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The aim of this work was to study the effect of the innovative combination of microcrystalline cellulose (MCC) and silver nanoparticles (Ag) on the poly (lactide acid) (PLA) composite properties, to modulate the PLA mechanical response and induce an antibacterial effect. The preparation and characterization of PLA-based composites with MCC and Ag nanoparticles by twin-screw extrusion followed by injection molding is reported. A film procedure was also performed to obtain PLA and PLA composite films with a thickness ranged between 20 and 60 lm. The analysis of disintegrability in composting conditions by means of visual, morphological, thermal, and chemical investigations was done to gain insights into the post-use degradation processes. Tensile test demonstrated the MCC reinforcing effect, while a bactericidal activity of silver-based composites against a Gram-negative bacteria (Escherichia coli) and a Gram-positive bacteria (Staphylococcus aureus) was detected at any time points and temperatures analyzed. Moreover, the disintegrability in composting showed that MCC is able to promote the degradation process. The combination of MCC and Ag nanoparticles in PLA polymer matrix offers promising perspectives to realize multifunctional ternary composites with good mechanical response and antibacterial effect, maintaining the optical transparency and the disintegrability, hence suitable for packaging applications. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: [87][88][89][90][91][92][93][94][95][96][97][98] 2012

Poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) based films containing two different plasticizers [Acetyl Tributyl Citrate (ATBC) and isosorbide diester (ISE)] at three different contents (15 wt %, 20 wt % and 30 wt %) were produced by extrusion method. Thermal, morphological, mechanical and wettability behavior of produced materials was investigated as a function of plasticizer content. Filmature parameters were also adjusted and optimized for different formulations, in order to obtain similar thickness for different systems. Differential scanning calorimeter (DSC) results and evaluation of solubility parameter confirmed that similar miscibility was obtained for ATBC and ISE in PLA, while the two selected plasticizers resulted as not efficient for plasticization of PBS, to the limit that the PBS–30ATBC resulted as not processable. On the basis of these results, isosorbide-based plasticizer was considered a suitable agent for modification of a selected blend (PLA/PBS 80:20) and two mixing approaches were used to identify the role of ISE in the plasticization process: results from mechanical analysis confirmed that both produced PLA–PBS blends (PLA85–ISE15)–PBS20 and (PLA80–PBS20)–ISE15 could guarantee advantages in terms of deformability, with respect to the PLA80–PBS20 reference film, suggesting that the promising use of these stretchable PLA–PBS based films plasticized with isosorbide can provide novel solutions for food packaging applications.

Composites of Phormium tenax fibers in a poly(lactic acid) matrix with fiber content of up to 40 wt%, produced by injection molding and twin screw compounding, were characterized by scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and mechanical tests (static and dynamic). Thermal analysis showed that cold-crystallization peak shifted to lower temperatures with increasing fiber content, confirming that the addition of Phormium fiber has the effect of promoting crystallinity. Dynamic mechanical analysis (DMA) results showed that the addition of Phormium fiber did not affect significantly the T(g) of the polymer and the area under the tan delta decreased with the addition of Phormium fiber. Tensile modulus has been consistently increased by reinforcing the composite with growing amounts of fibers, whilst the effect on tensile strength is less evident. SEM micrographs of fracture surfaces allowed highlighting failure modes of the composites, which included a diffuse presence of fiber pull-out and debonding. POLYM. COMPOS., 32: 1362-1368, 2011. (C) 2011 Society of Plastics Engineer

In order to evaluate the effect of processing conditions, composites of MaterBi-Y matrix with 15wt% sisal fibers are obtained with different temperature profiles and speeds of rotation of the screw, using a twin-screw extruder. Three different temperature profiles are selected. The speeds of rotation are 25, 60, and 80 rpm. The samples are obtained by compression at 180°C and 700 MPa for 10 min. The mechanical properties of composites increase when the rotation speed changes from 25 to 60rpm and then decreases. Fiber breakage increases with rotational speed, but aspect ratio increases too. Increased modulus with fiber aspect ratio is easily understood because longer fibers carry more tensile loads as a result of increase in transfer length. The decrease in the mechanical properties at a high rotational speed can be due to the degradation of the matrix. The impact properties increase when temperature increases. The decrease in impact properties at temperatures above 185°C can be due to the thermal decomposition of the material.

New formulations of plastisols based on low-toxicity plasticizers were proposed and characterized. Traditional phthalate plasticizers were replaced in the plastisols studied in this research by polymeric plasticizers (i.e., saturated polyesters), produced by the reaction of a diol and a carboxylic acid. The main drawback for the use of these plasticizers in formulations of PVC plastisols is a significant increase of the paste viscosity, which decreases their processability; thus, the use of additional additives to reduce viscosity is recommended. This study also includes the optimization of the processing conditions (cure temperature and time) of the proposed plastisols: complete cure was obtained at 140°C and 10 min. It is reported that the final properties of plastisols are very sensitive with respect to the processing conditions; in fact, insufficient plasticization or degradation can affect the material when processed out of the optimum conditions. The influence of the plasticizer concentration on mechanical and optical properties, such as tensile strength, hardness, brightness, and the like, is also reported. In summary, the proposed plastisols, with low-toxicity plasticizers, offer a valid alternative to traditional PVC plastisols based on phthalate plasticizers.

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