Polymeric impact modifiers

Improve both impact strength and rigidity of thermoplastics by using up the energy of crack propagation. Elastomers are prototypical toughening additives. Examples of high-polymeric impact modifier/thermoplastic matrix systems are EVA, CPE and MBS in PVC, EP(D)M and SBS in PA, and acrylic rubbers in polyesters. 

Polymeric impact modifiers Preservatives Slip aids/promoters Stabilisers (heat, ultraviolet) Viscosity aids... 

Inorganic fillers or polymeric impact modifiers can be used to improve the mechanical properties and the thermal resistance of the polymers, both virgin and recycled. Inorganic fillers, like calcium carbonate, glass fibers... 

In this scheme the sample is dissolved in THF and centrifuged at 20 000 rpm to isolate inorganic materials and polymeric impact modifiers together. The polymer is precipitated from the THF centrifugate with ethanol and isolated by filtration. The THF-ethanol filtrate is evaporated to dryness to yield the soluble organic additives. This yields a total of three fractions to examine. When a polymeric plasticiser is either known to be present or found to be present in the THF-ethanol-soluble fraction, then the isolated polymer is Soxhlet extracted with hot ethanol to remove residual non-extracted plasticiser. All fractions are examined by IR spectroscopy and use is made of reference spectra. 

Examination of the THF-insoluble fraction. This fraction consists of inorganic pigments and fillers such as chalk, titanium dioxide, alumina trihydrate, clay, etc. fire retardants such as antimony trioxide lead-based stabilisers such as TBLS or DBLP polymeric impact modifiers that are totally insoluble in THF, such as MBS and various acrylic rubbers and polymeric impact modifiers that are partially soluble in THF, such as nitrile rubber and some grades of ABS which, while mainly insoluble in THF, will yield a fraction consisting of SAN which is soluble in THF and will be found with the precipitated polymer. 

Introduction of ethylene copolymers and other polymers as high polymeric impact modifiers in PE or especially in PP is very important for applications in the automotive industry, where high impact strength is required even at very low temperatures (—20°C). The selection of components of the blend is essential for the production of quality products [57] —see also Chapter 22. 

Nucleating agents and high polymeric impact modifier efficiency are judged by the modifications in optical (polarizing microscope) and mechanical properties. 

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