Pultrusion system

Cure modelling of polyester pultrusion systems was carried out by Ng and Manas Zloczower (1989). A mechanistic model that couples free-radical polymerization and diffusion control (Section 1.2.3) was used for the cure kinetics and is shown here ... 

Pultrusion is a process for producing continuous lengths of reinforced plastic shapes with constant cross-sectional area. Pultrusion equipment is commercially available from a number of manufactures (Table 21.6) and a diagram of a typical pultrusion system is shown in Figure 21.64. Figure 21.65 shows an 8 MT machine with a hand-over-hand gripper system. 

Lackey and Vaughan (1997) presented basic information that can be used in the development of resin injection pultrusion systems. Experimental results and observations were presented to demonstrate the importance of factors such as injection chamber design, injection pressure, type of fibre and the elimination of voids for resin injection pultrusion systems. 

The characteristics of the three most common thermoset resin systems used in pultrusion are compiled in Table 11.2 [3]. It is noteworthy that unreinforced polyesters and vinylesters shrink 7-9% upon crosslinking, whereas epoxies shrink much less and tend to adhere to the die. These epoxy characteristics translate into processing difficulties, reduced processing speed, and inferior component surface finish. It is normal practice to use resin additives to improve processability, mechanical properties, electrical properties, shrinkage, environmental resistance, temperature tolerance, fire tolerance, color, cost, and volatile evaporation. It is normally the resin, or rather its reactivity, that determines the pulling speed. Typical pulling speeds for polyesters tend to be on the order of 10-20 mm/s, whereas speeds may exceed lOOmm/s under certain circumstances. Apart from the resins characterized in Table 11.2, several other thermosets, such as phenolics, acrylics, and polyurethanes, have been tried, as have several thermoplastics (as will be discussed in Sec. 11.2.6). 

Some fabrication processes, such as continuous panel processes, are run at elevated temperatures to improve productivity. Dual-catalyst systems are commonly used to initiate a controlled rapid gel and then a fast cure to complete the cross-linking reaction. Cumene hydroperoxide initiated at 50°C with benzyl trimethylammonium hydroxide and copper naphthenate in combination with tert-butyl octoate are preferred for panel products. Other heat-initiated catalysts, such as lauroyl peroxide and tert-huXyi perbenzoate, are optional systems. For higher temperature molding processes such as pultrusion or matched metal die molding at temperatures of 150°C, dual-catalyst systems are usually employed based on /-butyl perbenzoate and 2,5-dimethyl-2,5-di-2-ethylhexanoylperoxy-hexane (Table 6). 

Glass, carbon, and aramid fibers are used as unidirectional or fabric mat reinforcements, with E-glass/ polyester being the most commonly used system. The limitation of pultrusion is that only constant cross-section parts can be fabricated. However, a variety of hollow and solid profiles of any length can be manufactured. 

Several sections of this chapter discuss building materials (hoses and pipes, pavement, roofing, sealants, siding, and waterproofing). Here, we focus on wall materials and insulation in various extruded and molded profiles. Numerous polymers are used for these two applications. They include polystyrene, phenolic resin, polyvinylchloride, and polyurethanes for insulation purposes and polyvinylchloride, polyurethanes, and polyesters for wall systems and structural elements. The major methods of production include molding, extrusion, and pultrusion. 

Pultrusion is a continuous process involving pulling a collection of fibres on a creel system in the form of a roving, tow, mat or fabric through a resin bath (for impregnation) and then through a heated die to cure the resin and impart a constant cross-section to the product. Figure 6.7. 

Three-dimensional analyses of heat transfer and cure in pultrusion of epoxy-resin composites have been examined by Chachad et al. (1995, 1996) and Liu et al. (2000). Carlone et al. (2006) review finite-difference and finite-element process models used for predicting heat transfer and cure in pultrusion. In this work they recommend the following empirical nth-order cure model for predicting cure kinetics of epoxy-resin composites, which is then coupled to the system s energy balance to predict thermal properties and cure conversion ... 

Hybon 2011 Rovings. [PPG Industries/ Fiber Glass Prods.] Glass roving reinforcement for polyester and vinyl ester resin systems for pultrusion applies. 

In other cases, the multi-channel system will offer new functionalities like integrated gas, fluid or power transport. A very interesting application in the building industry would be the use of the side channels for incorporating pultruded carbon composite rods. The carbon rods could be incorporated and fixed during the pultrusion process of the technical plant stem under a certain pre-tension load. The use of the technical plant stems as... 

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