Polyolefins coupling agents

B. Sigworth. Additives for wood-filled polyolefins. Coupling agents. In Progress in Woodfibre-Plastic Composites Conference 2002, Toronto, Canada, May 23-24, 2002. 

Recommended for use as coupling agents are monoalkoxytriacyl titanates, such as isopropoxytriisostearyl titanate, Ken-React KR TTS or TYZOR ISTT [61417-49-0] which are useflil in mineral-filled polyolefin resins (526) chelated titanates, such as di(dioctyl)pyrophosphatooxoethylene titanate,... 

In some examples it is not necessary to prepare the organometallic-coupling agent R2MX2 beforehand. Thus coating glass fibres with a heptane or alcohol solution of titanium alkoxide promotes adhesion between the fibre and polymer, e.g., acrylic, polyolefins, polyester, polyamide and other thermoplastic resins. 

Reactive treatment is the most difficult in polyolefins, although occasionally successful attempts have been reported as shown in Fig. 15 for a PP/mica composite [89] the results presented in the figure were obtained by the application of an aminosilane coupling agent. In PP composites the most often used cou-... 

However, the chemical bonding theory cannot account for the increase in adhesion experienced between non-reactive matrices such as polyolefins and inorganic reinforcements in which chemical bonds will not be formed [4], This observation, among others, leads to an alternative proposal that an interphase composed of various constituents forms surrounding the reinforcement. This third phase in the composite is possibly formed through interdiffusion of physisorbed silane and matrix molecules in the interphase and perhaps via preferential adsorption of both matrix components as well as silane coupling agents on the reinforcement surface [5],... 

The living character of organolithium polymerizations makes such processes ideally suited for the preparation of pure as well as tapered-block copolymers. Diene-olefin pure-block copolymers have become important commodities because of their unique structure-property relationships. When such copolymers have an ABA or (AB) X [A = polyolefin, e.g., polystyrene or poly(a-methylstyrene) B = polydiene, e.g., polybutadiene or polyisoprene and X = coupling-agent residue] arrangement of the blocks, the copolymers have found use as thermoplastic elastomers (i.e., elastomers that can be processed as thermoplastics). 

Some authors combined the IPN concept with the use of compatibi-lizers similar to that mentioned in Section 2. These may be a coupling agent such as epoxy-functionalized polysiloxane, polysiloxane copolymers or an organofunctional grafted polyolefin such as poly(ethylene-co-methacrylate) or MA-g-EPDM (maleic anhydride grafted EPDM) [124,125, 133]. Knaub et al. [150] studied a poly(urethane-ureas)/PDMS semi-IPN in... 

Coupling agents for more inert polymers like polyolefins are often acid-modified versions of the matrix polymer, with maleic acid grafted polypropylene as a prime example. 

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... 

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). 

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)... 

At any rate, effects of lubricants with or without coupling agents in WPC are still largely unpredictable and mainly empirical. Nonmetal lubricants do not increase a chance for covalent bonds formation between coupling agents and wood fiber they just do not result in a functional damage of maleated polyolefins compared to that by metal-containing lubricants. 

Unite. [Aristech] Chemically modified polyolefins wiA anhydride functionality compatibiiizer for polymer blends and alloys, coupling agent in reinfaced and fill polymers, adhesive 2%eat for bonding polyolefins to various substrates. 

Miscellaneous Couplins Asents Examples in Table 5.48 show use of coupling agents that can, in theory, react at sites along the main chain of each of two immiscible polyolefins. Both examples involve concomitant dynamic vulcanization of an elastomeric, dispersed phase with the added crosslinking agent. 

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