D. Garcia-Sanoguera

Plasticizing effect of biobased epoxidized fatty acid esters on mechanical and thermal properties of poly(lactic acid)

Poly(lactic acid), PLA, is a polyester that can be produced from lactic acid derived from renewable resources. This polymer offers attracting uses in packaging industry due to its biodegradability and high tensile strength. However, PLA is quite brittle, which limits its applications. To overcome this drawback, PLA was plasticized with epoxy-type plasticizer derived from a fatty acid, octyl epoxy stearate (OES) at different loadings (1, 3, 5, 10, 15, and 20 phr). The addition of OES decreases the glass transition temperature and provides a remarkable increase in elongation at break and impact-absorbed energy. Plasticizer saturation occurs at relatively low concentrations of about 5 phr OES; higher concentration leads to phase separation as observed by field emission scanning electron microscopy (FESEM). Optimum balanced mechanical properties are obtained at relatively low concentrations of OES (5 phr), thus indicating the usefulness of this material as environmentally friendly plasticizer for PLA industrial formulations.

Mechanical and Thermal Properties of Polyvinyl Chloride Plasticized with Natural Fatty Acid Esters

From an industrial point of view, the use of new nontoxic and biodegradable plasticizers coming from natural resources is an interesting alternative to traditional plasticizers based on phthalates. In this study, two types of epoxidized fatty acids esters (EFAE) with different molecular weights have been used in order to produce flexible PVC with low toxicity. Different amounts of EFAE 201 and 401 have been considered in this study. Mechanical and thermal properties have been determined and morphology of fracture surface has been studied by scanning electron microscopy.

Optimization of atmospheric plasma treatment of LDPE films: influence on adhesive properties and ageing behavior

One of the major disadvantages of low density polyethylene (LDPE) films is their poor adhesive properties. Therefore, LDPE films have been treated with atmospheric pressure air plasma in order to improve their surface properties. So as to simulate the possible conditions in an industrial process, the samples have been treated with two different sample distances (6 and 10 mm), and treatment rates between 100 and 1000 mm s−1. The different sample distances are the distance of the sample from the plasma source. The variation of the surface properties and adhesion characteristics of the films were investigated for different aging times after plasma exposure (up to 21 days) using contact angle measurement, atomic force microscopy, weight loss measurements and shear test. Results show that the treatment increases the polar component () and these changes improve adhesive properties of the material. After the twenty-first day, the ageing process causes a decrease of wettability and adhesive properties of the LDPE films (up to 60%).

Recycling of Expanded Polystyrene from Packaging

Expanded polystyrene (EPS) is a commonly used polymer in the packaging industry. The great importance of EPS recovery is related to the materials short service life and the high volume of EPS waste. The aim of the present work was to reduce the volume of waste by its mechanical milling and crushing and subsequent reintroduction into mass production. The results of thermal and infrared analysis indicate that the material does not degrade during the recovery process; indeed, the thermal properties of the recycled material are even better than those of the virgin product. Tensile tests showed that the recycled and virgin materials have similar mechanical behaviour. From the results obtained we can conclude that recycled polystyrene can replace virgin polystyrene in some industrial processing, thus reducing the cost of the final product.

The effect of beta-tricalcium phosphate on mechanical and thermal performances of poly(lactic acid)

Orthophosphates are bioactive crystals with similar structure, in terms of elemental composition and crystal nature, to human bone. In this work, biocomposite materials were prepared with poly(lactic acid) (PLA) as matrix, and beta-tricalcium phosphate (β-TCP) as osteoconductive filler by extrusion-compounding followed by conventional injection molding. The β-TCP load content was varied in the 10–40 wt% range and the influence of the β-TCP load on mechanical performance of PLA/β-TCP composites was evaluated. Mechanical properties of composites were obtained by standardized tensile, flexural, impact, and hardness tests. Thermal analysis of composites was carried out by means of differential scanning calorimetry; degradation at high temperatures was studied by thermogravimetric analysis; and the effect of the β-TCP load on dynamical response of composites was studied by mechanical thermal analysis in torsion mode. The best-balanced properties were obtained for PLA composites containing 30 wt% β-TCP with a remarkable increase in the Young’s modulus. These materials offer interesting properties to be used as base materials for medical applications such as interference screws due to high stiffness and mechanical resistance.

Improvement of liquid absorption properties of nonwoven polypropylene substrates by low pressure plasma treatment with CH4-O2 mixture gas

The use of nonwoven textile substrates for filtration and absorption purposes is generalized due to the high surface area they can provide. Many of these applications require good wetting properties to increase efficiency. In this work, low pressure plasma treatment with a CH4-O2 mixture gas has been used to increase surface wettability and subsequent absorption properties on nonwoven polypropylene substrates. CH4 plasma treatment leads to a plasma polymerization process which results in hydrophobic surface finishing, but in combination with O2, it is possible to form a functionalized plasmapolymerized layer thus improving wetting properties. Changes in wetting properties have been studied by contact angle measurements showing that optimum wetting properties are obtained with exposure times to plasma treatment of about 10 min, and no significant changes are obtained for longer exposure times. Absorption efficiency has been followed by determining three different parameters by the guidelines of the UNE-EN-ISO 9073-6 standard: wetting time, liquid absorption capacity (LAC) and liquid propagation rate or absorption speed. All these properties are remarkably improved as the exposure time to CH4-O2 plasma increases; this improvement is remarkably high for relatively short exposure times (5–10 min) and no significant changes are obtained for long exposure times so that, it is possible to conclude that previous plasma treatment with exposure times in the 5–10 min range is an efficient method to improve overall absorption properties of nonwoven polypropylene substrates.

Mechanical and morphological characterization of novel vinyl plastisols with epoxidized linseed oil as natural‐based plasticizer

Poly(vinyl chloride) (PVC) is one of the most commonly used plastics in the current market due to its low cost and versatility in processing, combined with its satisfactory physical and chemical properties. However, there is an important problem associated to the use of plasticized PVC. This problem is regarding to the toxicity of the most common plasticized used like DOP, DEHP, DINP, due to its possible migration. This problem limits the use of the plasticized PVC in the industry. In this work we have used epoxidized linseed oil (ELO) as a non toxic plasticizer for PVC. This type of natural oil is characterized by acting as both plasticizer and stabilizer of PVC. With this purpose, ELO have been added to PVC. The processing conditions (temperature and time of curing) are vital to determine the final properties of the material. A study of the processing conditions shows the adequate temperature and time to achieve the optimum properties.

Processing and Characterization of Environmentally Friendly Composites from Biobased Polyethylene and Natural Fillers from Thyme Herbs

The main aim of this research work is to assess the potential of a distillery waste from thyme as multifunctional filler in natural fiber reinforced plastics (NFRP) with biobased polyethylene matrix. Several ethylene-based copolymers with different co-monomers (vinyl alcohol, methyl methacrylate, glycidyl methacrylate and acrylic acid) were used as compatibilizer agents to overcome the lack of compatibility between the highly hydrophobic matrix and the highly hydrophilic lignocellulosic filler. The effect of the compatibilizer type and amount, as well as the lignocellulosic filler content was followed by thermal, mechanical, morphological and rheological characterizations. In addition to the typical filler effect, thyme also provides a remarkable increase in thermal stability at moderate temperatures with a positive effect on widening the processing window. The compatibilizer agent that offers best balanced properties is the glycidyl methacrylate copolymer with a noticeable increase in stiffness, flexural and tensile strength. Regarding processability, the viscosity increases with the filler content. This is highly important at low shear rates but the effect is almost negligible at high shear rates typical of injection molding processes.

Utilización de técnicas Kanban para la gestión de tesis doctorales

The development of a doctoral thesis is a team work to be done by the doctorate and his supervisors. A huge list of jobs have to be faced by both. So, communication and coordination between them is mandatory in order an adequate support and track of the doctorate work is provided. This job presents how Kanban technique is applied in the development of a doctoral thesis. The Kanban techniques allow to organize tasks through boards, in a very visual and simple way which facilitates the communication between doctorate and the directors. Recently web and mobile applications that implement Kanban techniques have appeared. These applications allow a dalily collaboration in the thesis, they allow to assign tasks, to know the state of its progress, to hold conversations, to provide constant feedback and finally to see which tasks have already been completed. In a short time, a large part of emails, telephone conversations and chats to notify the status of a task have been eliminated. In a short time, a large part of emails, phone conversations and chats to notify the status of a task have been eliminated.

Study, mechanical characterization and mathematical modeling of compatible SEBS blends for industrial applications in orthopedics and childcare

In this work, a system of compatible blends based on two commercial grades of a thermoplastic elastomer, styrene-ethylene/butylene-styrene (SEBS), with extreme Shore A hardness values (5 and 90), was studied in order to obtain a range of different performance blends for orthopedic and childcare applications, where usually liquid silicone rubber is used. Mechanical properties of different blends were obtained, and Equivalent Box Model (EBM) was used for the prediction of the mechanical behavior. The results show good agreement between the theoretical model and experimental data of new blends of SEBS.