Novel flame retardant thermoset resin blends derived from a free-radically cured vinylbenzylated phenolic novolac and an unsaturated polyester for marine composites

A phenolic novolac resin has been chemically reacted with 4-vinylbenzyl chloride to introduce polymerizable vinyl benzyl groups. The modified novolac spontaneously polymerizes like styrene, is physically and chemically compatible with a typical unsaturated polyester (UP) resin, and can be free-radically cured (crosslinked) alone and in mixtures with UP using styrene as a reactive diluent. The cured vinylbenzylated novolac and co-cured blends of it with UP show superior flame retardance to cured UP alone and have potential applications as matrix resins in glass-reinforced composite laminates especially for marine structures

Recent developments in fire retardation and fire protection of fibre-reinforced composites

This article reviews recent work on fire retardation and fire protection of fibre-reinforced composites carried out in the laboratories of the Fire Materials Group at the University of Bolton. This work has concentrated mainly on the effects of fire-retardant additives and coatings on the fire performance of unsaturated polyester, vinyl ester and epoxy resin composites reinforced with glass fibres

Fire-resistant flax - reinforced polypropylene / polylactic acid composites with optimised fire and mechanical performances

Fabrics from commingled natural (flax) –thermoplastic (polypropylene (PP) / poly lactic acid (PLA) polymeric fibres were fire retarded with an oragnophosphonate flame retardant (FR). The fire retarded flax/PP and flax/PLA fabrics were melt pressed to prepare respective thermoplastic composites. The effect of FR concentration on the fire and mechanical properties of composites were studied and the results analysed in terms of concentration of FR elements in the composites. While the UL-94 test was used as a benchmark to achieve a V-0 rating, cone calorimetric parameters were used for in-depth analysis of fire performance. The results show that flax/PP and flax/PLA composites require a minimum 0.9 and 0.6 % phosphorus (P), respectively to achieve a V-0 rating in the UL-94 test. Mechanical properties, evaluated in tensile and flexural modes are however slightly impaired, most probably due to the acidity of the FR solution (pH = 3.2). In order to improve the mechanical properties, a buffer solution was used to change the pH to 6.0, which while having a minimal effect on mechanical properties of flax/PP, significantly reduced those of flax/PLA, and increased flammability of both composites and hence overall showed no benefit

Organophosphorus and organo-inorganic hybrid fire retardant coatings for polymers

Thin coatings of crosslinked poly(vinylphosphonic acid) display good adhesion and excellent fire-retardant barrier properties when applied to the surfaces of a typical thermoplastic, such as poly(methyl methacrylate), but perform relatively poorly in water-soak tests. Water-soak test performance can be significantly improved however by various hydrophobic modifications without detriment to fire performance

A cure modelling study of an unsaturated polyester resin system for the simulation of curing of fibre-reinforced composites during the vacuum infusion process

This study presents the cure kinetics and cure modelling of an ambient curing unsaturated polyester (UP) resin system for its cure simulation in the vacuum infusion (VI) process. The curing of the UP resin system was investigated using differential scanning calorimetry (DSC). The dynamic DSC test measurements were conducted to find out the ultimate heat of reaction and enable experimental conversion determination for the isothermal curing. The empirical autocatalytic cure kinetics model incorporating the Arrhenius law represented the cure behaviour. The results of the cure kinetics study, the cure model, the material properties and the boundary conditions were the inputs in PAM-RTM software for the simulation of the degree of cure and the exothermic temperature during the infusion and the room temperature curing stages. The simulation results were compared with experimentally measured data. A vacuum infusion (VI) experiment involving a non-crimp glass fibre preform was performed in order to monitor the curing using thermocouples and validate the temperature simulation result. It was shown that the degree of cure and the exothermic temperature of a room temperature curing thermoset resin system during the VI process could be predicted through the steps of this study

Multilevel Safety Climate in The UK Rail Industry: A Cross Validation of the Zohar and Luria MSC Scale

Despite a downward trend in injury rates in UK workplaces, accident occurrence remains an on-going issue for the rail workforce. Results from the RSSB annual survey reveal that there were 164 major injuries in 2016/17. Safety climate is defined as “shared perceptions with regard to safety policies, procedures and practices.” Many studies have examined the positive effects of safety climate on safety performances by individuals, teams, organizations. Despite widespread attempts to measure safety climate, the validity of measurement tools has not been systematically tested in the rail industry. The primary goal of our research was to validate Zohar and Luria’s (2005) Multilevel Safety Climate Scale in a sample of rail infrastructure workers (N = 528). A cross-validation strategy was adopted. Half of the data were used to conduct exploratory factor analysis (EFA), with the remaining data submitted to confirmative factor analysis (CFA). The statistical results reveal a three-factor structure with organizational safety climate (OSC), supervisor safety communication (SSC), supervisor safety monitoring (SSM). A nomological analysis showed that SSC and SSM presented distinct correlation patterns with other measures of relevance for safety, risk and health management. SSM was found more strongly related with variables such as: safety priorities; safety systems; reporting attitudes; safety compliance. On the other hand, SSC was mainly related with measures refereed to distinct forms of organizational support: supervisor support; peer support; support to change. Overall, our findings showed the validity of a multidimensional approach on the study of safety climate and safety supervision in the rail industry

Physical activity across age and study: a guide to data in six CLOSER studies

Explore the measures used to assess diverse aspects of physical activity within and across six CLOSER partner studie

Thermal degradation analysis and XRD characterisation of fibre-forming synthetic polypropylene containing nanoclay

Flammability of synthetic fibres is significantly worse than that of bulk polymers because of the high surface area to volume ratio and the low tolerance to high filler loadings in the fibre production process. Introducing nanocomposite structures has the potential to enhance the char formation at relatively low loadings of nanoparticulate fillers and hence can reduce the flammability of synthetic polymers and fibres. This paper reports thermal degradation analysis results in conjunction with TG analysis under different atmospheres and further studies of X-ray diffraction characterisation of fibre-forming polypropylene containing selected dispersed nanoclays. The concentrations of hydrocarbons, carbon monoxide and carbon dioxide released during the TG analysis have been monitored and analysed by using a combined electrochemical infrared analyser. The intensity changes of the crystallinity peaks and nanoclay peaks in the polymer and composites are discussed

Thermal stability, flammability and mechanical performances of unsaturated polyester–melamine resin blends and of glass fibre-reinforced composites based on them

A novel blend of unsaturated polyester (UP) resin with an inherently flame-retardant and char-forming melamine formaldehyde (MF) resin has been prepared with the aim of reducing the flammability of the former. MF resin, sourced as a spray-dried resin, was dissolved in diethyleneglycol solvent; the dissolved resin and the UP-MF blend were autocured by heating under conditions normally used for curing UP, i.e., room temperature for 24 h and post-curing at 80 ◦C for 12–24 h. The cured UP-MF blends, although heterogeneous in nature, were rigid materials having fire performances superior to those of the cured UP alone. The blends also burned, but with a much reduced smoke output compared with that from UP. Although the heterogeneity of the blends helped in improving the fire performances of the blends in terms of the MF domains forming a semi-protective char, acting as thermal barriers for the adjoining UP domains, and hence reducing their thermal degradation, the mechanical properties of composites based on them were impaired. Nevertheless, whilst UP/MF blends may not be suitable for use as matrices in glass-reinforced composites in load-bearing applications, they may lend themselves to applications as fire-retardant gel coats, especially in view of their low-smoke, char-forming attributes

On the utility of thermogravimetric analysis for exploring the kinetics of thermal degradation of lignins

The kinetics of pyrolysis of organosolv (TcA) and hydroxypropyl-modified (TcC) lignins have been investigated using thermogravimetric analysis (TGA). Three isothermal models (single first order, Guggenheim and Avrami-Erofeev) and one non-isothermal model (Kissinger) were used to analyse the mass-loss data. Sensible derived kinetic parameters, i.e., activation energy and pre-exponential factor, were obtained only for the initial stages of pyrolysis where the kinetics were approximately first order. Models that analysed TGA data beyond the initial stage gave inconsistent results, indicating the complexity of subsequent decomposition steps occurring at higher temperatures and/or longer times. The kinetics of the initial stage are important for designing routes to lignin's valorisation into useful products, such as carbon fibres, activated carbons, polymer additives, etc. TcC had a higher activation energy (41.5 kJ/mol) for initial decomposition than TcA (39 kJ/mol), consistent with its greater thermal stability observed previously during conversion of lignin-based fibres into carbon fibres