TPU/ABS blends

Since it possesses good properties of both PVC plastics and polyurethane elastomers, it has been used in those areas where PVC and polyurethane have traditionally played dominant roles. For example, it is a very promising replacement for flexible PVC used for medical purposes and in the food industry [I6,l7], because it essentially eliminates the concern regarding plasticizer contamination. It has been used in combination with the copolymer of butadiene and acrylonitrile (NBR) to make the abrasion-resistant aprons and rolls used on textile machines [18]. A PVC/TPU/ABS blend serves as a substitute for leather [19]. This could have a tremendous impact on the shoe industry. It has also been found to have an application as a building coating [20,21]. This trend will certainly grow and more applications will be found. This in turn should bring new developments in the material itself. 

Estane Thermoplastic polyurethanes, TPU, and TPU/SAN or TPU/ABS blends BE Goodrich/ Polyplastic... 

CONTENTS ABSTRACT, 747 INTRODUCTION, 748 THERMOPLASTIC POLYURETHANE, 748 POLYMER BLENDING, 749 TPU/ABS BLENDS, 750 TPU/PVC BLENDS, 752 TPU/STYRENE BLENDS, 753 TPU/POLYACETAL BLENDS, 754 TPU/OLEFIN BLENDS, 755 TPU/NYLON BLENDS, 756 TPU/POLYESTER BLENDS, 756 TPU/PVDF BLENDS, 757 TPU/ELASTOMER BLENDS, 758 OTHER TPU BLENDS, 758 TRENDS IN TPU BLENDS, 758 REFERENCES, 759 ABSTRACT... 

TPU/ABS blends can be used to mold or extrude seat adjuster housings, automotive interior panels, vent grills, aircraft seat tracts, snowmobile modular drive belts, and automotive filler panels. A family of TPU blends is being developed to compete in the flexible automotive bumper fascia market. Features of these blends include printability without adhesion promoter or primer, ease of processing. 

Blends of nitrile rubber with PVC or chlorinated PE, TPU, PA or their combination Chemigum TPE) show extremely high resistance to melt fracture and die swell. The material can be fed at high melt temperature into crosshead to promote strong melt-fusion with rigid plastics such as PVC/ABS blends during coextmsion. 

TPUs and polycarbonate blends and TPU/polycarbonate/ABS blends are used with the addition of the polycarbonate giving higher modulus and solvent stress cracking resistance as well as making processing of the TPU much easier. TPU/polycarbonate/polybutylene terephthalate blends are superior to their ABS analogue for resistance to environmental stresscracking resistance. 

Initially, two-component, PVC/TPU blends were proposed [B. F. Goodrich Co., 1960], but soon, PVC/TPU blends with a modifier, e.g., ABS [Waugaman et al., 1963] NBR or PA [Kepes, 1959] were disclosed. Blending was also carried out by mixing PVC with polyols and isocyanates then polymerizing these two [Dainichiseika Color Chemicals, 1983]. Commercial PVC/TPU (with NBR) are represented by Duralex . The materials are usually formulated for extrusion, e.g., for wire and cable insulation, hoses and packaging. 

To prepare the graft copolymer, a PO (MW = 50 to 1,000 kg/mol) was either dissolved or swollen in an inert hydrocarbon, monomers (>80 wt% of a methacrylic ester, CH2=C(CH3)COOR) and an initiator was added to the heated mixture while stirring. As a result, acrylic branches of a relatively high molecular weight (MW = 20 to 200 kg/mol) were grafted onto the PO macromolecules. The graft copolymer could be used as a compatibilizer-cwm-impact modifier in a variety of polymers selected from between PO, acrylic polymers, SAN, EVAc, PA, PEST, PC, POM, PAr, PVC, ABS, PVDC, cellulosics, polyester-polyether block copolymers, PEA, PEEK, PEI, PES, CPVC, PVDF, PPE, PPS, PSF, TPU, PAI, PCL, polyglutarimide, blends of PEST with PC or PVC [Ilendra et al., 1992, 1993]. 

Blends of PC/PET/TPU with EVAc-GMA and optionally MBS or ABS, have good flexural modulus, strength, weld line strength, solvent resistance, and impact behavior [Laughner, 1994]. PC blends with a polycaprolactone-polyurethane resin, TPU Pellethane , and either MBS or MBA showed similar behavior [Henton et al., 1993]. 

PPS and PEEK blended with a fluoro(co)-polymers and reinforced with either CF or GF were wear resistant with a short break-in period for forming a self lubricating film [Davies and Hatton, 1994]. Many commercial blends contain fluoropolymers (primarily PTFE) for the improved weatherability, wear and solvent resistance SUPEC — self-lubricating blend of crystalline PPS with PTFE and 30 wt% GF, Lubricomp blends from LNP and similar/JTP blends from RTP Co. (e.g., 15 wt% PTFE, 30 wt% GF and any of the following resins ABS, PA, PEST, PC, PE, PEI, POM, PP, PPE, PPS, PS, PSF, PVDF, SAN, TPU, PEEK, PES, etc.), Sumiploy from Sumitomo Chem. Co., etc. [Utracki, 1994]. 

ABS/TPU blends are used mostly for automotive parts, e.g., paintable, soft bumper fascias. They are mosfly formed by injection molding or extrusion. 

A recent commercial blend of ABS contains thermoplastic polyurethane elastomer as the main blend component. The blend was introduced in 1990 by Dow Chemical Co., under the trade name Prevail . These blends characteristically exhibit low modulus (340 to 1000 MPa) and high impact strength at low temperamres, e.g. notched Izod values of 370 to 1500 J/m at -29°C. The TPU component of the blend imparts high toughness and also allows paintabihty without a primer. ABS component imparts heat resistance (for paint ovens) and good tensile strength in the blend. The blend is projected to find applications in the automotive markets, particularly as paintable, soft bumper fascias. Typical properties of commercial ABS/TPU blends are shown in Table 15.6. 

Mixtures of polar polymers, such as PVC, PC, PMMA, TPU, PA, PEST, PGI, SAN, or ABS could be compatibilized by incorporation of two copolymers, the first containing vinyl alcohol, the second an anhydride. For example, blends of TPU with Phenoxy, EVAl, COPO, modified cellulose, and/or polyalkylene oxide, had attractive physical, optical and barrier properties, and were melt-processable without degradation. They could be transformed into films, sheets, or bottles with good barrier properties. Blends containing PA were used for films, tubes, toys, gears, bearings, shafts, curtain sliders, door rollers, etc. The blends with elastomers were reported suitable for improved wiper blades [La Fleur et al., 1994]. 

The blends can be injection molded, extruded, blow molded, or thermoformed. Transfer or compression molding, calendering, and solid state may also be used. They show hardness between that of TPU and ABS, superb toughness, chemical resistance, appearance... 

Blends of TPUs and Acrylonitrile-Polybutadiene-Styrene graft polymer (ABS) have been studied by a number of researchers [14-16]. The structures of the blends are very complex due to the complex polyblend of ABS, in which there is a rigid SAN copolymer with a rubbery graft butadiene polymer and the heterophase system of the TPU. The two polymers can benefit each other, as shown in Table 1. 

TPU can be blended with PVC combining the toughness and abrasion resistance of the TPU with the stiffness and high modulus of PVC together with cost reduction of TPU. Chlorinated polyethylene can also be used as a blend with TPU or with TPU plus PVC or with polyethylene in the latter case the chlorinated polyethylene acts as a carrier for the very incompatible polyethylene. Styrene-acrylonitrile copolymers (SAN) and the rubber-modified versions, ABS, have also been blended with thermoplastic polyurethanes. Again the stiffness and initial modulus are improved without much sacrifice of the low-temperature properties. 

Techniace TU is a blend of thermoplastic polyurethane (TPU) and ABS with intermediate hardness between TPU and ABS, superior toughness, chemical resistance, and good appearance. 

---