Materials Scientist – Polymer Processing £35,000–£45,000 (DOE) | Sheffield, UK | Full-time, Permanent
Join us in developing the next generation of sustainable materials.
Phast is an innovative materials company developing advanced bio-based polymers for high performance applications. Our mission is to replace conventional fossil-based plastics with sustainable alternatives without compromising performance.
We're looking for an experienced Materials Scientist to lead the development and scale-up of novel polymer formulations and processing from laboratory concept through to industrial manufacture. This is a hands-on role suited to someone who enjoys solving complex processing challenges and working with extrusion, compounding and polymer characterisation.
This position offers a unique opportunity to influence the development of entirely new material platforms that will be commercialised internationally.
The Role
You will work at the interface of materials science, polymer engineering and manufacturing, taking ownership of formulation development and processing optimisation. Your responsibilities will include:
• Designing and developing new polymer formulations based on bio-based and biodegradable polymers
• Operating and optimising twin-screw extrusion process
• Developing compounding recipes using fillers, fibers, plasticizers, impact modifiers and functional additives • Scaling formulations from laboratory to pilot and manufacturing scale
• Optimising extrusion parameters including: ◦ Screw configurations ◦ Temperature profiles ◦ Residence time ◦ Throughput ◦ Shear history
• Processing materials using extrusion and, where appropriate: injection moulding, compression moulding, thermoforming, film extrusion and filament production
• Characterising polymers using mechanical, thermal and rheological techniques • Interpreting material data to guide formulation improvements
• Working closely with commercial partners and equipment manufacturers during process development • Maintaining laboratory equipment and ensuring high quality experimental records
• Supporting intellectual property generation and technical documentation
• Contributing to grant-funded R&D programmes and collaborative industrial projects
• Ability to travel within UK/EU (up to 10% of the time)
About You
We're looking for someone who enjoys practical development work and has a passion for sustainable materials.
Essential Requirements • MSc or PhD in Materials Science, Polymer Engineering, Polymer Chemistry or a related discipline • Industrial experience developing polymer formulations • Experience operating twin-screw compounders • Strong understanding of polymer processing principles • Experience with thermoplastics processing • Experience with reactive extrusion techniques, such as maleic anhydride grafting for compatibilisation, peroxide-initiated chain modification, in-situ polymer compatibilisation, chain extension of biodegradable polyesters, and reactive coupling with fillers or fibres • Knowledge of polymer additives and their functions • Experience analysing mechanical and thermal material properties • Ability to independently design and execute experiments • Strong problem-solving skills • Excellent written and verbal communication skills
Desirable experience Experience in one or more of the following would be advantageous: • Bio-based polymers • Biodegradable polymers • Polyhydroxyalkanoates (PHAs) • Design of Experiments (DoE) • Statistical analysis • Rheology, DMA, DSC, TGA, FTIR, SEM
Personal qualities You are someone who: • Enjoys working in a fast-paced start-up environment • Likes solving challenging technical problems • Is curious and innovative • Takes ownership of projects • Works well independently and within multidisciplinary teams • Is practical and enjoys laboratory work • Is motivated by developing products with real environmental impact
What We Offer
• Salary of £35,000–£45,000, depending on experience • Starting date: September 2026 • Pension contribution • 25 days annual leave plus bank holidays • Opportunity to work with cutting-edge sustainable materials • Significant career progression within a rapidly growing company • Exposure to international collaborations and commercial product development • Opportunity to contribute to patented technologies and new product launches • Office and lab facilities at The Innovation Centre, 217 Portobello, S1 4DP, Sheffield, UK
Why Join Phast?
At Phast, we're building the future of sustainable polymers. Our technologies aim to eliminate persistent plastic waste while delivering the performance required by demanding industrial applications. You'll join a small, ambitious team where your ideas will directly influence the direction of the company, the products we develop, and the impact we make. If you're excited about translating innovative materials research into real-world products, we'd love to hear from you.
To apply, please send your CV and a brief cover letter outlining your relevant experience and interest in the role to [email protected]