The present work is concerned with the photodegradation and photostabilization of poly(3-hydroxybutyrate) (PHB) biopolymer. Two commercial grades of PHB were investigated, containing of 4.0% and 6.2% of hydroxyvalerate (HV) comonomer, named PHB1 and PHB2, respectively. Injection moulded specimens were exposed to ultraviolet radiation (UV-A) in the laboratory for periods of up to 12 weeks and then characterized by tensile testing, surface appearance, size exclusion chromatography (SEC), and scanning electron microscopy (SEM). The exposure to UV radiation caused great damaged on the surface color, reduction of molecular size and mechanical properties. The effects were more pronounced on PHB2, probably due a lighter surface color and less packed macromolecular structure which facilitates the transmission of light throughout the samples. Specimens of PHB1 were also injected with the addition of a UV absorber and antioxidant, resulting in a higher UV stability of PHB, as shown by a low reduction in molar mass and better mechanical properties.

Abstract Poly (butylene adipate-co-terephthalate) - PBAT is a synthetic biodegradable polymer commonly used for plastic film production from neat polymer or nanocomposites. The PBAT is submitted to high temperatures and shear rate during its processing. In the present study, the thermo stabilisation of PBAT by the addition of two types of stabilisers was studied using a torque rheometer at 60 rpm and two levels of temperature. The stabilisers were used as master batches with a percentage of 10% by weight of additive in the PBAT. Molecular weight, torque values after 10 minutes of mixing, and absorbance at 400 nm were used to evaluate the process of stabilisation. The primary and secondary antioxidant used here had a positive effect on both processing temperatures, 180 and 200 °C. The best results indicate that the primary antioxidant could be used alone to protect PBAT against thermodegradation reactions.

<title>Abstract</title><p>We studied the crystallization and melting phenomena of poly (3- hydroxybutyrate) (PHB), a biodegradable and biocompatible semi-crystalline thermoplastic, obtained from renewable resources. Its high crystallinity motivated several studies on crystallization and melting behavior, and also on ways to increase the amorphous polymer fraction. The effect of heating and cooling rates on the crystallization and melting of commercial PHB was investigated by differential scanning calorimetry. Several rates, ranging from 2.5 to 20 °C min^–1, were used to study the phase changes during heating/cooling/reheating cycles. The results showed that PHB partially crystallizes from the melt during the cooling cycle and partially cold crystallizes on reheating, and that the relative amount of polymer crystallizing in each stage strongly depends on the cooling rate. The melt and cold crystallization temperatures, as well as the rates of phase change, depend strongly on the cooling and heating rates.</p>

<title>Resumo</title><p>A Organização Mundial da Saúde (OMS) relata o câncer como uma das principais causas de morte no mundo. Uma modalidade de tratamento que vem sendo bastante utilizada no tratamento do câncer de próstata é a braquiterapia, que consiste na introdução de sementes com material radioativo no interior do orgão. Sementes de Iodo-125 podem ser inseridas soltas ou em cordas poliméricas fabricadas a partir do (poli(ácido lático-co-ácido glicólico)) (PLGA). Foi proposto neste trabalho, o estudo e desenvolvimento da metodologia de síntese do biopolímero PLGA. Os resultados obtidos demonstram que, através da metodologia utilizada, foi possível determinar os melhores parâmetros de reação (tempo e temperatura) para o PLGA na proporção 80/20 (lactídeo/glicolídeo). Com uma temperatura de 110 °C e tempo de reação 72h o rendimento da reação é superior a 90%. Os valores de massas moleculares obtidas entre os testes, ainda são baixos quando comparados com os valores obtidos por outros autores na literatura. Novos testes estão sendo conduzidos, utilizando dímeros preparados no laboratório. Testes substituindo o vácuo por uma atmosfera de nitrogênio também estão sendo realizados. Essas duas substituições podem aumentar o valor final da massa molecular do polímero. Em relação à caracterização, as técnicas utilizadas confirmaram a estrutura esperada do polímero.</p>

<title>Abstract</title><p>According to the World Health Organization, cancer is a leading cause of death worldwide. A radiotherapy method extensively used in prostate cancer is brachytherapy, where the area requiring treatment receives radioactive seeds. Iodine-125 seeds can be inserted loose or stranded in bioabsorbable polymers produced from poly(lactic-co-glycolic acid) (PLGA). We developed the synthesis methodology for PLGA and the results obtained show that it was possible to determine the optimal reaction parameters (time and temperature) for PLGA in 80/20 (lactide/glycolide) ratio. The yield was higher than 90% using a temperature of 110 °C and reaction time of 72 hours; however, the molecular weight values obtained are very low compared to those obtained by other authors. New tests using previously synthesized dimers and nitrogen atmosphere are being performed. These conditions could potentially increase the molar mass of PLGA. All techniques used confirmed the expected structure of the polymer.</p>

A coupled device extruder and injection moulding were used to prepare biocomposites in order to provide a continuous and large-scale production, and overcome the fiber degradation inside the extruder. Two types of biocomposites were prepared, Sisal/poly(buthylene adipate-co-terephthlate) – PBAT and Juta/poly(lactide acid)/poly(buthylene adipate-co-terephthlate) blend. The biocomposites were prepared with fiber as-received and alkaline treated. The mechanical properties of biocomposites were increased by the fibers content; and the alkaline treatment was efficient to promote a good adhesion between fiber and polymer. In the case of the Juta fiber, the alkaline treatment used was too strong and led to fiber degradation. The results presented here show an alternative and continuous process to obtain biocomposites with relevant mechanical properties using fiber roving and avoiding fiber degradation.

Samples of polypropylene (PP) and low-density polyethylene (LDPE) were submitted to ultraviolet radiation, in the natural environment and also in the laboratory. Chemical modifications were quantified by the carbonyl index (CI), mechanical properties and melt flow index. The degradation in the laboratory was comparatively faster than in the environment for both types of polymers. The accelerating factor was determined for the various properties investigated. This parameter, however, showed a large variation with the degradation criteria and the type of polymer. The existence of a "universal accelerating factor", therefore, was not observed in the current study.