SPECIALTY NATURAL RUBBER LATEX FOAM: FOAMABILITY STUDY AND FABRICATION PROCESS

ABSTRACT Specialty natural rubber (SpNR) latex, namely, deproteinized natural rubber (DPNR) latex and epoxidized natural rubber (ENR) latex, has been produced to meet specific product's requirements. However, SpNR is normally used in the form of block rubber to manufacture dry rubber products such as tires and automotive parts. The applications of SpNR latex into latex foam products will be diversified. Findings indicate that foamability of SpNR latex is lower compared to normal latex (LATZ) but shows longer stability time after foamed. Findings also indicate that foam collapse and foam coagulate are two main challenges in the fabrication process of SpNR latex foam. Despite these challenges, SpNR latex foam can be fabricated at different density levels. During the foaming process, additional foaming agent is required to fabricate a SpNR latex foam, which is different from fabricating a normal NR latex foam, especially at low latex foam density. Consequently, a higher level of sodium silicofluoride, used as the gelling agent, is required to set the cell structure of the foam. Findings also indicate that foam density influenced the gelling time and volume shrinkage of the SpNR latex foam. An ideal compounding, foaming, and gelling formulation to fabricate SpNR latex foam via Dunlop batch foaming process has been developed. Morphological study showed that all latex foams are open-cell structure, with lower density foam exhibiting higher porosity and mean pore size. Comparison on hysteresis behavior between DPNR and ENR latex foam indicated that ENR latex foam exhibits higher hysteresis loss ratio compared to DPNR latex foam.

A Novel Epoxy Resin Composition as a Lost Circulation Material: Formulation, Lab Testing and Field Execution

The novel resin composition described in this paper has been designed to treat moderate to severe losses. The resin composition comprises an epoxy resin and a chemical activator that undergo a polymerization reaction without any addition of water. The polymerization was designed to delay and successfully controlled to gel up and form the target resin composition after the fluid goes inside the wellbore. This is very important to avoid early setting of the fluid. The objective of this paper is to discuss the formulation of epoxy resin as a lost circulation material and also detail the lab testing and field execution. In this study, we used two different epoxy resins to study the development of the novel loss circulation material. One contains two epoxy groups and the other contains only one epoxy group. Two different chemical activators have been used in this study as well; each of them differs in the number of amine groups and geometry. The effect of these differences on the polymerization in terms of time and properties were investigated. In addition, the effect of the chemical activator concertation on the setting time of the resin composition was investigated to accomplish a controlled and a delayed polymerization. Also, the chemical conditions were evaluated to simulate a variety of downhole conditions to prove the effectiveness of this novel resin composition as a loss circulation treatment. The lab testing includes thickening time measurements. The novel resin composition is designed to have a controlled thickening time under a variety of downhole conditions. This is important to have an accurate placement of the fluid inside the wellbore; thus, avoiding an early setting of the fluid. We found that the thickening time of the resin composition can be controlled by mainly varying the concertation of the chemical activator. We found as well that changing the type of epoxy resin or chemical activator produce different gelling time and properties. We designed the loss circulation composition to provide a predictable and controlled pumping time. This novel resin composition can remain in a liquid phase from a few minutes to several hours based on the desired conditions. This is favorable in order to have an accurate placement of the fluid inside the wellbore over a predictable and controlled period of time. The final and target resin composition, will appear and gel as a solid thereby preventing loss circulation. The resin was pumped from the BHA in a single stage which helped mitigate and reduce the dynamic losses from 260 bbl./hr. to 200 bbl./hr. using only 25 bbls and eventually to zero.

Process standardization for alginate encapsulation of potentially probiotic Pediococcus pentosaceus DM101

The main objective of this study was to standardise the procedure for encapsulation of potentially probiotic breast milk isolate Pediococcus pentosaceus DM101 using sodium alginate by extrusion method. The encapsulation parameters were optimized by comparing the encapsulation efficiency obtained with varying concentration of sodium alginate (0.5, 1.0, 1.5 and 2.0%), calcium chloride (0.05, 0.1 and 0.2M) and gelling time (5, 10, 20 and 30 minutes). Encapsulation efficiency was ascertained by finding the survival percentage after exposing the encapsulated cells to acid stress (pH 2.0 for 3h). Encapsulation carried out using two per cent sodium alginate and 0.1M CaCl2 following 20 min gelling time was found to confer maximum protective effect. Encapsulation efficiency of alginate beads prepared under optimized conditions was found to be 81.37±2.44 per cent. The results endorse alginate encapsulation as a means to confer a protective shielding effect thereby facilitating effective probiotic delivery.

FORMULATION AND EVALUATION OF IN-SITU GEL CONTAINING LINEZOLID IN THE TREATMENT OF PERIODONTITIS

Objective: The intent to prepare and evaluate Linezolid in-situ gel in the treatment of periodontitis. Methods: pH-sensitive in-situ gel was formed by the cold method using a varying concentration of the drug, carbopol 934P and hydroxypropyl methylcellulose (HPMC) and carbopol 934P and sodium carboxy methylcellulose (CMC) (1:1,1:1.5,1:2,1:2.5). An optimized batch was selected based on gelling time and gelling capacity. The prepared in-situ gels were evaluated for appearance, pH, gelling capacity, viscosity, in vitro release studies, rheological studies, and finally, was subjected to drug content estimation and antibacterial activity test. Results: FTIR study shows drug and physical mixture were compatible with each other. The rheology of formulated in-situ gel exhibited a pseudoplastic flow pattern. this may be because when polymer concentration was increased the prepared formulations become more viscous and in turn delayed the drug release and from the prepared formulation, LF4 and SF4 have polymer concentrations i. e, 0.9% carbopol and sodium CMC showed drug release up to 12 h. Conclusion: When carbopol is appropriately mixed with other suitable polymers it forms an in-situ gel-forming system that was substantiated by the property to transform into stiff gels when the pH is increased. The in-situ gel was prepared using a combination of carbopol-HPMC and carbopol-Na CMC The formulations LF1 to SF4 showed high linearity (R2 = 0.490-0.682), indicating that the drug was released from the prepared in-situ gel by the diffusion-controlled mechanism. Thus, the formulation of batches LF4 and SF4 containing carbopol: HPMC and carbopol: NaCMC in 1:2 ratios were considered as optimum formulation based on optimum viscosity, gelling capacity and to extend the in vitro drug release.

Formulation, Optimization and Evaluation of Ion Triggered Ophthalmic in Situ Gel

Topical eye drop is the convenient and patient compliant route of drug administration, particularly for the treatment of anterior part diseases. Transport of drugs to the targeted ocular tissues is limited by various precorneal, active and stationary ocular barriers. The aim of developed, optimized and evaluated ion sensitive brimonidine tartrate in situ gel is patient compliance and maximum therapeutic activity in the treatment of glaucoma. The effect of independent variables that are polymer concentration on dependent variables like the percent drug release, gelling time and viscosity was studied. The optimized formulation was further evaluated for ex-vivo study and histopathology study. Experimental study showed that optimized in situ gel formulation (F6) showed in vitro, ex vivo sustained release with polymer sodium alginate and hydroxypropyl methyl cellulose (HPMC) K4M. The optimized formulation F6 presented increased retention time upto 8 hours. The developed in situ gel can be a promising ophthalmic formulation to increase retention time of formulation and hence it will reduce the intra ocular pressure. The histopathology studies reveals the safety of prepared formulation. The stability studies revealed no significant change in the drug content and physical properties.

A Study on Sebum Hardening Effect of ZnO Powder

Zinc oxide is transparent inorganic UV absorber and widely used as a sunscreen. But sunscreen on the skin is easily erased by sebum, so zinc oxide with a sebum curing function was studied. In this study, a zinc oxide powder was prepared using zinc chloride and sodium hydroxide via a hydrothermal synthesis method. The process conditions including reaction temperature and sodium hydroxide ratio were determined. Particle size was determined using XRD and SEM, and process tendencies were checked using the gelling test method. When the sodium hydroxide ratio was lower than 58.7 wt%, the gelling time was reduced, and when the temperature was lower than 60 ^o, the gelling time decreased. ZnO and Simonkolleite confirmed that the gelling time was reduced when the mixture comes out.

Nanosilica-Based Loss Circulation Composition to Cure Moderate to Severe Losses

The loss circulation composition comprising a combination of a nanoparticle-based dispersion and a chemical activator has been designed to treat moderate to severe losses. The nanomaterial used is an environmentally friendly nanosilica-based dispersion. The composition is designed to give delayed gelling of the nanoparticle-based dispersion. A major advantage of this technology is its ability to place the composition into the target loss circulation zone before the nanoparticle-based dispersion gels up. Premature gelling of the nanoparticle-based dispersion would avoid premature setting of the treatment fluid before it reaches the target zone. The newly developed system can be used effectively up to 300 °F. In this paper, experiments have been performed with three different types of nanoparticles differing in their surface charges and particle sizes. Two negatively charged nanoparticle-based dispersions with a particle size of 5 nm and 17 nm, respectively, and one positively charged nanoparticle-based dispersion with a particle size greater than 17 nm have been evaluated as loss circulation materials. Two different types of chemical activators, one organic and the other inorganic, have been used in this study, and their effect on the gelling time has been evaluated. The gelling time experiments have been done at four different temperatures viz. 150 °F, 200 °F, 250 °F, and 300 °F. The effect of activator concentration and different shear rates on the gelling time of the three nanoparticle-based dispersions has been studied. Permeability plugging tests have been performed using 2 mm slotted disks to evaluate the effectiveness in controlling moderate to severe losses.

Investigation of the Influence of Calcium Salts and Gelling Time on the Structural Mechanical Properties of Fruit Jam

Alginate beads attract attention as a encapsulation matrix of bioactive substances in food. However, the stability of beads depends on calcium ion and sodium alginate concentration, gelling time and others factors. The aim of this study is to investigate the influence of different types of calcium salts on the structural and mechanical parameters - the rupture force and rupture deformation at different gelling times of the pear jam prepared with soluble dietary fibers and inulin. The relationships between the rupture force and rupture deformation of the fruit jams were established. By increasing the gelling time from 24 hours to 48 hours, the rupture deformation of jams with 7% calcium lactate were reduced and in those with 7% CaCl2 the rupture forces increases. Any change in rupture force was observed for the jam with 3.5% CaCl2. This study demonstrated the practical application of different calcium salts for preparation of stable pear jam.

Structure and Rheological Properties of Glycerol Monolaurate-Induced Organogels: Influence of Hydrocolloids with Different Surface Charge

Organogel (OG) is a class of semi-solid gel, entrapping organic solvent within a three-dimensional network, which is formed via the self-assembly of organogelators. In the present study, OG was produced by glycerol monolaurate (GML) as organogelator. The influence of hydrocolloids with different surface charges (chitosan (CS), konjac glucomannan (KGM) and sodium alginate (SA)) on the physiochemical properties of OG was investigated. Rheological studies demonstrated that OG and pure hydrocolloid solution showed shear-thinning behavior. After incorporation of the hydrocolloid, the initial viscosity of OG was lowered from ~100 Pa·s to <10 Pa·s, and then the viscosity increased to more than 100 Pa·s at a low shear rate of 0.1–0.2 s−1, which subsequently decreased with a higher shear rate. OGs in the presence of hydrocolloids still kept the thermo-sensitivity, while the melting point of the OG decreased with the incorporation of hydrocolloids. Hydrocolloid addition greatly shortened the gelling time of the OG from 21 min to less than 2 min. The presence of hydrocolloids increased the particle size of oil droplets in the molten OG. Some aggregation and coalescence of oil droplets occurred in the presence of positive-charged CS and negative-charged SA, respectively. After gelling, the gel structure converted into a biphasic-like network. Hydrocolloids improved the hardness, stickiness and the oil-holding stability of OGs by 18.8~33.9%. Overall, hydrocolloid incorporation could modulate the properties of OGs through their different surface charge properties. These novel OGs have potential as nutrient carriers or low-fat margarine alternatives and avoid the trans-fatty acid intake.

The Effect of Silica-Filler on Polyurethane Adhesives Based on Renewable Resource for Wood Bonding

The aim of the study was to evaluate the applicability and performance of polyglycerol- and sucrose-based polyols as components of a simplified formulation of polyurethane adhesives. Colloidal silica was used as a viscosity control and reinforcing agent. The adhesives were examined in terms of reactivity, thermal stability, viscosity, work of adhesion, wetting, surface energy, and bonding strength on wooden substrates. Silica was found to increase gelling time, but markedly improved bonding strength and adhesion with substrates. Bonded solid beech wood samples prepared at 80, 110, and 130 °C showed shear strengths between 7.1 MPa and 9.9 MPa with 100% wood failure. The renewable resource-based polyols were demonstrated to be useful in formulation of polyurethane adhesives for furniture industry—especially with silica as a filler.