kpsi        15.2         -              12.5
Melting Point, F                  635          635            666
Glass Transition, F               250          250            -
HDT, F, 264 psi                   493          455            563
UL 94 Flammability                V-O          -              V-O
Specific Gravity                  1.67         1.63           1.65

Paul D. Carfagna, LCP business manager, says the Zenite line is based on a wholly aromatic copolyester resin technology. While the basic polymer chemistry is similar to previous LCP entries from DuPont, Carfagna says the main thrust distinguishing the newly commercialized Zenite grades is improvements in flow and processing characteristics, faster mold cycles, enhanced material toughness and more precise dimensional tolerances.

Besides the three commercial grades listed in the accompanying table, a developmental grade, Zenite 7130 HT (30% glass), is said to offer an even higher HDT of 572 F at 264 psi. Carfagna adds that DuPont continues to pursue development of its "amorphous" LCP, described as having an exceptionally high glass-transition temperature (above 350 F) but no crystalline melting point (PT, April '90, p. 97).

Carfagna says DuPont's strategy is to become "the low-cost producer" of LCPs. He predicts contract pricing for major customers using Zenite soon will fall below the typical $7-10/lb range for most LCPs.

Meanwhile, Hoechst Celanese Corp. in Chatham, N.J., the LCP market leader with its Vectra line, announced that it will introduce a new lower-priced line of liquid-crystal polymers by year end.

NEWS IN POLYOLEFINS

Several new-generation PE products emerged at the show. Dow Plastics added to its Affinity and Engage line of metallocene-based copolymers, and Himont released the first details on its Spherilene-process LLDPEs (see Technology Newsfocus). Phillips Chemical Co., Houston, launched the first new PE products to emerge from its rebuilt Houston production complex. Among these, Phillips formally commercialized its "low-density linear PE" (LDLPE), the company's first low-density PE (PT, Nov. '92, p. 63; June '93, p. 70). This hexene copolymer is said to be distinguished from other LLDPEs by its broad molecular-weight distribution ([M.sub.w]/[M.sub.n] = 15-20) and correspondingly broad processing window. This reportedly allows film grades, for example, to run on blown film equipment for LDPE, LLDPE, or HDPE without modifications.

In addition, Phillips has four new HDPEs:

* Marlex C594 is an extra-high-MW grade (0.956 g/cc, 5.8 HLMI) for large blow molded containers. It's said to offer better shear response and processability than similar grades, but with no sacrifice of toughness. C594 is also said to process at lower temperatures (400-420 F), provide better resin distribution--even in complex geometries, and give smoother surfaces. ESCR has also been improved to [is greater than]500 hr.

* Marlex C590 (0.955 g/cc, 23 HLMI) is for blow molding household and industrial containers, including bleach, detergent, and motor-oil bottles. It's said to offer ESCR of 80 hr--up to 200% higher than other resins of the same density. It can thus be blended with up to 50% post-consumer recycle (PCR), vs. 25-30% with other grades.

* Marlex B587 and B589 (0.952 g/cc) are new injection molding grades with narrow MWD, low taste and odor, and high flow (60 and 45 MI, respectively) for use in thin-walled food containers such as stadium cups and cups for ice cream and frozen fruit. Molding trials reportedly show 5-6% higher output than other thin-wall grades.

Among several new PP products from Himont Inc., Wilmington, Del., was Pro-fax PH-204 a homopolymer for thermoformed packaging and food-service items such as deli containers and lids, drinking cups, and trays. Himont says this 2-MFR resin, when used in conjunction with a new generation of high-speed, melt/solid-phase extrusion and thermoforming systems, can replace HIPS at a cost savings of up to 40%. An example of such equipment was the E74.1 shuttle-mold system shown at NPE by OMV U.S.A., Lake Geneva, Wis. This machine is said to orient the PP in the mold, adding clarity and stiffness. According to OMV, stiffness is increased by 30%, matching that of HIPS.