Microcellular Polylactide (PLA) and PLA/poly(butylenes succinate) (PBS) foams were prepared by batch foaming process with supercritical carbon dioxide. The introduced PBS phase was immiscible with the PLA matrix and separated as domains. The study of CO2 solubility in PLA and PLA/PBS blends indicated the addition of PBS decreased the gas solubility due to the poor affinity of CO2 for PBS. The crystallization behavior of PLA was enhanced by small amount of PBS with lower cold crystallization temperature and higher crystallinity. However, separated PBS droplets led to less perfect and small crystallites, which showed greatly effect for the PLA foaming process. The investigation on the foaming conditions dependence indicated the PLA/PBS blends required higher temperature and longer time for the cell growth, which were nucleated around the interface between PLA and PBS. With less CO2 content in the PLA or PLA/PBS blends after different desorption time, the final cell morphology exhibited more uniform size distribution with bigger average cell size and smaller cell density. Different from the well closed-cell structure for neat PLA foam, the PLA/PBS foam presented open cell structure due to the cell nucleation around the PLA/PBS interface and the lower melt strength of PBS phase. 相似文献
We report here the morphology and tensile properties of polylactic acid–cellulose nanofibre (PLA–CNF) microcellular nanocomposites. Two types of CNF were used for the nanocomposite preparation, native and surface acetylated CNF (ac-CNF). Samples were foamed in a mould to enable tensile testing. The effect of the mould use on the foam morphology was first assessed by comparison with free foamed samples. We found that the mould affected the cell growth stage of the foaming process in neat PLA foam while its effect was less important in nanocomposites. Stiffening and strengthening effect of CNF was greatly enhanced by foaming when compared to their solid counterparts. The most notable change in tensile properties was however the large increase in strain at break resulting in the high tensile toughness of microcellular PLA–CNF nanocomposites. Strain at break increased up to 7.5 times in neat PLA and up to 31.5 times in the foam containing 3% of CNF. Surface acetylation of CNF significantly affected the properties of foams with 9% of CNF loading: while foams with ac-CNF were stiffer, foams with native CNF exhibited higher strain at break and so higher overall toughness. 相似文献
Summary: In order to produce modified poly(lactic acid) (PLA) resins for applications requiring high melt viscosity and elasticity (e.g., low‐density foaming, thermoforming), a commercial PLA product has been reactively modified in melt by sequentially adding 1,4‐butanediol and 1,4‐butane diisocyanate as low‐molecular‐weight chain extenders. By varying amounts of the two chain extenders associated to the end group contents of PLA, three resulted samples were obtained. They were then structurally characterized by FTIR spectroscopy and molecular structure analysis. Their thermal, dynamic mechanical thermal properties and melt viscoelastic properties were investigated and compared along with unmodified PLA. The results indicated that chemical modification may be characterized as chain scission, extension, crosslinking, or any combination of the three depending on the chain extender amounts. The increase of PLA molecular weight could be obtained by properly controlling amounts of two chain extenders. The samples with increased molecular weights showed enhanced melt viscosity and elasticity. Such property improvements promised a successful application for modified PLA in a batch foam processing by producing foams with reduced cell size, increased cell density and lowered bulk foam density in comparison with plain PLA foam.
This research investigated a new method to produce geopolymer foams from blast furnace slag (BFS) with poly(lactic acid) (PLA) covering the developed porosity into the materials. A porous alkali-activated material was developed, and a biodegradable polymer was used to cover the geopolymer in the bulk state. Geopolymer foams were synthesized with a sodium metasilicate solution, and the porosity was developed by adding hydrogen peroxide (H2O2). Foams of materials were produced with two stoichiometries of 1.4 and 1.6 g/L between solid/liquid with a hydrogen peroxide solution. The dimensional stability was achieved after coating geopolymer foams with PLA, improving the molding capacity on different geometries for the composite materials. Specimens of the geopolymer foam/PLA composites were characterized by X-ray fluorescence (XRF), Fourier transformed infrared (FTIR), thermogravimetry (TGA), and field emission gun scanning electron microscopy (FEG-SEM). The permeation analysis of metal oxide particles through the composites foam specimens was performed using water dispersions containing bismuth oxide or titanium oxide. The test resulted in high performance in the retention of particulate materials. The highlights of the results indicated the efficiency in the synthesis of geopolymer foam, a good formation of porosity, and an effective PLA coating on the internal interfaces of geopolymer foam through the development of a new bulk state coating method, improving the dimensional stability and the retention of bismuth and titanium oxides particles by the produced geopolymer foams for water depollution. 相似文献
