Blends with PPS

Since PPS is crystalline we should expect it to produce blends with much better chemical resistance than amorphous materials such as PAES. It should also allow very substantial cost reduction and can improve melt flow. Union Carbide filed patents on PEEK/PPS blends as early as 1982 [15]. Kureha has developed materials with improved compatibility, melt flow, formability and mechanical properties [16] Ticona has filed patents on improved PEEK/PPS blends and the most recent patent provides a good summary of the historical developments [17]. Solvay has filed patents on PEEK/PPS blends for use in bearing surfaces - under the conditions tested the blends perform as well as pure PEEK compounds [18]. It is possible that this technology is used in some of Solvay s Avaspire grades. 

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The effect of a second polymer blended with PPS which causes enhanced nucleation of PPS has been previously observed. It was found that low concentrations (1—2 wt %) of poly(phenylene sulfide ketone) and poly(ether ether ketone), when melt-blended with PPS, function effectively to increase the nucleation density of PPS (149). 

Ha [29] has shown that in PP-HDPE (of high-den-sity PE) dynamically cured EPDM, the cured EPDM act as a compatibilizer to the HDPE-PP system. Blending was done in two ways. EPDM was cured first and then blended with PP and HDPE. In the second case, EPDM was cured in the presence of PP and HDPE using dicu-myl peroxide (DCP) as the vulcanizing agent. In EPDM-rich composition, mechanical properties were increased by increasing the concentration of DCP, whereas in PP-rich composition, the reverse was the case. 

One of the earliest references on compatibilizing a nylon-6-polypropylene blend using maleic anhydride grafted PP (PP-g-MAH) was the work of Ide and Hase-gawa published in 1974 [35]. In their study, the formation of a graft copolymer was confirmed by DSC after solvent extraction of the PP component. Blends with PP-g-MAH... 

Several liquid cryatalline polymers were melt blended with an amorphous (Ultem) and two semicrystalline (PEEK and PPS) engineering thermoplastics in a single screw extruder. Flat film was processed with different degrees of stretch imparted while the film was being cooled. In the case of Vectra, which was thought to be ideally suited to be blended with PPS based on thermal and rheological... 

The comonomer used for copolymerization with tetramethyl-4-piperidyl methacrylate influences the observed light stabilizing effect in blends with PP [302], The best efficiency was imparted by copolymers with styrene and alkyl acrylates. The most efficient copolymer with styrene was also tested in photo-oxidized cis- 1,4-polybutadiene and was found to be less efficient than 35a. 

Many EPR and EPDM elastomers show a block copolymer behavior. When blended with PP, they form emulsion-like dispersions. For the ease of compounding a small amount of PE may also be added. Furthermore, if the elastomeric phase is hghtiy crosslinked the morphology is more stable. The PP/EPR blends can be processed by all methods used for PP. They are characterized by good processability, dimensional stability, low... 

Polytransoctanamer (PTO) has been used as a high performance elastomer and in blends with commodity and engineering resins. Polyoctadecene (POD) blends with PP are thermochromic. The most interesting are the metallocene-type polycyclic polyolefins, e.g., polycyclopentene or polynor-bornene, either syndiotactic or isotactic with T =400-600°C. 

Linear, aromatic polyamides (PARA) are either liquid crystalline, semicrystalline, or amorphous. Mainly the latter resins are used in blends with PP, viz. PARA with PP-MA [Iwanami et al.,... 

PPE modified with either glycidol or epichlorohydrin blended with PP-MA, PP-GMA, ionomers, EVAl, PA, and PEST for moldability, solvent and heat resistance, mechanical strength Arashiro et al., 1994... 

PAr s are aromatic amorphous polyesters, viz. U-polymer , Ardel D-lOO, Durel , Arylon , etc. Their T = 188°C and HOT = 120-175°C. Blends with PPS have been developed to improve the performance of PAr — processability, rigidity and hydrolytic stability. 

Polyimides (PI) were introduced in 1962 as thermally non-processable Kapton . To improve processability, the main-chain flexibility was enhanced by incorporating segments with higher mobility, viz. polyamide-imide (PAl), polyether-imide (PEI), polyimide-sulfone (PISO), etc. These polymers are characterized by high T = 150-420°C and thermal resistance. They are blended with PPS to enhance its moldability, thermal stability and mechanical performance. 

In immiscible polymer blends with a high degree of immiscibility such as PP/PS, it has been shown that nucleation at the interface affects the crystallization behavior. Wenig et al. [1990] showed that, with increasing the amount of PS in a blend with PP, the nucleation shifted from preferentially thermal (related to the degree of undercooling) to more athermal. This was... 

Figure 3.43. DSC cooling curves (10°C/min) for PP/PS blends difference in the crystallization behavior in blends with PP as a matrix phase and as a dispersed phase [Santana and Muller, 1994],...

Holsti-Miettinen et al. [1992] and Ikkala et al. [1993] recently studied the crystallization behavior of PA-6 blended with PP. No shift of the crystallization temperature of the PA-6 matrix was observed in the blends the dispersed PP droplets did not influence the crystallization behavior of the matrix. 

Polyethylene Blends On account of their commercial interest, the crystallization of HOPE, LDPE and LLDPE in blends with PP has been extensively investigated. In these systems, the PP phase solidified already before the PE matrix starts crystallizing. 

Nadkami and Jog [1986] have reported on PPS/HDPE blends. The degree of crystallinity of HDPE was reduced when HDPE was the minor phase. Lurthermore, the T shifted to somewhat lower temperatures (by about 5°C) but only in those blends with a low HDPE content. Isothermal crystallization half-times for HDPE in its blends with PPS decreased as the HDPE content decreased, indicating an enhanced nucleation from the solidified PPS interfaces. 

PP/PA-6 maleated-PP (PP-MA) Thermal analysis and optical microscopy. One or two crystallization peaks were affected by PP-MA. T of PA-6 initially decreased Uien leveled off with PP-MA content, whereas that of PP was not affected. Blends with PP-MA showed concurrent crystallization at the T of PP. Moon et ah, 1994... 

Favis [1994] and Willis andFavis [1988] prepared compatibilized PA blends with PP and carboxylic acid-functionalized EMAA ionomer. Blends containing 90-10 parts PA-6, 0-30 parts EMAA ionomer, and 10-90 parts PP were combined in an internal mixer at 250°C and characterized by torque rheometry and SEM. Dispersed phase particle size vs. interfacial modifier concentration was determined. Emulsification curves were constructed. Effects of mixing protocol on blend properties were studied. Blends were also prepared containing HOPE in place of PP. 

PA-6 or PA-66 blends with PP e.g., Akuloy RM, Dexpro , Dexlon , Eref, Flexloy , Gapex , LAX 23, MCX-Q, NB, Novamid AC, Orgal-loy , Poliblend NH, Snialoy , Systemer S, Thermocomp , Ube Alloy CA, Ultramid KR, UTX) have flow properties similar to PP. This constitutes an improvement over the flow behavior of neat PA. The PA/PP blends are easier to extrude than PA is because the melt viscosity is... 

As discussed earlier, ethylene propylene rubber (EPR or EPM) has been blended with PP and PE to improve the impact strength and to render the materials softer. Recently, metallocene catalysts or postmetallocene catalysts provide new pathways to generate elastic copolymers that can replace EPR. These pathways possess cheaper manufacturing cost and generate new materials with better compatibility to PP or PE. Such new materials included ethylene-propylene random copolymers with dominant ethylene component (33-34) or propylene-dominant component (35 1), propylene-ethylene block copolymer (42), ethylene-octene copolymer (43), poly(propylene-co-ethylene) (44), ethylene-hexene copolymer (45), ethylene-butene copolymer (46), low isotactic PP (47), and stereoblock PP (48). These materials are generally compatible with PP or PE, thus can be used to tailor the toughness (or the softness) of... 

Practically, some of the above polyolefin copolymers have already been used to blend with PP in applications such as car bumpers and impact elastomeric goods. Although ethylene-propylene random copolymer has been the main component for such... 

The analysis of MFI values (Fig. 10.6b) shows that with a PP concentration up to 25 wt%, the blends have a low MFI value (the melt viscosity is high). Low additions of EPR, same as PE additions (Table 10.5), cause an increase in MFI values. Since propylene units belong to the molecular structure of EPR, it appears that at equal concentrations of PE and EPR in blends with PP, the concentration of hydrogen atoms, bonded to tertiary carbon atoms, is higher in the second case. That is why, specificities of I A-grafting reaction, related to the concentration and the reactivity of macroradicals, are more pronounced in PP/EPR than in PP/PE blends. 

They also cured EPDM without PP and then blended with PP. The effect of DCP concentration, intensity of the shear mixing, and rubber/plastic composition were studied. They found in blend cure that the melt viscosity increased with increasing DCP concentration in the blends of 75% EPDM and 25% PP but decreased with increasing DCP concentration in blends of 75% PP and 25% EPDM. Melt viscosity increased with increasing DCP concentration for all compositions in cure blend. With increasing intensity of the shear mixing, the melt viscosity decreased. Figures 14.12 and 14.13 show the results. 

Polypropylene film fiber is becoming of great commercial interest in many applications such as carpeting and woven sacks. It consists of an extruded film that is slit along the machine direction into narrow, fiber-like ribbons. These ribbons are then woven to make strong fabrics, nets, and sacks. Low-density polyethylene (LDPE) is sometimes blended with PP in slit film applications in order to reduce fibrillation and improve processability. 

In this and the following two sections we consider the data for a PLC and for different blends of that PLC with isotactic polypropylene (PP). The PLC used in this study was liquid crystalline copolyester PET/0.6PHB, where PET = poly (ethylene terephthalate), PHB = p-hydroxybenzoic acid and 0.6 is the mole fraction of PHB in the copolymer, manufactured by Unitika Ltd, Kyoto, Japan. The content of the PLC in the blends with PP was varied from 0 to 20 wt%. The samples were prepared by injection molding. PP, resin VB65 llB, was supplied by Neste OY, Finland. 

Mixing was performed by internal mixer (Haake Rheomix 600P). The mixing temperature was 180 °C, with a rotor speed of 100 rpm and 13 min mixing time. The indirect technique (IDT) was used to prepare nanocomposites, this involved mixing the MWCNTs with LNR separately, before it was melt blended with PP and NR in the internal mixer. TPNR nanocomposites were prepared by melt blending of PP, NR and LNR with MWCNTs in a ratio of 70 wt% PP, 20 wt% NR and 10 wt% LNR as a compatibilizer and 2 wt%, 4 wt%, 6 wt% and 8 wt% MWCNTs. 

Linear, aromatic polyamides (PARA) are either liquid crystalline, semicrystalline, or amorphous. Mainly the latter resins are used in blends with PP, viz., PARA with PP-MA (Iwanami et al. 1990), PARA with PE-MA, or PP and hydrazine (Yoshihara 1990). Blends of copolyphthalamide (PPA) with PP were compatibihzed using either PP-MA (Paschke et al. 1993, 1994) or PP grafted with acrylic acid (Brooks et al. 1993, 1994). 

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