Blends Based on PVC

Aliphatic polyesters based on various combinations of diols/dicarboxylic acids Ethylene-vinyl acetate copolymers (65-80 wt% VAc) 

Ethylene-vinyl acetate-carbon monoxide terpolymers Ethylene-ethyl acrylate-carbon monoxide terpolymers Ethylene-n-butyl acrylate-carbon monoxide terpolymers Ethylene-N,N-dimethyl acrylamide (17-25 wt% DMA) copolymers Chlorinated polyethylene ( 42 wt% Cl) 

Thermoplastic polyurethanes based on polyester soft blocks 

Poly(butylene terephtha]ate)-poly(tetramethylene ether) (AB)n block copolymers 

Chlorinated polyethylene offers miscibility with PVC at levels of 42 wt% Cl and higher, offering permanent plasticization potential [853]. At lower Cl levels, phase separation occurs but mechanical compatibility allows for impact modification of rigid PVC [854]. Poly(butylene terephthalate) (PBT) [855] and poly(butylene terephthalate)-poly(tetramethylene ether) (AB)n block copolymer miscibility [856-858] with PVC has been reported. NMR revealed pure phases of microcrystallites of both the block copolymer and PVC with miscibility of the amorphous phase [858]. 

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The thermal degradation of blends based on PVC, PMMA and PS was also monitored [4]. Recent studies of PMMA systems by Ramesh and coworkers showed that the low thermal resistance of PMMA was suppressed when it was blended with PVC [18], and suggested that the PMMA/PVC blend matrix is more heat-stable than a matrix formed by the PMMA homopolymer alone. 

Several commercial products of PVC/TPU blends are available. The BF Goodrich Chemical Group has a PVC/ TPU blend based on their Estane series TPUs. For example, their Estane 54620, a polyester-based TPU with a °ShA 85 hardness, shows excellent compatibility with flexible PVC. The blends are produced by mixing PVC, TPU, plasticizer, stabilizer, and lubricant in a twin-screw extruder. These polymeric blends show intermediate mechanical properties between PVC and TPU. 

Table 15.14. Comparison of the typical properties of the dynamically vulcanized ethylene terpolymer/PVC blends vs. similar elastomeric blends based on polypropylene...

Marossy K, Polymer blends based on plasticized PVC, 1st International Conference on Polymer Modification, Degradation, and Stabilization, Palermo, Italy, 2000. 

PVC is much too versatile to disappear from the scene altogether. PVC/ ABS foil, backed by semi-rigid PUR foam, is still the most widely used surface for instrument panels. More recently, PVC has been blended with PUR to provide more temperature resistant surfaces. The desire to eliminate volatiles altogether from surfaces exposed to temperature is producing new answers one of these is a flexible blend based on acrylonitrile, styrene and acrylic rubber. In 1993, Krauss-Maffei introduced a more radical development a process for producing a sintered thermoplastic surface on a foam backing in a single operation. 

Blends based on halogen-containing polymers are also significant [30-32]. Those based on halo-genated polyolefin/ethylene interpolymer blends are claimed to be single-phase systems [32]. They are often used where solvent and fire resistance is important. PVC/nitrile rubber/dioctyl phthalate blends are used in similar applications and also in footwear [30-32]. 

Clear coatings based on PVC latex are common on products such as wallpaper, shelf paper, and book covers. Fine-particle silica or diatomaceous earth can be used at low loadings to limit gloss. This effect can also be achieved by blending with PVDC latex such as Vycar 650 x 27 and 660 x 14. These products can also be used for moisture vapor barrier coatings. A special grade, Permax 803 PVDC/acrylic copolymer, is used as a barrier in automotive underbody coatings. 

A number of chemical products are derived from Sasol s synthetic fuel operations based on the Fischer-Tropsch synthesis including paraffin waxes from the Arge process and several polar and nonpolar hydrocarbon mixtures from the Synthol process. Products suitable for use as hot melt adhesives, PVC lubricants, cormgated cardboard coating emulsions, and poHshes have been developed from Arge waxes. Wax blends containing medium and hard wax fractions are useful for making candles, and over 20,000 t/yr of wax are sold for this appHcation. 

Until comparatively recently the bulk of general purpose phthaiate plasticisers have been based on the branched alcohols because of low cost of such raw material. Suitable linear alcohols at comparative prices have become available from petroleum refineries and good all-round plasticisers are produced with the additional advantage of conferring good low-temperature flexibility and high room temperature resistance to plasticised PVC compounds. A typical material (Pliabrac 810) is prepared from a blend of straight chain octyl and decyl alcohols. 

Bromine compounds are often used as flame retardant additives but 15-20ptsphr may be required. This is not only expensive but such large levels lead to a serious loss of toughness. Of the bromine compounds, octabromo-diphenyl ether has been particularly widely used. However, recent concern about the possibility of toxic decomposition products and the difficulty of finding alternative flame retarders for ABS has led to the loss of ABS in some markets where fire retardance is important. Some of this market has been taken up by ABS/PVC and ASA/PVC blends and some by systems based on ABS or ASA (see Section 16.9) with polycarbonates. Better levels of toughness may be achieved by the use of ABS/PVC blends but the presence of the PVC lowers the processing stability. 

The 8 values of both PVC and TPU are available. The selection of TPU should also be based on the application itself. For example, in the case of modifying PVC, if TPU is used as the substituent of liquid plasticizer, then it must have a good compatibility with PVC in order to make a homogeneouslike system. If TPU is just used to improve the toughness of PVC, then the amount of TPU in the blends is usually less than 15 parts (PVC as 100 parts), therefore, partial compatibility is enough. 

The results of Jamieson and McNeill cannot be accounted for by the intramolecular mechanism proposed by Grassie and coworkers [136,137] for the thermal degradation behavior of VC/VAc copolymers (Eqs, [28] and [29]). They can be accounted for much more convincingly by the alternative approach proposed by Naqvi based on polar interactions within the PVC matrix. Just like in copolymers even in blends, the polar carbonyl group of PVAc intensifies the concentration of like-poles in the PVC matrix resulting in destabilization. 

Based on the results of two amorphous compatible blend systems of 50/50 NC/PCL and 75/25 PVC/PCL, the following conclusion can be drawn. Compatible amorphous blend constituents show identical segmental orientation behavior, indicating good mixing at the molecular level. Thus, an amorphous compatible blend can exhibit the characteristics of a single homopolymer not only in its glass-transition behavior and mechanical properties but also in the uniform way in which the polymer chains orient. 

Pipe (436), mouldings (376) and sheet are formulated for high temperature use based on CPVC or blends of CPVC and PVC. 

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