Reinforced PPS composites

Developments by BASF in high-impact propylene copolymers produced by reactive blending, random propylene copolymers, glass fibre-reinforced PP composites and PP foams are reported. Properties and applications of these materials are described. 4 refs. BASF AG... 

SZABO J S., CZIGANY T., Investigation of static and dynamic fracture toughness of short ceramic fiber reinforced PP composites, J. Macromol. Sci., B41, 1191-1204, 2002. 

Ward and his coworkers investigated the interlayer adhesion in self-reinforced PP composites modified with different nano- and micron-sized particles [27-29]. They found that the introduction of a small amount of carbon nanofibers (CNFs) led to improved performance of polypropylene single-polymer composites obtained by hot compaction of oriented CNF/ PP tapes. The peel strength of a CNF/PP woven fabric composite was significantly increased. In addition, the authors pointed out that the drawn CNF/PP tapes showed substantial voiding around the fibers which were closed and sealed by the hot compaction process. As a result, the composite density increased to its initial value [27]. 

Table 14.1 Tensile and fracture properties of setf-reinforced PP composites modified with different contents of quartz particles.

Very recently, in our group, enhanced self-reinforced PP composites based on commercial PP fabrics were obtained by the film stacking method followed by compression molding introducing different contents of micron-sized quartz particles in the matrix films (unpublished results). Simultaneous improvements of composite tensile strength, ductility and fracture toughness were observed from the addition of quartz to the polymer matrix (Table 14.1). Enhanced degree of consohdation was obtained for the composites with quartz as evidenced from the improved mechanical properties and by SEM observations. This was also confirmed by acoustic emission analysis in situ in tensile tests. 

The loss of TS observed by Shubhra et al. is shown in Figure 9.8. It was found that TS values of the composites decreased slowly. For silk fibre/PP composites the TS value was 54.7 MPa whereas after 24 weeks of soil burial test it was 49.1 MPa. So, after 24 weeks of soil burial, silk fibre reinforced PP composite lost 10.2% TS, whereas silk-reinforced PP and NR blend (50 50) composite lost 24.3% TS. For silk-reinforced PP and NR blend (50 50) composites the TS value was 39.9 MPa whereas after 24 weeks of soil burial test it was 30.2 MPa. The author mentioned that this 14.1% higher loss of TS is due to incorporation of NR in the PP matrix. The author found that if NR is low (25% instead of 50%), the composite loses less TS value after 24 weeks of degradation test (from 42.4 MPa to 34.3 MPa, which is 19.1%). 

The loss of BS observed by Shubhra et al. is shown in Figure 9.9. It was found that BS values of the composites decreased more rapidly than TS values. For silk fibre/PP composites the BS value was 58.3 MPa whereas after 24 weeks of soil burial test it was 50.7 MPa. So, after 24 weeks of soil burial, silk fibre reinforced PP composite lost 13% BS whereas silk-reinforced PP and NR blend... 

Table 6.3 A comparison between untreated and plasma-treated wood fibre and sisal fibre reinforced PP composites, a and E denote tensile strength and tensile modulus, respectively...

Fig. 6.8 Tensile properties of hemp fibres and hemp fibre reinforced PP composites treated with different methods. Adapted Ifom [100]...

The ballistic properties of high performance fibers such as ultra high molecular weight polyethylene (UHMWPE) and aramid and their composites are very well known. The ballistic properties of flax, hemp, and jute fabric reinforced PP composites processed by hot compression molding have also been investigated. It has been shown that flax composites exhibited better properties when compared with hemp and jute composites [48]. 

Bodros and Baley [37] studied the tensile properties of water retted nettle fibers. Bacci et al. [39] investigated fiber yield of nettle cultivation and quality of fibers extracted by alkalization. Bacci et al. [38] compared the effects of different fiber extraction method combinations including water retting, mechanical decortication and enzymatic treatments on resultant fibers chemical composition and tensile properties. Bajpai et al. [40,41] prepared nettle fiber-reinforced poly lactic acid (PLA) and PP composites by compression molding. Bajpai et al. [42] studied the effects of various environments on the tensile strength of nettle fiber-reinforced PP composites. 

Partly due to their porous structures, plant fibers present high thermal, electrical and acoustical insulation performance and they can be incorporated in biocomposites produced for these causes [49]. Huda and Yang [7] measured the sound absorption capacity of corn husk and jute reinforced PP composites. They found their noise reduction is comparable, and higher sound absorption was achieved when the corn husks xmder-went enzyme treatment before composite manufacturing process. It should be considered that moisture absortion substantially deteriorates heat and electrical insulation performance [71]. 

Figure 14.12 Variation of tensile strength with filler loading for (1) untreated and (2) treated coir-reinforced PP composites.

Figure 14.13 SEM images of 20% coir-reinforced PP composites (A) untreated coir- and (B) treated coir PP composites.

Figure 14.17 Tensile strength of raw and treated jute fiber-reinforced PP composites.

Some important properties of carbon black filled and carbon fiber reinforced PP composites are compared with those of nonfilled PP grades in Table 1. 

In FCP studies performed on neat and discontinuous GF reinforced PP composites, it was found that the stable acceleration range is often preceded by a stable deceleration one [2-4]. The appearance of this range is due to a blunting process in which different matrix- and fiber-related events are involved. 

Figure 1 FCP response as a function of microstructural parameters for discontinuous GF-reinforced PP composites [3]. Note A and m are the parameters of the Paris-Erdogan power law function (see Equation (1)), respectively.

Figure 3 Difterence in the damage zone and related failure mechanisms between discontinuous fiber and mat reinforced PP composites (from the project DFG Ne 546/5-1).

In Figure 2 the tensile strength and Young s modulus of natural fiber reinforced PP-composites are shown and compared to those achieved by GF-reinforcement at the same reinforcement content (30 wt.%). 

Keywords automotive, automotive application, car components, automotive requirements, substitution of metals and polymers, interior parts, exterior parts, electrical applications, filled PP, elastomer-modified PP, thermoplastic polyolefins (TPO), GMT-PP, long-fiber reinforced PP, composites, market trends, glass fiber (GF) reinforcement. 

The benefits are more pronounced if we relate the flexural strength and thermal tolerance to the unit cost (US cents/cm ). Figure 1 shows those cost-related properties, mapping all the major thermoplastics t)rpes. The linear regression line shows that there is a weak correlation between cost-normalized flexural strength and heat tolerance, and the WFRP-S type wood fiber reinforced PP composite has a top position, being the cheapest solution when strong, heat-tolerant thermoplastic plates are required. 

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