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New PP copolymers & TPO's herald '90s 'engineering' polyolefins.

New PP Copolymers & TPO's Herald '90s 'Engineering' Polyolefins

"The 1970s and '80s were the era of benzene-based engineering thermoplastics. The '90s will be the era of olefinic engineering plastics." With those bold words, Dr. William Bowles, process research director for Quantum Chemical Corp.'s USI Div., Cincinnati, hinted at unprecedented capabilities in molecular tailoring of ethylene- and propylene-based polymers with the aid of new catalyst and polymerization technologies. In a recent press briefing, Dr. Bowles presented some evidence that the new era is already beginning to arrive, and that polyolefins are demonstrating the capability to compete with higher-cost "engineering" plastics. That evidence is most apparent in PP copolymers and TPO's though he also provided some advance glimpses of dramtic improvements to come in LLDPE and HDPE.


One of the cardinal benefits of new polymerization technologies being explored by Quantum is the ability to use new comonomers with ethylene and propylene, that have never been feasible before. (Several other polyolefin producers are pursuing this direction, as well--see PT, June '90, p. 91.) One example emphasized by Bowles is the ability to incorporate polar comonomers, which tend to "poison" conventional tends of polymerization catalysts. Polar compounds could impart new types of functionality, such as the following:

* Dyeable PP for fibers--now said to be possible;

* Incorporating stabilizers into the polymer, which could enhance medical-implant applications, for example, by better resisting attack by the body;

* Built-in vapor-barrier properties for applications such as automotive fuel tanks;

* Chemical coupling with fillers and reinforcements;

* Compatibilizing blends of other polymers.

One route to added versatility in comonomer incorporation is Quantum's new "Q Technology," which involves catalysts developed for its own proprietary low-pressure PE process. Quantum officials say that this technology will yield significant new commercial products in the next year or two. As just one hint of what's ahead, Quantum showed data on a developmental LLDPE that exhibits 300% greater tear strength than resin produced by Union Carbide's popular Unipol process. Q Technology is being developed initially for PE, though it may later be applied to PP. Quantum is starting out with two types of Q catalysts, one for injection molding resins and one for blow molding, both capable of producing a range of densities.

Another new area Quantum is working on is very-low-density PE, or VLDPE (also called Flexomers by Union Carbide), which are LLDPE's with high propylene or other comonomer content.


Exciting things are happening in the area of PP copolymers and TPO's. A new trend, according to Ted Klimek, who heads up PP development activities at Quantum, is toward random terpolymers of ethylene, butylene and propylene as alternatives to traditional random ethylene-propylene copolymers for film heat-seal layers. Lower FDA hexane extractables is one of the main attractions of terpolymers, according to Klimek.

In impact copolymers, one recent development has been medium-high-impact grades with high stiffness. Examples of these materials, which have been available for about a year, are shown in Table 1. (CIRCLE 6)

Another generation consists of high-stiffness/high-impact materials with low extractables, reportedly making them acceptable for retort packaging applications. Shown in Table 2, these have also been commercial for close to a year. (CIRCLE 7)

One of the newest developments are high-stiffness/"super-impact" copolymers developed for blow molded auto seat backs, though they have suitably low extractables for retort packaging and medical uses, says Quantum. An example is TR040, a product that has been out for less than six months and is not yet fully commercial; it also appears in Table 2. (CIRCLe 8)

Finally, Quantum reports successful initial sampling of in-reactor produced TPO's, which are said to offer better gloss and better HDT for a given rubber content than compounded versions. Examples are shown in Table A at the beginning of this article. Klimek notes that Quantum plans to investigate the applicability of these materials as matrix resins for new additions to the family of Nortuff talc- or glass-filled PP copolymers. (CIRCLE 9)
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Title Annotation:polypropylene; thermoplastics
Author:Naitove, Matthew H.
Publication:Plastics Technology
Date:Jul 1, 1990
Previous Article:High-melt-strength PP permits foam sheet extrusion.
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