Search results for "blend"

Synthesis of reactive hyperbranched and star-like polyethers and their use for toughening of vinylester–urethane hybrid resins

2004

A vinylester – urethane hybrid resin (VEUH) was toughened by adding various vinyl-functionalized branched polyethers in 10 and 20 wt%. Two sets of hyperbranched polymers (HBPs) with different branching density were compared with a set of six-arm star polymers. Besides the architecture, the polymers also varied in their characteristics (molecular mass and mass distribution, vinyl/hydroxy ratio). The morphology of the modified VEUH was studied by dynamic-mechanical thermal analysis (DMTA), transmission (TEM) and scanning electron microscopy (SEM). The toughness was characterized by the fracture energy ðGcÞ determined on compact tension specimens at room temperature. It was established that th…

Effects of organoclay on morphology and properties of nanocomposites based on LDPE/PA-6 blends without and with SEBS-g-MA compatibilizer

2009

LDPE/PA-6 blends (75/25 wt/wt) were added with SEBS-g-MA (S) and/or an organoclay (20A) using different compounding sequences and the morphology and the properties of the blends or composites were investigated. An XRD study of the nanocomposites with pure polymers showed that 20A is intercalated by LDPE or PA-6 chains, whereas it is exfoliated by S if the clay concentration does not exceed 10 wt%. The SEM investigation showed that both S and 20A behave as efficient emulsifying agents for the LDPE/PA-6 blends. However, their effect on the mechanical properties was found to be opposite: S enhanced toughness but lowered the stiffness, whereas 20A improved the elastic modulus but impaired the i…

Time–carbonyl groups equivalence in photo-oxidative aging of virgin/recycled polymer blends

2004

AbstractThe photo-oxidation behaviour of polymers is strongly dependent on the initial amount of carbonyl groups along the chains. The growing use of recycled post-consumer polymers coming from products used outdoors and then photo-oxidised, both pure and blended with the same virgin polymer, gives rise to an unpredictable behaviour of weathering resistance of products made with these materials. The present work shows that the carbonyl group–exposure time curves can be shifted along the time axis to give a single generalised master plot. It is then possible to predict the formation of the new carbonyl groups by knowing only the initial amount of the same carbonyl groups. The same shift fact…

Photooxidation and Stabilization of Photooxidized Polyethylene and of its Monopolymer Blends

2003

The increasing use of products from recycled polymers, or from blends with recycled polymers exposed to the outdoors, implies the need for good weathering resistance. This is particularly important when the recycled material comes, in turn, from products exposed during their lifetime to the sun. In this case the presence of C=O groups in the macromolecular chains strongly increases the photooxidative degradation kinetics of these secondary materials. In this work the change of the photooxidative degradation of blends of virgin and photooxidized polyethylene was evaluated as a function of the C=O content present in the material. As expected, the presence of the C=O groups strongly increases …

Research of the physical-chemical properties of adhesive radiation-modified thermosetting materials based on polyolefins and their composites

1999

The present paper surveys the investigation results of the adhesive behavior with steel of different polyethylenes (LDPE, HDPE) irradiated with γ-radiation in vacuum, oxygen, and air, using rheological, optical, thermomechanical and other methods. To study the adhesive contact, the technological parameters applicable to thermosetting polymer material were taken into consideration. The results show the suitable methods in order to obtain thermosetting polymer materials with improved adhesive and thermomechanical properties.

The role of the clay in morphology modification of the uncompatible polymer blends

2011

On the mechanism of compatibilization of polyolefin/liquid crystalline polymer blends with graft copolymers

2000

The compatibilization mechanism of some compatibilizers for blends of polyolefins with a liquid crystalline polymer (LCP) was studied. Polyethylene (PE) and polypropylene (PP) were blended with a semirigid LCP (SBH) in a batch mixer, either with and without compatibilizers. The latter were two commercially available samples of functionalized polyolefins, that is, a PE-g-MA (HDM) and a PP-g-AA (Polybond 1001) copolymer and some purposely synthesized PE-g-LCP and PP-g-LCP copolymers. Microtomed films of the binary and the ternary blends were annealed at 240 degrees C on the hot stage of a polarizing microscope and the changes undergone by their morphology were recorded as a function of time. …

Reactive Compatibilization of PBT/EVA Blends with an Ethylene‐Acrylic Acid Copolymer and a Low Molar Mass Bis‐Oxazoline

2004

DEVELOPMENT OF A BLENDED COURSE FOR ONLINE TEACHING: PROCESS AND OUTCOMES

2019

In this study, we outline the different steps and strategies followed to develop an online formation program aimed to higher education teachers. The aim of this program is to provide with teaching competencies to face the challenges of the next decade’s classroom, with a special focus on the role of digital technology in learning environments, through a combination of a self-managed course with a guided on-site training with real cases. A multicultural, multidisciplinary team conceives this blended learning format, which applies a storytelling approach for content generation and communication. A detailed description of the different factors and stages followed to undertake the project is pr…

Perceived support in e-collaborative learning: An exploratory study which make use of synchronous and asynchronous online-teaching approaches

2012

Published version of a chapter in the book: Advances in Web-Based Learning - ICWL 2012. Also available from the publisher at: http://dx.doi.org/10.1007/978-3-642-33642-3_2 This study compares four different learning environments for e-collaborative learning in two European countries related to the dimension of student’s mutual support. The theoretical baseline is Vygotsky’s zone of proximal development (ZOPD) and the socio-genetic approach of Piaget. The analyzed data are based on questionnaires collected over the time period of an entire semester including four different courses at the master’s level. These courses applied different e-collaborative approaches including a variety of tools f…