Microbial susceptibility of various polymers and evaluation of thermoplastic elastomers with antimicrobial additives

The incursion of microbial growth on polymeric products can deteriorate their performance and lead to the development of undesirable staining and odors. A growing trend in the industry has aimed to reduce microbial populations on high-touch surfaces via the use of antimicrobials to protect material aesthetics and durability or to prevent the spread of pathogenic microorganisms. In this study, a variety of plastic substrates (30 unique polymer compounds), including poly(acrylonitrile-co-butadiene-co-styrene), poly(butylene terephthalate), poly(etherimide), various thermoplastic elastomers (TPEs), poly(carbonates), and poly(amides), were screened for susceptibility to microbial attack using American Society for Testing and Materials (ASTM) G21 (fungi susceptibility), Japanese Industrial Standard (JIS) Z2801, and modified ASTM E1428-15a (bacterial susceptibility) test standards. TPEs were determined to be most susceptible to microbial attack under the appropriate environmental conditions. Subsequent studies assessed the use of an antimicrobial additive, zinc pyrithione (ZPT), for potential efficacy in a variety of TPE blends for diverse target market applications. ZPT proved to be very effective in protecting TPEs, reducing Staphylococcus aureus and Escherichia coli populations by 99.9% or more in JIS Z2801 testing and inhibiting fungal growth (rating = 0) according to the ASTM G21 standard.     

Use of statistical methods for estimation of total number of charges in a mass spectrometry experiment

Estimation of the number of ions in a mass spectrometry experiment is needed to determine instrumentation parameters such as ionization efficiency, collision-induced dissociation efficiency, ion-transfer efficiency, ion trapping efficiency, and preamplifier detection limit. This work aims at analyzing the statistical characteristics (primarily variance) in the intensities of the isotopic distributions, which depend on the number of ions in the cell. A mathematical derivation was developed based on the maximum likelihood estimation method, which estimates the most likely number of ions in the cell using a method known as nonrandom parameter estimation. The performance of the method improves with increase in the number of observed distributions. The method works well provided the spectra show isotopic resolution and is independent of the instrument or method used to arrive at the spectra.     

Mechanisms of molecular interactions in polybase–polyacid complex formed by copolymers of N,N‐dimethylaminoethylmethacrylate with alkylmethacrylates and methacrylic acid with ethylacrylate

Mechanisms of molecular interaction in the blends of a polybase, a copolymer of N,N‐dimethylaminoethylmethacrylate with methylmethacrylate and butylmethacrylate (PDMAEMA–MMA/BMA), with a polyacid, a copolymer of methacrylic acid with ethylacrylate (PMAA‐co‐EA), and plasticizer, triethylcitrate (TEC), have been investigated with FTIR Spectroscopy and potentiometry. To evaluate the strengths of hydrogen and ionic bonds in the polyelectrolyte complexes, quantum‐chemical calculations were performed. According to this analysis, the energy of ionic and hydrogen bonding diminishes in the order: multi‐component complexes involving protonated aminogroup of DMAEMA (ammonium cation) in the presence of chlorine counterion with ionized or unchanged carboxyl groups and water molecules (690–520 kJ/mol) > ternary H‐bonded acid‐base complexes associated with molecule of water (520–420 kJ/mol) > binary ionic complex of carboxylate anion and ammonium cation (404 kJ/mol) > H‐bonded complex of carboxylate and ammonium ions (257 kJ/mol) > binary H‐bonded complex of uncharged carboxyl group with ammonium cation (114 kJ/mol) > ternary H‐bonded complex of uncharged carboxyl group, aminogroup and water molecule (43 kJ/mol) > binary H‐bonded complex between nonionized carboxyl and amino groups (26 kJ/mol). Proton‐donating capability of functional groups in the studied polyelectrolyte blends diminishes in the order: HN⁺(CH₃)₂ ? > HOOC? > HO? . The proton‐donating capacity can be significantly improved in the presence of Cl^? ions, the effect of which may be appreciably inhibited if Na⁺ cations are available in the blend or solution. Proton‐accepting capability weakens in the order: uncharged aminogroup > carboxylate anion > uncharged carboxyl group > hydroxyl group. The results of quantum chemical calculations facilitate interpretation of FTIR spectra. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Prevention of lipid oxidation in muscle foods by milk proteins and peptides: A review

Muscle foods (especially fresh meat, precooked, and restructured meat products) are highly prone to lipid oxidation, which ultimately leads to certain problems, viz. discoloration, off-flavor, drip losses, loss of essential fatty acids and vitamins, and generation of toxic products. These problems can be minimized with the help of various agents and or techniques such as use of natural/synthetic antioxidants, metal chelating agents, physical conditions, vacuum packaging, and encapsulation techniques. Among these, the role of synthetic antioxidants is quite debatable due to certain health risks to humans. Among the natural molecules, milk proteins and their bioactive peptides offer a promising potential for the meat industry. Various forms of milk proteins and peptides including caseinates, whey proteins, skim milk, and milk co-precipitates can be used to prevent lipid oxidation in meat products either in the form of added ingredients or as edible coatings. However, in addition to prevention of lipid oxidation, they also provide nutritional benefits and improve the technological processing and shelflife of meat and meat products. This review focuses on the utilization, mechanism of action, and efficacy of milk proteins and peptides to inhibit lipid oxidation in muscle food products.     

Competitive hydrogen bonding mechanisms underlying phase behavior of triple poly(N‐vinyl pyrrolidone)–poly(ethylene glycol)–poly(methacrylic acid‐co‐ethylacrylate) blends

Differential scanning calorimetry (DSC) of triple blends of high molecular weight poly(N‐vinyl pyrrolidone) (PVP) with oligomeric poly(ethylene glycol) (PEG) of molecular weight 400 g/mol and copolymer of methacrylic acid with ethylacrylate (PMAA‐co‐EA) demonstrates partial miscibility of polymer components, which is due to formation of interpolymer hydrogen bonds (reversible crosslinking). Because both PVP and PMAA‐co‐EA are amorphous polymers and PEG exhibits crystalline phase, the DSC examination is informative on the phase state of PEG in the triple blends and reveals a strong competition between PEG and PMAA‐co‐EA for interaction with PVP. The hydrogen bonding in the triple PVP–PEG–PMAA‐co‐EA blends has been established with FTIR Spectroscopy. To evaluate the relative strengths of hydrogen bonded complexes in PVP–PEG–PMAA‐co‐EA blends, quantum‐chemical calculations were performed. According to this analysis, the energy of H‐bonding has been found to diminish in the order: PVP–PMAA‐co‐EA–PEG(OH) > PVP–(OH)PEG(OH)–PVP > PVP–H₂O > PVP–PEG(OH) > PMAA‐co‐EA–PEG(? O? ) > PVP–PMAA‐co‐EA > PMAA‐co‐EA–PEG(OH). Thus, most stable complexes are the triple PVP–PMAA‐co‐EA–PEG(OH) complex and the complex wherein comparatively short PEG chains form simultaneously two hydrogen bonds to PVP carbonyl groups through both terminal OH‐groups, acting as H‐bonding crosslinks between longer PVP backbones. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Non‐covalently crosslinked hydrogels displaying a unique combination of water‐absorbing,elastic and adhesive properties

BACKGROUND: Stringent requirements must be satisfied by biomedical adhesives, including biocompatibility, adhesion, cohesiveness and processability. The ability to change mechanical properties in response to environmental changes may also be desirable. In the present work the water‐absorbing, adhesive and mechanical properties of blends based on hydrogen bonding complexes between poly(N‐vinyl pyrrolidone), poly(ethylene glycol) (PEG) and poly[(methacrylic acid)‐co‐(ethyl acrylate)] were investigated. These blends, consisting of pharmaceutical‐grade components, exhibit pH‐sensitive swelling and dissolution, along with rubber‐like elasticity and bioadhesion. RESULTS: Polymer blend films remained intact at pH = 5.6 but underwent dissolution at pH = 7.4, the difference being attributed to deprotonation of acidic side‐chains, with loss of hydrogen bonding and development of charge repulsion. Sol release was primarily due to PEG. Films swelled at low pH instead of dissolving, in a manner that was pH‐dependent but PEG‐independent. Films displayed elastic properties comparable to cured elastomers when mildly swollen, with modulus and ultimate strength decreasing with increasing PEG content. Dry films were nearly tack‐free, but became more adhesive with increasing water content, up to a point where the film dissolved. CONCLUSION: Due to their biocompatibility and dissolution/mechanical properties, the bioadhesive polymer blends investigated may be suitable for numerous biomedical applications. Copyright © 2008 Society of Chemical Industry     

Giant magnetocapacitance in magnetoelectric BNT/NFO particulate composites

Journal of Materials Science: Materials in Electronics - Bi0.5Na0.5TiO3 (BNT) and NiFe2O4 (NFO) ceramics were synthesized using the sol–gel method. Further, a series...     

Speech waveform reconstruction from speech parameters for an effective text to speech synthesis system using minimum phase harmonic sinusoidal model for Punjabi

Multimedia Tools and Applications - Speech processing plays a vital role in current speech communication applications. The major objective of digital speech is transmission of messages among human...     

Meat analogues: Health promising sustainable meat substitutes

There is a scarcity of protein of high biological value due to rapid increase in the world population and limited natural resources. Meat is a good source of protein of high biological value but converting the vegetable protein into animal protein is not economical. There is a trend of production of healthy and delicious meat free food for satisfaction of vegetarian and personal well beings. This resulted in increasing use of low cost vegetable protein such as textured soy protein, mushroom, wheat gluten, pulses etc as a substitute for animal-protein. These simulated meat-like products, with similar texture, flavor, color, and nutritive value can be substituted directly for meat to all sections of the society.