A study of synthesis and characterization of compatibilizers for thermosetting-thermoplastic polymer blends

Modified copolymers or compatibilizers were prepared to blend thermosetting (phenol formaldehyde resin) and thermoplastic (PMMA/PS) polymers. Two compatibilizers, modified phenol formaldehyde-(s-triazine)-polystyrene, P(PF-g-S) and poly-(cinnamaldehyde-co-oxypropyleneoxyisophthaloyl-co-oxypropyleneoxyfumaroyl), P(C-g-E), were synthesized and characterized. The behaviour of the compatibilizers towards UV vacuum irradiation and heat was studied with low molecular weight P(PF-g-S) and P(C-g-E). Crosslinking was found to occur during the initial 20 h of UV vacuum irradiation, which was confirmed by solubility and swelling data. Thermal degradation of thermoplastic segments in P(PF-g-S) was found to occur initially during thermal exposure. Crosslinking of the degraded radical fragments and phenolic segments took place in the continued thermal exposure. A method yielding a simultaneous interpenetrating network (SIN) was adopted to increase the molecular weight of P(PF-g-S) and its allied copolymers which is a prerequisite for the present polymer blends. Condensation reaction in phenolic segments and addition reaction in thermoplastic segments were carried out simultaneously, the former reaction was carried out thermally and the latter by photo irradiation.     

Analysis of the size reduction of AgNPs loaded hydrogel and its effect on the anti‐bacterial activity

This article analyses the effect of the size reduced Silver (Ag) loaded hydrogel by (a) lyophilisation (S1) (b) ball milling (S2) techniques and its effect on anti‐bacterial activity. The g loaded hydrogel, S1 and S2 shows an increase in swelling with an increase in pH. The swelling is more for Ag loaded hydrogel in low pH. For pH above 7, the swelling ratio of Ag loaded hydrogel and S1 are almost the same while S2 shows very less swelling. The anti‐bacterial studies reveal that S1 and Ag loaded hydrogel reacted well in S. aureus (Staphylococcus aureus) but no zone formation was seen in S2 .whereas no zone was formed in S1 and S2 for E‐coli (Escherichia coli). As the next step, the anti‐bacterial activity of Ag loaded hydrogel with the addition of curcumin (CS1―size reduced by lyophilisation, CS2―size reduced by ball milling) and turmeric (TS1―size reduced by lyophilisation, TS2―size reduced by ball milling) were investigated. In case of E.coli, a zonal formation of 1.2 cm for TS1 and 1.1 cm for TS2 and 1 cm for CS1 and 0.2 cm for CS2 was observed. For S.aureus, 1.1  and 1 cm were seen for TS1 and CS1. TS2 and CS2 did not show any zone formation. These studies clearly show that size reduction by lyophilisation (S1, TS1 and CS1) is more efficient in all the cases when compared to the ball milling technique (S2, TS2 and CS2). Comparing TS1 with S1 and CS1, TS1 has highly efficient/effective anti‐bacterial properties than S1 and CS1. Therefore, lyophilised hydrogel incorporating turmeric and silver (TS1) is an excellent choice compared to using curcumin for wound dressing applications.     

Effect of dehydrochlorination of PVC on miscibility and phase separation of binary and ternary blends of poly(vinyl chloride), poly(ethylene-co-vinyl acetate) and poly(styrene-co-acrylonitrile)

The enhancement of miscibility at the lower critical solution temperature (LCST) of the blends poly(vinyl chloride)/poly(ethylene-co-vinyl acetate) (PVC/EVA), poly(vinyl chloride)/poly(styrene-co-acrylonitrile) (PVC/SAN) and poly(vinyl chloride)/poly(ethylene-co-vinyl acetate)/poly(styrene-co-acrylonitrile) (PVC/EVA/SAN) was observed at the micron level. Such miscibility is attributed to the dehydrochlorination and formation of hydrogen bonds between blend components. However, macrolevel immiscibility of these blends heated to the LCST was observed. Such microdomain compatibility of these blends gives a synergistic character. Brittle-type failure observed for LCST samples testifies to the synergism in treated blends. ©1997 SCI     

Weibull Probability Model for Fracture Strength of Aluminium (1101)-Alumina Particle Reinforced Metal Matrix Composite

In recent times, conventional materials are replaced by metal matrix composites (MMCs) due to their high specific strength and modulus. Strength reliability, one of the key factors restricting wider use of composite materials in various applications, is commonly characterized by Weibull strength distribution function. In the present work, statistical analysis of the strength data of 15% volume alumina particle (mean size 15 μm) reinforced in aluminum alloy (1101 grade alloy) fabricated by stir casting metho...     

Studies on biodegradation of crosslinked hydroxy terminated-poly(proplyene fumarate) and formation of scaffold for orthopedic applications

Biodegradation of crosslinked-hydroxy terminated-poly(proplyene fumarate) (X-HTPPF) has been studied in simulated physiological media to assess the formation of porous scaffold structure for bone growth and remodeling in load bearing orthopedic applications. Variation in crosslink density and surface hydrophilicity of X-HTPPF are observed due to non-stoichiometric mass of reacting partners. These variations influence absorption of the medium and biodegradation during aging. Though the initial absorption of medium is relatively higher with the crosslinked polymer (PNVP1) having 63.6% HT-PPF and 36.4% comonomer n-vinyl pyrrolidone (NVP) during the initial period of aging, the weight loss due to subsequent degradation with time is relatively lesser. PNVP1 undergo slow degradation with formation of fibril structure on the surface. The present crosslinked material PNVP1 is a candidate for the load bearing orthopedic applications.     

Studies on in vitro biostability and blood compatibility of polyurethane potting compound based on aromatic polymeric MDI for extracorporeal devices

Polyurethane potting compound based on aromatic isocyanurate of polymeric MDI, poly propylene glycol (PPG400) and trimethylol propane (TMP) has significant favourable properties, good pot life and setting characteristics. The cured potting compound of this formulation has appreciable thermal stability and mechanical properties. In vitro biostability of cured potting compound has been found to be excellent without any significant degradation in simulated physiological media and chemical environment. Studies on blood-material interaction and cytotoxicity reveal in vitro blood compatibility and compatibility with cells of this potting compound.     

Fault Classification in Phase‐Locked Loops Using Back Propagation Neural Networks

Phase‐locked loops (PLLs) are among the most important mixed‐signal building blocks of modern communication and control circuits, where they are used for frequency and phase synchronization, modulation, and demodulation as well as frequency synthesis. The growing popularity of PLLs has increased the need to test these devices during prototyping and production. The problem of distinguishing and classifying the responses of analog integrated circuits containing catastrophic faults has aroused recent interest. This is because most analog and mixed signal circuits are tested by their functionality, which is both time consuming and expensive. The problem is made more difficult when parametric variations are taken into account. Hence, statistical methods and techniques can be employed to automate fault classification. As a possible solution, we use the back propagation neural network (BPNN) to classify the faults in the designed charge‐pump PLL. In order to classify the faults, the BPNN was trained with various training algorithms and their performance for the test structure was analyzed. The proposed method of fault classification gave fault coverage of 99.58%.     

Changes in content of organic acids and tea polyphenols during kombucha tea fermentation

Kombucha tea is a fermented tea beverage produced by fermenting sugared black tea with tea fungus (kombucha). Tea polyphenols which includes (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG) and theaflavin (TF) have been reported to possess various biological activities. The present study focused on changes in content of organic acid and tea polyphenols in kombucha tea prepared from green tea (GTK), black tea (BTK) and tea manufacture waste (TWK) during fermentation. Concentration of acetic acid has reached maximum up to 9.5 g/l in GTK on 15th day and glucuronic acid concentration was reached maximum upto 2.3 g/l in BTK on 12th day of fermentation. Very less concentration of lactic acid was observed during the fermentation period and citric acid was detected only on 3rd day of fermentation in GTK and BTK but not in TWK. When compared to BTK and TWK very less degradation of EGCG (18%) and ECG (23%) was observed in GTK. TF and thearubigen (TR) were relatively stable when compared to epicatechin isomers. The biodegradation of tea catechins, TF and TR during kombucha fermentation might be due to some unknown enzymes excreted by yeasts and bacteria in kombucha culture.     

A New Method in Selective Assembly to Minimize Clearance Variation for a Radial Assembly Using Genetic Algorithm

Selective assembly is the method of obtaining high-precision assemblies from relatively low-precision components. A relatively smaller clearance variation is achieved than in interchangeable assembly, with the components manufactured with wider tolerance. In selective assembly, the mating parts are partitioned to form selective groups with smaller tolerance, and the corresponding groups are assembled interchangeably. The mating parts are manufactured in different machines, using different processes, and with different standard deviations. Therefore, the dimensional distributions of the mating parts are not similar. In selective assembly, the number of parts in the corresponding selective groups is not similar and will result in surplus parts. The clearance variation is also very high. In this article, a new method is proposed in selective assembly. Instead of assembling components from corresponding selective groups, the components from different combination of selective groups can be assembled to achieve minimum clearance variation. Genetic algorithm is used to find the best combination of the selective groups for minimizing the clearance variation. A case of hole and shaft (radial) assembly is analyzed in this article, and the best combination is obtained to minimize assembly clearance variation. The assembly is done in three stages to completely use all the components. The best combination for the selective groups and the resulting clearance variations are tabulated. The surplus parts are minimized to a large extent.