Reinforced thermoplastics surface

Reinforced thermoplastic parts are generally abraded and cleaned prior to adhesive bonding. However, special surface treatment such as used on the thermoplastic resin matrix may be necessary for optimum strength. Care must be taken so that the treatment chemicals do not wick into the composite material and cause degradation. It may not be a good idea to use chemical surface treatment without first verifying that the treatment does not degrade the substrate. 

Figure 6. Adhesion at the rubber-resin interface in the rubber-reinforced thermoplastics, type III (assuming that most of the grafting takes place on the surface of latex particles)...

Vectra LCPs consist of parallel, closely packed, fibrous chains in injection molded parts which give the polymer a wood-like appearance at fracture surfaces and also give it seU-reinforcing properties that are at least as good as those of conventional fiher-reinforced thermoplastics. ICI supphes LCPs (self-reinforcing polymers) under the trade name Victrex SRP. Excellent physical properties, low comhnstihility and smoke generation, resistance to chemicals and solvents, and stahihty towards radiation are some of the important properties of LCPs. 

To summarize, many fibre-reinforced thermoplastics are not suitable for extended exterior exposure where the maintenance of appearance is important unless their surface is protected. Some unprotected applications that are found include car door handles, rear-view mirror housings and body panels (for all of which polyamides, polyethylene terephthalate and polybutylene terephthalate are used), as well as parts for caravans, boats and snowmobiles. 

Table 8-1 compares PUR-RIM and injection molding of unreinforced and glass fiber reinforced thermoplastics, in the production of parts with large surface areas. RIM also is comparable to resin transfer molding (RTM ... 

This concept has been demonstrated by the work of Liu and Kontopoulou [45] and Bailly and Kontopoulou [27] on silica-reinforced thermoplastic olefins (TPOs). Their data have shown that when silica resides in the PP matrix, the improvements in Young s and flexural modulus are accompanied by unchanged or even slightly improved impact strength (Figure 2.12). The effects on impact properties were particularly beneficial when surface-modified silica (mSi02) was used. 

The electrical properties of pitch based semi-conductive carbon fibers have been determined by Okubo et al [191] and Gerteisen [192] examined carbon fiber reinforced thermoplastics with controlled surface resistivity. The techniques used for measuring the conductivity in carbon fibers have been described by Maslii and Panasenko [193]. 

Gerteisen SR, Carbon fibre reinforced thermoplastics with controlled surface resistivity, Eng Plastics, 9(2), 126-134, 1996. 

Hoffman WP, Scanning probe microscopy of carbon fiber surfaces, Carbon, 30, 315, 1992. Flemming T, Kress G, Flemming M, A new aligned short carbon fiber reinforced thermoplastic prepreg, Advanced Composite Materials, 5(2), 151-159, 1996. 

Reinforcing fibers can be modified by physical and chemical methods. Chemical and physical modifications of natural fibers are usually performed to correct the deficiencies (described above) of these materials, especially to impart bonding and adhesion, dimensional stability, and thermoplasticity. Surface modification of natural fibers can be used to optimize properties of the interface. 

Polymers reinforced with cellulose fibers have received much attention in recent years because of their low density, nonabrasive, combustible, nontoxic, low cost and biodegradable properties. Several authors have reviewed recent advances in the use of natural fibers in composites like flax [ 1 ], jute [2,3], straw [4], kenaf [5,6], coir [7-9], fique [10], among others. Natural fibers have been used to reinforce thermoplastics and thermosets polymers in automotive and aerospace applications [11]. The influence of surface treatments of natural fibers on interfadal characteristics was also studied [12-17], and Joshi et al. [18] compared the life-cycle environmental performance of natural fiber composites with glass fiber composites. In this study, natural fiber composites were found to be environmentally superior in most applications. 

D. Cho, and H.S. Lee, Eflect of liber surface modification on the interfacial and mechanical properties of kenaf fiber-reinforced thermoplastic and thermosetting polymer composites. Compos. Interface 16(7-9), 711-729 (2009). 

The glass-reinforced thermoplastic polyester resins are nnusual in that they are the first thermoplastic that can compare with, or are better than, thermosets in electrical, mechanical, dimensional, and aeep properties at elevated temperatures (approximately 150°C), while having superior impact properties. The glass fiber concentration usually ranges from 10 to 30 percent in commercially available grades. In molded parts, the glass fibers remain slightly below the surface so that finished items have a very smooth surface finish as well as an excellent appearance. 

Amorphous silica lacks a definite shape and an orderly atomic latticework. Types of amorphous silica include glass, vitreous glass fiber, large flocculated silica gel, diatomaceous earth, and opaline phase-fused silica in granular and powder form. These products provide high purity, reinforcement, great surface area, flatting properties, and thixotropy. Fused silica has an extremely low coefficient of linear thermal expansion and has become quite popular, especially in electronics applications. The amorphous silicas are compatible with thermosets, thermoplastics, silicone rubber, and other elastomers. 

A shutoff ring that involves a closure of a sharp corner against a flat surface is recommended for reinforced thermoplastics (see Fig. 4-9). This provides a positive cutoff should some of the fibers be trapped in the closure. 

Table 5-3 lists some solvents suitable for bonding glass-reinforced thermoplastics. A dope containing 10-15% dissolved resin is reconunended for solvent bonding to compensate for the relatively rough surfaces of GRTP. ... 

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