Elastomer modification

The classic technology is the modification of general purpose polystyrene with styrene butadiene to produce high impact PS. Butadiene has also long been used, especially in ABS. Polyisoprene is a more recent modifier. Initially, modification could be achieved simply by compounding but, with improvement in technology, copolymers were developed and the function was taken upstream to the reactor. 

With the advent of polyolefins, a different system was needed, especially when, with the development of PP, it was clear that its useful mechanical properties fell 

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AGE-Gontaining Elastomers. Modification by addition of a small amount of AGE to the two polymers mentioned above allows for sulfur... 

There are also the high modulus elastomers. Modifications to the chemistry of producing the low modulus elastomers allow for the processing of tough polymers with flexural modulus as high as 250,000 psi (1,723 MPa). These are used in a variety of large industrial and consumer parts. 

If tougher adhesive bonds are required than are attainable from conventional epoxy resins, they can be modified. A typical example involves the carboxyl-terminated elastomer modifications discussed earlier. A modified base resin is first formed as follows (pbw) ... 

In the mid-60 s carboxyl-terminated polybutadiene/acrylo-nitrile (CTBN) liquid polymers were introduced for the purpose of epoxy resin modification. These telechellc polymers are essentially macromolecular diacids. They offer processing ease (and therefore advantage) over the solid carboxylic nitrile elastomers. It is no surprise that the epoxy prepreg industry (adhesive and non-adhesive varieties) found the liquid and solid carboxylic nitrile elastomer species useful together in processing liquid and lower molecular weight solid epoxy resins where elastomer modification was needed. 

In each instance of nitrile elastomer modification - whether rubber is added to the epoxy portion or to the hardener portion -the level of rubber largely determines whether a toughened or a flexibilized epoxy results. The former is characterized by little loss in thermal/mechanical properties. The latter shows a dominant influence of the added rubber. 

At lesser rubber levels, heavy duty solventless coatings models based on dlethylenetrlamlne or fatty polyamide cures, showed elastomer-modification (10 phr rubber level) to advantage in Gardner impact, mandrel bend and corrosion-resistance testing (41). Impact testing (direct and reverse) gave 110 and 60 in-lbs, respectively for the rubber-modified fatty polyamide cured epoxy coating (14 days at R.T.), whereas a control formulation tested 10 in-lbs in each mode. 

Elastomer modification of two-package epoxy coatings has been carried out either with rubber addition to the epoxy component or to the hardener component. Amine-reactive nitrile liquids have been examined extensively in polyamide cured epoxy coatings. The... 

The chemical literature reveals relatively new and varied interests for nitrile elastomer-modification of epoxy resins in diverse areas of coatings and primers. Desirable properties such as impact resistance, mandrel bend and adhesion improvement are attainable with little or no sacrifice in critical film properties. In some instances, it is documented that proper elastomer modification of select epoxy coatings will enhance corrosion and moisture resistance. This may relate to better film/substrate adhesion durability. The combined literature, journal and patent, has led to continuing study of nitrile elastomer modified epoxy coatings. 

The best results were obtained with the silicone elastomer modification (resin E). Tg, CTE and viscosity are slightly affected but remain In acceptable ranges. 

By virtue of significant advances in chemical coupling and glass-fiber sizing technology, chemically coupled polypropylene composites can be manufactured to exhibit strength and stiffness required for elevated temperature applications, for example, in hot climates or under the hood in automobiles (60-150°C). At the other end of the temperature spectrum, elastomer modification plus filler addition to maintain stiffness provides the means for low-temperature impact resistance in subzero Arctic locations (-30 to -40°C). 

Keywords blends, processing, elastomer modification, d)mamic vulcanization, morphology, injection molding, extrusion molding, thermoplastic elastomer, thermoplastic dynamic vulcanizates (TDV), application. 

Pocius, A. V., Elastomer modification of structural adhesives . Rubber Chem. TechnoL, 58, 1985, 622. 

Both carboxyl and amine liquid polymers have provided chemistries amenable to elastomer modification, with the polybutadiene—acrylonitrile copolymer providing solubility parameters close to if not equaling those of base epoxy resins. 

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