Transparent Polyurethane Elastomers

TYPICAL PROPERTIES OF OH-TERMINATED POLYBUTADIENE URETHANES CONTAINING 50 phr OF VARIOUS PROCESS OILS 

Also the reaction temperature has a dominant effect on transparency and 130°C is usually suitable. 

One can predict whether an initially transparent PU elastomer will become only translucent in time. If the differential scanning calorimetry spectrum of the material does not show any endothermic peaks developing as the material ages, then its transparency will be permanent. 

The relative ratios of polyol to diisocyanate blocks can control transparency especially in the harder types of PUs and also transparent but softer PUs can be made using lower polyol/diisocyanate block ratios in conjunction with a mixed chain-extender system. 

An otherwise opaque or translucent PU formulation can be made to be transparent by using triols in the chain-extender system. 

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PROCESSING OF TRANSPARENT THERMOPLASTIC POLYURETHANE ELASTOMER BY INJECTION MOULDING... 

Polyurethane elastomers have been made from these perfluoro-polyethers in both opaque and transparent forms and covering the following range of properties ... 

Rimplast (Trade name of Petrarch Systems, USA). These are a series of IPN blends of high molecular weight silicone rubber with polyurethane. Toyoho (Trade name of Toyobo, Japan). A series similar to those of Biomer. Transparent PU elastomers. These are based on aliphatic diisocyanates and used for artificial organs. Compatibility with blood is achieved through either the incorporation of polysiloxane or surface treatment of the PU with heparin or albumen. 

Some of the advantages of polyurethane elastomers vs. conventional rubber are improved abrasion resistance, better tear resistance, transparency, ozone resistance, and pourability for cast molding and curing. On the other hand, polyurethane elastomers possess disadvantages such as poor high-temperature service, poor resistance to certain chemicals, poor resistance to hot, moist environments, and sometimes higher material costs. 

Sonnenschein M F, Rondan N, Wendt B and Cox J M (2004) Synthesis of transparent thermoplastic polyurethane elastomers, J Polym Sci Part A Polym Chem 42 271-278. Sonnenschein M F, Lysenko Z, Brune D A, Wendt B L and Schrock A K (2005) Enhancing polyurethane properties via soft segment crystallization. Polymer 46 10158-10166. 

Table 10.4 Abrasion Loss (Per DIN 53516 and ISO 4649) of BASF Elastollan 600 Grades Polyether-Polyurethane Transparent Thermoplastic Elastomers [3]...

P.R.248 exhibits excellent bleed resistance in plasticized PVC. Transparent specimens equal step 8 on the Blue Scale for lightfastness, while 1/3 SD samples match step 7. The pigment does not perform as well in terms of weatherfastness, for instance in PVC plastisols for coil coating. P.R.248 was also recommended for use in elastomers, polyurethane, and unsaturated polyester. 

Both series of polyurethanes were prepared using a prepolymer technique in which reactants were mixed at 70 °C/1 hour, cast into molds at 105 °C/2 hours, and cured at 80 °C/14 hours. The BD/MDI hard segment contents ranged from 0% (transparent, colorless homopolyurethanes) to 30% w/w (opaque, white copolyurethanes). All elastomers were characterized using DSC, dynamic mechanical, and tensile stress-strain measurements. 

TRANSPARENCY AND POLYURETHANE (PU) CHEMICAL COMPOSITION (ALL PU ELASTOMERS WERE ONE YEAR OLD OR OLDER)... 

SK Chemicals produces a thermoplastic polyurethane (TPU) [9] under the trade name Skythane . Being the bridge between rubbers and plastics, this TPU elastomer has innovative potentials for uses requiring special characteristics, such as transparency, elasticity, durability, and resistance to chemical attack, in addition to excellent physical and mechanical properties Table 14 lists grades and properties of Skythane . 

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