Luís A. Pinheiro

Nanocrystalline cellulose extracted from pine wood and corncob

The extraction of nanocrystalline cellulose from agro-residues is an interesting alternative to recover these materials. In the present study, nanocrystalline cellulose was extracted from pine wood and corncob. In addition, microcrystalline cellulose was used as a reference to compare results. Initially, the lignocellulosic residues were submitted to delignification pre-treatments. At the end of the process, the bleached fibre was submitted to acid hydrolysis. Additionally, microparticles were obtained from the spray-drying of the nanocrystalline cellulose suspensions. The nanocrystalline cellulose yield for the pine wood was 9.0-% of the value attained for the microcrystalline cellulose. For the corncob, the value was 23.5-%. Therefore, complementary studies are necessary to improve the yield. The spray-dried microparticles showed a crystallinity index of 67.8-% for the pine wood, 70.9-% for the corncob and 79.3-% for the microcrystalline cellulose. These microparticles have great potential for use in the production of polymer composites processed by extrusion.

Multivariate analysis of the spectroscopic profile of the sugar fraction of apple pomace

Pomace, the main by-product of apple juice processing, contains all the fruits compounds such as minerals, sugars, fibers, enzymes and secondary metabolites after bioprocessing. Dried pomace from four apple varieties (Gala, Fuji, Catarina and Joaquina) was used to extract fructose, glucose, and sucrose, the main soluble sugars contained in apple pomace, to verify the possible use of the sugar fractions. The concentrated sugars were characterized by NMR and FTIR. The partial least squares method (PLS) applied to the NMR and FTIR spectra revealed large amounts of fructose, glucose, and sucrose, without the presence of others compounds. Principal component analysis (PCA) discriminated the studied apple varieties, with a 99% level of significance, as function of the amount of each sugar in the respective extracts.

Determination of non-isothermal crystallization rate constant of a rotational molding grade LLDPE

The purpose of the present paper was to test the validity of the nonlinear regression method for calculating the non-isothermal crystallization rate constant of the Nakamuras model of a rotational molding grade LLDPE directly from non-isothermal crystallization experiments carried out in a single cell DSC. Cooling rates of 50, 40, 30, 20, 10 and 5 oC/min were used with samples of 3.0 mg under nitrogen atmosphere. Here, good agreement was observed between the experimental relative crystallinity curves and the simulated ones using the calculated parameters by nonlinear regression. It shows that this method can be used to determine the Nakamuras non isothermal rate constant for using in simulation of the cooling phase of rotational molding. In this paper it was used 10-3, 10-4 and 10-14 as the initial crystallinity in the Nakamuras model. However the best average results for all cooling rates was obtained when 10-4 was used. Average spherulitic dimensions of LLDPE studied in this paper did not change significantly with different cooling conditions.

CARACTERIZAÇÃO POR RESSONÂNCIA MAGNÉTICA NUCLEAR DE SUCOS DE MAÇÃ OBTIDOS POR PREPARAÇÕES ENZIMÁTICAS

In this work, 1H Nuclear Magnetic Resonance (1H NMR) was employed to evaluate changes in apple juice in response to the addition of Panzym® Yieldmash and Ultrazym® AFP-L enzymatic complexes and compare it with premium apple juice. The juice was processed at different temperatures and concentrations of enzymatic complexes. The differences in the results were attributed mainly to the enzyme concentrations, since temperature did not cause any variation. A quantitative analysis indicated that the concentration of fructose increased while the concentrations of sucrose and glucose decreased in response to increasing concentrations of the enzymatic complexes.

Optimization of wood flour acetylation by factorial design and partial least squares regression

Acetylation was performed to reduce the polarity of wood and increase its compatibility with polymer matrices for the production of composites. These reactions were performed first as a function of acetic acid and anhydride concentration in a mixture catalyzed by sulfuric acid. A concentration of 50%/50% (v/v) of acetic acid and anhydride was found to produced the highest conversion rate between the functional groups. After these reactions, the kinetics were investigated by varying times and temperatures using a 32 factorial design, and showed time was the most relevant parameter in determining the conversion of hydroxyl into carbonyl groups.

Influence of Reprocessing in the formation of functional groups during low density polyethylene aging

In recent years, the interest in polymer recycling has increased. However, in every reprocessing step the material undergoes shear stress and is affected by temperature and oxygen. The aim of this paper is to investigate the influence of multiple extrusion in the generation of functional groups, namely hydroperoxide, carbonyl, and transvinylene. Low density polyethylene was reprocessed three times in a single screw extruder. In each recycling step hot pressed films were prepared. These films were submitted to a heat treatment in an oven with air circulation and renovation to proceed with aging tests at different times and temperatures. The results obtained showed that all functional groups had their concentration increased with the increase in number of reprocessing, the aging time and temperature of the heat treatment. The factorial design was applied to verify the influence of these parameters. All the parameters had significant effects, since their regression coefficients had the same order of magnitude, with the most influential parameter being the aging temperature, followed by the aging time and number of extrusions. Most of the interactions were influential, indicating that the formation of functional groups depends upon their interaction, and not only on their isolated effects.

Factorial design to quantify the influence of extrusion parameters in the mean residence time

Residence time distribution (RTD) is a very important parameter in extrusion, either for simple polymer processing or for special processes like compounding, blending, reactive compatibilization, and controlled degradation. This work deals with the values of mean residence time (tn) as a function of the number of 45 degrees kneading elements in the screw profile, screw speed, and feeding rate. The tn values were calculated from the RTD curves, which in turn were determined by the technique of a marker added as a pulse in the steady state polymer flow. The values of tn were empirically modeled as a function of those parameters. The results showed that feeding rate is the most influent parameter, followed by number of kneading elements and screw speed. The modeling has given a quadratic function relating tn and the operational parameters tested.

Characterisation of Cassava Bagasse and Composites Prepared by Blending with Low-Density Polyethylene

ABSTRACT The main objective of this study was to characterise the cassava bagasse and to evaluate its addition in composites. Two cassava bagasse samples were characterised using physicochemical, thermal and microscopic techniques, and by obtaining their spectra in the mid-infrared region and analysing them by using x-ray diffraction. Utilising sorption isotherms, it was possible to establish the acceptable conditions of temperature and relative humidity for the storage of the cassava bagasse. The incorporation of cassava bagasse in a low-density polyethylene (LDP) matrix was positive, increasing the elasticity modulus values from 131.90 for LDP to 186.2 for 70% LDP with 30% SP bagasse. These results were encouraging because cassava bagasse could serve as a structural reinforcement, as well as having environmental advantages for its application in packaging, construction and automotive parts. Key words: Manihot esculenta Crantz , residue, polymers * Author for correspondence: demiate@uepg.br

Correlation between Surface Energy and Adhesion Force of Polyethylene/Paperboard: A Predictive Tool for Quality Control in Laminated Packaging

Poor adhesion continues to be a problem for manufacturers of laminated packaging. Therefore, the aim of this research was to study the effect of flame treatment, the type of coating, and starch application on the adhesion force of polyethylene/paperboard. The force of adhesion was determined using the peel test method; the paper surface energy was assessed by contact angle analysis; and paperboard roughness was determined by profilometer. The flame treatment did not affect the surface roughness but significantly increased the paperboard surface energy. The paperboard coated with polar latex showed much higher surface energy than the paperboard coated with nonpolar latex. The adhesion force of polyethylene presented a linear correlation to the surface energy of the paperboard. Therefore, the surface energy of paperboard is an excellent indication of its adhesion force to polyethylene, and this represents a very reliable and practical method in terms of quality control in the paper industry for producing laminated packages.

Development and characterization of post-consumer rubber tire powder, high density polyethylene and ethylene-octene-1copolymer ternary mixtures

Scrap tires are considered a type of waste that litters landfills and the environment in general. Due to its chemically cross-linked structure, this material cannot be recycled by conventional processes because it does not melt. This work examined the production of polymeric composites using high density polyethylene (HDPE) filled with rubber tire powder (RTP). Ethylene-octene-1 copolymer (C2C8), an elastomeric material, was also added to improve the mechanical properties. Morphological analysis showed a good interfacial adhesion when C2C8 is added to the mixture. Raman spectroscopy coupled to optical microscopy revealed that the HDPE phase encapsulated the rubber tire particles. The mixtures containing C2C8 and RTP presented lower ultimate tensile strength and elastic modulus, but the impact strength of the binary and ternary mixtures was much higher than that of neat HDPE.