Maleated polyolefins

So far there has been little use in the volume thermoplastics such as PVC and polyolefins. The main exception would seem to be the use of amino-silane treated glass in conjunction with maleated polypropylene in polypropylene compounds. 

Poly[styrene-co-(2-hydroxy-4 -vinylbenzophenone)] was less efficient in PS than 2-hydroxy-4-methoxybenzophenone [334]. Similarly, PE films doped with 4-dodecyloxy-2-hydroxybenzophenone (0.1 mol%) were more stable than PE doped with copolymers of ethylene with polymerisable benzophenones having a comparable content of chromophores [54]. The efficiency of a SAN type LS, a terpolymer of 2-hydroxy-4-(4-vinylbenzyloxy)benzophenone with acrylonitrile and styrene did not exceed that of conventional LS [84]. No efficiency loss of 2-hydroxy-4-methacryloyloxybenzophenone in ABS was observed after bonding into a terpolymer with styrene and acrylonitrile. The homopolymer was slightly inferior to both the monomer and terpolymer [84]. A better protection of PP was provided by poly[(2-hydroxy-3-allyl-4-methoxyphenylbenzophenone)-co-dibutyl maleate] than with 2-hydroxy-3-allyl-4-methoxybenzophenone [335] (stabilization tests were performed in the presence of phenolic antioxidants). A comparable or better light stabilizing efficiency of poly[vinyl acetate-co-(5-methylacryloyloxy salicylate)] or poly(2-allylphenyl salicylate-co-dioctyl maleate) than that of alkyl-phenyl salicylates was observed in polyolefins [335]. 

Direct chemical reaction between functional groups, so that graft or block copolymers are formed. For example, a polyolefin may be maleated so that it may then react with a polyamide during melt blending to give an imide that functions as the compatibilizer. 

The technique involves the uses of rotatable sampling ports that enable the polymer to be removed and quenched as it passes particular zones (corresponding to different values of LID) as shown in Figure 1.37 (Van Duin et al, 2001). In this way 2g of polymer can be collected for off-line analysis in about 3-5 s. For the above polymers, the most common profile for product formation along the axis of the extruder was one that followed the profile for the decomposition of the peroxide with time (and thus distance along the extruder). Reaction of MA was very rapid, and there was an exponential growth in the amount of maleated polyolefin as the MA was consumed. 

Moad also notes that the most common grafting modifications made to polyolefins are via maleic anhydride, maleate esters, styrene, maleimides, acrylates and their esters, and vinyl silanes. Other polymer systems (Fink, 2005) that undergo grafting are polystyrene/maleic anhydride (useful for PA6/PS blends), PVC/butylmethacrylate (for improved processi-bility), PET/nadic anhydride, starch/vinyl acetate and starch/methyl acrylate (for improved water resistance). 

MALEATED POLYOLEFINS (POLYBOND, INTEGRATE, FUSABOND, EPOLENE, EXXELOR, OREVAC, LOTADER, SCONA,... 

It should be taken into account that maleated polyolefins can slowly react with air moisture during storage, and form free acid. As a result, chemical reactivity of the coupling agents decrease. Hence, care should be taken to keep maleated polyolefins dry, or heat them up before usage in order to regenerate the anhydride chemical structure. 

Maleated polyolefins are usually used at 1-5% by weight in a WPC formulation, and their retail price is around 1.50/lb. Hence, they cost 1.5-7.5 0/lb of the formulation. This can be compared to the most expensive (in the final formulation) ingredient, a polymer matrix itself, which costs around 70 0/lb, and at 30-40% content (by weight), it costs 21-28 0/lb of the formulation. Therefore, coupling agents may add about 4-20% of a total cost of the materials in the formulation. Plastic often costs about 60-80% of the formulation. 

Let us consider several of the most known maleated polyolefins as coupling agents in WPG. They are... 

TABLE 5.12 Effect of maleated polyolefins on fiexural and tensile modulus of WPC (the data were assembled based on Tables 5.7 and 5.11)... 

The same coupling agents, both maleated polyolefins and silanes, affect flexural modulus of WPC quite differently, from decreasing through practically no effect, to increase up to 20-40% (Tables 5.7, 5.11, and 5.12). 

With respect to tensile modnlns, of 11 cases in Table 5.7, five maleated polyolefins show decrease in the property (an Epolene, maleated polypropylenes and a Polybond), in five cases there was practically no effect (within 10% of the control), and in only one case an increase by 24% was observed (Polybond 3029). 

Of 29 cases of maleated polyolefins effects on WPC flexnral strength, listed in Table 5.9 and 5.11, in five cases the apparent increase was within 20%, which was within a common error margin, mainly for low concentrations of Polybonds and Fnsabond (less than 2% w/w), and in 24 cases an increase of flex strength was observed in the range of 30-230% (Epolenes, Polybonds, Ensabonds, Integrates, and Orevac). 

As soon as the maleated coupling agents were introduced into the WPC, it was noticed that their effect often significantly depends on lubricants employed in the same system. The most striking was a conflicting effect between maleated polyolefins and metal stearate lubricants (Tables 5.15 and 5.16)... 

The effect of conflicting of the maleated polyolefins with zinc stearate and other metal-containing stearates is commonly known in the industry. Therefore, a number of companies have developed nonmetal lubricants, such as Ferro Corporation RC-553, RC-571, RC-572, RC-576, SXT 3100 (see Table 5.16 Ferro s SXT 2000 is a blend of metal stearates with other nonmetal lubricants [3]), Struktol TPW-113 (Struktol s TPW 104 contains zinc stearate), Lonza Glucolube WP-2200 (a new proprietary amide lubricant that contains no metal stearates [12]). 

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