Preparation and characterization of UV-cured epoxy nanocomposites based on o-montmorillonite modified with maleinized liquid polybutadienes

The Effect of Oxetane as Active Diluent on Cationic UV Curing System of Fluorine-Containing Epoxy Prepolymer

A series of fluorine-containing polyacrylic epoxy (FPAE) prepolymers with different fluorine content and molecular weight are synthesized by solution free radical polymerization of hexafluorobutyl methacrylate (HFBMA), butyl acrylate (BA), and glycidyl methacrylate (GMA). The synthesized prepolymers show high conversion and low volume shrinkage. The effect of different types of active diluent for the cationic UV curing of FPAE was investigated, among which oxetane exhibits better comprehensive property than epoxy and vinyl ether. The formulations with the optimal ratio of different functionality oxetane combination show good flexibility, adhesion, hydrophobicity, and antistain property.

Increase of tensile strength and toughness of bio-based diglycidyl ether of bisphenol A with chitin nanowhiskers

It is challenging to reinforce and toughen thermoset epoxy resins. We describe a slurry-compounding technique to transfer a uniform dispersion of chitin nanowhiskers (CW) in ethanol into an epoxy matrix. The incorporation of the hydrophilic CW reinforces the oil-soluble diglycidyl ether of bisphenol A (DGEBA). The resultant CW/epoxy bionanocomposites were transparent and showed considerably enhanced thermal and mechanical properties with tensile strength, modulus, toughness, and elongation at break being increased by 49%, 16%, 457%, and 250%, with only 2.5 wt.% CW. This improvement in strength and toughness is rare for thermoset epoxy/rigid nanofiller systems. We hypothesize that CW with many free amine groups could function not only as a nanofiller but also as a macromolecular polyamine hardener that participates in epoxy curing. The strong covalent interaction between the filler and the matrix allowed for efficient load transfer across the interfaces, which accounted for the greater strength and toughness.

Characterization of Nanocomposites by Thermal Analysis

In materials research, the development of polymer nanocomposites (PN) is rapidly emerging as a multidisciplinary research field with results that could broaden the applications of polymers to many different industries. PN are polymer matrices (thermoplastics, thermosets or elastomers) that have been reinforced with small quantities of nano-sized particles, preferably characterized by high aspect ratios, such as layered silicates and carbon nanotubes. Thermal analysis (TA) is a useful tool to investigate a wide variety of properties of polymers and it can be also applied to PN in order to gain further insight into their structure. This review illustrates the versatile applications of TA methods in the emerging field of polymer nanomaterial research, presenting some examples of applications of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA) and thermal mechanical analysis (TMA) for the characterization of nanocomposite materials.

Chemical and physical properties of self-crosslinked poly(vinyl chloride)/nitrile rubber nanocomposites prepared by melt-mixing process

In this article, poly(vinyl chloride) (PVC)/acrylonitrile butadiene rubber (NBR)/clay nanocomposites were melt-mixed using the computerized Brabender plasticorder. During preparation of the nanocomposites self-crosslinking (crosslinking without aid of any crosslinking agent) occurs and affects all properties of a sample. The extent of crosslinking reaction depends on the processing temperature, rotor speed and mixing temperature and it increased with increasing each of mixing parameters. The mechanism of the self-crosslinking reaction was examined by the Fourier transform infrared spectroscopy test. The morphology of the materials was characterized using X-ray diffraction and scanning electron microscope. The swelling test and tensile test were applied to distinguish the effects of self-crosslinking phenomena on physical properties of NBR/PVC nanocomposites. Dynamic mechanical thermal analysis tests of nanocomposites were also performed to study the physical properties, such as glass transition temperature (T g). The results showed that the crosslinking reaction made a material more strong with high modulus and tensile strength. Thus, it can be deduced that crosslinks convert the NBR/PVC nanocomposites to stiffer materials that are less penetrable by the solvent. The results drawn from the loss tangent (tan δ) curves of nanocomposite samples can be used as further evidence for the above conclusions.

Photochemical Methods for the Preparation of Complex Linear and Cross-linked Macromolecular Structures

In this contribution, the current state of the art is summarized and an overview of photoinitiating systems for both radical and cationic polymerizations and their potential application in the preparation of complex linear and cross-linked macromolecular structures are described. Recent relevant studies have been devoted to developing novel free radical and cationic photoinitiators having spectroscopic sensitivity in the near-UV or visible range. Photoinitiated controlled radical polymerization methods leading to tailor-made polymers with predetermined structure and architecture are briefly presented. Several synthetic methodologies for the preparation of epoxy and (meth)acrylate based formulations containing clay or metal nanoparticles are also summarized. The nanoparticles are homogenously distributed in the network without macroscopic agglomeration. Applicability to both free radical and cationic systems is demonstrated.