Mixer blending of styrene

Motionless Mixer Blending of Styrene/ Acrylonitrile Copolymer and Nitrile Rubber to Form ABS... 

In the first one, the two materials are blended on a rubber mill or in an internal mixer. Blending of the two materials can also be achieved by combining emulsion latexes of the two materials together and then coagulating the mixture. Peroxide must be added to the blends in order to achieve some crosslinking of the elastomer to attain optimum properties. A wide range of blends are made by this technique with various properties. Most common commercial blends of ABS resins may contain 70 parts of styrene-acrylonitrile copolymer (70/30) and 40 parts of butadiene-nitrile rubber (65/35). 

Dharmarajan et al. [1995] have prepared com-patibilized blends of PO/PP/styrene copolymer. Blends of 100-0 parts PP, 0-100 parts SMA, 0-15 parts EP-g-l° amine (0.3 mol % amine), and 0-5 parts PP-2° amine (0.4 wt% amine) were combined in an internal mixer at 220°C. Blends were characterized by FTIR, DMTA, TEM, rheology, mechanical properties, lap shear adhesion, and paint adhesion. Properties were compared for blends containing either of the two amine-functionalized polymers alone. 

Even in the phase separated blends, where some degree of partial miscibility or compatibility exists between the components, simple melt blending in an intensive shear mixer is adequate for making a well dispersed, reasonably stable blend product with useful combination of properties, such as polypropylene/ethylene-propyl-ene rubber blend, ABS/polycarbonate blend, etc. The self-compatibUizing nature of these blends stems from partial miscibility and the mutual interpenetration of polymer chains at the interface. Slight modifications of the polymer backbone are often employed, particularly in the case of styrenic and ABS resins to induce partial miscibility with other resins. 

Vainio et al. (1997, 1996a) have compatibilized PEST/PP blends by graft copolymer formation between acid-terminated polyester and oxazoline-grafted PP. Specifically, 30 parts PBT was mixed with 0-70 parts PP and 0-70 parts PP-g-oxazoline in an internal mixer at 250 °C or TSE at 240 °C. Blends were characterized by SEM, torque rheometry, DMA, and DSC. Oxazoline-functionalized PP was prepared by grafting PP with ricinol oxazoline maleinate in the presence of styrene monomer + RI. The inclusion of styrene monomer suppresses radical-induced decomposition of PP. Some cross-linked copolymer... 

Processing conditions or chemical reactions occurring in one or both phases of the blend can strongly affect the phase inversion. Of course, these two parameters have a direct effect on the viscosity ratio of the components. The same blend of polyamide/styrene-acrylonitrile copolymer developed phase morphology where PA6 is the matrix when processed using a single-screw extruder, whereas the inverse situahon occurred when the blend was mixed several times in a laboratory mixer. 

BR rubbers or high styrene ESBR rubber. Usually, these rubbers are not compatible [9]. Figure 1.5 shows, for example, the DSC thermograms of SSBR/BR (75/25) samples mechanically blended in an internal mixer at 50°C and solution (cyclo-hexane) blended. The Tg-value of the BR phase (-110°C) is unaffected however, the glass-rubber transition of the SSBR phase is influenced on the low temperature side. The two transition effects clearly present are an indication for the non-compatibility of these two polymers. 

TseUos et al. [1997] have compatibilized PO/styrene copolymer blends through crosslinked copolymer formation between PO alcohol groups and anhydride groups on styrene copolymer. Specifically, 50 parts EVAl (1.6-7.5% VAl) was mixed with 50 parts SMA (8.4-14.7 mol% MA) in an internal mixer at 200°C. The blends were characterized by torque rheometry, FTIR, DSC, TGA, selective solvent extraction, and mechanical properties as a function of mole ratio alcohol to anhydride. Blend properties were compared to those with EVAc in place of EVAl. 

The 80%/20% binary blends PE/PS and PP/PS were subjected to F-C reaction for compatibilization performed under nitrogen atmosphere in a Banbury mixer. Different concentrations of catalyst (AICI3) and 0.3% of cocatalyst (styrene) were added to the completely melted and mixed physical blends. The blends and catalyst concentrations are weight based. High MW commercial grades of linear low density polyethylene (LLDPE), and injection-grade polypropylene and polystyrene were used as homopolymers. The compatibilization conditions and MW of the homopolymers are given in Table 20.1. Blend names are listed in nomenclature. 

In particular, a microporous poly(/-lactide) (PLLA) composition can be prepared using poly(styrene) (PS) and as compatibilizer a copolymer from a lactide and styrene. Binary blends and compatibilized ternary blends are prepared by melt mixing the polymers and copolymer in a Brabender internal mixer with roller blades, under a constant high flow of dry nitrogen. Dry nitrogen is required to avoid a dramatic melt degradation of the PLLA. Prior to blending, PLLA and PS are dried for 48 /z in a vacuum oven at 70°C. 

PPE is not miscible with SMA containing as much as 28 % MA (Witteler et al. 1993). To compatibilize these two resins, Koning et al. (1993b, 1996) have added a monoamine-terminated PS that can form a graft copolymer with SMA. Since the amine-terminated PS is miscible with PPE, compatibilized PPE-SMA blends are obtained. Specifically, 30 parts of unfunctionalized PPE was blended (internal mixer at 220 °C, or mini-SSE at 280 °C, or TSE at 326 °C) with 56 parts SMA (28 % MA) and 14 parts amine-functionalized PS. The blend was characterized by TEM, SEM, mechanical and thermal properties, DMA, and GPC copolymer detection. The effect of pre-reacting amine-terminated PS with SMA was studied. The blend properties were compared to those for uncompatibilized blends. Blends were also made containing ABS -i- SEBS. Eurther examples of compatibilizing copolymer formation in PPE-styrene copolymer blends are shown in Table 5.43. 

In principle a liquid additive can be added to polymers anywhere from the base of the hopper to an add-on mixer at the screw tip. In a few cases such as plasticisers with polyvinylchloride (PVC) polymer powder and hydrocarbon oil with styrene/butadiene thermoplastic elastomer pellets, batch premixing can be used, during which the polymer absorbs the liquid. The dry blend can then be processed by the extruder. 

Chen et al. prepared PVC/nano-CaCOs and PVC/acrylonitrile-butadiene-styrene terpolymer (ABSj/nano-CaCOs composites by melt-mixing different concentrations of stearic acid modified nano-CaCOs with the matrices in a highspeed two-roll mixer at different processing temperatures. TEM study revealed that the nano-CaCOs particles with size of 30-45 nm were dispersed uniformly at nanometer-scale in both PVC and the PVC/ABS blend. In particular a monodispersion of nano-CaCOs in the PVC matrix was observed at filler content of lOphr. This is a rare example where nano-CaCOs can achieve truly mono-... 

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