Polyurethane/glass fibre reinforcement

Flexible plastics and rubbers can, as a matter of fact, only be treated with rubber-elastic lacquers, mainly on the basis of polyurethane, which, moreover, should be resistant to oxidation, oils, fuel and UV light. Besides, polyurethane lacquers are often used for several other plastics, such as PVC, polyamides, ABS and glass-fibre reinforced resins. 

The PFM films may also be backed with a glass fibre reinforced polyurethane foam. This technology is already being used in thermoplastic roof modules and gives rise to parts having low weight, high stiffness and excellent thermal insulation. 

A typical layered structure consists of two thin, glass-fibre-reinforced polymer skins bonded to a thick, lightweight honeycomb core (Fig. 4.5a). Such sandwich panels are used in railway carriages and aircraft there are similar structures inside many skins. Other examples are less obvious the space between the outer container and the toughened polystyrene liner of a refrigerator is filled with rigid polyurethane foam. 

Polyurethane foam is used with facings such as paper, glass fibre, plasterboard or glass fibre reinforced concrete. The facings and foam are layers connected in series, so the temperature drop across each layer is added for the steady-state heat flow. If layer i has thickness Lj and conductivity ki then the overall U-value of the product is given by... 

Plastics and rubbers occur most frequently as conveyor belts and straps as well as in cables and pipes. Ventilating conduits and chutes are made of glass-fibre-reinforced polyester. In addition, in-situ expanded rigid polyurethanes have recently been gaining ground as thermal insulating materials. 

A study of glass fibre reinforced soybean oil-based polyurethane indicates that the mechanical properties such as tensile strength (259 c 270 MPa), flexural strength (418 cf. 444 MPa), tensile modulus (17 ct 18.6 GPa) and flexural modulus (18 cf. 27 GPa) of the soybean-based composites, were comparable with those of composites based on petrochemical (Jeffol) polyurethane. Since this soybean oil-based polyurethane composite offers better thermal, oxidative and hydrolytic stability than those based on petrochemicals, vegetable oil-based polyurethane composites could offer a viable alternative to petrochemical-based composites. 

Polyurethane adhesives currently used to bond most thermosets, including glass fibre reinforced plastics (GRP), sheet moulding compound (SMC), glass fibre reinforced epoxy (GRE), and thermoplastic composites including ABS, PVC, acrylics, polycarbonates, etc., are pre sented in Table 20. 

In the special case of pipelines operating at relatively high temperatures such as for the transmission of heavy fuel oil at up to 85°C, heat insulation and electrical insulation are provided by up to 50 mm of foam-expanded polyurethane. As a further insurance against penetration of water, and to prevent mechanical damage, outer coatings of polyethylene (5 mm), butyl laminate tape (0-8 mm) or coal-tar enamel reinforced with glass fibre (2-5 mm) have been used. 

Fibre reinforced polymers (FRPs) are composed of a reinforcement material (glass, aramid or carbon fibres) surrounded and retained by a (thermoplastic or thermosetting) polymer matrix (unsaturated polyester, epoxy, vinyl ester, or polyurethane). FRPs were first used in the rehahiUtation of reinforced or pre-stressed concrete, but they have also been widely used in the reinforcement of timber structures. 

Loos (2011) reported that investigators from Bayer Material Science LLC, USA and Moulded Fibre Glass, Cleveland, USA have developed a prototype wind turbine blade 0.74 m long manufactured from polyurethane reinforced with carbon nanotubes (CNT PU). The researchers claim that the advanced material has a specific tensile strength five times and 60 times that of carbon fibre composite and aluminium, respectively, and is tougher than carbon fibre-reinforced polymer (CFRP) but the excellent properties of these materials come with a price penalty. 

RRIM polyurethanes are an extension to Reaction Injection Moulding (RIM) which is a relatively recent, but now established, plastics processing technique. Simplified, RRIM is the inclusion of a reinforcement - short glass fibres - into one of the components used in the RIM process. However, the inclusion of glass reinforcement into one of the reactive components, usually the polyol, has meant that certain processing equipment modifications were necessary in order to handle the... 

Based on information for glass-reinforced Bayflex GR 110/50 (using 0.2 mm length hammer-milled glass fibre) Bayer leaflet PU52113e. For further details, see Seel, K. and Klier, L., Reinforced polyurethanes for car body parts, Kunststoffe 11 (1981) 9, 577-584. 

Structural adhesives based on polyurethanes are used widely in the transport industry, especially for bonding plastics reinforced with glass or other fibres. They are used also as sealants in glazing for motor vehicles—most notably following the introduction in recent years of front and rear windows bonded as elements in the construction. 

New technology for reinforcing ABS with long fibres has been developed by Dow Plastics. It is described as Vitamins (because it can be introduced in the feed hopper of a plastics processing machine) and involves the use of a thermoplastic polyurethane as a compatibilizer between the glass and the ABS matrix (for it has good compatibility with both). 

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