Long-chain Additives Research Articles

Influence of the chemical structure of different carboxymethylcelluloses on the performance of clay dispersions

Abstract The aim of this work was to evaluate the influence of the chemical structure of carboxymethylcellulose (CMC) on the rheological performance and fluid loss of clay dispersions. The dispersions were prepared with a fixed content of bentonite clay (15 g/350 mL of water) and different concentrations of CMCs (0.5, 1.0, 2.0 g/350 mL of water). After aging for 24 h in ambient and static conditions, the dispersions were tested in a viscometer. Apparent and plastic viscosities, yield point and gel strength were obtained using the viscometer, according to Petrobras’ standard (EP-1EP-00011-A). The filtrate volume was determined using the API filter press. The results showed that the addition of long chain, low degree of substitution and lower substitution uniformity of CMC contribute to the flocculation phenomenon. In addition, the different chemical characteristics of CMC only influence fluid loss when the ionic strength of the dispersion is set to any other value than zero.

Flocculation Effect of Macromolecule

Citation: Chang Q. Flocculation Effect of Macromolecule. Polym Sci. 2016, 2:1. In the early years, it was found that colloidal dispersions can be made more sensitive to precipitation by the addition of small quantities of macromolecules. These macromolecules are referred to as flocculants currently. The macromolecular flocculants commonly used in early time are polyelectrolytes. Their flocculation mechanism is considered to be the simple charge neutralization. If the charges of macromolecular ions are opposite to that of particles, flocculation and precipitation will take place. But in the later period, it has been discovered that some non-ionic macromolecules, even the macromolecules with the same charge as the colloidal particle have sensitive or flocculation effect. Therefore, neutralization is not the only mechanism of their flocculation. Now we think long-chain additives, such as gelatin, can sometimes bring about a rather loose flocculation by a bridging mechanism in which the molecules are adsorbed with part of their chain on two or more particles. Such flocculation normally occurs over a narrow range of additive concentrations; at higher concentration protective action is obtained, since bridging can occur only under conditions where the remaining particles still have empty surface, thus further adsorption of the additive is possible.

Exploring the Photophysics of Curcumin in Zwitterionic Micellar System: An Approach to Control ESIPT Process in the Presence of Room Temperature Ionic Liquids (RTILs) and Anionic Surfactant

In this manuscript, we have modulated the photophysical properties of curcumin in a zwitterionic (N-hexadecyl-N,N-dimethylammonio-1-propanesulfonate (SB-16)) micellar aggregates with addition of room temperature ionic liquids (RTILs) as well as commonly used anionic surfactant (SDS), using steady-state and time-resolved spectroscopic techniques. To modulate the photophysics, first we studied its interaction with an SB-16 micellar system, then to further exploit its photophysics, three RTILs (EmimES, EmimBS, EmimHS) with variation of alkyl chain lengths as well as SDS were used. It is observed that the rate of degradation of curcumin is drastically decreased after partitioning into the zwitterionic micellar system. It is shown that the dynamics of excited state intramolecular proton transfer (ESIPT) processes can be controlled by using those RTILs and SDS. Our study also reveals that the hindrance of nonradiative processes of curcumin, i.e., ESIPT is more pronounced in the case of RTIL containing a long alkyl chain compared to a small one. However, most interestingly the addition of long chain (dodecyl) anionic surfactant (SDS) promotes the ESIPT process of curcumin. We have also studied the effect of the addition of inorganic salt and compared the results with RTILs. The present work demonstrates an effort to decipher the photophysics of curcumin in zwitterionic micellar systems by monitoring its excited state dynamics.

Sequences from the First Fibronectin Type III Repeat of the Neural Cell Adhesion Molecule Allow O-Glycan Polysialylation of an Adhesion Molecule Chimera

Polysialic acid is a developmentally regulated, anti-adhesive polymer that is added to N-glycans on the fifth immunoglobulin domain (Ig5) of the neural cell adhesion molecule (NCAM). We found that the first fibronectin type III repeat (FN1) of NCAM is required for the polysialylation of N-glycans on the adjacent Ig5 domain, and we proposed that the polysialyltransferases recognize specific sequences in FN1 to position themselves for Ig5 N-glycan polysialylation. Other studies identified a novel FN1 acidic surface patch and α-helix that play roles in NCAM polysialylation. Here, we characterize the contribution of two additional FN1 sequences, Pro(510)-Tyr(511)-Ser(512) (PYS) and Gln(516)-Val(517)-Gln(518) (QVQ). Replacing PYS or the acidic patch dramatically decreases the O-glycan polysialylation of a truncated NCAM protein, and replacing the α-helix or QVQ shifts polysialic acid to FN1 O-glycans in full-length NCAM. We also found that the FN1 domain of the olfactory cell adhesion molecule, a homologous but unpolysialylated protein, could partially replace NCAM FN1. Inserting Pro(510)-Tyr(511) eliminated N-glycan polysialylation and enhanced O-glycosylation of an NCAM- olfactory cell adhesion molecule chimera, and inserting other FN1 sequences unique to NCAM, predominantly the acidic patch, created a new polysialyltransferase recognition site. Taken together, our results highlight the role of the FN1 α-helix and QVQ sequences in N-glycan polysialylation and demonstrate that the acidic patch primarily functions in O-glycan polysialylation.

Inter‐relationship between processing conditions and mechanical properties of blown film from different polypropylenes and high melt strength polypropylene blends

AbstractThe aim of this study is the improvement of process stability and film properties of various matrix polymers by the addition of long chain branched (LCB) polypropylene (PP) in the blown film process. Three commercially available PP grades were dry‐blended with two different high melt strength (HMS) PP grades with varying weight content in the range of 5, 10, and 20%. Maximum solid output was determined on a Hosokawa blown film line with a film thickness of 50 μm. Thickness was adjusted by proper relation between output and take‐up ratio (TUR). The blow‐up ratio (BUR) was varied from 1 : 2 to 1 : 3 and 1 : 4 in connection to the output rate and HMS‐PP content. Research showed an increase of the output due to the additon of HMS‐PP in various matrix polymers and different processing conditions. Influences on mechanical properties related to process parameters concerning stiffness and impact energy were found. Due to the addition of HMS‐PP in a heterophasic PP‐copolymer (PP‐I) the maximum solid output increases up to 50% as well as tensile properties were enhanced. Stiffness of the blown film is independent of the output and the BUR both in machine direction (MD) and transverse direction (TD). In contrast a reduction of the process stability and solid state properties were determined with homo‐PP (PP‐H) and random‐PP (PP‐R) mixtures. Decreasing impact energy of the heterophasic copolymer was determined with increasing HMS‐PP content. In comparison to the enhanced stiffness, toughness decreases which refers to a higher brittleness due to the addition of HMS‐PP. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Poly(ADP-ribose)-binding zinc finger motifs in DNA repair/checkpoint proteins

Post-translational modification (PTM) of proteins plays an important part in mediating protein interactions and/or the recruitment of specific protein targets. PTM can be mediated by the addition of functional groups (for example, acetylation or phosphorylation), peptides (for example, ubiquitylation or sumoylation), or nucleotides (for example, poly(ADP-ribosyl)ation). Poly(ADP-ribosyl)ation often involves the addition of long chains of ADP-ribose units, linked by glycosidic ribose-ribose bonds, and is critical for a wide range of processes, including DNA repair, regulation of chromosome structure, transcriptional regulation, mitosis and apoptosis. Here we identify a novel poly(ADP-ribose)-binding zinc finger (PBZ) motif in a number of eukaryotic proteins involved in the DNA damage response and checkpoint regulation. The PBZ motif is also required for post-translational poly(ADP-ribosyl)ation. We demonstrate interaction of poly(ADP-ribose) with this motif in two representative human proteins, APLF (aprataxin PNK-like factor) and CHFR (checkpoint protein with FHA and RING domains), and show that the actions of CHFR in the antephase checkpoint are abrogated by mutations in PBZ or by inhibition of poly(ADP-ribose) synthesis.

High Flow TPO Compounds Containing Branched EPDM Modifiers

Abstract Polymer blends of ethylene-propylene elastomers and polypropylene plastics, referred to as thermoplastic olefins, are finding increasing use in automotive applications. The combination of attractive mechanical properties, low raw material cost and recyclability make these materials ideal substitutes for expensive engineering thermoplastics (polycarbonate/polybutylene terephthalate alloys) and nonrecyclable polyurethane systems. The primary application is in automotive bumper fascia. This paper describes the addition of long chain branched ethylene-propylene elastomers in thermoplastic olefin compounds containing a high flow polypropylene resin matrix. In such compounds, the modifier molecular architecture plays an important role in impact toughening. The results clearly indicate that linear modifiers such as traditional ethylene-propylene copolymers are ineffective in impact toughening, while long chain branched polymers provide enhanced impact resistance with a ductile failure mode in high flow polypropylenes.

Is docosahexaenoic acid necessary in infant formula? Evaluation of high linolenate diets in the neonatal rat.

Neural accretion of docosahexaenoic acid (DHA) is thought to play an important role in the neural development of human infants. The lack of DHA in infant formulas contributes to the lowered neural accretion of DHA observed in formula-fed infants relative to those breast-fed. We hypothesized that lowering the dietary linoleic acid (LA) to alpha-linolenic acid (LNA) ratio may lead to increases in the level of DHA in the developing brain and retina. Lowering the LA to LNA ratio from 10:1 to 1:1 and to 1:12 in the artificially reared (AR) neonatal rat pup resulted in a significant increase in the percentage of brain DHA between AR dietary groups. The brain level of DHA in the AR group fed a 1:12 ratio was similar to that of a dam-reared reference group. However, levels of DHA in the retina of all AR groups were significantly lower than that of the (chow fed) dam-reared group. It appears that LNA may serve as an adequate substrate for the accretion of DHA in the brain, but not the retina of the developing rat. In both the brain and the retina, levels of arachidonic acid in the AR pups fed the 1:1 ratio were similar to that of the dam-reared group. However, levels in the 1:12 group were significantly reduced. The addition of long chain n-3 polyunsaturates such as DHA to infant formula may therefore be necessary for adequate neural DHA accretion and optimal neural development.