Different in Vivo Reactivity Profile in Health Care Workers and Patients with Spina Bifida to Internal and External Latex Glove Surface-Derived Allergen Extracts

BACKGROUND: Allergy to natural rubber latex is a well-recognized health problem, especially among health care workers and patients with spina bifida. Despite latex sensitization being acquired in health institutions in both health care workers and patients with spina bifida, differences in allergen sensitization profiles have been described between these two risk groups. OBJECTIVE: To investigate the in vivo reactivity of health care workers and patients with spina bifida to extracts of internal and external surfaces of latex gloves and also to specific extracts enriched in major allergens for these risk groups. METHODS: Gloves from different manufacturers were used for protein extraction, and salt precipitation and hydrophobic interaction chromatography (HIC) were applied to obtain the enriched latex extracts. The major latex allergens were quantified by an enzyme immunoassay. The extracts obtained were tested in 14 volunteers using skin prick tests (SPT). RESULTS: Latex glove extracts enriched in the hydrophobic allergens that are most often seen in patients with spina bifida were obtained by selective precipitation, whereas HIC produced extracts enriched in the hydrophilic allergens commonly found in health care workers. The health care workers had positive SPTs to glove extracts from internal surfaces and to the hydrophilic allergen-enriched extracts. By contrast, patients with spina bifida had larger skin reactions both to external glove extracts and to the extracts enriched with the hydrophobic major allergens for this risk group. Despite the protein concentration of these extracts being less than half the concentration of the commercial extract, the weal-and-flare reactions were of similar magnitude. CONCLUSION: Using novel latex extracts, our study showed a different in vivo reactivity pattern in health care workers and in patients with spina bifida to extracts of the internal and external surfaces of gloves, which suggests that sensitization may occur by different routes of exposure, and that this influences the allergen reactivity profiles of these risk groups

Exploring the properties of genetically engineered silk-elastin-like protein films

Free standing films of a genetically engineered silk-elastin-like protein (SELP) were prepared using water and formic acid as solvents. Exposure to methanol-saturated air promoted the formation of aggregated β-strands rendering aqueous insolubility and improved the mechanical properties leading to a 10-fold increase in strain-to-failure. The films were optically clear with resistivity values similar to natural rubber and thermally stable up to 180 °C. Addition of glycerol showed to enhance the flexibility of SELP/glycerol films by interacting with SELP molecules through hydrogen bonding, interpenetrating between the polymer chains and granting more conformational freedom. This detailed characterization provides cues for future and unique applications using SELP based biopolymers.

Prospects for biopolymer production in plants.

It is likely that during this century polymers based on renewable materials will gradually replace industrial polymers based on petrochemicals. This chapter gives an overview of the current status of research on plant biopolymers that are used as a material in non-food applications. We cover technical and scientific bottlenecks in the production of novel or improved materials, and the potential of using transgenic or alternative crops in overcoming these bottlenecks. Four classes of biopolymers will be discussed: starch, proteins, natural rubber, and poly-beta-hydroxyalkanoates. Renewable polymers produced by chemical polymerization of monomers derived from sugars, vegetable oil, or proteins, are not considered here.

Materials nanocomposits a partir de whiskers de cel•lulosa i matriu polimèrica de cautxú

De acuerdo con los objetivos generales del proyecto y plan de trabajo previsto, para esta anualidad, se obtuvieron fibras y microfibras de celulosa a partir de dos fuentes: celulosa vegetal de pino y eucalipto y celulosa bacterial. Las microfibrillas han sido utilizadas como material de refuerzo para la fabricación de materiales compuestos a partir de caucho natural, policaprolactona y polivinil alcohol. Las muestras se fabricaron mediante la técnica de "casting" en medio acuoso y temperatura ambiente. Las muestras fueron caracterizados en sus propiedades mecánicas, físicas y térmicas. Se observó que, en general, la adición de las microfibrillas de celulosa en las matrices poliméricas provoca una mejora sustancial en las propiedades mecánicas del material en comparación con el polímero sin reforzar. Los resultados pueden resumirse de la siguiente manera: 1.Fabricación de materiales compuestos a base de caucho natural y fibras de celulosa. Se obtuvieron fibras y nanofibras de celulosa que fueron modificadas químicamente y usadas como refuerzo en matriz de caucho. Los resultados mostraron mejora de propiedades mecánicas del material, principalmente en los materiales compuestos reforzados con nanofibras. 2. Obtención de whiskers de celulosa y su utilización como material de refuerzo en una matriz de policaprolactona. Se obtuvieron whiskers de celulosa a partir de pasta blanqueada. La adición en una matriz de policaprolactona produjo materiales compuestos con propiedades mecánicas superiores a la matriz, con buena dispersión de los whiskers. 3. Obtención de fibras de celulosa bacterial y nanofibras de celulosa, aislamiento y utilización sobre una matriz de polivinil alcohol. Se obtuvo celulosa bacterial a partir de la bacteria Gluconacetobacter xylinum. Además se fabricaron nanofibras de celulosa a partir eucalipto blanqueado. La celulosa bacterial como material de refuerzo no produjo importantes mejoras en las propiedades mecánicas de la matriz; en cambio se observaron mejoras destacables con la nanofibra como refuerzo.

Production of renewable polymers from crop plants

Plants produce a range of biopolymers for purposes such as maintenance of structural integrity, carbon storage, and defense against pathogens and desiccation. Several of these natural polymers are used by humans as food and materials, and increasingly as an energy carrier. In this review, we focus on plant biopolymers that are used as materials in bulk applications, such as plastics and elastomers, in the context of depleting resources and climate change, and consider technical and scientific bottlenecks in the production of novel or improved materials in transgenic or alternative crop plants. The biopolymers discussed are natural rubber and several polymers that are not naturally produced in plants, such as polyhydroxyalkanoates, fibrous proteins and poly-amino acids. In addition, monomers or precursors for the chemical synthesis of biopolymers, such as 4-hydroxybenzoate, itaconic acid, fructose and sorbitol, are discussed briefly

Studies on Xanthate/Dithiocarbamate Accelerator Combination in NR/BR Blends

Zinc butyl xanthate [Zn(bxt)2] was prepared in the laboratory . The effect of this xanthate with zinc diethyl dithiocarbamate (ZDC) on the vulcanization of natural rubber ( NR), polybutadiene rubber (BR), and NR/BR blend has been studied at different temperatures. The amounts of Zn (bxt)2 and ZDC in the compounds were optimized by varying the amount of ZDC from 0 . 75 to 1.5 phr and Zn (bxt)2 from 0 . 75 to 1 .5 phr. The cure characteristics were also studied . HAF filled NR, BR, and NR / BR blend compounds were cured at different temperatures from 60 to 150 C. The sheets were molded and properties such as tensile strength, tear strength, crosslink density and elongation at break, compression set, abrasion resistance, etc. were evaluated. The results show that the mechanical properties of 80NR/20BR blends are closer to that of NR vulcanizates, properties of 60NR/40BR blends are closer to BR vulcanizates, while the 70NR/30BR blends show an intermediate property.

Synergism of Xanthate/Dithiocarbamate Accelerator in Carbon Black Filled NR Compounds

Zinc salts of ethyl, isopropyl and butyl xanthates were prepared in the laboratory. The effect of these xanthates with zinc diethyldithiocarbamate (ZDC) on the vulcanization of HAF filled NR compound has been studied at different temperatures. The rubber compounds with the three xanthate accelerators and ZDC were cured at various temperatures from 60°C to 150°C. The sheets were moulded and properties such as tensile strength , tear strength , cross-link density, elongation -at-break, compression set, heat build up, abrasion resistance, flex resistance , etc. were evaluated . The properties showed that zinc xanthate/ZDC accelerator combination has a positive synergistic effect on the mechanical properties of NR compounds. The curing of HAF filled NR compound containing zinc xanthate /ZDC is slightly slower than the curing of the corresponding gum compounds . It is observed that, by gradually increasing the amount of the accelerator, the cure time of black filled NR compound can be made equal to that of the gum compou

Recycling of NR Based Cured Latex Material Reclaimed with 2,2'-Dibenzamidodiphenyldisulphide in a TruckTire Tread Compound

It is observed that reclamation of natural rubber latex based rubber using 2,2'-dibenzamidodiphenvldisulphide as reclaiming agent is an optional methodology for recycling of waste latex rubber (WLR). For progressive replacement of virgin natural rubber by the reclaim, two alternatives curing system were investigated: adjustment or reduction of the curing system with increasing reclaim content, to compensate for the extra amount of curatives brought along by the reclaim. For fixed curing system, as if the reclaim were equivalent to virgin NR. The cure behavior, final crosslink density and distribution, mechanical properties, and dynamic viscoelastic properties of the blends with reclaimed WLR are measured and compared with the virgin compound. The morphology of the blends, sulfur migration, and final distribution are analyzed.The mechanical and dynamic viscoelastic properties deteriorate for both curing systems, but to a lesser extent for fixed curing system compared to adjusted curing system. With the fixed cure system, many properties like tensile strength and compression set do still deteriorate, but tan 6 and Mrrr„/Murxr, representative for the rolling resistance of tires are improved. On the other hand, with the adjusted cure system both mechanical and dynamic properties still deteriorate.

Improved Mechanical Properties of NR/EPDM and NR/Butyl Blends by Precuring EPDM and Butyl

Ethylene-propylene-diene rubber (EPDM) and isobutylene-isoprene rubber (IIR) were compounded, precured to a low degree, and then were blended with natural rubber (NR). The compounding ingredients for NR were then added and the final curing was done. NR/ EPDM and NR/IIR blends, prepared using this method, were found to possess much improved mechanical properties as compared to their conventional counterparts. The optimum precuring crosslink density that has to be given to the EPDM and IIR phases has been determined.

Utilisation of IIR Tube Reclaim for Developing NR/IIR Blends

Butyl (IIR) tube reclaim (RR) was mixed with carbon black filled natural rubber (NR) compounds at various percentages. The blend containing a low percentage of RR was found to show improved ageing resistance and improved processability with out much reduction in the mechanical properties.

Polymer-Solvent Interaction Parameter for NR/SBR and NR/BR Blends

Polymer-solvent interaction parameters for the blends of natural rubber (NR) with styrene-butadiene rubber (SBR) and polybutadiene rubber ( BR) are calculated using the Flory-Rehner equation by equating the network density of the vulcanizates in two solvents.

Studies on the Cure Characteristics of Elastomer Blends

Blends of natural rubber (NR) with styrene-butadiene rubber (SBR), polybutadiene rubber (BR), ethylene-propylene terpolymer (EPDM) and acrylonitrile-butadiene rubber (NBR) were vulcanised using an efficient vulcanisation (EV) system and a semi-EV system. Compatible blends show a definite pattern of curing whereas the incompatible blends show no such pattern.

Studies on the Cure Characteristics and Vulcanizate Properties of 50 / 50 NR /SBR Blend

Blends of 50/50 natural rubber (NR) and styrene-butadiene rubber (SBR) are vulcanized using several conventional and semi-EV systems. The cure characteristics and vulcanizate properties are compared. The quantity and quality of crosslinks in each case are deciphered by chemical probes to correlate them with the vulcanizate properties.

Studies on the Cure Characteristics and Vulcanizate Properties of 50/50 NR/BR Blend

A carbon black filled 50/50 Natural Rubber (NR)/Polybutadiene Rubber (BR) blend is vulcanized using several conventional systems designed by varying the amounts of sulphur and accelerator . The cure characteristics and the vulcanizate properties are compared. The quality and quantity of crosslinks in each case are deciphered by chemical probes to correlate them with the vulcanizate properties.

Effect of Blending Techniques on the Curing of Elastomer Blends

Compounding of styrene-butadiene copolymer/polybutadiene , natural rubber/ ethylene-propylene-diene terpolymer and natural rubber/butadiene-acrylonitrile copolymer blends was done in three different ways and their curing behaviour and the tensile properties of the es are compared.