Thermal stability and flame retardancy of polyurethanes

The rising concern towards environmental issues and, on the other hand, the need for more versatile polymer-based materials has led to increasing interest about polymer composites filled with natural-organic fillers, i.e. fillers coming from renewable sources and biodegradable. The composites, usually referred to as “green”, can find several industrial applications. On the other hand, some problems exist, such as worse processability and reduction of the ductility. The use of adhesion promoters, additives or chemical modification of the filler can help in overcoming many of these limitations. These composites can be further environment-friendly when the polymer matrix is biodegradable and comes from renewable sources as well. This short review briefly illustrates the main paths and results of research (both academic and industrial) on this topical subject, providing a quick overview (with no pretence of exhaustiveness over such a vast topic), as well as appropriate references for further in-depth studies.

Green composites: A brief review

Coumarins in polymers: From light harvesting to photo-cross-linkable tissue scaffolds

This century has witnessed remarkable achievements in green technology in material science through the development of natural fiber reinforced composites. The development of high-performance engineering products made from natural resources is increasing worldwide day by day. There is increasing interest in materials demonstrating efficient use of renewable resources. Nowadays, more than ever, companies are faced with opportunities and choices in material innovations. Due to the challenges of petroleum-based products and the need to find renewable solutions, more and more companies are looking at natural fiber composite materials. The primary driving forces for new bio-composite materials are the cost of natural fibers (currently priced at one-third of the cost of glass fiber or less), weight reduction (these fibers are half the weight of glass fiber), recycling (natural fiber composites are easier to recycle) and the desire for green products. This Review provides an overview of natural fiber reinfocred composites focusing on natural fiber types and sources, processing methods, modification of fibers, matrices (petrochemical and renewable), and their mechanical performance. It also focuses on future research, recent developments and applications and concludes with key issues that need to be resolved. This article critically summarizes the essential findings of the mostly readily utilized reinforced natural fibers in polymeric composite materials and their performance from 2000 to 2013.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/mame.201300008

Progress Report on Natural Fiber Reinforced Composites

Composites science and technology

Nanocomposite materials obtained from natural rubber (NR) reinforced with different amounts of cellulose II nanoparticles (in the range of 0 to 30 phr) are studied by dielectric spectroscopy (DS). For comparative purposes the pure materials, NR and cellulose, are also investigated. The dielectric spectra of the nanocomposites exhibit: (a) two overlapped α-relaxations associated respectively with the dynamic glass transitions of NR (faster process) and of the lipid present in NR; (b) a β-relaxation associated with local chain dynamics of cellulose and (c) a relaxation process associated to the presence of traces of water in cellulose. The spectra exhibit conductivity phenomena at low frequencies and high temperatures. The samples were also studied in the dry state. An explanation is given concerning the cellulose effect on the dielectric properties of the dry and wet nanocomposites.

/pdf/dielectric-spectroscopy-of-natural-rubber-cellulose-ii-4f2wnl5eny.pdf

Dielectric spectroscopy of natural rubber-cellulose II nanocomposites

Rubbers, to be turned into useful materials from the commercial applications point of view, need the addition of a few other ingredients which, upon vulcanization, will impart the desired characteristics to the material. In this paper, historical aspects of vulcanization are revised as well as the evolution of the additives used in most of the formulations.

/pdf/aspectos-historicos-da-vulcanizacao-2ijf1nuk2q.pdf

Aspectos históricos da vulcanização

Poly(ethylene-co-propylene-co-diene) (EPDM) compositions filled with mixtures of aluminium hydroxide (ATH) and carbon black (HAF) were evaluated for electrical applications. Mechanical and flammability tests were carried out in order to find out the relative amounts of the two fillers which would give the best balance of properties, mainly to meet the Brazilian Society for Technical Standards-ABNT. For good flame resistance, amounts as high as 160 phr ATH, at least, must be used.

Mechanical and flammability properties of ATH-Filled EPDM compositions

Melt rheology, cure characteristics, and mechanical properties of blends of polychloroprene (CR) and polybutadiene rubber (BR) in the presence and absence of phosphorylated cardanol prepolymer (PCP) were studied. The melt rheology parameters of the blends over a wide range of shear rates and temperatures were studied using a capillary rheometer (Rheoflixer SWO). The plasticizing effect of PCP in the blends was indicated by reduction in apparent melt viscosity and activation energy for melt flow. Good compatibility between the blend components (CR and BR) in the presence of PCP was evidenced by the lower values of principal normal stress difference. The self crosslinking behavior of the blends in the presence and absence of PCP was studied at different temperatures, using a Brabender Plasicorder and the kinetic parameters of crosslinking were evaluated. The cure characteristics of blends of CR and BR containing different dosages of PCP (0–10 phr) in a semi efficient vulcanization system were also studied at temperatures ranging from 150°C to 180°C, using an oscillating disk rheometer. The increase in tensile modulus, tensile strength, and tear strength of the vulcanizates in the presence of 5 phr of PCP is presumed to be an indication of reinforcement resulting from accelerated cross linking reaction as evidenced by higher chemical crosslink density index. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3195–3200, 2006

Studies on blends of polychloroprene and polybutadiene rubber containing phosphorylated cardanol prepolymer: Melt rheology, cure characteristics, and mechanical properties

In this work, sodium montmorillonite clay was added, as filler, to nanocomposites of natural rubber (NR) and cellulose II (regenerated cellulose) in amounts varying from 0 to 5 phr (per hundred resin). Natural rubber (NR)/cellulose II/montmorillonite nanocomposites were prepared by co-coagulating NR latex, montmorillonite aqueous suspension and cellulose xanthate. The clay was previously exfoliated in water, and the resulting suspension was then added to the mixture of NR latex with cellulose xanthate. Morphological, rheometric, mechanical, and dynamic mechanical properties were evaluated, and an increase in these properties was observed upon the addition of cellulose and clay nanomaterials to the rubber matrix. The results show the advantage in using cellulose as a nanopolymer as well as MMT as nanofiller. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Leila L. Y. Visconte

Papers

Dielectric spectroscopy of natural rubber-cellulose II nanocomposites

Aspectos históricos da vulcanização

Mechanical and flammability properties of ATH-Filled EPDM compositions

Studies on blends of polychloroprene and polybutadiene rubber containing phosphorylated cardanol prepolymer: Melt rheology, cure characteristics, and mechanical properties

Preparation, structure, and properties of montmorillonite/cellulose II/natural rubber nanocomposites