Blends compatibilisers

New Orleans, La., August 1999, p.752-3 POLYSTYRENE/POLYPROPYLENE POLYMER BLEND COMPATIBILISATION WITHOUT ADDITION OF PREMADE BLOCK OR GRAFT COPOLYMERS OR FUNCTIONALISATION Furgiuele N Khait K Torkelson J M (ACS,Div.of Polymer Chemistry)... 

It is concluded that IR spectroscopy provides information on qualitative as well quantitative analyses of rubbery materials, apart from their microstructures (that is, whether cis or trans, syndiotactic, atactic or isotactic). Different types of rubber blends (compatibilised or self-crosslinked) can be identified by the infrared spectroscopy. Synthesis, and degradation of polymers can also be followed by IR spectra. Mechanism of interaction between rubbers and fillers, can also be studied by IR-spectra. Different types of chemical reactions like the milling behaviour of rubbers, mechanism of adhesion and degradation can also be studied with the help of IR spectroscopy. The technique plays a great role in the product analysis under reverse engineering. 

There are a number of polymeric compatibilisers, e.g., block/graft copolymers like tri-block copolymers of SBS used mostly in styrenic blend compatibilisation, and functionalised polymers with certain functional groups (epoxidised or maleated), which can act like a surfactant . 

Particularly important for immiscible polymer blends (compatibilisers, coupling agents, interfacial agents). ... 

Mahanta and co-workers [71] prepared a blend of rPC, recycled acrylonitrile-butadiene-styrene (rABS) and nanoclay, Cloisite SOB or Cloisite 15A. The blend was compatibilised with both PP-g-MA and solid epoxy resin. The mechanical properties of the rABS/rPC blend without a compatibiliser decreased in comparison to neat matrices. However, upon the addition of 5 wt% of a PP-g-MA compatibiliser, the mechanical properties improved. Similarly, further addition of the epoxy led to a synergistic behaviour in mechanical performance, particularly the modulus and tensile strength. Also, a greater improvement of the modulus was achieved in the rPC-rich blend by simultaneously adding two nanoclays. The thermal stability of the blends compatibilised with PP-g-MA and epoxy exhibited positive thermal properties. 

Deyrail Y, Mighri F, Bousmina M, Kaliaguine S. Polyamide/polystyrene blend compatibilisation by montmorillonite nanoclay and its effect on macroporosity of gas diffusion layers for proton exchange membrane fuel cells. Fuel Cells 2007 7 447-52. 

Papke N. and Kargar-Kocsis J., Thermoplastic elastomer based on compatibilised poly(ethyleneterphtha-late) blend Effect of rubber type and dynamic curing. Polymer, 42, 1109, 2001. 

For general aspects on sonochemistry the reader is referred to references [174,180], and for cavitation to references [175,186]. Cordemans [187] has briefly reviewed the use of (ultra)sound in the chemical industry. Typical applications include thermally induced polymer cross-linking, dispersion of Ti02 pigments in paints, and stabilisation of emulsions. High power ultrasonic waves allow rapid in situ copolymerisation and compatibilisation of immiscible polymer melt blends. Roberts [170] has reviewed high-intensity ultrasonics, cavitation and relevant parameters (frequency, intensity,... 

Usually polymeric substances of appropriate chemical structure and morphology which promote the miscibility of incompatible materials. Block copolymers are especially useful surfactants at the polymer/polymer interface because the two blocks can be made up from molecules of the individual polymers to be mixed. Typical compatibilisers in polymer blends are LDPE-g-PS in PE/PS CPE in PE/PVC acrylic- -PE, -PP, -EPDM in polyolefin/PA and maleic-g-PE, -PP, -EPDM, -SEBS in polyolefin/polyesters. 

Another important class of copolymers synthesized by chain polymerisation are block (or sequenced) copolymers diblock and triblock copolymers being the most important ones. They are very useful as compatibilisers (emulsifiers) in immiscible polymer blends. Another major use is as thermoplastic elastomers. Both uses are best explained through the example of butadiene-styrene block copolymers. 

Copolymers (graft or block) made of immiscible sequences give rise to biphasic morphologies depending on the ratio of immiscible sequences (or of their lengths). Such possible microstructures are reported in Figure 33. A minor phase can be dispersed as nodules (spheres) or filaments (cylinders) while, when concentrations of both phases get similar, lamellar (interpenetrated) structures can appear. It should be noted that rather similar morphologies could also be found in (compatibilised) polymer blends. 

Blends of poly (ethylene terephthalate) (PETP) and polypropylene (PP) with different rheological properties were dry blended or compounded, and extrusion foamed using both physical blowing and chemical agents, and the foam properties compared with those of foam produced from the individual components in the absence of compatibilisers and rheology modifiers. The foams were characterised by measurement of density, cell size and thermal properties. Low density foam with a fine cell size was obtained by addition of a compatibiliser and a co-agent, and foamed using carbon dioxide. The presence of PP or a polyolefin-based compatibiliser did not effect... 

A novel approach is used to compatibilise a blend without addition of premade copolymers or functionalisation of polymers lacking functional groups. Solid-state shear pulverisation (S3P) processes polymers at temperatures below the melt transition (for semicrystalline polymers) or the glass transition (for amorphous polymers). The polymer, introduced as pellets or flakes into the pulveriser. 

A stndy was made of the effects of foam formulation and process conditions and liner composition on the adhesion of HCFC-141b blown rigid PU foam thermal insulation to refrigerator liner protective layers made of ABS, high-impact PS (HIPS), PE and blends of HIPS and PE containing a compatibiliser and adhesion promoter. A tensile test was used to quantify the level of adhesion before and after thermal cycling, and the Brett mould was used for laboratory simulations of foam adhesion within... 

J. Pospfsil, I. Forteln, D. Micheilkovei, Z. Kruli , and M. Slouf, Mechanism of reactive compatibilisation of a blend of recycled LDPE/HIPS using an EPDM/SB/aromatic diamine co-additive system, Polym. Degrad. Stab., 90(2) 244-249, November 2005. 

Diblock copolymers, especially those containing a block chemically identical to one of the blend components, are more effective than triblocks or graft copolymers. Thermodynamic calculations indicate that efficient compat-ibilisation can be achieved with multiblock copolymers [47], potentially for heterogeneous mixed blends. Miscibility of particular segments of the copolymer in one of the phases of the bend is required. Compatibilisers for blends consisting of mixtures of polyolefins are of major interest for recyclates. Random poly(ethylene-co-propylene) is an effective compatibiliser for LDPE-PP, HDPE-PP or LLDPE-PP blends. The impact performance of PE-PP was improved by the addition of very low density PE or elastomeric poly(styrene-block-(ethylene-co-butylene-l)-block styrene) triblock copolymers (SEBS) [52]. 

Inmiscible blends of HDPE or LDPE with PS have been compatibilised with various graft copolymers, such as PS-graft-PE, PS-graft-EPDM or block copolymers such as SBS triblocks, SEBS, PS-block-polybutadiene [53, 54]. The same block copolymers are suitable for PP-PS blends [55]. 

Compatibility of PE with PVC is improved by poly(ethylene-graft-vinyl chloride) or partial chlorinated PE. To compatibilise blends of PE with PET, common for the scrap of beverage bottles, EPDM or SEBS are effective additives [56]. 

The ionic aggregates present in an ionomer act as physical crosslinks and drastically change the polymer properties. The blending of two ionomers enhances the compatibility via ion-ion interaction. The compatibilisation of polymer blends by specific ion-dipole and ion-ion interactions has recently received wide attention [93-96]. FT-IR spectroscopy is a powerful technique for investigating such specific interactions [97-99] in an ionic blend made from the acid form of sulfonated polystyrene and poly[(ethyl acrylate - CO (4, vinyl pyridine)]. Datta and co-workers [98] characterised blends of zinc oxide-neutralised maleated EPDM (m-EPDM) and zinc salt of an ethylene-methacrylic acid copolymer (Zn-EMA), wherein Zn-EMA content does not exceed 50% by weight. The blend behaves as an ionic thermoplastic elastomer (ITPE). Blends (Z0, Z5 and Z10) were prepared according to the following formulations [98] ... 

Kandola, B. K., Smart, G., Horrocks, A. R., Joseph, P., Zhang, S., Hull, T. R., Ebdon, J., Hunt, B., and Cook, A., Effect of different compatibilisers on nanoclay dispersion, thermal stability, and burning behavior of polypropylene-nanoclay blends, J. Appl. Polym. Sci., 2008, 108, 816-824. 

Polycaprolactone aliphatic polyesters have long been available from companies such as Solvay and Union Carbide (now Dow Performance Chemicals) for use in adhesives, compatibilisers, modifiers and films as well as medical applications. These materials have low melting points and high prices ( 4-7 per kg in 2005). PCL is predominantly used as a component in polyester/starch blends such as... 

The company claims easy processing results from the high compatibility of the blend components. The formulation consists of more than 10% PLA (purchased from NatureWorks LLC) plus a biodegradable co-polyester and special additives. FKuR says a special combination of compatibilisers permits coupling between the PLA and the co-polyester. The compound is homogeneous, which allows the film to be drawn down to 8 microns. Film up to 110 microns thick is 90% degraded after twelve weeks in composting conditions. 

Chlorinated polyethylene was evaluated as a compatibiliser forpoly(vinyl chloride) composites containing 25% or 40% wood flour. The compositions also contained lubricants, a stabiliser and a processing aid. Following blending, the composites were characterised by rheology studies and measurements of melt strength. The addition of chlorinated polyethylene significantly enhanced the processability of... 

In the field of thermoplastic immiscible blends, the emulsifying activity of block copolymers has been widely used to solve the usual problem of large immiscibility associated with high interfacial tension, poor adhesion and resulting in poor mechanical properties. An immiscible thermoplastic blend A/B can actually be compatibilised by adding a diblock copolymer, poly(A-b-B) whose segments are chemically identical to the dissimilar homopolymers, or poly(X-b-Y) in which each block is chemically different but thermodynamically miscible with one of the blend component. Theoretical... 

The use of polysilanes as photoinitiators of radical polymerization was one of the hrst means whereby they were incorporated within block copolymer structures [38 0], albeit in an uncontrolled fashion. However the resulting block copolymer structures were poorly defined and interest in them principally lay in their application as compatibilisers for polystyrene (PS) and polymethylphenylsilane blends PMPS. The earliest synthetic strategies for relatively well-defined copolymers based on polysilanes exploited the condensation of the chain ends of polysilanes prepared by Wurtz-type syntheses with those of a second prepolymer that was to constitute the other component block. Typically, a mixture of AB and ABA block copolymers in which the A block was polystyrene (PS) and the B block was polymethylphenylsilane (PMPS) was prepared by reaction of anionically active chains ends of polystyrene (e.g. polystyryl lithium) with Si-X (X=Br, Cl) chain ends of a,co-dihalo-polymethylphenylsilane an example of which is shown in Fig. 2 [43,44,45]. Similar strategies were subsequently used to prepare an AB/ABA copolymer mixture in which the A block was poly(methyl methacrylate) (PMMA) [46] and also a multi- block copolymer of PMPS and polyisoprene (PI) [47]. 

Thus, it appears that chemical reactivity or ionic-cross interactions could lead to in situ compatibilising or miscibility enhancement during melt-mixing. However, several questions remain. How does the reactivity modify the thermodynamic balance, the reciprocal miscibility or the rheological behaviour of the melt Or, how the covalent or ionic bonding influence the interfacial adhesion processability and final mechanical properties of the immiscible blends ... 

In our previous study (17), PE/BMA-salt blends were shown to be conpatible (not in the thermodynamic sense) for a given mixing technique and parameters. It was also pointed out that there is separate crystallisation of PE and EMA-salt in PE/EMA-salt blends, without any perturbation of the crystal structure or degree of crystallinity of the other coiqionent. Since the interactions leading to the compatibilisation of the mechanical properties in PE/EMA-salt blends do not occur in the crystalline phase, they must be present in the amorphous phase. 

The problem of physical blends is not only the formation of a stable morphology. A more important problem for the users of such materials is the changing and most often the lowering of material properties. Table 9 [13] lists the effect of the reactive compatibilisation of polypropylene PA-6 blends of different compositions ... 

To improve the miscibility of polymer systems, a well-known method is to add compatibilisers or to form compatibilising compounds during processing. These substances are located in the interface layer and improve the blend morphology and the material properties. 

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