As mentioned before, PVC formulations have very diverse properties, for example, PVC alloys. This variety of properties is due to the proper compatibility of PVC resins with a large number of additives.
Some VC additives such as stabilizer, softener, lubricant, impact resistance modifier and process aid were reviewed in previous chapters. In this article, polymer additives of polyvinyl chloride formulations (alloys) have been studied.
These types of additives are fundamentally different from other types. The main difference is actually the limitation of their use due to their high molecular mass and as a result their low compatibility with the PVC matrix.
Some types of polymer lubricants are also immiscible with PVC, but in order to prevent the formulation from sticking to the metal surfaces of the equipment, a small amount of them should be added to the PVC formulations.
Considering that the miscibility of two polymers is usually considered as a criterion for predicting the feasibility of using a polymer additive. One of the ways to check miscibility is to determine the glass transition temperature of the system. If two polymers have good miscibility with each other, there will be a glass transition temperature for the mixed system of two polymers, which is between the glass transition temperatures of the two polymers. Of course, it should be noted that having two glass transition temperatures does not mean that the alloy of two polymers is unsuitable.
PVC alloy compatibilizers
There is not much technology about PVC adaptors. This may be because polyvinyl chloride can produce good alloys with a small number of polymers, and most other polymers are not alloyed because their process temperatures are higher than the degradation temperature of PVC.
Currently, the most widely used compatibilizer for polyvinyl chloride alloys with polyolefins is chlorinated polyethylene (CPE). Of course, CPE is not a strong compatibilizer, because it cannot penetrate uniformly in the critical distance of entanglement of the alloy.
PVC alloys with high thermal deformation temperature
Glutaramide copolymers
In this copolymer, relatively large rings and numerous carbonyl groups respectively increase the glass transition temperature and make it compatible with PVC. Usually, this copolymer is used in PVC formulations with a combination of 65/35 imide to methyl methacrylate ratio, molecular weight of about 90,000 and glass transition temperature of 140 degrees Celsius.
PVC softeners
ABS alloy (acrylonitrile/butadiene and styrene)
ABS is prepared from the continuous phase of SAN and dispersed particles of polybutadiene to modify impactability. Polybutadiene is usually dissolved in the monomer and precipitates during polymerization and forms the desired final morphology. It is necessary to remember that the polybodiene in the alloy is oxidized by ozone in the ultraviolet light, reducing the impact resistance of the alloy and making it brittle.
Saprel
This alloy has high impact strength and deformation temperature and is a relatively complex combination of several polymer components.
In order to recognize this alloy, its components must be examined. For example, the ABS in it has enough SAN that it can be mixed with PVC.
Styrene maleic anhydride copolymer alloys
These alternating copolymers are soluble up to 10% in PVC, which is probably due to the presence of carbonyl functional groups in maleic anhydride.
Flexible PVC alloys
The glass transition temperature of standard PVC softeners is very low and often below -100 degrees Celsius. Therefore, these materials have a good performance in reducing the glass transition temperature of PVC and preparing very flexible soft heat elastomers.
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