Polypropylene matrix

First, thermal behaviour of decabromobiphenyl ether 1 will be described. The thermal reactivity of this compound depends on the applied conditions the pure compound reacts completely different in comparison to its reaction in polymeric matrices. Thermolysis of the pure compound gives a good yield (60 %) of hexabromobenzene. The main products obtained by incineration in th DIN oven at three temperatures for pure 1 and of 1 within a polypropylene matrix are shown in Table 1. 

Blending of a soft rubber, possibly partially vulcanized, dispersed in a rigid thermoplastic matrix. For example, EPDM can be dispersed in a polypropylene matrix leading to ... 

TPOs, mainly PP/EPDM produced by blending of a polypropylene matrix and a dispersed unvulcanized EPDM or by copolymerization of polypropylene and sequences of EPDM TPVs... 

Earlier we found that the addition of alkyl-modified poly(propylene imine) dendrimers to polypropylene leads to fibers which can be dyed in conventional acid or disperse dyeing processes [3]. The alkyl chains make the additive compatible with the polypropylene matrix, while the polar core of the dendrimer can act as a receptor for the dye molecules. This host-guest behavior is analogous to the principle of the dendritic box as described by Meijer et al. [30] and elaborated by Baars et al. for dye extraction processes [31]. 

The dyeing of polypropylene fibers, being an item of research for decades, is successfully accomplished with partially stearate-modified hyperbranched polyesteramides. The long alkyl chains ensure compatibility with the polypropylene matrix. The mixing-in of hyperbranched polyesteramides via extrusion affected neither the melt spinning process nor the final polypropylene fiber properties. The modified fibers are dyeable under standard conditions as are, e.g., polyesters or cotton. They can even be used for printing for example a picture pattern on a polypropylene carpet. 

Medina, E.M.G. (1996) Alignment and management of talc platelets in polypropylene matrix by the application of shear controlled orientation injection moulding (SCORIM) technology. PhD thesis, Brunei University, UK... 

Chauve et al. [253] utilized the same technique to examine the reinforcing effects of cellulose whiskers in EVA copolymer nanocomposites. It was shown that larger energy is needed to separate polar EVA copolymers from cellulose than for the nonpolar ethylene homopolymer. The elastomeric properties in the presence of spherical nanoparticles were studied by Sen et al. [254] utilizing Monte Carlo simulations on polypropylene matrix. They found that the presence of the nanofillers, due to their effect on chain conformation, significantly affected the elastomeric properties of nanocomposites. 

B. B. Marosfoi, S. Garas, B. Bodzay, F. Zubonyai, and G. Marosi, Flame retardancy study on magnesium hydroxide associated with clays of different morphology in polypropylene matrix, Polym. Adv. Technol., 2008, 19 693-700. 

Products composed of one type of plastic only. Examples are monolayer foils used, e.g., in packaging for bakery or in the form of bags for household application. It is worth noting that a mono-material film, consisting, e.g., of polypropylene, may contain more than one component. If the film is coloured, this is obtained by mixing a polypropylene matrix with a colourant carried by another polypropylene, normally of lower molecular weight. 

In a recent study, the interphases for different fiber/polymer matrix systems were investigated. By using phase imaging the differences in local mechanical property variation in the interphase of glass fiber reinforced epoxy resin (EP) and glass fiber reinforced polypropylene matrix (PP) composites could be unraveled. As shown in Fig. 3.68, the glass fiber, the interphase and the PP matrix can be differentiated based on their surface mechanical properties as assessed qualitatively by TM phase imaging. 

In the intermittent contact mode phase images shown in Fig. 3.74 a clear contrast between the constituent phases can be observed both for the compression-molded hmsPP (panel a), as well as for the blown film (in the machine and transverse direction in panels band c, respectively). The soft EPR phase appears with dark phase contrast indicating that a substantial amount of energy is dissipated in this phase compared to the PP phase. The EPR particles measure 1 pm or smaller in diameter dispersed in the polypropylene matrix. The horizontal lines and the occasional vertical streaks in the images are artifacts of microtoming. 

In intumescent fire retardant application, clay was combined with ammonium polyphosphate and pentaerythritol in the polypropylene matrix. The fire retarding properties depended on the composition of clay. Ammonium polyphosphate played the role of carbonization catalyst and pcnlacrylhrilol the role of carbonization agent. 

The last example of macroheterogeneous lamellar solids concerns talcs that are common fillers for polyolefinic matrices because their crystalline structure induces the crystallization of, say, the polypropylene matrix. Of course, talcs are natural products whose superficial properties depend on the location of the mine. Their characteristics are reported in Table 3. 

Electron Spin Resonance Study of Hindered Piperidine Derivatives in Polypropylene Matrix in the Presence of Other Additives... 

A recent investigation into the possible ester bond formation between a maleated polypropylene and wood liber when the reaction is performed in a molten polypropylene matrix came again to an ambiguous conclusion [28]. The authors have noticed that dne to overlapping infrared absorption spectra for all the initial ingredients and (presumably) final products of the coupling reaction, the results are not a clear proof of any kind, and from this lack of evidence no statement can be made. ... 

The oil resistance and chemical resistance of nitrile rubber is generally superior to that of EPDM rubbers. However, the highly polar nature of acrylonitrile comonomer is responsible for the high incompatibility between nitrile rubber and polypropylene. The dispersability and the stability of nitrile rubber dispersions in the polypropylene matrix are poor. Hence a reactive compatibilization technology was used [Coran and Patel, 1983], It consisted of blending a small amount of a low molecular weight amine-terminated butadiene-acrylonitrile copolymer (ATBN,... 

In order to preserve the affinity with the nonpolar polypropylene matrix, the substitution of a small fraction of the matrix by another polypropylene with just a few polar groups grafted onto its backbone has been proven, in the last 20 years, to be a very effective strategy to promote isotactic polypropylene for engineering polymer applications. 

The presence of mineral reinforcements such as talc or mica, as foreign solid particles embedded into a polypropylene matrix, usually induces a nucleation effect. A signihcant increase in the crystalline content of the polymer is evidenced if compared with the neat polymer when processed at the same setup conditions that are necessary to ensure a good accommodation of the solid particles into the amorphous phase of the polymer in order to obtain a material with a good mechanical performance (27). The comparison between PP/mica and PP/talc composites in terms of their mechanical behavior under dynamic conditions in the solid state agrees with the morphological features derived from their chemical structures of both minerals (28). 

Because the 57Vratio is proportional to the specific surface of the mineral and being higher for mica than for talc, it follows that specific surface would always be lower for mica than for talc particles. Then for the same crystaHine amount of the polypropylene matrix, a higher fraction of amorphous phase involved in the coating of talc particles than in the coating of mica particles would be expected. 

Such kind of considerations about the finite dimensions of the interfacial area at the polymer/mineral interphase must be taken into account when we try to modify the interface by substituting a part (frequently a little part is enough) of the polypropylene matrix with a chemically modified polypropylene by grafting of polar groups. Also, the structural characteristics of such chemically modified polypropylene must be considered, mainly its molecular weight, if crystalline or not, and the nature and number of polar grafts. 

Figure 13.6 Examples of correlation between responses from different scales when the interfacial modifier is changed Left, tensile strength at break point (up) and relative crystalline variation for the polypropylene matrix (down) versus the grafting level in the interfacial modifier right, elastic moduli (tensile/DMA) ratio (up) and components of the complex modulus from DMA tests (down) versus the grafting level in the interfacial modifier. (From References 32 and 55 with permission of John Wiley Sons, Inc. and Elsevier, respectively.)...

The crystallization behavior and kinetics under isothermal conditions of iPP/SBH and HDPE/SBH blends, compatibilized with PP-g-SBH and PE-g-SBH copolymers, respectively, have been investigated (71). It has been established that the LCP dispersed phase in the blends plays a nucleation role for the polyolefin matrix crystallization. This effect is more pronounced in the polypropylene matrix than in the polyethylene matrix, due to the lower crystallization rate of the former. The addition of PP-g-SBH copolymers (2.5-10 wt%) to 90/10 and 80/20 iPP/SBH blends provokes a drastic increase of the overall crystallization rate of the iPP matrix and of the degree of crystallinity. Table 17.4 collects the isothermal crystallization parameters for uncompatibilized and compatibilized iPP/SBH blends (71). On the contrary, the addition of PE-g-SBH copolymers (COP or COP 120) (2.5-8 wt%) to 80/20 HDPE/SBH blends almost does not change or only slightly decreases the PE overall crystallization rate (71). This is due to some difference in the compatibilization mechanism and efficiency of both types of graft copolymers (PP-g-SBH and PE-g-SBH). The two polyolefin-g-SBH copolymers migrate to blend interfaces and... 

The micrographs of polypropylene/epoxy blends shown in Fig. 21.13 contain epoxy particles of diameter 3-4 pm dispersed in polypropylene matrix (70/30). When the blend was compatibilized with MAH-g-PP, fine epoxy particles with an average diameter of 1 pm were dispersed in the PP matrix, that is, the maleic anhydride group of the MAH-g-PP reacted with epoxy group to form a copolymer and acted as a compatibihzer (48). The reaction between the two groups was evident from torque measurements during mixing. 

Carbon black formed chain-like stmcture within the nonpolar polypropylene matrix in the form of agglomerates rather than as individual particles because of the poor wetting of carbon black. The carbon black distribution in PP was relatively... 

The epoxy phase is dispersed in polypropylene matrix, the particles are elongated and there was no migration of carbon black to PP due to the good affinity between epoxy and carbon black (Fig. 21.27a). Therefore, the blends exhibited similar volume resistivity as that of the simultaneously melt-mixed blends. The micrographs of PP/CB/epoxy system in Fig. 21.27b revealed partial migration... 

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