Fabricating processes reinforced thermoplastics

Important are behaviors associated and interrelated with plastic materials (thermoplastics, thermosets, elastomers, reinforced plastics, etc.) and fabricating processes (extrusion, injection molding, blow molding, forming, foaming, reaction injection molding, etc.). They are presented so that the technical or non-technical reader can readily understand the interrelationships. 

There are many methods used to convert a liquid resin and glass fibres into useful solid structures. Fabrication processes for reinforced plastics as a whole, including thermoplastics, have already been described in Chapter 2. This section focusses on the more common methods used in the chemical process industry and indicates their place in that market. 

Nitrile butadiene rubber (NBR), which is formaldehyde-resistant, is the predominantly used elastifying component for phenoplastics. The resin and rubber interreact during the curing process. Natural rubber is incompatible with phenolic resins. At a rubber content of 25 %, the modulus of elasticity, at 1,000 N mm , has already fallen into the middle range of unreinforced thermoplastics. The impact strength reaches the values of type 74 (fabric chips, reinforced). Their form stability when exposed to heat is below that of type 31 at temperatures below 100 °C. 

However, plastics processors must continually update their procedures and/or acquire additional knowledge on how to process plastics. New developments in this field are unlimited. This book has emphasized that it is not difficult to process plastics, and has reviewed the many fabricating processes used to produce many different sizes and shapes of thermoplastic and thermoset commodity and engineering resins, which are used either unreinforced or reinforced (in composites). As explained, process selection depends basically on product performance requirements, shape, required dimensional tolerances, plastics processing characteristics, production volume, and cost (1-3, 317-326). 

Autoclave molding, the process of curing thermoset resins at elevated temperature and pressure in an inert environment, has an important role in the fabrication of continuous fiber reinforced thermoplastics. While most companies view thermoplastics as an alternative to traditional autoclave long-cycle processing, they have come to accept the following reasons for the autoclave processing of thermoplastic matrices ... 

Compounds are short (/w 0.3 mm) or long (> 0.6 mm) fibre reinforced thermoplastic or thermoset polymeric materials, which are processed automatically (injection or compression moulding), have good (mechanical) properties (for automotive, electric and electronic applications) and are relatively cheap. Composites contain continuous fibres (rovings, fabrics or mats), usually combined with thermosets, have excellent mechanical (structural) properties, but are very expensive because lack of an industrial process (mainly used in aerospace and aircraft industry). 

Although thermoplastics, thermosets and elastomers can be used as matrix of polymer composites, thermosets are more widely used mainly due to the processing techniques employed in their manufactme, that allow for the easy use of long fibers, mats and fabrics as reinforcement. Thermosets are also generally more thermally stable than thermoplastics, and these two reasons lead to products with significantly higher mechanical properties which are less affected by thermal variations than thermoplastic composites [1,2,12],... 

With regard to methods of fabrication, all processes in Table 1.1 that are applicable to unfilled, unmodified thermoplastics can also be used for discontinuous systems (with the exception of expandable bead molding). In addition to thermoforming, hot stamping of reinforced thermoplastic sheets mostly containing randomly oriented continuous or discontinuous fibers is used for the production of large semistructural parts. Fillers can also be used in the thermoset processes in Table 1.1, often in combination with the primary continuous fiber reinforcement. The content and inherent properties of the additive, as well as its physical/chemical interactions with the matrix, are important parameters controlling the processability of the composite. 

Comoforming n. A fabrication process that combines vacuum-formed thermoplastic shapes with cold-molded fiberglass-reinforced resin to produce parts having excellent surface appearance and weatherability. 

A series of works has been done in this field of growing interest for the purposes of improving the dispersibility of nanoparticles in solvents and their compatibility in polymers [25]. Mostly, the graft polymerization is conducted via two routes (1) monomers are polymerized from active compounds (initiators or comonomers). PMMA is a commonly used thermoplastic matrix for fibers, sheets, and particles. There have been several studies on PMMA-fiber composites prepared by in situ polymerization [26], solution mixing [27], or melt blending [28]. The last one is already an industrial process for fabricating carbon fiber-reinforced thermoplastic composites. 

Ostgathe, M., Breuer, U., Mayer, C. and Neitzel, M. (1996) Fabric reinforced thermoplastic composites - Processing and Manufacturing, in Proceedings of the European Conference on Composite Materials ECCM-7, London, UK, 1996, Vol. 1, (ed. M. Bader), Woodhead Publishing, Cambridge, UK, pp. 19 200. 

It has been well recognized that melt blending of a thermotropic liquid crystalline polymer (LCP) and an isotropic polymer produces a composite in which fibrous LCP domains dispersed within the blend act as a reinforcement il ). The so-called insitu composite possesses several advantages in comparison with the inorganic reinforced thermoplastic composites. Firstly, LCP lowers the blend viscosity in the actual fabrication temperature range (3-5), Hence, the enhanced processability endows moldability for fine and complex shaped products. 

Lim T C, Ramakrishna S and Shang S M (2000) Strain field of deep drawn knitted fabric reinforced thermoplastic composite sheets, J Mater Process Technol 97 95 99. 

Walter Lachowecki, Fiber Glass Reinforced Thermoplastics Part 1—Properties, Design Tip and Applications Part 2—Processing and Fabricating . Plastics Design and Processing (June and July 1969). 

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