bluuebunny/crossref_metadata_2025 huggingface dataset:
Tribological property and oxidation stability evaluation of rice bran oil with silicon dioxide nanoparticles and spicy aroma-based herbal oils as additives
Authors: Kamal Vivek V , Pradeep Nakul , Santhakumari amma Rani , Arif Muhammed , Thampi Ananthan D , Edla Sneha
Published: March 2023

Around the globe, the majority of industries are utilizing mineral oil-based lubricants because of their cost, availability, and compatibility with different engineering materials. The progressive depletion and negative impacts of mineral oil-based products on the environment have led to the search for some potential alternatives. Biodegradable and nontoxic vegetable oils are considered a potential replacement for mineral oils. However, they exhibit certain limitations such as less oxidation stability, poor cloud, and pour point characteristics. In the present study, herbal oils are used as novel antioxidants, and also the synergetic effect of nanoparticles and herbal oils are studied. The modified rice bran oil (MRBO) was formulated using rice bran oil (RBO) as base oil with optimum concentrations of additives such as ginger oil (GO), black pepper (BP) oil, and silicon dioxide nanoparticles. The wear scar diameter (WSD) was reduced significantly by 18.8% after the addition of 0.05 wt.% of SiO2 to RBO. The synergetic effect of herbal oils and SiO2 has significantly reduced the coefficient of friction (COF) of RBO by 15.5%. The oxidation stability of developed oil was also found to be better than RBO when compared to that of commercial lubricant (COM).
‘Now I think you have been bewitching and bewildering me’: The utilisation of Aporia in Game-Based Approaches as a means of deconstructing and reconstructing power relations
Authors: Jones Ruan Jon , Mckeever Jonathon Thomas , Morley David
Published: March 2023

Work considering the influence of power dynamics and potential confounders such as social status is beginning to receive more attention in physical education literature. While power dynamics deserve particular attention in student-centred and social constructivist pedagogies, exploration of this topic has largely escaped the grasp of Game-Based Approaches (GBAs). This position paper aimed to review current micro-interactional research in physical education and to propose the utilisation of four key principles as a means to disrupt power dynamics in GBAs, namely: (a) teaching paradoxically; (b) ethical dilemmas; (c) unfamiliar games; and (d) Socratic questioning. Two illustrative vignettes present the practical application of these principles to produce a state referred to in Classical Greece as Aporia (impasse or without passage). Building on the work of Joy Butler, we argue that student insights gained in these moments of Aporia are central to the disruption of power-based barriers to learning.
Effects of mental contrasting on sleep and associations with stress: A randomized controlled trial
Authors: Schmidt Laura I , Neubauer Andreas B , Stoffel Martin , Ditzen Beate , Schirmaier Jana , Farrenkopf Claudia , Sieverding Monika
Published: March 2023

Mental contrasting with implementation intentions (MCII) has been successfully applied to improve health-related behaviors (e.g. exercise). We explored its effectiveness to improve sleep outcomes beyond effects of sleep hygiene (SH) information, and investigated associations with stress. Eighty university employees (mean age: 29.6, SD = 4.5) were randomized to either a MCII + SH or a SH-only condition. During a baseline-week and a post-intervention week, sleep duration (Fitbit Alta and self-report), sleep quality, and stress were assessed daily and saliva was collected to assess the cortisol awakening response (CAR). In total, self-reported sleep quality and duration increased, but there was no meaningful condition*week interaction for sleep parameters or CAR. Higher average stress was associated with shorter sleep duration and lower sleep quality. Within-person, days with higher stress were followed by nights with lower sleep quality. Despite overall improvements, effects of MCII were not confirmed. MCII might be less effective to improve behaviors which are less controllable.
Factors influencing the mental health of autistic children and teenagers: Parents’ observations and experiences
Authors: Mukherjee Suzanne , Beresford Bryony
Published: March 2023

The high prevalence of mental health and behaviour problems among autistic children and adults is an issue of concern to the autism community. Many studies have been undertaken to identify the factors that protect against/or increase the risk of such difficulties. However, this research is dominated by quantitative observational studies. In this study, we sought to investigate the same issue using a qualitative research approach, positioning parents as experts and eliciting their theories as to what influenced their child’s mental health from diagnosis to the late teenage years. In-depth interviews were undertaken with 33 parents (30 mothers, 3 fathers) of 31 autistic teenagers (21 males, 10 females) aged between 15 and 19 years (median 17 years) purposively sampled from an existing cohort (QUEST). Parents believed a wide range of child-centred, developmental and socio-environmental factors had played a role in their child’s mental health, alongside life events involving loss and separation. A number of these factors have received little or no research attention to date (e.g. aspects of the school environment). The findings have important implications, highlighting factors that should be given priority in future research, as well as interventions needed to support the mental health of autistic teenagers.

Lay abstract

Autistic people are more likely to experience mental health difficulties compared to neurotypical people. It is very important that we understand what increases the risk for mental health difficulties, and what helps to protect against them. So far, research on this for children and young people has only investigated a small number of factors and these have been chosen by researchers and clinicians. This study took a different approach in which parents’ expertise in their children was recognised. Parents were asked to tell the story of their autistic teenagers’ mental health from diagnosis in early childhood through to the present, and to explain the ‘theories’ they developed about what affected their child’s mental health – positively and negatively – and how. Parents believed a wide range of factors played a role. These include: (1) aspects of their child (e.g. their autistic traits, intelligence); (2) aspects of their surroundings (e.g. the efforts parents make to prevent and respond to their child’s difficulties, features of the school they attend, availability of social activities); (3) changes their child experienced growing up (e.g. puberty, awareness of being autistic); and (4) life events involving loss and separation. Many of the factors parents identified as important have received little or no research attention to date. The findings suggest issues that should be considered in future research and reveal ways that support for parents and autistic children and teenagers can be improved.
Bisphenol-A release from thermoplastic clear aligner materials: A systematic review
Authors: Peter Elbe , J Monisha , George Suja Ani
Published: March 2023

Aim:

The aim of the present study was to undertake a systematic review of the available evidence on the release of bisphenol-A (BPA) from thermoplastic materials used in the fabrication of clear aligners (CA).

Methods:

Electronic databases, such as MEDLINE (via PubMed), Google Scholar, Scopus, Cochrane Library, Web of Science, OpenGrey, and the U.S. National Institute of Heath-Clinical Trials, were searched up to 27 October 2022. In vivo/in vitro studies that assessed the release of BPA from different thermoplastic CA materials, with or without a control group, were selected. The risk of bias (RoB) in the randomised controlled trials (RCT) and in vitro studies was assessed using the Cochrane RoB tool and the guidelines for the reporting of pre-clinical studies, respectively. The quality of evidence was determined using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) Pro tool.

Results:

Six studies were considered for review from a total of 1926 records. This included one RCT and five in vitro studies. Only two studies found leaching of BPA, while four did not report any traces. The RoB was found to be moderate to high. The GRADE evidence level ranged from low to very low. Five of the included studies were conducted in vitro. Significant heterogeneity among the included studies prevented a quantitative synthesis.

Conclusion:

In light of the available conflicting evidence, BPA release from CAs can neither be confirmed nor denied. Safety remains questionable until high-quality in vivo trials prove otherwise.

Registration:

PROSPERO CRD42022310434.
Resisting Europeanisation: Poland’s education policy and its impact on the European Education Area
Authors: Klatt Gosia
Published: March 2023

Since the 2004 accession to the European Union (EU), Poland, like many other post-communist countries, have gone through a significant process of convergence to the EU institutions, laws and processes. In this process, the European values, policies and institutions have become an important reference point for the legitimacy of major national system reforms. In education, there have been a significant number of reforms aligned with ‘European standards’ as integration with the EU was seen as a priority for Poland’s national interest. This paper is interested in the changing policy discourses that have been defining and legitimising Poland’s education policy objectives, with a particular attention given to the idea of ‘quality education’ and the role of education. In this way, it is also interested in the processes of Europeanisation and de-Europeanisation – turning away from ‘EU-isation’ of policies. The emerging picture from the analysis illustrates the tensions between the neoliberal and populist policy discourses pursued by a variety of Polish governments, including significant policy shifts under the government of the Prawo i Sprawiedliwość (PiS) (Law and Justice) coalition.
The Use of Chemical Coupling Agents in Glass Reinforced Polyolefins
Authors: Cameron R. , Constable R.C.
Published: March 2023

European demand for glass filled reinforced polyolefins continues to show significant growth rates. The main drive behind this is material replacement within the automotive and household appliance markets. In particular the automotive industry is turning towards glass filled polypropylene components both to reduce weight and increase recyclability.

One route by which the performance of glass filled composites can be improved is by incorporating chemical coupling agents. In this paper the property enhancement achievable with POLYBOND 3002, supplied by BP Chemicals, is described. In addition development work with glass filled polymer alloys is presented.
Microstructure of Composite Materials Using Small-Angle Neutron Scattering and Contrast Variation: Approaches toward Understanding the Structure of Carbon Black-Elastomer Mixtures
Authors: Hjelm Rex P. , Seeger Philip A. , Wampler Wesley A.
Published: March 2023

Mixed composites of rubber and carbon black are of fundamental importance to rubber technology, and neutron scattering provides a unique view of structure in these interesting and complex systems. This is due, in part, to the nature of the interaction of the neutron with nuclei, which is a function of the specific nucleus, not on atomic number, per se. This allows neutrons to be used to probe fluctuations in chemical and isotopic composition and density in a manner that is a distinct from x-rays or electrons. This aspect of neutron scattering has been used extensively in the study of multicomponent systems, even when components have elements of similar atomic numbers. The large difference in scattering from some isotopes—hydrogen and deuterium being the most important example—can be used to enhance fluctuations in these systems and thus to probe structures that are not accessible by other methods.

We describe the use of small-angle neutron scattering in carbon black, elastomer and carbon black elastomer mixtures using the method of contrast variation. In this approach the sample is suspended in solvents containing different proportions of perdeuterated and protonated molecules. The variation in scattering observed as a function of solvent scattering power gives information on the distribution of components within the sample. Our first experiences using this approach show the potentials of the technique. The use of solvents near the average scattering length density of the carbon black allows observation of non-uniformity in carbon black particles that has not been previously noted. Further, we have established that the shape of the scattering curves in N762 carbon black can be explained as scattering from spherical particles of size and polydispersity measured by electron microscopy. In N121, in which the particle sizes are smaller than N762, contribution to the scatter from the carbon black particle interactions is observable. In gels of solvent extracted carbon black and elastomer we find that the scattering is dominated by carbon black density fluctuations. We find further that the elastomer coats the carbon black particles, at least in N762. There are differences in the association of the carbon blacks in solvent extracted mixtures compared to the carbon blacks suspended in cyclohexane. There may be changes, as well, in the elastomer conformation in the mixtures compared to the polymer alone in cyclohexane. These differences are small in gels containing low concentrations of polyisoprene and carbon black, but are quite profound in a gel containing styrene butadiene rubber with high concentrations of components. Further measurements and modelling of die data will be needed to come to a more satisfactory picture of carbon black morphology and elastomer conformation in the solvent extracted mixtures.
Substitution Group Effects on Gas Sorption and Diffusion into Polyimides
Authors: Toi Keio , Suzuki Hirotaka , Ito Tomoyasu , Ikemoto Isao , Kasai Tetsuo
Published: March 2023

The sorption and diffusion of carbon dioxide below 1 atm were measured for seven polyimide films by a volumetric sorption method and a permeation method. The diffusivities of carbon dioxide were correlated with packing density (reciprocal of specific free volume) for ail except two polyimides. When the packing density of the polymer was increased, the diffusivities decreased. But, as the packing density was increased further, the diffusivities increased. The substituent sulphone = SO 2 promotes hydrogen bonding and causes the polymer main chain to pack densely. Consequently the gas diffusion of this polymer is rather low. The packing density of these two polymers may not be successfully calculated by Bondi's method. However, all die diffusion coefficients decrease linearly with an increase in the cohesive energy density (CED) which is calculated by the group contribution method of van Krevelen. These results suggest that the gas diffusions of polyimides correlate with CED more than with the packing density.
Cracking of Poly(Vinylidene Fluoride) Due to Chemical Attack
Authors: Stirling C.D. , Van Tilburg V.S.M. , Miller N.A.
Published: March 2023

The effects of exposure of poly(vinylidene fluoride) (PVDF) to various chemical solutions has been investigated. Scanning electron microscopy (SEM) was used to examine the exposed samples for signs of chemical attack and cracking, while tensile and flexural bend tests were used to determine the effects of exposure on mechanical properties. Samples exposed to 50% sodium hydroxide exhibited both chemical attack and cracking together with a significant loss in ductility. Exposure to 16% sodium hypochlorite and concentrated sulphuric acid did not give either chemical attack or cracking but exposure to sulphuric acid did cause significant loss of mechanical properties. From the results obtained it was concluded that the cause of cracking in 50% sodium hydroxide was chemical embrittlement, whereby a brittle layer was formed on the surface of the material. This brittle layer subsequently cracked under applied tensile stress. The actual mechanism by which the brittle layer was formed was not established. The cracking was not considered to be due to environmental stress cracking as this requires the simultaneous action of tensile stress and cracking medium.
Studies on Aluminium Sheets Bonded by Ternary Blends of Poly(Vinyl Chloride), Epoxidised Natural Rubber and Carboxylated Nitrile Rubber with Respect to Dynamic Mechanical Properties and Adhesion Strength
Authors: Kalidaha Amiya K. , De P.P. , Tripathy D.K. , De S.K.
Published: March 2023

The peel strength of aluminium-aluminium joints bonded by an adhesive based on ternary 75/25/175 poly(vinyl chloride)/epoxidised natural rubber/carboxylated nitrile rubber blends was found to depend on moulding time. Dynamic mechanical studies of the Al-blend-Al composite structures provide useful information on adhesion. In addition, the composite structures were found to exhibit broad tan δ spectra from 0.093 to 0.411 over the temperature range from -2°C to 200°C. These composite structures may find use in various vibration isolation applications.
Mesostructures and the Tensile Strength and Fatigue Endurance of Aligned Fibre Composites
Authors: Piggott M.R. , Loken D.
Published: March 2023

Mesostructures are structures which are middle rank in size, and usually unintentional. They provide a direct link between production processing and final properties of a composite. In this study an orientation mesostructure, i.e. fibre waviness, was artificially introduced into aligned carbon fibre composites using optical fibres (80–250 μm in diameter) oriented at right angles to the carbon. Although this caused severe curvature of the fibres, it was over very short lengths (a few microns) and appeared not to be the cause of the reduction in tensile strength of these composites. Instead it was concluded that the fibre crowding effect in the cross section of the optical fibre caused fibre contacts, and hence fibre damage, which weakened the composite. The tensile strengths of the composites without the optical fibres were higher than values quoted by the manufacturers, but were still less than theoretical values, probably due to stress concentrations in the end tabs. Better tensile testing methods therefore appear to be needed before embarking on a more detailed examination of the effect of mesostructures on tensile strength of unidirectional composites. Fibre waviness has also been suggested as a possible initiator of damage during the fatigue of aligned fibre composites. In this work, the presence of the optical fibres induced “ply cutting”. This could have resulted from the fibres in the regions of high fibre volume fraction rubbing against each other. The largest optical fibre caused, in addition, massive splitting of the specimen, in agreement with a mechanism previously proposed for the early stages of fatigue failure of these composites.
Amorphous and Semi-Crystalline Nylon-6: Processing and Properties
Authors: Avramova Nadka
Published: March 2023

The influence of processing conditions on the structure and properties of nylon-6 are investigated. Amorphous nylon-6 is obtained and its properties are compared with those of semi-crystalline nylon-6.

The kinetics of crystallization of nylon-6 depends strongly on the previous thermal prehistory of the melt. The recently observed cumulative character in the structural memory of nylon-6 is successfully applied for obtaining this polymer in a pure amorphous state. It was demonstrated that a critical temperature exists above which the “memory” of this polymer can be erased, and this critical temperature is close to the equilibrium melting temperature T m°. The value of T m ° ≍280°C was evaluated using an independent technique. Melt annealing above this temperature suppresses the crystallization process due to destruction of all crystal nuclei. Amorphous nylon-6 was obtained by ultraquenching of its melt, previously treated at a temperature above T m °, to a temperature well below the glass transition region.

The ultraquenched nylon-6 is characterized by amorphous initial structure and improved mechanical properties. The thermal behaviour, crystallization and mechanical properties are investigated by differential scanning calorimetry (DSC), wide angle X ray scattering (WAXS) and mechanical testing. After drawing and annealing, the tensile strength and elasticity modulus of initially amorphous nylon-6 increase three times and the elongation at break decreases by half as compared with conventionally quenched samples.

The thermal treatment in vacuum of semi-crystalline nylon-6 affects both the structure and the molecular weight. It is demonstrated that the most important factor for the improvement of mechanical properties is the orientation in the amorphous regions. The lower die initial degree of crystallinity, the better are the orientation and the mechanical properties of nylon-6. The best mechanical properties of initially amorphous nylon-6 are explained by achievement of better orientation of molecules in the amorphous regions.
Effect of Polyetheretherketone Oligomer on the Mechanical Properties of Polyetheretherketone with Aromatic Liquid Crystalline Copolyester Blends
Authors: Yazaki Fumihiko , Suzuki Kiyotaka , Yosomiya Ryutoku , Zheng Yubin
Published: March 2023

The mechanical properties of blends of polyetheretherketone (PEEK) with an all aromatic liquid crystalline copolyester (LCP) have been investigated. Additionally, PEEK oligomers were added as a third component to the above blends in order to improve the mechanical properties. The flexural modulus and tensile strength decreased except for the blends with low LCP. In contrast, the addition of the PEEK oligomers has little effect on modulus, but flexural and tensile strength were clearly improved and the ESCA absorption caused by carbonyl group was also reduced by addition of PEEK oligomer to PEEK/LCP blend. The improvement of the mechanical properties of the blend may be due to the formation of a crosslinked product which behaves as a good compatibilising agent for PEEK with LCP during the blending process.
The Effect of Mixer Type and Processing Conditions on the Morphology of Polyamide/Polypropylene Blend
Authors: Vainio Tommi P. , Seppälä Jukka V.
Published: March 2023

The effect of mixer type and processing conditions on the morphology of immiscible binary polyamide/polypropylene blend was studied. Blends were prepared in seven different mixers operating at various screw speeds. Changing the screw speed altered the shear stress and mixing intensity applied to the melt, and also the viscosity ratio.

Average panicle sizes of the dispersed phase (PP) and the particle size distributions were determined for extruded and for subsequently injection moulded blends. The number average particle size level achieved in the melt blending was fairly well transferred to the injection moulded blend although the size distribution was broadened after the injection moulding due to the formation of both small (≍1 μm) and large (>10 μm) particles. The morphology of the skin region was very different from that of the core region in both the extruded and the injection moulded blends. The dispersed phase droplet size was dependent on screw speed to some degree. This dependency was greatest for the single screw extruder. Particle size correlated strongly with shear stress, specific mechanical energy input, and mixing intensity of the mixer. Shear stress, we were led to conclude, is a more important factor in controlling the morphology than the shear-rate-dependent viscosity ratio. Mechanical properties of the blends were poor due to weak adhesion at the interface of the blend components. Additionally, we found that melt blending promoted a better and more homogeneous dispersion in the injection moulded blend.
Novel All-Hydrocarbon Thermosetting Resins as Matrix Materials for Carbon and Glass Fibre Composites Materials I: Reinforcements
Authors: Muthiah Jeno , Mathias Lon J.
Published: March 2023

An all-hydrocarbon resin was synthesized using commercially available materials. The resin undergoes spontaneous cure at around 200°C and cationic cure at around 100°C. This resin gives composites with excellent properties when used with glass and carbon fibres. Flexural modulus values (DuPont DMA) of ca 66 GPa were obtained for carbon fibre composites compared to 42 GPa for epoxy/carbon composites made in our laboratories using commercially available materials. The modulus value at 300°C dropped to 10% of the room temperature value for epoxy composites, whereas the new material maintained 60% of its room temperature value. When brought back to ambient temperature, the modulus value had increased to 81 GPa for the new resin samples while that of the epoxy composite dropped to 23 GPa, Glass fibre composites with the new resin performed similar to the analogous epoxy material up to 200°C but maintained their properties up to 300°C while those of the epoxy composite were drastically reduced. Boiling water treatment had a large affect on the epoxy-glass samples but no observable affect on the glass composites made with the new resin. Scanning electron micrographs showed bonding of the new resin to both carbon and glass fibre surfaces. TGA analysis of both resin and composites showed decomposition beginning at 375°C. This new thermosetting resin thus offers a low-cost approach to glass and carbon composites possessing excellent thermal and physical properties, and out standing hydrolytic stability.
The Influence on their Resilience of a Partial Removal of the Deforming Stress on Compressed Elastomers
Authors: Tobisch K.
Published: March 2023

If there is a relatively low reduction in the original deforming stress applied to an elastomer seal which is subjected to a constant compression during its practical use, this may result in a considerable drop in its resilience and the sealing capacity associated with this. The degree of the stress relaxation caused by a specific reduction in the initial deforming stress in addition to the viscoelastic and ageing processes in the elastomer was determined for six vulcanisates and a thermoplastic elastomer during long-term storage at 23, 70 and 1000°C. The stress relaxation values determined in this way were compared to the results of stress relaxation tests performed according to DIN 53 537 (method B). In parallel to the relaxation measurements, a determination was made of the compression set which is obtained if the heated and deformed test pieces are cooled to room temperature in the clamping device before the stress is removed.
Silica nano-composites of Allyl Diglycol Carbonate Resin
Authors: Frounchi M. , Burford R.P. , Chaplin R.P.
Published: March 2023

Composites of poly allyldiglycolcarbonate (ADC) and nano-sized silica particles were investigated in search of an alternative method to improve the fracture toughness of ADC resin. Transmission electron microscope studies revealed relatively uniform dispersion of silica particles in the resin. Dynamic mechanical analysis measurements indicated that an increase in the glass transition temperature of ADC resin was also accompanied by a higher flexure modulus. A small but significant increase in the fracture toughness of the composites was also observed. The fracture surfaces studied by scanning electron microscopy did not reveal silica particles even at very high magnification and appeared to be featureless smooth surfaces.
High-Performance Aromatic Polyimide Fibres. 4. A Copolymer Fibre Containing BPDA-OTOL-PPD (100/70/30)
Authors: Shen Dexing , Wu Zongquan , Liu Jiang , Wang Lixiao , Lee Sangkug , Harris Frank W. , Cheng Stephen Z.D. , Blackwell John , Wu Tzongming , Chvalun Sergei
Published: March 2023

A copolyimide has been synthesized from 3,3',4,4′-tetracarboxybiphenyl dianhydride (BPDA), 3,3′-dimethyl-4,4′-diaminobiphenyl (OTOL) and p-phenylene diamine (PPD) in a mole ratio of 100/70/30 through a one-step polymerization at elevated temperature. It has been spun as fibres by dry-jet wet spinning. The tensile modulus of the fibres reaches 120 GPa, with a tensile strength of 3.2 GPa. Such high tensile properties are the result of the high draw ratio (up to x8) while annealing at 400°C. The homopolyimide (BPDA-OTOL) is found to adopt a triclinic crystal lattice, based on wide angle X-ray and electron diffraction experiments. In the copolyimide, it's crystal lattice is disturbed by the introduction of the PPD comonomer. As the draw ratio of the copolymer fibre is increased, the crystallinity, overall orientation and the apparent axial crystallite sizes also increased, as evidenced by wide angle X-ray diffraction, optical birefringence and density measurements. These structural developments critically affect the tensile properties of the fibres. The glass transition temperature of the copolyimide is 308°C, based on thermal mechanical measurements. Dimensional stability is retained up to about 300°C. At around 100–250°C, a subglass transition is observed in dynamic mechanical measurements, and is assigned as a β relaxation. The activation energy of this relaxation is 140 hJ/mol, based on its frequency dependence. The α relaxation corresponds to the glass transition. As the crystallinity increases with drawing, this relaxation is suppressed due to the restriction of molecular segmental motion.
Processing and Mechanical Properties of Strands of Liquid Crystalline Copolyester and Copolyesteramide
Authors: Kyotani Mutsumasa , Kaito Akira , Nakayama Kazuo
Published: March 2023

Extrusion moulding behaviour, mechanical and morphological properties of thermotropic liquid crystalline copolyester (LCP-A) and copolyesteramide (LCP-B) strands were investigated using a co-rotating twin-screw extruder, tensile testing, x-ray diffraction measurements, and scanning electron microscopic observation. Extrusion pressure and torque of LCP-B strands were larger than those of LCP-A strands under the same extrusion conditions, reflecting a difference in the apparent melt viscosity of the two polymers. The LCP-B strands obtained in this study had more homogeneous diameters, as compared with the LCP-A strands. The irregularity in diameter of the LCP-A strands tended to become smaller with increasing the length-to-diameter ratio (l/D) and output flow rate. The molecular orientation of LCP-B strands rose rapidly with draw ratio and reached almost a plateau at a much lower one, whilst that of the LCP-A strands became slowly higher with draw ratio. The tensile modulus and strength of LCP-B strands increased gradually with a draw ratio, even after the molecular orientation of the strands levelled off. The effect of the draw ratio on the molecular orientation and the mechanical properties of the strands was discussed from a morphological point of view.
Effects of Compatibilisers on the Properties of Polyvinyl Chloride/Nonpolar Rubbers Blends
Authors: Zhang Yinxi , Zhang Yong , Han Shuyu , Zhang Xiangfu , Yang Changqing
Published: March 2023

The effects of some commercial polymers used as a third component on the properties of the PVC blends with nonpolar rubbers, such as BR, SBR, EPDM, NR and reclaimed rubber, were studied. It was found that NBR-18 was a very efficient compatibiliser for PVC/nonpolar rubbers blends in a wide range of blend composition, and the mechanical properties of these blends were significantly improved even when the NBR-18 content was as low as 2%. The presence of NBR-18 in PVC/nonpolar rubbers blends promoted better dispersion of PVC particles in rubber matrix, and the interfacial adhesion between PVC and the rubber phases was significantly improved by the co-vulcanisation of NBR-18 and nonpolar rubbers as well as the same compatibility of PVC with NBR-18. The PVC/NBR-l8lnonpolar rubbers ternary blends have not only good mechanical properties but also good oil and low-temperature resistance and excellent electrical insulation property.
Acoustic Emission Characteristics and Fracture Properties of Epoxy Moulding Compound Filled with Spherical Silica Particles
Authors: Ohta Mutsuko , Nakamura Yoshinobu , Hamada Hiroyuki , Maekawa Zen-ichiro
Published: March 2023

The effects of particle size and surface treatment on the acoustic emission (AE) characteristics and the tensile strength of epoxy resin filled with spherical silica particles were studied. The particle content was 70 wt%. Four kinds of spherical silica particles having different mean sizes in the range from 6–31 μm were used. In order to improve and decrease the adhesion of the interface between particle and epoxy matrix, the particles were treated with silane coupling (A) and silane decoupling (B) agents, respectively. The A- and B-treated particle-filled systems were compared with the untreated particle-filled system. As the particle size increased, the tensile strength decreased and AE events increased. The tensile strength was higher in the order of the A-treated > the untreated > the B-treated systems. Fewer AE events were generated in both A- and B-treated systems than in the untreated system. Scanning electron microscopic observation of fractured surfaces was carried out to clarify the reason of the above results.
New Method of Measurement of Thermodynamic Diffusion Coefficients of Electrolytes in Polymers
Authors: Polishchuk Alexandre Ya. , Zaikov Guennadii E. , Zimina Lidia A. , Lobo Victor MM. , Valente Artur J.M.
Published: March 2023

A new application of the open-ended conductimetric capillary cell for measuring thermodynamic diffusion coefficients of electrolytes in polymers of different hydrophilic character is presented. Diffusion coefficients of potassium chloride in hydrophilic (PVA) and hydrophobic (POxB) polymers have been measured and prove the applicability of the cell to measure diffusion coefficients in polymer-solvent-electrolyte systems. The theoretical basis of the method is the formulation of diffusion equations in terms of the chemical potential gradient of the diffusing species, and the validity of this approach has been justified by experimental results.
Moisture Absorption and its Influence on the Tensile Properties of Glass-Fibre Reinforced Polyamide 6,6
Authors: Akay M.
Published: March 2023

The equilibrium amounts of moisture absorbed by a range of grades of glass fibre reinforced polyamide 6,6 were approximately proportional to the weight fraction of the polymer. However, the moisture diffusivity was found to be also a function of variations in specimen preparation and microstructure. The diffusivities of the moulded composite specimens indicated a law of mixtures relationship; whereas those with machined edges differed significantly.

Moisture-induced deterioration of tensile strength was most severe up to 1.5% and 3% by weight moisture contents for the glass-fibre containing and unfilled polyamide 6,6, respectively. Moisture ingress, as would be expected, resulted in increased elongations to failure for the unfilled polymer but caused almost no variation in the elongation behaviour of the reinforced polymer.
Agricultural Wastes as a Base for Synthesis of Vinyl Polymer-Cellulose Composites
Authors: Hebeish A. , El-Sisi F. , El-Halwagy A. , El-Kashouti M. , Omar H.
Published: March 2023

Cellulose pulps prepared from bagasse, rice straw, cotton stalk and wood sawdust were polymerized in the presence of acrylic acid(AA) and acrylonitrile(AN) with binary mixtures. Potassium persulphate was used as the initiating system. The treatment was carried out under different conditions including concentration of AA and AN, composition of AA/AN binary mixture, potassium persulphate concentration, material to liquor ratio, time and temperature of polymerization. Based on the results obtained, appropriate conditions for the preparation of vinyl polymer-cellulose composites were established. The maximum total conversion occurred at 0.5% K2S2O8 along with 5% AA and 5% AN at 70°C for 60 minutes using a material-to-liquor ratio of 1:20. The treated samples were monitored for polymer yield, carboxyl and nitrogen contents as well as swellability and solubility. Results indicated that the total conversion (grafting and homopolymerization) increased by increasing K2S2O8 concentration irrespective of the land of cellulose pulp used. Nevertheless the percent polymer yield and percent graft yield follow the order: > Bagasse > rice straw > cotton stalk ≥ wood sawdust. The nitrogen content is higher the higher the concentration of AN in the AA/AN binary mixtures regardless of the kind of agricultural waste. Carboxyl content is higher, the higher the concentration of AA in the AA/AN binary mixture. The swellability of the composite is governed by the composition of the AA/AN binary mixture and it is higher, the higher the concentration of AN in the AA/AN binary mixture irrespective of the kind of cellulose source, but with the certainty that swellability of the composites follows the order: Bagasse > rice straw > cotton stalk > wood sawdust. The solubility of the composite is also governed by the composition of AA/AN binary mixture and it is higher the higher the concentration of the AA in the mixture and follow the order: Rice straw ≥ wood sawdust > cotton stalk ≥ bagasse
Thermostabilisation of Polyisoprene by Phenol Grafting in Carbene Synthesis
Authors: Davydov E.Ya. , Pustoshnyi V.P. , Vorotnikov A.P.
Published: March 2023

The comparison between traditional and grafted antioxidants shows that grafted antioxidants has qualitative advantages.

DTBP produces the most promising results in the study. The results suggest that hindered phenols grafted by carbene synthesis on macromolecules will stabilise P.I. and other elastomers.
Biocompatibility Testing of Thermoplastic Elastomers for Use in Hard Tissue Replacements
Authors: Helsen J.A. , Jaecques S. , Simon J.-P. , Mattheeuws D.
Published: March 2023

The resistance of two types of thermoplastic elastomers to the near-realistic combined action of compressive and shear fatigue was assessed as part of an overall study of the biocompatibility of this class of elastomers. After fatigue the SEM of the low temperature fractured surface, the kinetics of swelling in a 3% acetic add solution, the dynamic mechanical properties (DMTA), the change in crystallinity (by FT-IR and WAXS) and the change in size of the voids (SANS) revealed subtle but small fatigue damage after cyclic loading between 150 and 1500 kPa over about 107 cycles. It may be concluded tentatively that the elastomers studied are potential candidate materials for endoprosthetic use.
Lap Joint Theory Revisited
Authors: Jones R. , Chiu W.K. , Tomas J. , Trippit B.
Published: March 2023

This paper discusses the stress analysis of adhesively bonded joints and therefore, by analogy, bonded repairs. Attention is focused on the effects of the rate dependence of structural adhesives and it is shown that the use of rate independent solutions to obtain the adhesive shear stresses and shear strains, cannot be said to be generally conservative.
Grafting of Acrylamide to Loomstate Cotton Fabric Using Potassium Permanganate-Thiourea Redox System
Authors: Abdel-Hafiz S.A.
Published: March 2023

Graft polymerisation of acrylamide (Aam) to loomstate cotton fabric using a KMnO4 H2N-C-NH2 system was studied under a variety of conditions. The polymerisation reaction was studied with respect to graft yield, homopolymer total conversion and graft efficiency. Results indicated that the polymerisation reaction was found to depend upon the concentrations of potassium permanganate, thiourea and acrylamide, as well as upon the pH of the reaction medium, reaction time and temperature of polymerisation. Based on detailed investigation of these parameters, the optimal grafting was obtained with 0.04 g/1 kMnO4; 0.06 g/1 thiourea; pH 3; temperature 80°C and time 60 minutes.
The Role of Particle Strength and Filler Volume Fraction in the Fracture of Alumina Trihydrate Filled Epoxy Resins
Authors: Phipps M.A. , Pritchard G. , Abou-Torabi A.
Published: March 2023

The critical strain energy release rate, Glc, and the critical stress intensity factor or fracture toughness, Klc, of alumina trihydrate (ATH) filled epoxy resin have been determined as a function of filler volume fraction, using tapered double cantilever beam and single edge notch geometries respectively. GIc showed a maximum at a filler volume fraction of approximately 0.18. The fracture toughness increased linearly up to a filler volume fraction of 0.55. It is proposed that the predominant toughening mechanism depends on the volume fraction of filler and that ATH particles are strong enough for crack pinning to constitute the main toughening mechanism in the intermediate volume fraction region. At low volume fractions and with unstable crack propagation, crack blunting is also important. When the volume fraction is very high, ductile responses by the resin matrix are less easy and particle fracture becomes common, reducing the scope for crack pinning. The value of the breakaway parameter in the crack pinning model of Green was estimated in terms of the particle size.
The Effect of Internal Structural Changes on the Properties of Multi-Layer Fabrics for Composite Reinforcement
Authors: Hill B.J. , McIlhagger R. , Harper C.M.
Published: March 2023

This paper considers the factors involved in the weaving of interlinked multi-layer fabrics. It details the methods employed to form the interlinking structure in an integrated 4-layer reinforcement, why these particular methods were chosen and how the information can be used to produce similar interlinked reinforcements with different proportions of yarn in the through-the-thickness (Z) direction. Test results for the fabrics are enumerated.
Control of Additives
Authors: Merkx Stephan
Published: March 2023

The European Commission has been working on the harmonization of food contact regulations of the individual EU Member States for over two decades. Harmonization has been achieved in the area of regenerated cellulose film and ceramics and for some aspects of plastics. A considerable amount of food contact legislation is still to be formulated and there is enough reason to look back at the achievements in the field of Community food contact legislation, and to learn from the experience gained so far. The legislative system for plastics food contact materials as it has been developed so far is becoming very sophisticated and it must be feared that it is going to lose touch with reality. Regulations are getting tougher and more specific whilst the quality of plastics food contact materials is continuously improving as a result of constant progress in plastics technology. This paper describes the position of additives in plastics - an area still to be harmonized - and gives recommendations on how future Community food contact legislation on additives in plastics could be formulated taking into account aspects of practicability and enforceability, without compromising public health.
Shrinkage Control in Fibre Reinforced Polymers I: Toughness Improvements Expected
Authors: Piggott M.R.
Published: March 2023

The fracture toughness of polymer composites made with glass and carbon fibres is not very great; they tend to split and delaminate easily and can also break easily across the fibres. While delamination resistance can be markedly improved by using tough polymers, this is not the case with across-the-grain toughness. Instead, the polymer shrinkage stress needs to be reduced. In this paper an earlier theory on the effect of the polymer shrinkage stress on toughness is developed further to eliminate some approximations and to take account of the fibre debonding process. It is shown that debonding can be a factor which limits the toughness achievable. Thus, although very large increases in toughness are possible if the shrinkage stress is reduced to an optimum value, the actual toughness that can be achieved is determined by the fibre-matrix bond strength. Consequently a well bonded composite can only be toughened to a limited extent: further improvements are dependent on weakening the bond, with consequent loss in shear strength. Nevertheless, there is a window of opportunity for toughness improvement if the shrinkage pressure can be controlled by chemical or other means.
Micro-Organism Adhesion to Polymer Surfaces and its Role in Biodegradation
Authors: Gumargalieva K.Z. , Kalinina I.G. , Mironova S.N. , Zaikov G.E.
Published: March 2023

Fourier Transform infra red spectra of conidien microscopic fungi, capable of accumulating on and degrading polymers, have been studied, and an interpretation is provided. It is possible to define and predict their hydrophoby, which is the crucial factor in microorganism adhesion to solid (e.g. polymer) surfaces, and hence in biodegradation.
Effect of Particles on the Wear and Friction of Glass Fibre Reinforced Plastic Composites
Authors: Srivastava V.K. , Pathak J.P.
Published: March 2023

The main work of the present research program is to study the wear and friction properties of mica and mica/zirconia filled unidirectional glass-fibre-reinforced epoxy resin composites as a function of the filler content and driving load. Wear and friction coefficient rate decrease with increasing filler contents. But the increase was found only after reaching the optimum ratio of filler and fibre-epoxy contents.
Macrokinetics of the Degradation of Polyesterurethanes in Model Biological Media
Authors: Trosteniuk N.V. , Gumargalieva K.Z. , Zaikov G.E.
Published: March 2023

The degradation of samples of thrombo-resistant films of segmented polyesterurethanes (Avcothane® and Biomer®) in water and acidic solutions (acidic phosphates) has been investigated. Avcothane, being the copolymer of a segmented polyurethane with polydimethylsiloxane, degraded in water at a noticeable rate, whereas biomer samples were hydrolytically stable. It was shown that degradation from the surface of the Avcothane samples is controlled by decomposition of the siloxane component, as a result of hydrolysis. The values of the decomposition rate constant obtained allowed the authors to predict the time required for degradation of the surface layers of polyesterurethane (Avcothane), responsible for the thromboresistance.
Studies on the Synthesis of Polyarylates with Allylic Side Groups. Part 2. Photocrosslinking of Polyarylates
Authors: Brzozowski Zbigniew K. , Zadrozna Irmina , Kowalczyk Tomasz , Syromyatnikov Vladimir S.
Published: March 2023

Copolyarylates obtained from bisphenol-A and its diallyl derivative formed with isophthaloyl chloride via interfacial polycondensation were investigated. Mechanical test results were used to monitor the process of photocrosslinking. Investigations revealed that the photocrosslinking efficiency of a new monoazide photoinitiator was greater than that of a bisazide. Photoinitiator mixtures were found to improve photocrosslinking relative to solutions containing a single photoinitiator.
The Role of Rate Effects of Adhesives and Graphite/epoxy in Structural Design
Authors: Chiu W.K. , Jones R.
Published: March 2023

This paper discusses the significance of the non-linear mechanical behaviour of a thermoset adhesive, FM73, in the design and analysis of bonded joints. This adhesive is widely used in the bonded repair of metallic aircraft structures. The results presented in this paper include test data conducted at room temperature and at an elevated temperature. The time dependent properties of this film adhesive are shown to be significant even at room temperature. There was considerable stress relaxation observed during strain hold experiments and the adhesive was also found to demonstrate significant creep characteristics during creep tests. The monotonic shear stress/strain behaviour and time dependent characteristics can be adequately described using a unified theory of plasticity. This paper also presents results from a finite element analysis of a adhesively bonded joint. These results show that significant error in the analysis may result during monotonic loading if the rate dependency of the adhesive is not taken into account. This has significant implications in the design and analysis of bonded joints.