New metallocene TP elastomers tackle films, fibers, TPOs.The Vistamaxx family of propylene-ethylene specialty elastomers recently unveiled by ExxonMobil Chemical (see PT, Aug.'03, p. 92) holds promise in a broad range of applications from very soft fabrics and films to very hard TPOs. Made with the company's Exxpol metallocene catalyst Metallocene catalyst A transition-metal atom sandwiched between ring structures having a well-defined single catalytic site and well-understood molecular structure used to produce uniform polyolefins with unique structures and physical properties. technology and a new solution polymerization Solution polymerization is a method of industrial polymerization. In this procedure, a monomer is dissolved in a non-reactive solvent that contains a catalyst. The heat released by the reaction is absorbed by the solvent, and so the reaction rate is reduced. process, Vistamaxx thermoplastic elastomers can be used on their own or as modifiers for other polyolefins. They will be commercially available within the first half of 2004 from a new plant being built in Baton Rouge Baton Rouge (băt`ən r  zh) [Fr.,=red stick], city (1990 pop. 219,531), state capital and seat of East Baton Rouge parish, SE La. , La.Described as having a special semi-crystalline structure, Vistamaxx is said to be very compatible with other polymers and very easy to process. Properties of the new elastomers can be tailored for specific applications through control of molecular weight, MW distribution, composition distribution, and degree of crystallinity (see Table 1). Initial targets include elastic non-woven fabrics for medical apparel, personal care, and even car-seat covers. According to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. product development manager George Racine, elasticity has been lacking in the widely used polypropylene non-woven fabrics. Vistamaxx elastomers are also aimed at elastic films, TPO (Twisted Pair Only) Refers to the use of twisted pair wire when other options are available. For example, a TPO suffix at the end of 3com Ethernet adapter model numbers indicates the card has only an RJ45 connector. modification, and tie layers for polyolefin-to-polyolefin bonding. Their advantages in these applications are said to include elasticity, adhesion, softness, and toughness. Markets range from automotive interior and exteior parts to packaging, personal care, and wire/cable. Elastic cast films Mono- or multi-layer cast films that require elasticity--such as baby diapers and hospital gowns--are promising applications for Vistamaxx. The key is that these films can be processed on conventional polyolefin cast film equipment, notes Hans Van Brackle, global technology manager. Vistamaxx can be used on its own or in blends to deliver elastomeric properties plus the processability of PE and PP. Resulting films can compete with polyurethanes, SEBS, and other styrenics. Films have been produced with a density of less than 1.0 g/cc, tensile strength tensile strength Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material. When stresses less than the tensile strength are removed, a material completely or partially returns to its of more than 3000 psi, and secant secant, in mathematics. 1 In geometry, a secant is a straight line cutting a curve or surface. If it intersects the curve in two different points, as in the secant of a circle, the segment of the secant between the points is called a chord. modulus of 2350 to 3240 psi (Table 2). Some applications require a film to maintain its key properties at elevated temperatures in storage and use. Tests of Vistamaxx cast films showed no change in modulus from room temperature to 212 F. In contrast, film of a 0.870-g/cc ethylene-octene plastomer suffered a significant decrease in modulus around 94 F. Impact modification Vistamaxx elastomers also are said to be well suited to impact modification of high-flow PP homopolymers and impact copolymers. ExxonMobil is initially targeting TPO auto exterior and interior trim. Racine says non-automotive TPO applications in household goods and healthcare are also being explored. Trials have shown that TPO compounds made with the new elastomers combine excellent impact properties with higher stiffness and flow than typical TPOs utilizing low-density ethylene copolymers such as ethylene-propylene or ethylene-octene plastomers. This benefit is achieved with a lower loading of Vistamaxx modifier (programming) modifier - An operation that alters the state of an object. Modifiers often have names that begin with "set" and corresponding selector functions whose names begin with "get". , which has the added advantage of reducing cost. Recent trials demonstrated the impact properties of blends of a 35 MFR MFR, n See myofascial release. PP and a 0.860-g/cc octene plastomer at 30% loading compared with those of a Vistamaxx elastomer elastomer (ĭlăs`təmər), substance having to some extent the elastic properties of natural rubber. The term is sometimes used technically to distinguish synthetic rubbers and rubberlike plastics from natural rubber. of similar density at various loadings (Fig. 1). At loadings of 30% and 25% Vistamaxx, the impact properties at room and low temperatures are substantially better than those of the plastomer blend. With a loading of 20% Vistamaxx, the impact properties are equivalent to that of the blend containing 30% of the plastomer. [FIGURE 1 OMITTED] At the 20% loading, flexural flexural pertaining to the flexure of a joint. flexural deformity fixation of joints in flexion. In the newborn called contracted calves or foals. modulus of the Vistamaxx blend is 150,000 tamaxx blend is around 21 g/10 min vs. about 14 g/10 min for the plastomer blend. Good polyolefin adhesion Vistamaxx elastomers have excellent compatibility with other poyolefins in coextrusion or overmolding. ExxonMobil is exploring the materials' adhesion to PP or EPDM EPDM Ethylene-Propylene-Diene-Monomer EPDM Enterprise Product Data Management EPDM Ethylene Propylene Dimonomer (industrial/commercial piping/plumbing components) EPDM Engineering Product Data Management at bonding temperatures below those of standard polyolefin processing. According to Racine, potential applications range from packaging and consumer goods consumer goods Any tangible commodity purchased by households to satisfy their wants and needs. Consumer goods may be durable or nondurable. Durable goods (e.g., autos, furniture, and appliances) have a significant life span, often defined as three years or more, and to auto interior trim. Vistamaxx could eliminate the need for adhesives and high bonding temperatures that can adversely affect the materials being joined. Adhesion trials show the excellent compatibility of Vistamaxx with PP. Results of T-peel tests on a three-layered laminate with Vistamaxx on the outside and PP or HDPE HDPE abbr. high-density polyethylene in the center appear in Fig. 2. Vistamaxx shows excellent adhesion to PP at bonding temperaturea above and below the melting temperature Melting temperature may refer to:
[FIGURE 2 OMITTED] TABLE 1--PROPERTY RANGE OF VISTAMAXX TP ELASTOMERS Density, g/cc 0.86-0.89 MFR, g/10 min 1-25 Mooney Viscosity, ML 10-30 Tg, C -10 to-35 Melting Point, C 40-160 Hardness, Shore A 50-90 Tensile Str., psi 1200-1500 Elongation, % 100-1500 Elastic Recovery, % 80-97 TABLE 2--CAST FILM PROPERTIES Gauge, mil 4.5 Elmendorf Tear, g/mil MD 96 TD 100 Tensile Strength, psi MD 3050 TD 2660 Break Elongation, % MD 750 TD 830 Secant Modulus, psi MD 3240 TD 2350 Tensile Set-First Cycle, % MD 12 TD 9 Tensile Set-Second Cycle, % MD 7 TD 5 NEED TO KNOW MORE? ExxonMobil Chemical Co., Houston (281) 870-6314, www.exxonmobilchemical.com RELATED ARTICLE: Super-soft TPVs for grips and TPEs for overmolding. Two TP elastomer families for soft-touch grips, pads, and gaskets have been introduced by Teknor Apex Co.'s Thermoplastic A polymer material that turns to liquid when heated and becomes solid when cooled. There are more than 40 types of thermoplastics, including acrylic, polypropylene, polycarbonate and polyethylene. Elastomer's Div. in Pawtucket, R.I. One is the Uniprene 2000 thermoplastic vulcanizates, which include grades softer than any other TPVs on the market. They have Shore hardnesses of 15A, 25A, and 35A, while no other TPV TPV Temporary Protection Visa (Australia) TPV Terminal Punto Venta TPV Third-Party Verification TPV Thermophotovoltaic TPV Thermoplastic Vulcanizate (thermoplastic elastomer) TPV Total Payment Volume is softer than about 45A, Teknor says. The new grades retain high impact resistance down to -60 C, suiting them for replacing SEBS and TPO in parts subject to extreme climatic conditions. Meanwhile, Teknor's new SEBS-based Tekbond 6700 family consists of 45A, 55A, and 65A grades that boast higher adhesion than other TPEs to nylon 6 and 66, including glass-filled grades. In contrast to other TPEs, the new grades do not need to be heated to bond well to nylon, so they work equally well in insert molding and the more complex and costly two-shot molding. The new materials also retain excellent peel strength after immersion in brake and transmission fluids. Tel: (800) 556-3864, www.teknorapex.com |
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