Pultruded profiles

The primary UPR end markets are construction, automotive, and marine industries widi applications such as house paneling, tub and shower applications, chemical-resistant storage tanks, pultruded profiles, and fiberglass composite boat hulls. The UPR industry is mature, with a world production close to 1.7 million tons (Table 2.2), but must face two important issues increasingly strict regulations for styrene emissions and poor recycling potential for polyester thermosets.48 49... 

Characteristic Cast resin Filled resin Glass-reinforced laminate Filament-wound laminate Pultruded profile... 

The.se examinations are used to define the type of fiber formats, principal directions, and degree of anisotropy, as shown in Fig. 1. For some systems (e.g. pultruded profiles) two or three fiber formats will be used together. 

Different TP pultrusion processes are used. As an example Thermoplastic Pultrusion Technologies (TPT), Yorktown, VA, USA, uses a hot-melt injection process for pultruding RP thermoplastic. Unlike TS pultruded profiles, TP profiles can be postformed and reshaped. Higher continuous use temperatures are possible with some TP matrices, and line speeds are faster with raw materials usually costing less. 

Pultruded profiles are ideal for electrical trunking, conduit, and high voltage line insulators where outdoor environmental conditions are likely to be harsh (for impact, chemicals, moisture, and heat). 

Associated with any composite grating system is a hand rail and stairwell to go with it. These are made from suitably designed pultruded profiles. Such systems find favour where sound floorings and escape ways are essential. The electrochemical industry has long been a user of the systems and now we see more and more of their use on off-shore oil platforms. 

Figure 9.19 shows an installation at the Dow Stade membrane chlorine plant. It was built in 1996 by Techno Composites Domine Gmbh, using Bekaert profiles made with Derakane 440-40 epoxy vinyl ester resin. The installation includes stairwells, handrails, walkways cable trays and safety cages. GRP and pultruded profiles in particular were used for their resistance to the chemicals being handled - notably sodium hydroxide, sodium hypochlorite and brine. Their electrical resistance was also a factor in this electrochemical plant [11]. 

Since pultruded profiles have low shear stiffness, shear deformations must be taken into account. Additionally, second-order effects like lateral-torsional buckling have to be considered carefully. 

Thick section parts require a longer time for the heat to penetrate and start the reaction than do thin sections. Therefore, they run more slowly. Once the curing process starts, the exothermic reaction can produce temperatures which are too high, resulting in in-built stresses and possible cracking. It is, therefore, very desirable with pultruded profiles to minimise the wall thickness. 

Products for outdoor use such as wall cladding, can be press moulded in many variants from SMC or BMC. Pultruded profiles can also achieve B1 fire status if a resin such as DCPD or unsaturated polyester/MMA is used with up to 250 phr of ATH as part of the additive package. The classification of flame resistant GRP systems in the SBI test will be a great boost for the materials enabling them to satisfy the fire protection rules of the future. 

Singh B, Gupta M (1998) Report No. F(C) 0176, Suitability assessment of JRP pultruded profile as door frame materials in buildings. CBRI, Roorkee... 

EPTA Publication (2008), What is Pultrusion 9th World Pultrusion Conference, Profiting from Pultruded Profiles 26-28 March 2008. 

EN13706 General European spedfications for pultruded profiles... 

When a cost-effective pultruded profile is used, mechanical means are needed to provide the shear connection with the concrete. 

In terms of geometry of the pultruded parts, there is no theoretical limit for their length. Practical limitations are related to the plant layout and transportation requirements, which often means setting the maximum length of pultruded profiles and bars at 12 m. CFRP strips, which are very thin and flexible, are usually coiled onto long spools containing several dozen metres of material. 

Several pultmsion companies use Barcol hardness testers to assess the degree of cure of the produced parts. This enables the tracing of products with insufficient degree of cure of the resin matrix, which leads to lower mechanical performance. The quality control of pultruded produced parts can also include other mechanical characterisation tests which can sometimes be carried out in the laboratory facilities of pultrusion companies. EN 13706-3 (CEN, 2002) defines two grades of FRP pultruded profiles, specifying minimum values for material properties and the relevant test methods. The requirements for certain applications (e.g. petroleum and natural gas industries) can be stricter and often include aspects related to fire reaction and fire resistance behaviour, e.g. NBR 15708-1 (ABNT, 2011). 

FRP elements have to be connected to one another, since shape sizes are limited by production constraints and there are size limitations associated with transportation and handling operations. Connections of FRP pultruded profiles are divided into the following categories ... 

Mechanical fastening, adhesive bonding and combinations thereof are the most common techniques for joining FRP pultruded profiles (Zhou and Keller, 2005). 

Until quite recently, the structural shapes of pultruded profiles have been copied from steel construction, usually reproducing thin-walled open (I, H, L, C) or tubular (square, rectangular, circular) cross-sections. Figure 9.8 shows the most typical shapes of the so-called first-generation profiles, which are normally composed of glass fibres embedded in polyester or vinylester based resin matrix - GFRP pultruded profiles. 

Typical fibre architecture of the laminates of pultruded profiles (courtesy of Strongwell). 

As mentioned earlier, the mechanical properties of GFRP profiles produced by the biggest manufacturers may exhibit considerable differences. In this context, in 2002, CEN published the European Standard EN 13706 (CEN, 2002), which defines the specifications for pultruded profiles. This standard establishes the test methods to determine several material properties (mechanical, physical and thermal), and it further defines two grades of profiles, specifying the minimum material properties a profile has to exhibit in order to be included in those grades. 

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