Polytek PT Flex 85 – Flexible Polyurethane Casting Rubber Shore A85 for Moulds & Production Parts

PT Flex 85 is a pourable two-component polyurethane rubber that cures at room temperature (RTV) to a flexible rubber with a Shore A85 hardness, a yellow/amber end product and very high tensile strength and abrasion resistance. With a working time of 5 minutes and a demould time of approximately 2 hours at 23°C, this product offers the process reliability professional mould makers require. The mix ratio is 1:1 (A:B) by weight. Full physical properties are reached after a post-cure of 16 hours at 60°C or 7 days at room temperature. PT Flex 85 is ideally suited to applications where dimensionally accurate reproduction, repeated demoulding and long mould service life are essential.

Key Benefits

• Hardness Shore A85: flexible yet dimensionally stable rubber – suitable for moulds with undercuts and repeated release.
• Tensile strength 5,81 MPa (842 psi): withstands repeated demoulding – longer usable mould life.
• Elongation at break 183%: easy demoulding of complex geometries without distortion.
• Tear strength 34,0 N/mm (194,2 pli): high resistance to tearing at deep undercuts.
• Linear shrinkage 0,16%: dimensionally accurate castings with fine detail retention.
• Working time 5 minutes: fast production throughput with demoulding after approximately 2 hours.

Typical Applications

• Production of casting moulds for plaster, wax, resin and concrete at art foundries and design studios
• Prototyping, model making and rapid prototyping
• Prop and set building for film, theatre and events
• Reproduction of sculptures, reliefs and ornaments in art and restoration
• Short-run casting and production of functional parts
• Castings in large masses where repeated moulds are required

Processing Instructions:

1. Ensure components A and B are at room temperature. Briefly stir component B if the label indicates.
2. Accurately weigh the components in a ratio of 1 part A to 1 part B (by weight).
3. Mix thoroughly by hand with a flat stir stick, scraping sides and bottom, until a homogeneous, streak-free mass is obtained. Avoid mixing in air.
4. Optionally degas the mixture briefly in a vacuum chamber to remove air bubbles; recommended for fine reproduction detail.
5. Pour the mixture within the 5-minute working time slowly from a single point into the mould.
6. Cure at minimum 15°C. Demould after approximately 2 hours; full properties after a post-cure of 16 hours at 60°C or 7 days at room temperature.

Manufactured by Polytek® Development Corp., US manufacturer of high-quality casting and mould-making materials for professional and industrial applications.

Important Warning: Diisocyanates and Moisture Sensitivity

Note: this product contains diisocyanates (MDI) in component A and is classified as Danger. It may cause an allergic skin and respiratory reaction and is suspected of causing cancer. Work only in a well-ventilated area and wear nitrile or butyl rubber gloves, eye and face protection and protective clothing; use respiratory protection if ventilation is inadequate. Since 24 August 2023, the EU REACH restriction (2020/1149) requires professional and industrial users to have completed valid diisocyanate training. Both components react with atmospheric moisture: reseal packaging immediately after use and store dry between 15 and 35°C. Read the safety data sheets for components A and B before use.

Professional Support

PT Flex 85 is a reliable choice for professional mould makers requiring reproducible results. Unsure whether it suits your model or casting material? Perform a test cure on an identical surface, or contact Silicones and More for advice on processing, release agents and hardness selection.