Synthesis and characterization of hydroxyl terminated poly(butadiene)-g-poly(glycidyl azide) copolymer as a new energetic propellant binder

Summary Poly(glycidyl azide), PGA, was grafted onto Hydroxyl Terminated Poly(butadiene), HTPB, via free radical mechanism. PGA-macro azoinitator and HTPB polymer mixture was casted from solution and the polymer film was kept at 90°C for 4 hours. The grafted polymer was isolated from the product by fractional precipitation and characterized by NMR and FT-IR spectroscopy. Graft copolymer structure was also confirmed that volume ratio of nonsolvent to the solution of the graft copolymer was between those of corresponding homopolymers. TGA traces of the block polymers were containing two different maxima at 253°C (for PGA units) and 469°C (for HTPB units). Because of the incompatibility of the blocks, DSC curve showed two T_g's which belong to the related segments.     

High-Modulus Columns for Liquefaction Mitigation

This paper presents the performance of a shopping complex in Turkey where the soils were improved with jet-grout columns and preload fills and subjected to the 1999 Kocaeli Earthquake (M = 7.4). Under construction at the time of the earthquake, the Carrefour Shopping Center covers an area of 55,000?m2 and is founded on shallow footings, mats, and slabs-on-grade that rest on soft, saturated alluvial sediments consisting of clays, silts, and sands. High-modulus columns constructed by jet grouting were installed at close-to-moderate spacings to reduce anticipated static settlements in the clays and mitigate liquefaction in the sands. The site was subjected to a peak acceleration of approximately 0.2g during the earthquake. Grouting had been completed for about two-thirds of the site when the earthquake struck. Following the event, a field reconnaissance found stark contrast between the performance of the improved and unimproved sections. The jet-grout-treated areas suffered no apparent damage, whereas the unimproved sections of the complex, along with nearby untreated building sites, commonly suffered liquefaction-related settlements of up to 10 cm. This is the only case history known to the authors that documents the field performance of high-modulus columns used in this manner for liquefaction mitigation and direct instrumented measurement of liquefaction-induced settlements.     

Enhancing compatibility between poly(lactic acid) and thermoplastic starch using admicellar polymerization

An alternative method to improve the compatibility between poly(lactic acid) (PLA) and cassava starch (CS) is proposed and investigated. Admicellar polymerization is used to modify the surface of CS with poly(methyl methacrylate) (PMMA) in order to make it more hydrophobic and hence more compatible with PLA. The increased hydrophobicity of PMMA modified cassava starch (MS) is validated by contact angle measurement. Results from iodine test, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) confirm the formation of PMMA film on MS surface. Mechanical properties of PLA‐CS and PLA‐MS blends are investigated to compare their compatibility. Noticeable improvements in blend tensile strength and elongation at break evidently show that MS is more hydrophobic as well as more compatible with PLA than CS. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43755.     

ESR studies of molecular motions at the interphase region of a blendlike polymeric material

The molecular motions of spin probes at the interphase region of poly(methyl methacrylate) particles sterically stabilized by polyisobutylene (PIB) were studied by ESR spectroscopy. The correlation times (τ) were measured by using the methods of Freed and Kivelson. Activation energies for different modes of motion were calculated at wide temperature range between ?140 and 140°C. Viscosities were estimated in methanol saturated PIB channels in the polymer particles. © 1994 John Wiley & Sons, Inc.     

Effect of gamma irradiation on the properties of tyre cords

Gamma irradiation of high tenacity Nylon 6.6 (Ny 66) and polyester (PET) tyre cords was investigated. The untreated and treated tyre cords with different twist levels were irradiated at different dose rates in air. The effects of irradiation on both Ny 66 and PET cords were not found to be depending on the twist levels of the cords. The changes in the mechanical and thermal properties with absorbed dose at two different dose rates were measured. The mechanical properties were observed to deteriorate with increasing dose for Ny 66 cords, whereas remained almost unchanged for PET cords both in greige and dipped forms. Hot shrinkage value for the greige Ny 66 cords was found to be improved, i.e. decreased. This decrease was much lower for greige PET than Ny 66 cords. It is concluded that PET cord has higher radiation resistance than Ny 66 cord and the effects of high energy irradiation on tyre cords have to be taken into consideration during tyre design if pre-vulcanization with high energy radiation is to be applied.     

Radiation-induced degradation of galactomannan polysaccharides

In this study, guar gum, tara gum and locust bean gum were irradiated in a gamma cell in the solid state. The change in their molecular weights were determined by size exclusion chromatography analysis and the change in their viscosity values with change of temperature and irradiation dose were determined. Chain scission yield, G(s), and degradation rate values were calculated. The calculated G(s) values is 1.09 ± 0.16, 1.07 ± 0.06, 0.85 ± 0.10 for GG, TG and LBG, respectively. The effect of mannose-galactose ratio and initial molecular weight of these gums on the degradation behavior were discussed.     

Physico-chemical characteristics of chemically activated cement containing boron

The use of colemanite ore waste (CW) containing boron as a cement replacement material increases the long-term strength of the concrete. Despite this benefit, the use of CW is limited due to the low-early strength of the CW concrete. The study reported below intended to eliminate this problem. The experimental part comprises two stages: in the first stage the possibility of using CW instead of natural gypsum has been investigated through several tests. In the second stage, a number of chemical activators, namely, sulphonated melamine formaldehyde (SMF) condensates, sulphonated naphthalene formaldehyde (SNF) condensates, _Na2SO4${\mathrm{Na}}_2{\mathrm{SO}}_4$, and calcium chloride were used. The results showed that replacement of natural gypsum by CW results in an acceptable initial and final setting time of cement and increases the compressive strength of the mortar at long term. The addition of chemical activators into the system accelerated pozzolanic reaction and considerably increased early strength of the mortars. The results also indicate that chemical activators not only alter the rate of cement paste hydration, but the microstructure of mortar as well.     

Teacher beliefs and technology integration practices: A critical relationship

Early studies indicated that teachers’ enacted beliefs, particularly in terms of classroom technology practices, often did not align with their espoused beliefs. Researchers concluded this was due, at least in part, to a variety of external barriers that prevented teachers from using technology in ways that aligned more closely with their beliefs. However, many of these barriers (access, support, etc.) have since been eliminated in the majority of schools. This multiple case-study research was designed to revisit the question, “How do the pedagogical beliefs and classroom technology practices of teachers, recognized for their technology uses, align?”     

An investigation on the use of tincal ore waste, fly ash, and coal bottom ash as Portland cement replacement materials

The possibility of using tincal ore waste (TW), coal bottom ash (BA), and fly ash (FA) as partial replacement in concrete was examined through a number of tests. The properties examined include setting time, compressive strength, mortar expansion, water consistency of mortar, and microstructure. The results showed that compressive strength of all specimens containing 1 wt.% of TW was higher than that of the control at the 28th day of curing. At 90 days, the contribution to strength by BA+TW and FA+TW was higher than in the concrete-prepared equivalent TW beyond 3 wt.% of Portland cement (PC) replacement. With the replacement of 3-5 wt.% of PC by TW, the compressive strength of the concrete decreased compared to control concrete. However, the values obtained are within the limit of Turkish Standards (TS). Adding BA or FA with TW improved the performance relative to TW replacement only. Increasing replacement of TW gives rise to a higher setting time. As a result, TW, BA, and FA samples may be used as cementitious materials.     

Fourier transform infrared photoacoustic studies of the adsorption behavior of poly(2‐hydroxypropyl methacrylate) at solid–liquid interface

Adsorption of poly(2‐hydroxypropyl methacrylate) on alumina from dimethylformamide was studied by ultraviolet (UV) and Fourier transform infrared (FT‐IR) photoacoustic spectroscopy (FTIR PA) techniques. Adsorbent amount and concentration effects were investigated. The adsorption results are in conformity with Langmuir's isotherm. The differences observed in Langmuir parameters were explained by polymer–polymer, polymer–solvent, polymer–adsorbent, and solvent–adsorbent interactions. The fraction of carbonyl groups attached to the surface of alumina was calculated with a curve‐fitting computer program. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2750–2756, 2002