This paper reports the analysis of the C=O stretching region of poly(L-lactide). This spectral band splits into up to four components, a phenomenon that a priori can be explained in terms of carbonyl-carbonyl coupling or specific interactions (such as C-H...O hydrogen bonding or dipole-dipole). Hydrogen bonding can be discarded from the analysis of the C-H stretching spectral region. In addition, low molecular weight dicarbonyl compounds of chemical structure similar to that of PLLA, such as diacyl peroxides, show a remarkable splitting of the carbonyl band attributed to intramolecular carbonyl-carbonyl coupling. Several mechanisms can be responsible for this behavior, such as mechanical coupling, electronic effects, or through-space intramolecular TDC (transition dipole coupling) interactions. Intermolecular dipole-dipole interactions (possible in the form of interchain TDC interactions) are proven to be of minor relevance taking into account the spatial structure of the PLLA conformers. The Simply Coupled Oscilator (SCO) model, which only accounts for mechanical coupling, has been found to predict adequately the relative intensity of the symmetric and asymmetric bands of dicarbonyl compounds. The dispersion curves predicted for PLLA by the SCO model also match those given by more general treatments, such as Miyazawa's first-order perturbation theory. Hence, the SCO model is adopted here as an adequate yet simple tool for the interpretation of band splitting caused by intramolecular coupling of polylactide. The four components observed in the C=O stretching band of semicrystalline PLLA are attributed to the four possible conformers: gt, gg, tt, and tg. The narrow bands observed for the interlamellar material are attributed to highly ordered chains, indicating the absence of a truly amorphous phase in the crystalline polymer. The interphase seems to extend over the whole interlamellar region, showing the features of a semiordered metastable phase. In amorphous PLLA, bands corresponding to gt, gg, and tt conformers also can be resolved by second derivative techniques, and curve-fitting results provide information about the conformational population at different temperatures.

This paper reports a DSC and FTIR study of blends of poly(l-lactide) (PLLA) with poly(vinylphenol) (PVPh). According to the single T g criterion, miscibility has been found in all the compositions range for the blends obtained by solution/precipitation in a dioxane/hexane pair. However, phase separation has been observed for PVPh-rich blends obtained by solvent casting from dioxane solutions. The T g of the blends shows negative deviation from linearity. Hydrogen bonding has been found, and the band attributed to hydrogen-bonded carbonyl groups is shifted about 18 cm-1, suggesting relatively weak hydroxyl−ester hydrogen bonds. The equilibrium melting points of pure PLLA and different blends have been recorded, and the values of the interaction parameter χ12 = −0.42 and the interaction energy density B = −8.8 cal/cm3 have been calculated. The negative value of the interaction parameter confirms a thermodynamically miscible blend. The value of B is similar to the value found in poly(ε-caprolactone) (PCL)/PVPh. This small difference between both systems is feasible because the weaker attractive interactions found in PLLA/PVPh counteract against weaker repulsive interactions, as the solubility parameter of PLLA (δ = 10.1 (cal/cm3)1/2) is closer to PVPh (δ = 10.6 (cal/cm3)1/2) than the solubility parameter of PCL (δ = 9.2 (cal/cm3)1/2).

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Binder Jetting Metal Additive Manufacturing (BJ-MAM), known also as metal 3D-printing, is a powder bed-based additive manufacturing technology. It consists of the deposition of liquid binder droplets to selectively join powder particles to enable the creation of near-net shaped parts, which subsequently are consolidated via sintering process. This technology is known for its capability to process a wide range of different materials and for its orientation towards large volume production series. Binder Jetting has recently been drawing the attention of both the research sphere as well as several industrial sectors. The present review study encompasses the various and most remarkable aspects of BJ-MAM part fabrication. The review covers the material selection and characterisation considerations, followed by the manufacturing process features and the parameter effect on different part properties. It concludes with an overview concerning the most recent case studies with regards to diverse metal alloy developments.

Blends of poly(DL-lactide) (PDLLA) with poly(vinylphenol) (PVPh), obtained by solventcasting and solution/precipitation, have been studied by DSC and FTIR. DSC results obtained in the first heating scan suggest that as-prepared blends are phase separated in nearly pure components. In addition, the initial FTIR spectra of the as-precipitated blends show no sign of specific interactions, which is also consistent with the phase separation. In solution/precipitation blends, the first calorimetric scan shows an exothermic peak attributed to the enthalpy of mixing. To our knowledge, this is the first polymer blend system for which this thermodynamic parameter has been possible to directly measure. The exothermic peak occurs at temperatures just below the T g of PVPh. The consecutive DSC scans show a single Tg for the whole composition range, indicating complete miscibility. The interaction energy density (B) has been calculated and shows a strong dependence on composition. The decrease in B (in terms of absolute value) as the content of PVPh decreases is related to the higher energy consumed to break its strong autoassociation. Phase separation into the neat polymers for the as-prepared blends is attributed to accessibility issues between interacting groups, including steric shielding, group spacing, and chain stiffness, aggravated by blending temperatures below the corresponding T gs. At high temperatures thermal motion increases chain mobility, allowing the development of an intimately mixed single-phase blend. On the other hand, phase separation is observed in solution-cast blends with high PVPh content, certainly due to the ∆χ effect, resulting in macroscopic domains that prevent obtaining a homogeneous blend at high temperatures in the absence of a shearing mechanism. Interaction development during heating has been followed by FTIR. Both the hydroxyl and carbonyl stretching regions indicate hydrogen bonding between OH groups of PVPh and CdO groups of PDLLA, suggesting weaker interactions than in other PVPh/polyester systems.