An Efficient Thermal Cure Profile for Thick Parts Made by Reactive Processing of Acrylic Thermoplastic Composites

The process of curing of large thick composite parts needs attention regarding the formation of residual stresses. Similarly, novel reactive thermoplastics need investigating to produce an efficient thermal cure profile that decreases the risk of warpage and residual stress. In this work, the polymerization kinetics of the Elium resin system is investigated by differential scanning calorimetry (DSC) tests, the analysis of thermo-grams, and the parameters of Kamal and Sourour’s semi-empirical model. A numerical model based on finite elements was set up to reproduce the temperature fields during part consolidation. Several processing conditions were investigated (dwell temperature, environment, heat exchange) in order to predict the thermal gradient within the part. The optimal cure profile was identified as a function of process parameters with the aim of minimizing the thermal gradient within the composite element. The analysis revealed that, for the reactive thermoplastic Elium, the consolidation in facilities with high thermal exchange may increase the risk of residual stresses within the parts, erasing the advantage of short cure cycles.

Joining Titanium by Means of Ceramic Adhesives

Ceramic adhesives are an interesting alternative to traditional methods to join metal to ceramics such as fastening, vacuum brazing and gluing. Ceramic adhesives are made of an inorganic matrix with a filler (alumina, zirconia, silica, etc.), and they require a thermal cure cycle in order to establish adhesion. In this work, the adhesion between two different adhesive and Ti6Al4V is studied in details and the influence of the curing cycle is analyzed. Two different adhesives have been used, the first made of a phosphate matrix with an alumina filler, the second made of a silicate matrix wit an alumina filler. The results indicates that in the case of the first adhesive a high temperature cure it is necessary in order to establish a strong adhesion with the metal; on the contrary the second adhesive is capable to create a strong bonding already at low temperature.

Calixarene–based cyanate ester resin for high-temperature material

p-tert-Butylcalix[4]arene-derived cyanate ester resins, both single and binary systems, were synthesized and studied for their thermal properties. The results showed that pure calixarene cyanate ester can be thermally cured at comparatively high temperature, which remains in original powder state after thermally cured. So the pure calixarene cyanate ester resin fails to meet the processing demands of resin-matrixed composite. In this work, p-tert-butylcalix[4]arene cyanate ester was chemically functionalized to have highly decreased thermal cure temperature (by copolymerization with epoxy, bisphenol A cyanate ester (BPACE), and polysilazane (PSZ), respectively). The binary resins were thermally cured into monolithic materials. The optimal acceleration of thermal cure reaction was achieved with an addition of 10% PSZ. The addition of epoxy resin decreased thermal resistance and carbon yield of p-tert-butylcalix[4]arene cyanate ester and addition of BPACE slightly decreased thermal resistance and carbon yield, while PSZ highly improved thermal resistance and carbon yield. Glass transition temperature of the co-cured resin of calixarene cyanate ester with 10% PSZ was much higher than that of conventional BPACE. Calixarene cyanate ester possesses much better property than that of conventional BPACE resin.

3D printing of high performance cyanate ester thermoset polymers

We report 3D printing of a ‘pure’ thermal cure cyanate ester for the fabrication of robust 3D printed structures through the formulation, tailoring and post processing of a custom ‘ink’ for Direct Ink Writing.

Bio-oil as Substitute of Phenol for Synthesis of Resol-type Phenolic Resin as Wood Adhesive

The bio-oil from fast pyrolysis of cornstalks was used as substitute of phenol to synthesize resol resin as an ideal wood adhesive. The effects of formaldehyde/phenol (F/P) molar ratios and oil/phenol (O/P) weight ratios on rehology, thermal cure, thermal resistance and adhension of plywoods were investigated. With the increase of bio-oil used in bio-resol, the gel time of the prepared bio-oil modified resol resin (bio-resol resin) increased gradually, and the exothermic peak temperature of thermal cure shifted slightly higher. It was found that the bio-resin with bio-oil/phenol = 0.5 (weight ratio) and F/P = 1.5 (molar ratio) had the best comprehensive properties. The plywoods made with the bio-resol resins fulfilled the standards of E0and type I plywood, implying the bio-resol resins was a new environment-friendly adhesive.