Object reacting with adhesive

In the plasma process [48], air at low pressure is passed through an electric discharge, where it is partially dissociated into the plasma state and then expanded into a closed vacuum chamher containing the plastic object to be treated. The plasma reacting with the surfaces of the plastic alters their physicochemical characteristics in a manner that affords excellent adhesion to surface coatings. The process can be used for batch processing of plastics products, including films which may he unreeled in the vacuum chamber for treatment. 

The binder infiltrates the material and reacts with the powder, causing the layer to solidify in the printed areas by, for example, activating an adhesive in the powder. The binder also penetrates into the underlying layers, producing interlayer bonding. After the first cross-sectional portion is formed, the previous steps are repeated, building successive cross-sectional portions until the final object is formed. 

Strength and release of acidic components [127]. Therefore, FDM and SLS are not suitable for 3D printing of biodegradable PUs. In recent years, most of the studies turned to the other methods to successfully print objects. Pfister et al. adopted adhesive ZPll (mixture of cellulose and starch) to 3D print biodegradable PU [128]. Unfortunately, the adhesive was water-soluble and the mechanical properties of the final products could not be maintained. To overcome this shortcoming, isocyanate was added to the adhesive ZPll to react with PU. While some success was achieved in increasing the water-resistance and tensile strength, the final products were shown to swell when implanted [128]. 

In particular, HEMA hydrogels have found widespread biomedical use mainly for the production of soft contact lenses . However, their surface properties must be modified to improve cell adhesion and proliferation in order to produce polymeric scaffolds suitable for tissue engineering applications. This objective can be achieved by introduction of charged groups onto the hydrogel surface. Accordingly, preformed HEMA hydrogels were reacted for 24 hours with succinic anhydride (SA) (Scheme 1) or 1,4-diaminobutane (DAB) in DMF solution (Scheme 2), at 50 and 100 °C, respectively. 

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