Surface modified rubber

Composite Particles, Inc. reported the use of surface-modified rubber particles in formulations of thermoset systems, such as polyurethanes, polysulfides, and epoxies [95], The surface of the mbber was oxidized by a proprietary gas atmosphere, which leads to the formation of polar functional groups like —COOH and —OH, which in turn enhanced the dispersibility and bonding characteristics of mbber particles to other polar polymers. A composite containing 15% treated mbber particles per 85% polyurethane has physical properties similar to those of the pure polyurethane. Inclusion of surface-modified waste mbber in polyurethane matrix increases the coefficient of friction. This finds application in polyurethane tires and shoe soles. The treated mbber particles enhance the flexibility and impact resistance of polyester-based constmction materials [95]. Inclusion of treated waste mbber along with carboxyl terminated nitrile mbber (CTBN) in epoxy formulations increases the fracture toughness of the epoxy resins [96]. 

Bauman R D, Surface-modified Rubber Particles in Footwear, ACS Meeting Rubber Division, Anaheim, CA, 6-7 May, 1997. 

A new approach to modification of thermosetting epoxy or polyurethane systems (Plastics Technology, p. 14 (April 1994)) involves surface modified rubber or UHMW-PE particles. These particles after reaction with Cl, 0 or F allows for improved properties (toughness, tear resistance, abrasion resistance, modified coefficient of friction) in the noted thermosets. 

SMR surface modified rubber SSE sohd-state extrusion... 

Waste rubber tire powder from track and passenger tires was treated by various concentrations of nitric acid and 30% hydrogen peroxide (Yehia et al., 2004). Surface-modified rubber powder was used as a filler in NR mixes. The incorporation of rubber powder up to 20phr in combination with a... 

The subject of rubber as a filler is dealt with in the entry entitled Surface-modified rubber particles for pol)nirethanes. Hydrated alumina, otherwise known as alumina trihydrate (ATH), is considered under the heading Flame retardants inorganic oxide and hydroxide systems. Some mechanical property considerations are dealt with in the entry entitled Fillers their effect on the failure modes of plastics. ... 

Surface-modified rubber particles are commercially available [2]. At the time of writing, the rubber is derived from scrap automotive tyres. Rubber particles consisting of other types of rubber, scrap or virgin in origin, can also be surface-modified. Currently, grades of rubber particles are available in sizes ranging from diameters of 1.5 x 10 m (10 mesh) down to less than 7.5 x 10 m (200 mesh). 

Surface-modified rubber particles are quite hygroscopic. The polar surface readily absorbs moisture from the atmosphere. Laboratory studies have shown that treated rubber particles can absorb as much as 1.4% moisture by weight, and that the particles can absorb moisture at a rate greater than 0.6%/hour when exposed to the atmosphere. As many polyurethane formulations are sensitive to moisture, the treated rubber particles must be dried before use in many systems. 

The physical properties of composites made with surface-modified rubber particles in polyurethanes can be custom tailored over a very broad range. When rubber particles are combined with a pol5mrethane that has a similar hardness, the end properties are comparable. This is exemplified in Table 1, where the properties of a composite consisting of 15% treated rubber particles and 85% pol)mrethane are nearly indistinguishable from those of the base polyurethane. Composites comprising as much as 70% treated rubber particles have been shown to have good engineering properties. 

Property Unfilled polyurethane 15% Surface-modified rubber particles 85% polyurethane ... 

Surface-modified rubber particles are VISTAMER R4060, from Composite Particles, Inc. 

Treated rubber is the only known reinforcing, elastomeric filler. The use of surface-modified rubber, in general, does not make the formulation harder and less flexible. In contrast, most other fillers are inorganic minerals, which reduce the elastomeric properties of a polyurethane formulation. Oils are used as fillers for some polyurethanes and to increase their flexibility. However, oils are certainly not reinforcing fillers, and they significantly reduce overall properties. 

The dynamic properties of polyurethane composites made with treated rubber particles can also be very similar to those of the unfilled polyurethane. Comparison of d5mamic mechanical analysis (DMA) curves for composites composed of surface-modified rubber particles in polyurethane and corresponding curves for the unfilled polyurethane show nearly identical hysteretic heating. End products, such as wheels and rollers, made in either unfilled pol5mrethane or in composites comprising treated rubber particles/pol)mrethane have essentially identical heat build-up in dynamic applications. 

The incorporation of up to about 15% surface-modified rubber particles in polyurethane formulations is generally straightforward and requires little... 

Figure 2 Inclusion of surface-modified rubber particles in pol)oirethane formulation increases the coefficient of friction.

Surface-modified rubber particulates constitute the only known reinforcing, elastomeric filler. These rubber particles can be readily combined with polyurethane to manufacture end-products that have reduced raw material costs and, in some cases, better physical properties. This new class of materials promises to open significant new markets for polyurethanes by altering their performance/price ratio and making them more competitive with other materials. 

---