Creating Solutions that Bond

Published 10-18-2022 

By: Bryan R. Morris, Senior R&D Engineer & Nastausha Hefner, Marketing Manager - STOCKMEIER Urethanes USA, Inc.

STOCKMEIER Urethanes’ Stobicoll® R polyurethane (PUR) binders are moisture cured, single component, systems available in pigmented and unpigmented liquid-form. Our low requirements of binder-to-rubber provide vibrant color and superior bonding in finished applications such as: 

  • Wheel stops 

  • Speed bumps 

  • Handicap ramps 

  • Sign bases 

  • Pavers for playgrounds and decks 

  • Parking chocks 

  • Bumper plates (barbell weights) 

  • Landscape edging 

  • Sports flooring 

  • Your custom idea! 

When considering the Stobicoll® R portfolio of products, the question isn’t if we have the right binder, it’s which binder will perform ideally with your processes and desired end-properties. We have something for every application! Our binders are available in 100% PUR and economical varieties that deliver quality and performance to every cycle. Every product in the Stobicoll® R line of binders is designed to offer the best balance of: 

  • Premium quality - flexibility, toughness and durability 

  • Ease of processing - extended working time with fast back-end cure (reduces precure and decreases scrap) 

  • Competitive pricing 

  • Aromatic and aliphatic grades available to suit any end requirements 

With over 30 years of experience, STOCKMEIER Urethanes is the leader in the market of bonding recycled tire. Utilizing our expertise in this market, our sales and technical staff work directly with our customers to understand current processes and end-product demands to not only satisfy all expectations but to exceed them. If you’re experiencing an issue with your current material or process, please reach out to us! We are experts at trouble shooting, and certainly have the right product for your application.  

Polyurethane Binder Basics 

What is a polyurethane binder? A polyurethane binder is a liquid urethane that reacts with moisture to form a tough and flexible film. The liquid PUR reacts by externally added moisture and/or by reaction through atmospheric moisture. The higher the ambient humidity and heat, the faster the reaction time. Adversely, low heat and ambient humidity will prolong the cure time of the material. There are seven principal criteria that will affect the cure speed of a moisture-cure binder: 

  • Ambient temperature and/or added heat 

  • Ambient humidity - Reaction conditions with the same material being used in arid climates will be different than those in humid climates leading to differences in binder reactivity. 

  • Added moisture - either directly or indirectly from the moisture content of the rubber feedstock or any other aggregate being bound 

  • Pressure applied during molding process -higher pressure provides more compression and increased heat transfer 

  • Mixing intensity - high shear creates frictional heat 

  • Binder selection - we offer slow to fast setting chemistries 

  • Added catalysts such as our Stobiblend Z series  

The packaged material should be stored in a dry area. The lids and fittings should be tightly sealed after use. Valves should be thoroughly cleaned after each use to avoid seizing the fittings by cured material. Stobicoll® R binders are moisture-cure systems. If the product is contaminated with moisture, including ambient moisture from the air, the material will start to cure which could lead to skin on the surface. Pails, drums or totes not adequately sealed, could result in an increase in viscosity and/or loss of final mechanical properties. 

Processing Polyurethane Binders 

STOCKMEIER binders can be supplied in tanker quantities, 275-gallon totes, 55-gallon drums and 5-gallon pails. When draining material from the supplied packaging, particularly drums and totes, air will be drawn in as the material is drawn out. If the relative humidity is high, the air that is drawn in will contain a high content of moisture which can then react with the remaining material inside of the packaging. This reaction can lead to a thickening of the material and skin formation. Thickened material may be more difficult to process, and a skin could clog the discharge valve, hose or pump that the material is flowing through. To avoid moisture contamination, we strongly encourage the use of desiccants. Desiccants are pellets capable of removing the moisture from the air and are supplied in disposable or refillable cylinder-cartridges that are equipped with tote or drum fittings. The desiccant cartridge allows for the flow of air through the packaged material while effectively removing the moisture. 

Unpigmented binders, which range in color from clear to dark brown, are mainly used to bond precolored aggregate or rubber crumb. Due to economics, aromatic binders are the product of choice for most applications where color stability is not the dominating concern. When true color fastness is desired, the use of an aliphatic binder is strongly recommended. Aromatic binders will discolor or “yellow” after extended exposure to UV whereas our aliphatic materials are completely color-stable over time. The yellowing or ambering effect is the result of oxidation of the aromatic materials. While there is an aesthetic effect, the properties of the bound part are not impacted. Care should also be taken with the rubber or aggregate that is chosen (EPDM, TPV, etc.). If the pigments used to color these materials are not UV stable, a loss of color and vibrancy is possible over time regardless of the binder used. 

STOCKMEIER Urethanes is the leader in pigmented, PUR binders. These materials both color and bind the aggregate at the same time. Our customers can combine two or three processes into one step mitigating excess material inventory and processing, avoiding the addition of non-stable solid pigments or liquid coatings, which can be messy and prone to user addition-variation, to achieve optimal coverage and color brilliance. Utilizing only the highest UV-stable pigments and specialized dispersion processes, our products provide high hiding-power at low consumptions with a variety of color options. Our pigmented binders are engineered with anti-sedimentation characteristics but remixing after extended storage, particularly at elevated heat, is strongly recommended for optimum color uniformity and intensity. Recommended mixers will have a lid that threads on the tote lid. This lid minimizes the contact of moist air with the binder. Over mixing should be avoided particularly in hot and humid environments. Over mixing provides no benefit and can cause unnecessary inclusion of atmospheric moisture.   

Polyurethane Binders Provide a Second Life to Recycled Tires  

Finding methods to mitigate the materials that go into landfills is critical to the health of our communities and planet. Before tires were recycled and utilized to make colored rubber for playgrounds and mulch (and a variety of other consumer goods), they would go straight into the landfill. It is mind boggling to think that around 280 million tires are discarded each year by American motorists.1 Converting these tires to crumb and buffings allows for the tires, which were once garbage and an environmental concern, to be converted into commodities that created wealth and jobs. It doesn’t get much better than that! 

Polyurethane and Rubber Sign BasesWhile many things that make their way into the trash are biodegradable and decompose over time, tires certainly do not fall into this category. Tires are engineered to last. Their hollow and curved shape fill excessive space and causes them to settle unevenly and rise to the surface which in turn can harm landfill covers. Due to their chemical composition, tires are excellent retainers of heat. This retention of heat comes with the risk of ignition and, once tire rubber begins to burn, it is extremely difficult to extinguish. Flames from the burning of tires in large quantities can release dense and unhealthy smoke. Granulating the tires into smaller sizes and converting them into molded parts mitigates or eliminates this possibility. STOCKMEIER Urethanes takes great pride in its goal to one day eliminate the disposal of tires going into landfills. Turning waste into value and jobs is The Smart Solution!