Flammability of polyesters

The flammabilities of a series of polyesters, varying both the diol length and the degree of aromaticity of the diacid units were evaluated using cone calorimetry. Addition of inorganic additives, copolymerization with sulfoisophthalate ionomeric units and with the phosphorous flame retarding agent, phospholane, were also examined. A strong, linear relationship between the polymer carbon:hydrogen ratio and various flammability indicators was established. The phospholane was demonstrated to produce only a modest reduction in flammability, whereas the isomeric comonomer produced an unexpectedly strong reduction in all aspects of flammability tested. Addition of inorganic modifiers resulted in varied, and relatively modest changes in polyester flammability.     

Facile fabrication of poly(vinyl alcohol) gels and derivative aerogels

A facile preparation of poly(vinyl alcohol) (PVOH) hydrogels and their derivative PVOH/montmorillonite clay aerogels is reported, using water as solvent and divinylsulfone as crosslinking agent, making use of an environmentally friendly freeze drying process. The materials exhibit significantly increased mechanical properties after crosslinking. The compressive modulus of an aerogel prepared from an aqueous suspension containing 2 wt% PVOH/8 wt% clay increased 29-fold upon crosslinking, for example. Crosslinking of the polymer/clay aerogels decreased the onset decomposition temperature as measured by thermogravimetric analysis, and generated a more continuous structure at higher clay contents. Such polymer/clay aerogels are promising materials for low flammability applications.     

Modification of polymers using multilayered “smart pellet” additives: Part II

A magnesium-based inorganic whisker was compounded with polypropylene and with polysulfone (FP/PP and FPSF/PP^*, respectively) and then multilayered into alternating structures with unfilled polypropylene (PP). These multilayered materials were cut into FP/PP and FPSF/PP^* “smart pellets”, which were then added to polypropylene matrix polymer as masterbatches to deliver potential reinforcement to injection molded parts. The morphologies of both the smart pellets and the composites produced with them were studied by scanning electron microscopy (SEM). The inorganic whiskers were found to be aligned in the machine direction in the smart pellets. Mechanical properties of the composites were investigated by performing tensile, flexural, and impact strength tests. Inorganic whiskers combined with PSF offered higher flexural modulus in comparison to those via conventional blending; no significant improvement was observed in tensile modulus or impact strength of these composites.     

Acellular Dermal Matrix Used in Diabetic Foot Ulcers: Clinical Outcomes Supported by Biochemical and Histological Analyses

Diabetic foot ulcer (DFU) is a diabetes complication which greatly impacts the patient’s quality of life, often leading to amputation of the affected limb unless there is a timely and adequate management of the patient. DFUs have a high economic impact for the national health system. Data have indeed shown that DFUs are a major cause of hospitalization for patients with diabetes. Based on that, DFUs represent a very important challenge for the national health system. Especially in developed countries diabetic patients are increasing at a very high rate and as expected, also the incidence of DFUs is increasing due to longevity of diabetic patients in the western population. Herein, the surgical approach focused on the targeted use of the acellular dermal matrix has been integrated with biochemical and morphological/histological analyses to obtain evidence-based information on the mechanisms underlying tissue regeneration. In this research report, the clinical results indicated decreased postoperative wound infection levels and a short healing time, with a sound regeneration of tissues. Here we demonstrate that the key biomarkers of wound healing process are activated at gene expression level and also synthesis of collagen I, collagen III and elastin is prompted and modulated within the 28-day period of observation. These analyses were run on five patients treated with Integra^® sheet and five treated with the injectable matrix Integra^® Flowable, for cavitary lesions. In fact, clinical evaluation of improved healing was, for the first time, supported by biochemical and histological analyses. For these reasons, the present work opens a new scenario in DFUs treatment and follow-up, laying the foundation for a tailored protocol towards complete healing in severe pathological conditions.     

Study of diffusion through LDPE film of Di-n-butyl phthalate

The apparent diffusion coefficients (D) across a PE-LD film of Di-n-butyl phthalate (DnBP) dissolved in isooctaneand ethanol,werecalculated indifferentways and compared. DnBP, a common plasticizer of plastics and printing inks, may be a possible contaminant of flexible packaging and PE-LD is the most common food-contacting polymer. To perform diffusion measurements, small plastic sachets filled with solutions of the contaminant were used at three different temperatures. The D coefficients of the two solvents and dissolved DnBP were calculated using the lag time method, a formula taking into account the molar weight and absolute temperature,and an equation based on the initial concentration and the amounts migrated after subsequent times. The results demonstrated great solvent interference in the plasticizer diffusion across polyethylene; in particular as far as isooctane is concerned, a remarkable co-diffusion of both the plasticizer and the non-polar solvent must be assumed. Isooctane quickly penetrates PE-LD but ethanol also diffuses across PE-LD, although at a greatly reduced speed. These facts must be considered for realistic prediction of migration or effectiveness of the functional barrier.     

Control of coefficient of thermal expansion in elastomers using boron nitride

The thermal expansion properties of three commercial elastomers; Pebax®, Estane® and Hytrel® modified with 2.5–10 wt % boron nitride were investigated. The glass transition temperatures of the filled materials were relatively unaffected; however boron nitride did effectively reinforce all the three elastomers as seen by dynamic mechanical analysis and tensile tests. The coefficients of thermal expansion of the composite materials do not obey the rule of mixtures and show a large decrease without the loss of ductility typically associated with filled elastomers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5153–5161, 2006     

Lignin/Carbohydrate Complex Isolated from Posidonia oceanica Sea Balls (Egagropili): Characterization and Antioxidant Reinforcement of Protein-Based Films

A lignin fraction (LF) was extracted from the sea balls of Posidonia oceanica (egagropili) and extensively dialyzed and characterized by FT-IR and NMR analyses. LF resulted water soluble and exhibited a brownish-to-black color with the highest absorbance in the range of 250–400 nm, attributed to the chromophore functional groups present in the phenylpropane-based polymer. LF high-performance size exclusion chromatography analysis showed a highly represented (98.77%) species of 34.75 kDa molecular weight with a polydispersity index of 1.10 and an intrinsic viscosity of 0.15. Quantitative analysis of carbohydrates indicated that they represented 28.3% of the dry weight of the untreated egagropili fibers and 72.5% of that of LF. In particular, eight different monosaccharides were detected (fucose, arabinose, rhamnose, galactose, glucose, xylose, glucosamine and glucuronic acid), glucuronic acid (46.6%) and rhamnose (29.6%) being the most present monosaccharides in the LF. Almost all the phenol content of LF (113.85 ± 5.87 mg gallic acid eq/g of extract) was water soluble, whereas around 22% of it consisted of flavonoids and only 10% of the flavonoids consisted of anthocyanins. Therefore, LF isolated from egagropili lignocellulosic material could be defined as a water-soluble lignin/carbohydrate complex (LCC) formed by a phenol polymeric chain covalently bound to hemicellulose fragments. LCC exhibited a remarkable antioxidant activity that remained quite stable during 6 months and could be easily incorporated into a protein-based film and released from the latter overtime. These findings suggest egagropili LCC as a suitable candidate as an antioxidant additive for the reinforcement of packaging of foods with high susceptibility to be deteriorated in aerobic conditions.     

In-situ immunophenotyping study of hepatic-infiltrating cytotoxic cells in chronic active hepatitis C

L-Xyloascorbic acid (L-xylo-AsA) and its three stereoisomers, D-xyloascorbic acid (D-xylo-AsA), L-araboascorbic acid (L-arabo-AsA) and D-araboascorbic acid (D-arabc-AsA), have been considered to show some differences in vitamin C activity. In this paper the effect of L-xylo-AsA, D-xylo-AsA, L-arabo-AsA and D-arabo-AsA on the activity of dopamine beta-hydroxylase was studied to clarify whether or not the structural specificities of these stereoisomers have different effects on enzyme activity. The maximum velocity (Vmax) of the hydroxylation and Km for ascorbic acid were calculated using double-reciprocal plotting. Vmax for L-xylo-AsA was estimated to be 201 nmol/min/mg protein and those of D-xylo-AsA, L-arabo-AsA and D-arabo-AsA were 157 nmol/min/mg protein, 112 nmol/min/mg protein and 194 nmol/min/mg protein, respectively. Km for L-xylo-AsA was 1.5 mM and those for D-xylo-AsA, L-arabo-AsA and D-arabo-AsA were 2.3 mM, 2.7 mM and 1.4 mM, respectively. The effect of D-arabo-AsA on the activity of dopamine beta-hydroxylase was almost the same as that of L-xylo-AsA, while D-xylo-AsA and L-arabo-AsA showed smaller effects. Our results suggest that the configuration at carbon 4 might be more important than that of the hydroxyl group at carbon 5 for the development of the activity as a cofactor for dopamine beta-hydroxylase reaction.