Recent Advancements towards Sustainability in Rotomoulding.

Rotational moulding is a unique low-shear process used to manufacture hollow parts. The process is an excellent process method for batch processing, minimal waste and stress-free parts. However, the process has drawbacks such as long cycle times, gas dependency and a limited palette of materials relative to other process methods. This review aimed to shed light on the current state-of-the-art research contributing towards sustainability in rotational moulding. The scope of this review broadly assessed all areas of the process such as material development, process adaptations and development, modelling, simulation and contributions towards applications carving a more sustainable society. The PRISMA literature review method was adopted, finding that the majority of publications focus on material development, specifically on the use of waste, fillers, fibres and composites as a way to improve sustainability. Significant focus on biocomposites and natural fibres highlighted the strong research interest, while recyclate studies appeared to be less explored to date. Other research paths are process modification, modelling and simulation, motivated to increase energy efficiency, reduction in scrap and attempts to reduce cycle time with models. An emerging research interest in rotational moulding is the contribution towards the hydrogen economy, particularly type IV hydrogen vessels.

A new mathematical model derived from transient (creep) analysis to estimate the vaginal retention of semi-solid dosage forms.

The performance of vaginal drug delivery systems is dependent on their retention. This study presents a novel mathematical method to estimate the vaginal retention of semi-solids. Using creep analysis, the elastic and residual compliances are determined from the discrete retardation spectrum and used to determine the retention times (RT), defined as the time required for the formulations to enter the terminal viscous zone of deformation and hence flow. RT of commercially available products (CAP) and selected prototype formulations were determined, the estimated RT of CAP broadly aligning with their prescribed clinical usage. Candidate formulations composed of hydroxyethylcellulose (HEC, 3%/5%w/w) and polyacrylic acid (PAA, 1%/3%w/w) were manufactured using, and further diluted with simulant vaginal fluid (SVF) or simulant seminal fluid (SSF) and their RT subsequently determined. Increasing polymer concentration and pH enhanced the estimated RT whereas dilution reduced RT. Notably, the formulation composed of 5%HEC/3% PAA (SSF) maintained its RT on dilution due to swelling of suspended PAA particles, thus representing a strategy to develop vaginal semi-solids that are resistant to dilution and hence removal. The mathematical model described is reproducible, straightforward to use and is recommended as a tool in formulation development to estimate the retention of vaginal semi-solids.

The modification of PLA and PLGA using electron-beam radiation.

The degradable polymers polylactide (PLA) and polylactide-co-glycolide (PLGA) have found widespread use in modern medical practice. However, their slow degradation rates and tendency to lose strength before mass have caused problems. The aim of this study was to ascertain whether treatment with e-beam radiation could address these problems. Samples of PLA and PLGA were manufactured and placed in layered stacks, 8.1 mm deep, before exposure to 50 kGy of e-beam radiation from a 1.5 MeV accelerator. Gel permeation chromatography testing showed that the molecular weight of both materials was depth-dependent following irradiation, with samples nearest to the treated surface showing a reduced molecular weight. Samples deeper than 5.4 mm were unaffected. Computer modeling of the transmission of a 1.5 MeV e-beam in these materials corresponded well with these findings. An accelerated mass-loss study of the treated materials found that the samples nearest the irradiated surface initiated mass loss earlier, and at later stages showed an increased percentage mass loss. It was concluded that e-beam radiation could modify the degradation of bioabsorbable polymers to potentially improve their performance in medical devices, specifically for improved orthopedic fixation.