This research work aims to study the influence of the reprocessing cycles on the mechanical, thermal, and thermomechanical properties of polylactide (PLA). To this end, PLA was subjected to as many as six extrusion cycles and the resultant pellets were shaped into pieces by injection molding. Mechanical characterization revealed that the PLA pieces presented relatively similar properties up to the third reprocessing cycle, whereas further cycles induced an intense reduction in ductility and toughness. The effect of the reprocessing cycles was also studied by the changes in the melt fluidity, which showed a significant increase after four reprocessing cycles. An increase in the bio-polyester chain mobility was also attained with the number of the reprocessing cycles that subsequently favored an increase in crystallinity of PLA. A visual inspection indicated that PLA developed certain yellowing and the pieces also became less transparent with the increasing number of reprocessing cycles. Therefore, the obtained results showed that PLA suffers a slight degradation after one or two reprocessing cycles whereas performance impairment becomes more evident above the fourth reprocessing cycle. This finding suggests that the mechanical recycling of PLA for up to three cycles of extrusion and subsequent injection molding is technically feasible.

2 AbstractThe present work is focused on the development of binary blends from poly(hydroxybutyrate) (PHB) and poly(caprolactone) (PCL). Miscibility, mechanical and thermal properties as well as blends morphology are evaluated in terms of the blend composition. Binary PHB-PCL blends were manufactured by melt compounding in a twin screw co-rotating extruder and injection molded. Composition of PHB-PCL covered the full range between individual polymers at 25 wt% increments. The obtained results show that PCL acts as an impact modifier thus leading to an increase in flexibility and ductility as the PCL content on PHB-PCL blends increases with a noticeable increase in elongation at break and on

This paper presents a study on the stabilization of polypropylene (PP) against thermo-oxidation and UV radiation by using natural phenolic compounds derived from structures of flavonoids: a flavone (chrysin), a flavanol (quercetin), two flavanone glycosides (hesperidin and naringin) and flavanoligand (silibinin). Thermal stabilization has been assessed in an oxidizing atmosphere by means of differential scanning calorimetry (DSC) both in isothermal as well as dynamic conditions. In addition, the effectiveness of these phenolic compounds as thermal stabilizers at high temperature 2 has been quantified with the use of thermogravimetric analysis (TGA). Stabilization against UV radiation has been estimated by studying the morphology changes of the exposed surfaces by scanning electron microscopy (SEM); also surface chemical changes have been followed by infrared spectroscopy (FTIR). Global results show that flavonoid compounds of type flavonols (quercetin and silibinin) provide the best results in stabilizing both against oxidation and against the action of UV radiation.

In this investigation a fully biobased composite material has been obtained using a biobased polyethylene obtained from sugar cane as matrix and eggshell (ES) as filler. ES was studied in order to replace mineral carbonate calcium as polymer filler, which is commonly used. In order to do this the ES has been chemically modified and then its potential for the development of a biocomposite was evaluated. The filler adhesion to the polymer matrix has been improved using titanate particle treatment which has been chosen between silane and zirconate. The use of titanate as coupling agent enlarges the range of operating temperatures and also improves the interfacial bonding as it is displayed in impact fracture surface. Mechanical, thermal and rheological analysis were carried out in order to analyze the effect of the modified ES loading percentage. Thermal analysis showed a proportional effect of the filler load over the degradation temperature and an inversely effect over the enthalpy. Effect of the modified ES content on mechanical properties of PE/ES was also studied. The results showed that the modified CaCO3 can effectively improve the mechanical properties of bio PE, improving stiffness, hardness, flexural and tensile modulus. The amount of filler increases the viscosity, this fact specially hinders the processing processes which work with low shear rates.

Epoxidized soybean oil (ESBO), obtained from a renewable resource was used in the production of thermoset resins. Samples of the ESBO were initially treated with maleic anhydride, equal mixture of catalyst (1,3‐butanediol anhydrous and benzyldimethylamine) and the mixture was cured for 5 h at different temperatures. After the curing process, the ratio between the ESBO and the anhydride (ratio EEW:AEW) was evaluated in terms of the different mechanical properties produced using flexural, Shore D hardness and Charpy impact tests. The sample with the best mechanical properties was that with an EEW:AEW ratio of 1:1.0 which leads to best balanced behavior and this could be representative for the maximum crosslinking degree. Also, thermal characteristics were evaluated during the crosslinking process using differential scanning calorimetry, In addition, other thermal characteristics of the cured materials were obtained by determining the heat deflection temperature and the Vicat softening temperature. The coefficient of thermal expansion was determined using thermo‐mechanical analysis. In accordance with the mechanical behavior, the best thermal properties were obtained for samples with an EEW:AEW ratio of 1:1.0. As a result of this work, a biologically based epoxy resin with good mechanical properties and flexibility was obtained.

Abstract. This research work aims at the compatibilization of poly(lactic acid)/poly(butylene adipate-co-terephthalate), PLA/PBAT binary blends by using cottonseed oil derivatives, i.e. epoxidized (ECSO) and maleinized (MCSO) cottonseed oil. The potential of these vegetable oil-based compatibilizers are compared versus the effects of a conventional styreneacrylic oligomer. The base PLA/PBAT binary blend composition was 80 wt% PLA/20 wt% PBAT and the amount of compatibilizer was set to 1 and 7.5 wt%. The effects of the different compatibilizers were evaluated on PLA/PBAT films in terms of mechanical and thermal properties as well as blend's morphology by field emission scanning electron microscopy (FESEM). Complementary, biodisintegration tests in controlled compost soil and surface properties were evaluated to assess the effects of the compatibilizers. Addition of 1 wt% ECSO and MCSO led to a remarkable increase in the elongation at break up to values over 100% with regard to neat PLA. Despite this, maximum elongation at break was obtained for the compatibilized PLA/PBAT blend with 7.5 wt% MCSO, reaching values of about 321.2% respect neat PLA keeping mechanical resistant properties, such as Young's modulus and tensile strength, at high levels. Therefore, vegetable oil-derived compatibilizers stand out as environmentally friendly additives for PLA/PBAT binary blends with improved properties.

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Poly(lactic acid), PLA‐based green composites were obtained with hazelnut shell flour (HSF) derived from the food industry thus leading to fully biodegradable materials with attracting properties. The hazelnut shell flour content varied in the 10–40 wt% range. An increase in the degree of crystallinity with increasing HSF was detected, mainly due to the nucleating effect of lignocellulosic particles. The thermodimensional stability was noticeably improved with increasing HSF amount as evidenced by a remarkable decrease in the coefficient of thermal–linear expansion. Increasing HSF leads to stiffer materials as HSF particles act as interlock points that restrict polymer chain motion. Addition of hazelnut shell flour as filler in PLA‐based green composites leads to fully biodegradable composites with balanced mechanical and thermal properties. Furthermore, it gives a solution to upgrade wastes from the hazelnut industry and contributes to lower the cost of PLA‐based materials. POLYM. COMPOS., 39:848–857, 2018. © 2016 Society of Plastics Engineers