Epoxy-grafting functionalization

Section 19.S.1.2), and reported increases in toughness comparable to those achieved with CTBN. A further, but inconclusive, study compared pre-formed poly(n-butyl aciylate)-based particles made by emulsion and by suspension polymerization [97]. Dispersion polymerization in an epoxy resin has been used to give directly dispersions of acrylic rubber particles in the epoxy for subsequent use in toughening epoxy resins [98]. Core-shell toughening particles comprising 70 wt% of CFOSslinked polybutadiene cores, with a grafted functionalized shell have been claimed [99] to improve the fracture toughness of a methylene dianiline cured epoxy resin by a factor of 10. 

The quantitative bulk conversion of unsaturated functional groups in PHAs to epoxides has been achieved by reaction with m-chloroperbenzoic acid as the chemical reagent [107]. No chain scission of the macromolecular chain was observed. Epoxy-modified PHAs are chemically even more reactive than unsaturated PHAs and therefore could be useful in further chemical reactions (e.g. grafting of therapeutic important substances) [108]. 

Itoh et al. [141] patented a blend of polyurethane and silicone gum with vinyl groups. The crosslinking reaction of the silicone component was achieved using a radical generator. Chorvath et al. [142] also patented a system composed of polyamide or polyester as the thermoplastic and vinyl-containing polysiloxane cured by a peroxide or non-peroxidic initiator such as 3,4-dimethyl-3,4-diphenylhexane (HTV). Moreover, they added different compatibilizers such as amino-terminated or amino-grafted polysiloxane, epoxy- or isocyanato-functionalized polysiloxane. 

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... 

Functionalized, liquid polybutadiene derivatives have also been developed as hybrid flexiblizers for epoxy resins. Carboxyl-terminated butadiene/acrylonitrile polymers, butadiene homopolymers, and maleic anhydride-amino acid grafted butadiene homopolymers have been used as flexibilizers to impart good low-temperature strength and water resistance to DGEBA-based epoxy adhesives. An epoxy system toughened by polybutadiene with maleic anhydride is claimed to provide a hydrophobic backbone, low viscosity, softness, and high tensile strength and adhesion (Table 7.10). 

Matsuda s study outlined one of a number of techniques that can be used to produce high-quality wood materials from wood meal, but can also be used to introduce carboxyl groups to wood surfaces thereby greatly increasing the reactivity of the modified surfaces with epoxy groups. This allows techniques like the introduction of vinyl or vinyl groups to be used as a pretreatment to facilitate grafting of functional monomers or polymers to wood surfaces. 

Many authors elucidated functionalization of polymers containing reactive oxirane moieties. Epoxidized NR, BR, IR and/or the respective model hydrocarbons, poly (butadiene-co-isoprene, various epoxy resins, poly (2,3-epoxypro-pyl methacrylate) and its copolymers or grafted systems were mostly exploited. Stabilizers based on epoxidized unsaturated rubbers are of the top interest. The mechanism of the functionalization process was studied in details by means of 3,4-epoxy-4-methylheptane and 1,2-epoxy-3-ethyl-2-methylpentane as model compounds [289]. The ring opening of the asymmetric oxirane is regiospecific. Aliphatic primary amines attack the least substituted carbon atom and can be involved in crosslink formation. Aromatic primary and secondary amines are less reactive than aliphatic ones because of their lower basicity the attack on the least substituted carbon atom is however preferred too. 

Two examples are shown in Figs. 25 and 26, where Qc and Ojlhrij are plotted as a function of 2. In the first case we compare interfaces between an epoxy and either PS or high-impact PS, where both interfaces have been reinforced with the same deuterated end-grafted chain, while, in the second case, we compare interfaces between polyamide 6 (PA-6) and either polypropylene (PP) or a PP-based alloy with a PP matrix and 70% EPDM rubber particles, where both interfaces have been reinforced with the same type of grafted PP chains. Two observations can be made ... 

Fig. 32. Maximum achievable fracture toughness of interfaces between A and B polymers reinforced with block copolymers or end-grafted chains as a function of the degree of polymerization N of the reinforcing block. (A) PS-b-PMMA between PPO and PMMA ( ) dPS-COOH chains in a HIPS matrix grafted on an epoxy interface ( ) dPS-COOH chains in a PS matrix grafted at an epoxy interface (O) PS-b-PVP chains at the interface between PS and PVP. Data from [22,36,38,40]...

For styrene-based random copolymers, functional groups can be introduced into the polymer chains via copolymerization with functional styrene derivatives, because the electronic effects of the substituents are small in the metal-catalyzed polymerizations in comparison to the ionic counterparts. Random copolymer R-6 is of this category, synthesized from styrene and />acetoxystyrene.372 It can be transformed into styrene// -vinylphenol copolymers by hydrolysis.380 The benzyl acetate and the benzyl ether groups randomly distributed in R-7 and R-8 were transformed into benzyl bromide, which can initiate the controlled radical polymerizations of styrene in the presence of copper catalysts to give graft copolymers.209 Epoxy groups can be introduced, as in R-9, by the copper-catalyzed copolymerizations without loss of epoxy functions, while the nitroxide-mediated systems suffer from side reactions due to the high-temperature reaction.317... 

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