Latex-based nanocomposites

Nanoparticles have been widely used as filler in polymer because of their unique reinforcing effect. There are many compounding methods for nanocomposites. The recent development on latex nanocomposites, a group of special nanocomposites, is reviewed in this chapter. They include carbon black/latex nanocomposite, silica/latex nanocomposite, layered silicate/latex nanocomposite, ZnO/latex nanocomposite, carbon nanotubellatex nanocomposite, lignin/latex nanocomposite, starch/latex nanocomposite, nano-fiber/latex nanocomposite, and Chitin whiskers/latex nanocomposite. Advanced compounding techniques and the latest advance on these latex nanocomposites are described. The nanoreinforcing theories of latex nanocomposites are also studied.

Hypoallergenic variants of the major latex allergen Hev b 6.01 retaining human T lymphocyte reactivity

Hev b 6.01 is a major allergen of natural rubber latex with sensitization of 70–86% of latex glove-allergic subjects. Recently, we mapped the immunodominant T cell sites of Hev b 6.01 to the highly IgE-reactive hevein (Hev b 6.02) domain. Hev b 6.01 contains 14 cysteine residues with multiple disulphide bridges stabilizing tertiary conformation. With the goal of a standardized specific immunotherapy we developed hypoallergenic Hev b 6.01 mutants by site-directed mutagenesis of selected cysteine residues (3, 12, 17, and 41) within the Hev b 6.02 domain. Peptides corresponding to the Hev b 6.02 domain of two of the mutants were also synthesized. These mutants and peptide variants showed markedly decreased or ablated latex-allergic patient serum IgE binding by immunoblotting and ELISA. Basophil activation testing confirmed markedly decreased activation with successive cysteine substitutions of the mutants and complete abrogation with the Hev b 6.02 (Cys 3, 12, 17, 41 Ala) peptide. Retention of T cell reactivity is crucial for effective specific immunotherapy and all mutants and peptide variants maintained their latex-specific T cell reactivity. The ablated allergenicity but retained T cell reactivity of the Hev b 6.02 (Cys 3, 12, 17, 41 Ala) peptide suggests this peptide is a suitable candidate for inclusion in a latex immunotherapy preparation.

Self-assembled natural rubber/multi-walled carbon nanotube composites using latex compounding techniques

Functionalization of multi-walled carbon nanotubes (MWCNTs) plays an important role in eliminating nanotube aggregation for reinforcing polymeric materials. We prepared a new class of natural rubber (NR)/MWCNT composites by using latex compounding and self-assembly technique. The MWCNTs were functionalized with mixed acids (H2SO₄/HNO₃ = 3:1, volume ratio) and then assembled with poly (diallyldimethylammonium chloride) and latex particles. The Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy were used to investigate the assembling mechanism between latex particles and MWCNTs. It is found that MWCNTs are homogenously dispersed in the natural rubber (NR) latex as individual nanotubes since strong self-aggregation of MWCNTs has been greatly depressed with their surface functionalization. The well-dispersed MWCNTs produce a remarkable increase in the tensile strength of NR even when the amount of MWCNTs is only 1 wt.%. Dynamic mechanical analysis shows that the glass transition temperature of composites is higher and the inner-thermogenesis and thermal stability of NR/MWCNT composites are better, when compared to those of the pure NR. The marked improvement in these properties is largely due to the strong interfacial adhesion between the NR phase and MWCNTs. Functionalization of MWCNTs represents a potentially powerful technology for significant reinforcement of natural rubber materials.

Forces measured between latex spheres in aqueous electrolyte : Non-DLVO behavior and sensitivity to dissolved gas

An atomic force microscope was used to measure the forces acting between two polystyrene latex spheres in aqueous media. The results show an electrostatic repulsion at large separations which is overtaken by an attractive “hook” that pulls the two spheres into contact from a considerable range (20−400 nm), much larger than could be expected for a van der Waals attraction. The range of operation of this attraction varies from one experiment to another and is not correlated with electrolyte concentration. However, the range is found to decrease significantly when the level of dissolved gas in the water is reduced.

Mohair research update 17 : wearer comfort of mohair textiles - does mohair have an allergy problem?

Many aspects of textiles affect the comfort or discomfort experienced by people. The effects of variations in thermal, moisture transmission, air permeability, size, fit, aesthetics and static electrical properties on textiles have been known for many years (Slater, 1977). Problems experienced with wearer comfort, both sensory and functional, have increased in commercial importance for all animal fibres. Surveys have shown that consumers report that prickle discomfort from wearing wool next to the skin is a negative market attribute for wool (IWS, 1993; Millard Brown, 2007).

Rubber latex yield and physiology of rubber tree with tea tree oil treatments

To examine the effects of tea tree oil on rubber latex yield and the resulting latex physiological parameters of rubber tree （Hevea brasiliensis），clean water and 20%，40%，60%，80% and 100% of tea tree oil were applied on the tapping cut of rubber trees. The data were analyzed by Duncan test and its results showed that when compared to clean water （ck），80% and 100% of tea tree oil stimulation significantly promoted rubber latex yield（P＜0.05）. In addition，the latex physiological parameters changed with the sucrose content（P＜0.01），magnesium ion content （P＜0.01） and inorganic phosphorus content （P＜0.01） of latex significantly increasing and thiol content significantly deceasing （P＜0.01）. The effect of tea tree oil treatments on rubber yield was similar to the impact of 0.5% ethrel stimulation. However，compared to ethrel stimulation，100% tea tree oil treatment significantly increased dry rubber and sucrose contents （P＜0.01） and decreased thiol content （P＜0.01）. Thus，tea tree oil treatment involved different latex yield promotion mechanisms than that of ethrel stimulation.

Potential links between the emerging risk factors for food allergy and vitamin D status

A variety of hypotheses have been proposed to explain the recently described increase in food allergy among children living in developed countries. In this study, we summarize the emerging risk factors for IgE-mediated food allergy in early life, and then review the evidence for and against an association between low vitamin status (VDS) and food allergy.

We consider whether each of the epidemiological variables that have been associated with food allergy may also be associated with VDS; and argue that future studies must adequately account for the potential relationships between risk factors for food allergy and VDS, and must also discriminate between vitamin D derived by sun exposure, diet and oral supplementation.

Preparation and characterization of natural rubber/silica nanocomposites using rule of similarity in latex

Rule of similarity and latex compounding techniques were combined for the first time to prepare natural rubber/nanosilica (NR/SiO2) nanocomposite with core-shell nanosilica-poly (methyl methacrylate) (SiO 2-PMMA) particles and PMMA-modified natural rubber matrix (NR-PMMA). The microstructure of SiO2 and nanocomposites with different SiO 2 contents was characterized by fourier transform infrared spectroscopy (FTIR); the morphology of nanocomposites was investigated with scanning electron microscopy (SEM); the tensile strength was characterized by tensile testing machine and the thermal stability of composites was studied by thermal gravimetric analysis. Results showed that PMMA chains have successfully grafted onto the surface of SiO2, and the core-shell SiO 2-PMMA nanoparticles and NR-PMMA latex have been perfectly incorporated. SiO2-PMMA nanoparticles are evenly distributed over the NR matrix with an average size in the range of 60-100 nm at the low content (SiO2? 3 wt%), while aggregations are apparently observed when 5 wt% SiO2 is loaded. In addition, NR/SiO2 composities possess a considerable improvement in ageing resistance compared with the pure NR. The tensile strength of composite increases from 6.99 to 12.72 MPa, reaching the highest value at a 0.5 wt% SiO2 loading, and then the figure decreases gradually because of the aggregation of SiO2 nanoparticles. It is anticipated that the reported process is to provide a simple and economic way for preparing NR composites.