Macromolecular modifiers

Macromolecular modifiers are used to improve some physical properties, mainly mechanical properties of polymers. They have found wide-spread application in the reduction of basic defects of polymers in their glassy state, mainly their resistance to low-energy impact, and they are used also to modify rheological properties of polymer melts [1]. 

---

It is generally admitted that the glassy polymer that forms the basic structure, that is, the matrix of the system, should have a high molecular weight. This is based on the fact that the quantity of the elastomer, the macromolecular modifier, needed to obtain a high impact strength decreases as the molecular weight... 

Macromolecular Modifiers Used as Polymer Processing Aids... 

Chapter 2. Some macromolecular modifiers can also act as processing aids, and for PVC the most efficient ones are acrylic and methacrylic polymers, MBS and ABS terpolymers, EVA copolymers, (vinyl chloride)-(vinyl acetate) copolymers, or (vinyl chloride)-propene copolymers. The efficiency of these modifiers as PVC processing aids is related to a good mutual polymer-polymer miscibility. The miscibility of EVA copolymers with PVC depends on the vinyl acetate content of the EVA. The copolymers with more than 50% vinyl acetate are already miscible with PVC, and they are used mainly as processing aids. 

Sometimes a macromolecular modifier may produce undesired effects. Such is the case of Microthene F (powdered PE) recommended by U.S.I. Chemicals Co. (Div., National Distillers and Chemical Corp., U.S.) as a PVC modifier. When blended with PVC at 6% by volume, the notched impact strength of the material goes to a maximum value of 9 kJ m [92] adding more Microthene will lower this value. Since this modifier acts also as a lubricant, it lowers the processibility of PVC blends. 

To use substances that absorb light, impacts, or to use radical, oxygen or decomposition product quenchers (UV absorbers, macromolecular modifiers, stabilizers, antioxidants, flame retardants, etc.). 

The range of properties and usefulness of cellulosic libers has been increased by preparation of cellulosic products that contain macromolecularly modified cellulosic fibers, usually referred to as cellulose copolymers. A cellulose copolymer is cellulose covalently linked to a polymer, so that separation by solvent extraction is difficult without first degrading the cellulose, e.g. by hydrolysis... 

---