Poly(e-caprolactone) (PCL)/layered double hydroxide (LDH) nanocomposites were prepared success- fully via simple solution intercalation. The nonisothermal melt crystallization kinetics of neat PCL and its LDH nano- composites was investigated with the Ozawa, Avrami, and combined Avrami-Ozawa methods. The Ozawa method failed to describe the crystallization kinetics of the studied systems. The Avrami method was found to be useful for describing the nonisothermal crystallization behavior, but the parameters in this method do not have explicit meaning for nonisothermal crystallization. The combined Avrami- Ozawa method explained the nonisothermal crystallization behavior of PCL and its LDH nanocomposites effectively. The kinetic results and polarized optical microscopy obser- vations indicated that the addition of LDH could affect the mechanism of nucleation and growth of the PCL matrix. The Takhor model was used to analyze the activation ener- gies of nonisothermal crystallization. V C 2010 Wiley Periodicals,

Crystallization behavior of poly(ε-caprolactone)/layered double hydroxide nanocomposites

Photoinitiated crosslinking polymerisation

The formation of densely crosslinked networks by chain crosslinking photopolymerization is discussed in relation to selected applications in the electronics industry. All of these applications make use of the high speed and of the latitude to meet other requirements by variation of the chemical structure of the monomers. The selection comprises:

1.

The coating of optical fibers;




2.

The replication of optical discs;




3.

The replication of aspherical lenses, used for laser read-out of these discs.

Network formation by chain crosslinking photopolymerization and some applications in electronics

UV-radiation curing of acrylate/epoxide systems

Photopolymerization kinetics of dimethacrylates using the camphorquinone/amine initiator system

Nanocomposite materials made of silicate platelets randomly dispersed in a crosslinked polyurethane-acrylate have been readily produced by photoinitiated polymerization. The mineral filler (bentonite) was treated by an ammonium salt or an acrylated amine to make it organophilic and allow the acrylic resin containing a photoinitiator (aromatic ketone) to penetrate into the expanded organoclay galleries. The photoinitiated crosslinking polymerization reaction was followed in real time by infrared spectroscopy and shown to proceed extensively (>95% conversion) within a few seconds of UV-irradiation. The flat X-ray diffraction spectra recorded with the UV-cured material shows that the layered silicate has been completely exfoliated, thus demonstrating that a nanocomposite material has well been produced. This method of synthesis presents the distinct advantages associated with the UV-curing technology, namely, a solvent-free formulation undergoing ultrafast polymerization at ambient temperature in the presence of air.

Ultrafast synthesis of bentonite-acrylate nanocomposite materials by UV-radiation curing

Highly crosslinked aliphatic and aromatic polyurethane-acrylate (PUA) coatings have been obtained by photopolymerization of multifunctional monomers. The discoloration and chemical modifications occurring upon accelerated QUV aging were monitored by UV and IR spectroscopy. The polymers were found to undergo photooxidation and loss of carbamate and phenyl groups, with lower quantum yields (10−3 mol photon−1) than in related linear polymers. Hydroxy-phenyl benzotriazole UV-absorbers have a limited effect on the degradation rate, at the concentration used (0.5%). Hindered amines (HALS) are substantially more effective, especially in aliphatic PUA. A 20-fold increase in the stabilization efficiency was found with the UVA + HALS combination. Aromatic PUA are more difficult to stabilize, because of the strong absorption and photolysis of the phenyl group which yields colored products. Radical-induced oxidation is predominant in aliphatic PUA and develops with long kinetic chains, while in aromatic PUA it competes with direct photolysis.

T. Bendaikha

Papers

Ultrafast synthesis of bentonite-acrylate nanocomposite materials by UV-radiation curing

Photodegradation of UV‐cured coatings II. Polyurethane–acrylate networks

Photopolymérisation de macromères multifonctionnels—I. Étude Cinétique☆