Polypropylene/polyurethane laminates

THE DIELECTRIC LOSS OF POLYPROPYLENE FILMS AND POLYPROPYLENE-POLYURETHANE LAMINATES AT CRYOGENIC TEtlPERATURES... 

The constituent polypropylene layers in all the commercially prepared polypropylene-polyurethane laminates were PP-F films. The single polyurethane layer in the PP-U-PP(B) and PP-U-PP(C) laminates contained a blue dye, as did the two polyurethane layers in the 3PP-2U(A) laminate. The two polyurethane layers in the 3PP-2U(B) laminate contained a violet dye. 

Fig. 5. The dielectric loss at 100 Hz of polypropylene-polyurethane laminates, as well as the PP-F from which they are made, as a function of temperature. The low temperature (4.2 to 10 K) data are shown on an expanded scale in the inset. See text for nomenclature.

The Dielectric Loss of Polypropylene Films and Polypropylene-Polyurethane Laminates at Cryogenic Temperatures... 

Mahoney et a/.87 have described the reaction of polyurethane foam and superheated water at 200 °C for 15 min, which leads to toluene diamines and polypropylene oxide. Hydrolysis of polyurethane and rubber mixtures has been used as a method not only of recovering valuable chemicals from the polyurethane fraction, but also to separate the polymers because rubber is inert to hydrolysis.89 The degradation takes place by contact with saturated steam at 200 °C for 12 h. This process may find particular applications in the treatment of rubber/polyurethane laminations. 

Water-borne adhesives are preferred because of restrictions on the use of solvents. Low viscosity prepolymers are emulsified in water, followed by chain extension with water-soluble glycols or diamines. As cross-linker PMDI can be used, which has a shelf life of 5 to 6 h in water. Water-borne polyurethane coatings are used for vacuum forming of PVC sheeting to ABS shells in automotive interior door panels, for the lamination of ABS/PVC film to treated polypropylene foam for use in automotive instmment panels, as metal primers for steering wheels, in flexible packaging lamination, as shoe sole adhesive, and as tie coats for polyurethane-coated fabrics. PMDI is also used as a binder for reconstituted wood products and as a foundry core binder. 

The laminating adhesive for Samples 1-3 was a 100 25 mix of an isocyanate terminated polyurethane prepolymer based upon polypropylene glycol and MDI (amount of free monomer approximately 25%) and a tri-functional polypropylene glycol with a molecular weight of approximately 450. 

In sports such as athletics, traditional materials have been almost completely replaced by synthetic materials. Sports surfaces in modern indoor stadiums are usually made from a porous structure of rubber crumb and a binder such as polyurethane. Other polymeric materials used include flexible PVC or rubber sheet, polyolefins, polypropylene (PP) grasses, and foam laminates. 

If the RP product requires flexibility, the choice is limited to plastics such as EVA, ionomer, polyethylene, vinyl, polypropylene, fluorocarbon, silicone, polyurethane, plastisols, acetal, nylon, natural rubber, or some of the rigid plastics that have limited flexibility in thin sections e.g., thin laminations are quite flexible. 

A summary is presented of measurements of the dielectric loss characteristics of six commercial polypropylene films, as well as laminates consisting of two or three polypropylene films bound together with a polyurethane. 

The results of the measurements of tan 6 from 4.2 to 323 K at 100 Hz for all the laminates are plotted in Fig. 5. The data for the PP-F film from which the laminates were made are also included for the purpose of comparison. Confining ourselves to temperatures below 200 K, the following features may be noted. All the laminates exhibit a loss peak below 4.2 K, as evidenced by the upswing in tan 6 with decrease in temperature below 10 K. This peak may be attributed to the antioxidant in the polypropylene layers. In addition, all the laminates, including the PP-U-PP(A) in which the polyurethane layer contains no dye, exhibit a very broad and pronounced loss peak centered at 150 K. This peak is a characteristic of the polyurethane and, on the basis of what is known about the relative proportions of polyurethane in the various laminates (there are uncertainties concerning the relative thickness of the polyurethane layers in them), its magnitude appears to increase in accord with increasing polyurethane content. 

The aspects of interest concerning the laminates are the relative contributions of the polypropylene and polyurethane layers to tan 6 in the region 4 to 10 K. Any changes that the PP-F layers undergo due to heat or other effects associated with the laminating process must be taken into account in this connection. 

To examine these factors, some additional experiments were carried out using the PP-U-PP(C). One of the polypropylene layers was stripped from this laminate, leaving all the polyurethane attached to the other layer. The stripped layer of polypropylene was then folded on itself and the dielectric loss characteristics of the resulting doubled-up layer (henceforth referred to as OU see Fig. 6), were measured. The remaining polypropylene film with the adhering polyurethane layer was doubled up to form a sandwich consisting of two outer polypropylene layers and two inner polyurethane layers, thus effectively producing a laminate in which the polyurethane is twice as thick as in the PP-U-PP(C). The dielectric characteristics of this new laminate (henceforth referred to as 2U) were also measured. 

It is important to note that values of tan 6 at 4 to 10 K for the OU sample coincide closely to those of the annealed PP-F. In both cases, the dielectric loss is lower than that for the unannealed PP-F. This may be attributed to a suppression of the 30 K peak in the former two samples. In short, this illustrates that the polypropylene layers in the laminates undergo changes during the lamination process that must be taken into account in an analysis of the relative contributions of the polypropylene and polyurethane to tan 6. 

Adjustable breathability is an area where responsive barriers have already found commercial applications. For example, a thermoresponsive breathable membrane using shape memory polyurethane has been developed by Mitsubishi Heavy Industries (SMP Technologies Inc., 2010). It can be laminated onto various types of textiles to provide waterproof, windproof yet breathable clothing. Another strategy based on a temperature-activated breathable monolithic film sandwiched between two layers of spunbond microfibrous polypropylene has been used by Ahlstrom Corp. to develop medical gowns that combine protection against virases with comfort and breathabUity (Rodie, 2005). 

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