Cited by. Back to tab navigation Download options Please wait Article type: Paper. DOI: Download Citation: Discuss. For example, c r o s s - l i n k e d copolymers of polycarbonate and polychloroprene have been prepared i n the presence of molybdenum and manganese carbonyls as i n i t i a t o r s Most IPNs are heterogeneous systems comprised of one rubber and one glassy phase. Segregation of hard segments.
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PLATZER Multicomponent Polymer Systems on mechanical properties and thus y i e l d s either high impact strength or reinforcement that are both dependent on phase c o n t i n u i t y. Thermoset IPNs are characterized by suppressed creep and flow and were pioneered by L. F r i s c h 38b , and coworkers, i n A t y p i c a l example 37 i s an elastomer such as butadiene or e t h y l aerylate c r o s s - l i n k e d with divinylbenzene as the f i r s t polymer.
The i n i t i a t o r i s potassium for butadiene, and benzoin for the other monomers. Simultaneous IPNs are formed by homogeneously mixing together monomers, prepolymers, l i n e a r polymers, i n i t i a t o r s , and crosslinkers. The r e s u l t a n t urethane prepolymer was then mixed with polystyrene to form an IPN.
One of the f i r s t mechanical thermoplastic IPNs was that prepared by Exxon Chemical and made by melt blending ethylene-propylene E-P copolymer or EPDM w i t h p o l y p r o p y l e n e i n the presence of a s m a l l amount of peroxide as c r o s s - l i n k i n g agent. Their properties, and therefore t h e i r end uses, are strongly dependent on the degree of c o m p a t i b i l i t y of the components.
Compatible Polyblends. Very few p a i r s of polymers are completely compatible. The best known example i s the polyblend of p o l y p h e n y l e n e oxide poly-2,6-dimethyl-l,4-phenylene oxide with high-impact polystyrene 41 , which i s s o l d under the trade name of Noryl.
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These compatible blends e x h i b i t p h y s i c a l properties that are intermediate to those of the components. Most p o l y b l e n d s are heterogeneous and consist of a polymeric matrix i n which another polymer i s embedded. In c o n t r a s t to copolymers i n which the components are l i n k e d by strong covalent bonds, the components i n polyblends adhere together only through van der Waals forces, d i p o l e i n t e r a c t i o n , or hydrogen bonding. These are prepared to improve c e r t a i n physical properties.
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Blends that d i s p l a y an intermediate degree of c o m p a t i b i l i t y are u s u a l l y based on random copolymers r a t h e r than matched c o m p o s i t i o n s and have been termed mechanically compatible This combination i s selected to toughen b r i t t l e polymers with elastomers.
M i s c i b i l i t y 43 between the two components plays an important r o l e. A more uniform polyblend of higher impact strength can be obtained by b l e n d i n g s t y r e n e homopolymer e i t h e r w i t h a g r a f t polymer of styrene on polybutadiene or with an SBS terblock polymer. ABS went through an analogous development. The impact resistance of polypropylene at low temperature has been improved by p o l y b l e n d i n g w i t h EPDM or E-P rubber to make possible the a p p l i c a t i o n of t h i s material i n the automotive indust r y.
The low-temperature properties of polyamides such as nylon 6 and n y l o n 66 have been improved by p o l y b l e n d i n g w i t h e t h y l e n e copolymers or s p e c i a l l y grafted polybutadiene P o l y c a r b o n a t e i s being blended w i t h ABS to lower the V i c a t softening temperature and to make i t more thermoformable Polyblends i n which both phases are r i g i d are made w i t h the i n t e n t i o n of improving melt flow and mechanical properties or for the purpose of reducing shrinkage.
Polyblends i n which both components are soft are mixtures of various elastomers. For example, treads of automobile t i r e s are made of a polyblend of SBR with either natural rubber or cis-polybutadiene. Composites may be c l a s s i f i e d into four groups, as shown i n Table I I.
In modern composites, such as i n the case of epoxy r e s i n s r e i n f o r c e d w i t h carbon f i b e r s 51 , the polymer matrix has only a secondary function: to separate the i n d i v i d u a l f i b e r s from one another and to t r a n s f e r energy to the f i b e r surface; the fibers almost completely withstand the mechanical load. F i l l e d and reinforced polymeric materials may be c l a s s i f i e d i n t o four groups, as shown i n Table I I.
Reinforced Thermoplastics. To o b t a i n good adhesion between the i n o r g a n i c m a t e r i a l s and the m a t r i x , m u l t i f u n c t i o n a l s i l a n e s are added as coupling agents and provide the necessary binding force of the same magnitude as the secondary forces i n polyblends.
The polymeric matrix i t s e l f must have a higher elongation than the r e i n f o r c i n g material i n order to use the strengthening effect completely. S i x t y - f i v e years ago, i n a paper presented before the American Chemical Society, L. Baekeland 55 discussed the usefulness of phenol-formaldehyde resins that, when compounded with wood f l o u r , could be molded. Powdered minerals such as s i l i c a or china c l a y are often used to improve water resistance.
Reinforced Thermosets. In contrast to f i l l e r s that do not enhance the strength of thermosets, g l a s s f i b e r , mat, and c l o t h are capable of increasing the strength of phenolics, unsaturated polyesters, and epoxies s i g n i f i c a n t l y , i l l u s t r a t e d i n Table IV. Novel composites are approaching the strength of s t e e l. The s t i f f n e s s of the composite i s even more i n f l u e n c e d by the reinforcing material.
Table I I I. Reinforced Unreinforced with Short Glass Fibers 1. Table IV. Klempner, D. Wall, F. Ham, G.
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Coarse-graining in simulations of multicomponent polymer systems
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Swarc, M. Nature , , Dunlop Company Ltd. Phillips Petroleum Company; U. Patent 3 , Hendricks, W. Eschwey, H. Morton, M. Cooper, S.