PVC blends

Blends of poly(vinyl chloride) (PVC) and a-methylstyrene—acrylonitrile copolymers (a-MSAN) exhibit a miscibiUty window that stems from an LCST-type phase diagram. Figure 3 shows how the phase-separation temperature of 50% PVC blends varies with the AN content of the copolymer (96). This behavior can be described by an appropriate equation-of-state theory and interaction energy of the form given by equation 9. 

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. 

Blending of ABS with other polymers is not restricted to the aim of raising the distortion temperature. Blends with PVC are made for various purposes. For example, 80 20 ABS/PVC blends are used to produce fire-retarding ABS-type materials, as already mentioned, while 10 90 blends are considered as impact-modified forms of unplasticised PVC. ABS materials have also been blended with plasticised PVC to give a crashpad sheet material. 

Flgure 4 tanS versus temperature for NBR-PVC blends curve 1-BMI/MBTS curve 2-S/PNDA curve 3 = DHBP/ PETA. Source Ref. 21. 

Wang and Chen [41] studied the compatibility problems of incompatible NBR-PVC blends. Poly(vinyl-idene chloride-covinyl chloride) is reported to act as an efficient interfacial agent. Blends of PVC, NBR, and the copolymer were prepared by the solution casting technique using THE as a solvent. Improvement in mechanical properties can be achieved in NBR-PVC blend by the addition of different types of rubbers [42]. Different rubbers include NR, styrene butadiene (SBR) and butadiene (BR). Replacement of a few percent of NBR by other rubbers will improve the mechanical properties and at the same time reduce the cost of the blend. 

Poly(hydroxyphenyl maleimide)-b-PBA was added to thermosetting phenol resin to improve heat resistance [63]. PVC blended with poly(vinyl copolymer having cyclohexyl maleimide group)-b-PVC showed improved heat resistance and tensile strength with thermal stability during processing [64]. 

Cortes et al. [975] have used on-line p,SEC-CGC for rapid determination of a great variety of additives in an emulsion ABS-PVC blend, HIPS and a styrene-acrylate-ethylene rubber polymer. These systems are difficult to analyse, because of the high levels of insolubles such as fillers, pigments, or rubber modifiers. The additives were separated from the polymer fraction in a polymer/additive dissolution using p,SEC, and were... 

As already indicated in Scheme 2.12, XRF is profitably used for general screening of polymer formulations on inorganic components, before and after extraction. In the case of several PVC blends, such screening has indicated the presence of Cl, Ca, Ti, Cr, Fe, Zn, Mo, Cd, Sn, Sb and Pb [255]. It is well known that X-ray radiation may cause radiation damage, such as coloration of PVC samples during XRF analysis. 

Apex N PVC blend with nitrile rubber Teknor Apex... 

Di(2-ethylhexyl) adipate may be released into the environment during its manufacture and distribution, during PVC blending operations and cutting of PVC film, and from consumer use and disposal of finished products (lARC, 1982 Environmental Protection Agency, 1998). 

There is no doubt that this dispersion effect occurs but the magnitude of the spectral differences appear in most cases to be considerably larger than would be predicted by dispersion effects. For example, the poly(e-caprolactone) (PCL) and poly (vinyl chloride) (PVC) blend has been studied 252,253) and for this system the refractive indices are identical. In this case, there are obvious frequency shifts and broadening of the carbonyl band as a function of PVC concentration as shown in (Fig. 21). Nine percent of the original area of the carbonyl peak is involved in the shifted frequency absorption. Clearly, for this system, chemical interaction effects are being observed. In fact, PCL can be viewed as a macromolecular plasticizer for PVC. The blend system polyO-propiolactone) PPL and PVC was studied 2S3). In contrast to the PCL/PVC system, the PPL/PVC system was incompatible over the entire range of compositions. 

Figure 5.8 Images from a PMMA-PVC blend. These images show that both components are highly...

Compatible and incompatible polyester - PVC blends have been considered. Examples include systems, poly-X-caprolactone (PCL)/PVC which are compatible [5,28], in the melt and exhibit partial compatibility in solid state and poly-P-propiolactone (PPL)/PVC blends which are known to be incompatible [5, 28]. Figure 5.9 shows the infrared spectra of the carbonyl stretching vibration (in the range 1600-1800 cm-1) for the different blends. 

Specific interactions between PCL and PVC are clearly indicated. In the solid state (Figure 5.9a) the spectrum of neat PCL indicates the presence of crystalline (1724 cm 1) and amorphous (1737 cm"1) bands. At mole ratios up to 2 1 of PVC to PCL, the spectra indicate that in the solid state the blends consist of crystalline and amorphous phases. As the PVC concentration increases, a parallel increase of the intensity of the amorphous band is observed. Moreover, the frequency shifts observed for both the crystalline and amorphous bands as a function of the composition of the blend suggests that specific interactions between the two polymers occur. No shift is observed in the carbonyl stretching vibration of PPL/PVC blends, in the molten state or in the solid state over the entire range of compositions and the two polymers are incompatible [28]. 

After having studied in our laboratory, polymer blends of amorphous polymers poly-c-caprolactone and poly (vinyl chloride) (1,2) (PCL/ PVC), blends with a crystalline component PCL/PVC (3,4), poly(2,6-dimethyl phenylene oxide) (PPO) with isotactic polystyrene (i-PS) (5) and atactic polystyrene (a-PS) with i-PS (6), we have now become involved in the study of a blend in which both polymers crystallize. The system chosen is the poly(1,4-butylene terephthalate)/poly(ethylene terephthalate) (PBT/PET) blend. The crystallization behavior of PBT has been studied extensively in our laboratory (7,8) this polymer has a... 

The compatibility, mechanical properties, and segmental orientation characteristics of poly-e-caprolactone (PCL) blended with poly (vinyl chloride) (PVC) and nitrocellulose (NC) are described in this study. In PVC blends, the amorphous components were compatible from 0-100% PCL concentration, while in the NC system compatibility teas achieved in the range 50-100% PCL. Above 50% PCL concentration, PCL crystallinity was present in both blend systems. Differential IR dichroism was used to follow the dynamic strain-induced orientation of the constituent chains in the blends. It was found for amorphous compatible blends that the PCL oriented in essentially the same manner as NC and the isotactic segments of PVC. Syndio-tactic PVC segments showed higher orientation functions, implying a microcrystalline PVC phase. 

The orientation functions for a 75/25 PVC/PCL blend are presented in Figure 5, which shows that the PCL chains in the 75% PVC blend orient in essentially the same way as the isotactic segments and the other folded-chain PVC segments represented by the 693 cm 1 peak. This peak is shifted from 691 cm 1 for pure PVC. The shape and magnitude of the orientation functions for the carbonyl and 693-cm"1 C-Cl peak are similar to the orientation functions shown for the amorphous 50% NC blend. 

---