Comparative Study Report of SBR Latex and Other Adhesives

SBR latex is widely used in the backing of tufted and woven carpets due to its strong adhesion, good wear resistance, and low cost. In comparison, acrylic latex, natural latex, and polyurethane (PU) adhesives each have their own advantages and disadvantages. Below, we conduct an in-depth comparative analysis of these adhesives from six perspectives—adhesion performance, wear resistance and flexibility, cost and supply stability, environmental aspects (VOC emissions/biodegradability), processing performance, and application examples—and conclude with recommendations on their suitable application scenarios and development trends in carpet manufacturing.

1. Adhesion Performance

• SBR Latex: Exhibits excellent bond strength. Industry sources indicate that SBR latex generally provides higher adhesion than other latex types, forming strong bonds with various substrates (e.g., polypropylene spunbond, polyester felt, jute backing) as well as carpet fibers. In tufted and woven carpet production, carboxylated SBR latex (XSB) is commonly used as a backing adhesive, offering high initial tack and outstanding shear resistance to lock the carpet pile in place.

• Acrylic Latex: Also offers high adhesion. Product datasheets highlight that acrylic latex can accommodate higher filler loadings and delivers “excellent bonding” and “outstanding tuft-locking strength” on fibers and backing materials. This makes acrylic latex advantageous in applications requiring strong bonding and pile stability. In practice, acrylic latex is widely used in the third layer of carpet backing (film backing) or in “crosslinked backing” processes, and it can also serve as a fiber-bonding adhesive.

• Natural Latex: Natural rubber latex has inherently high viscosity and tack, but its bond strength and durability are generally inferior to those of modified synthetic latexes. Adhesion strength of natural latex depends heavily on formulation and processing conditions, and it contains proteins that may cause allergenic reactions, limiting its industrial use in carpets. Natural latex typically offers good wet tack (due to high viscosity), but dried-film strength and weather resistance do not match SBR or acrylic latex.

• PU Adhesives: PU adhesives typically exhibit very strong bonding, forming robust attachments to a wide range of materials (fabrics, plastics, metals). Commercial waterborne PU adhesives (e.g., moisture-cure PU) have good penetration and adhesion performance, curing at low temperatures, and are widely used in carpet tile installation and industrial carpets. Compared to SBR and acrylic, PU adhesives generally offer the highest peel and shear strengths, making them suitable for high-demand applications. Note that PU adhesives often require two-component mixing (isocyanate + polyol) or single-component moisture-curing processes, so their application is more complex, but the cured bond is exceptionally strong and stable.

2. Wear Resistance and Flexibility

• SBR Latex: Demonstrates excellent wear resistance and flexibility. The butadiene segments in SBR provide exceptional elasticity and elongation in the cured film, maintaining high flexibility and crack resistance after curing; the styrene segments enhance wear resistance, giving SBR films good abrasion performance. Therefore, carpets backed with SBR latex retain their shape and structural stability even under frequent foot traffic and flexing.

• Acrylic Latex: Generally offers good wear resistance and flexibility. High–solids acrylic latexes (often crosslinked) are used in sports flooring and coatings, where they are reported to have “excellent adhesion, flexibility, and abrasion resistance”. Overall, acrylic films are slightly harder than pure rubber, resulting in marginally lower flexibility, but formulations often include plasticizers or crosslinkers to improve flexibility. Acrylic latex films also have better weather resistance (UV and aging) compared to SBR, making them suitable for indoor use without compromising wear performance.

• Natural Latex: Possesses extremely high elasticity and flexibility once cured, making it resistant to fatigue cracking. Natural latex films’ wear resistance depends on formulation and crosslink density; generally, their abrasion resistance is comparable to or slightly below that of SBR, and natural latex is prone to oxidation and aging, leading to inferior performance in humid environments compared to modified synthetic latexes.

• PU Adhesives: PU adhesive coatings exhibit superior durability and abrasion resistance. Once cured, PU films combine hardness and toughness, resisting repeated flexing and wear. They remain flexible across wide temperature ranges without cracking, making PU adhesives ideal for applications demanding both elasticity and abrasion resistance. Compared to acrylic, PU films are softer and may show slight deformation under prolonged static loads, but careful formulation can balance toughness and hardness to meet specific requirements.

3. Cost and Supply Stability

• SBR Latex: As a petroleum-derived product, SBR latex benefits from large-scale industrial production. Its monomers (styrene and butadiene) are widely available, making supply abundant and prices relatively low and stable. According to U.S. labor statistics, synthetic rubbers (including SBR) have generally stable pricing, whereas natural rubber prices fluctuate more widely. Thus, in terms of cost and supply stability, SBR latex outperforms natural latex.

• Acrylic Latex: Raw materials—acrylic ester monomers (e.g., butyl acrylate)—also have stable supply chains (petrochemical origin). Prices tend to be moderate to slightly higher than SBR. In recent years, as demand for acrylic latex has risen, production has expanded, but monomer pricing remains subject to oil market fluctuations, causing moderate price variability. Overall, acrylic latex costs more than SBR (some sources note “acrylic latex costs are somewhat higher than SBR”) but increased production capacity has alleviated price pressures to some extent.

• Natural Latex: Being an agricultural product, natural latex pricing is highly influenced by plantation area, disease outbreaks, weather conditions, and international demand, leading to significant volatility. It typically costs more than both SBR and acrylic latex, and supply is constrained by regional climates. Major producing countries like Thailand and Malaysia have large outputs, but natural disasters or plant diseases can easily tighten supply. Therefore, natural latex lacks the cost advantage and supply stability of synthetic latexes.

• PU Adhesives: Water-based or solvent-based PU adhesives rely on raw materials such as MDI (methylene diphenyl diisocyanate) and polyether polyols, whose global production is concentrated among a few large manufacturers. MDI supply is relatively stable but still influenced by oil prices and downstream demand. PU adhesive costs generally exceed those of latex-based adhesives; when supply disruptions occur (e.g., plant shutdowns), PU adhesive availability can be affected. In summary, PU adhesives are more expensive than latex adhesives (though sometimes slightly cheaper than high-end acrylic formulations) and have moderately stable supply.

4. Environmental Considerations (VOC Emissions and Biodegradability)

• VOC Emissions: SBR latex often contains residual styrene and butadiene monomers, which can volatilize and produce odors. Studies (e.g., Foobot) indicate that carpets backed with SBR adhesives emit significant levels of styrene-related VOCs, and 4-phenylcyclohexene (4-PCH) has been identified as a primary source of “new carpet odor” in SBR-backed carpets. European research recommends “avoiding SBR latex and asphalt adhesives, as they hinder carpet recycling and should be replaced with non-toxic alternatives”. By contrast, modern waterborne acrylic latex and VAE (vinyl acetate–ethylene) latex systems contain little or no solvents and can be formulated with ultra-low or zero VOC emissions, effectively odorless in many cases (for example, BASF promotes carpet adhesives with “ultra-low VOC and zero odor” features). PU adhesives (especially waterborne moisture-cure types) emit negligible VOCs upon curing; one study reported that VOC emissions from PU adhesives dropped to almost zero after 28 days of curing. Natural latex contains no synthetic solvents, resulting in minimal VOC emissions; however, it often requires small amounts of ammonia or stabilizers, which can release minor ammonia or VOCs—still substantially lower than synthetic latexes.

• Biodegradability: Natural latex is a natural polymer and is highly biodegradable. In contrast, acrylic latex, SBR latex, and PU adhesives are all synthetic polymers and not readily biodegradable, meaning their waste persists in the environment. Consequently, natural latex has the edge in environmental friendliness, though its supply limitations restrict large-scale use. Synthetic latex systems require proper end-of-life handling, such as thermal recovery or specialized recycling processes.

5. Processing Performance (Cure Time, Operating Temperature, Compatibility)

• SBR Latex: Processing is straightforward, typically as a one‐component aqueous emulsion. Formulations often include thickeners (e.g., acrylic‐based thickeners) and large amounts of fillers (e.g., calcium carbonate) to reduce cost. After coating, removal of water by oven drying or hot air circulation yields a film. SBR latex films can form at room temperature, but enhanced crosslinking requires higher temperatures or added vulcanizing agents. Viscosity remains stable after opening the container; cure time depends primarily on drying conditions—usually 2–5 minutes at 80–120 °C in an oven for initial film formation, with full crosslinking requiring longer or additional processing. SBR latex is highly compatible with fillers, has low equipment requirements, and exhibits good storage stability.

• Acrylic Latex: Also a one‐component aqueous emulsion, often self‐crosslinking or combined with crosslinking agents (e.g., silane, isocyanate crosslinkers) to accelerate cure and enhance properties. Smaller polymer particle size leads to faster film formation compared to SBR latex; films can form at room temperature in a few hours. When crosslinkers are added, durable, water-resistant films form rapidly at low temperatures. Acrylic latex accepts high levels of filler and thickeners. Compatibility with various additives is good (e.g., UV absorbers, flame retardants). In summary, acrylic latex processing is flexible, with quick film formation and cure.

• Natural Latex: Requires an alkaline pH (around 10) for stability; degassing is usually needed to remove air. After coating, film formation occurs at ambient temperature, but the drying process is sensitive to temperature and humidity. Natural latex can absorb moisture; during drying, shrinkage and cracking can occur, so formulations often include antioxidants and plasticizers. Cured films are very soft, but their mechanical strength depends on crosslink density. In high-temperature conditions, natural latex films may deform (e.g., become tacky or flow), so processing temperatures are limited.

• PU Adhesives: Typically two-component systems (base + curing agent) or single-component moisture-cure adhesives that rely on ambient humidity. Two-component PU adhesives require on-site mixing and have an open time (tens of minutes to hours) after which curing begins; full cure may take hours to days. Single-component moisture-cure PU cures via moisture in air, requiring 24–48 hours at room temperature for substantial cure. PU adhesives are sensitive to temperature: low temperatures lengthen curing time, while high temperatures accelerate reactions. Humidity control is critical (low humidity slows cure), so processing environments must be carefully managed. PU adhesives do not require oven drying—curing occurs via chemical crosslinking in situ—and typically tolerate less filler than latex systems (only small amounts of filler to maintain strength). In short, PU processing is more complex, requiring accurate metering and environmental control, but yields a stable, durable film.

6. Actual Application Cases and Industrial Use

• Tufted and Woven Carpets (Broadloom/Tufted Carpet): Represent about 90 % of the global carpet market. Standard practice uses calcium carbonate–filled SBR latex for backing, bonding the secondary backing and locking the pile fibers in place. SBR adhesives—especially carboxylated SBR (XSB)—are promoted for their “excellent adhesion” and “low-VOC, odorless” characteristics in industrial applications.

• Commercial/Modular Carpets (Carpet Tiles): For ease of replacement and recycling, carpet tiles often use acrylic or PU adhesives. Acrylic latex, thanks to its “low VOC, excellent weather resistance, and strong adhesion,” is commonly applied to the backing of carpet tiles for installation on various substrates. A supplier of acrylic latex notes that its product is suitable for “crosslinked backing processes” in tufted carpets, replacing SBR to achieve higher filler loading and greater flexibility. PU adhesives are frequently used in high-end commercial carpets and specialty carpets (e.g., antimicrobial, weatherproof) due to their exceptional bond strength and durability. In architectural carpet installation, single-component moisture-cure PU adhesives have replaced conventional solvent-based adhesives, enabling greener construction practices.

• Carpet Underlay and Flooring Adhesives: Some carpet underlays (e.g., foam, felt pads) use latex coatings (natural or synthetic) to improve adhesion. Flooring adhesives for wall-to-wall carpets are generally acrylic latex or mixed adhesives, requiring high initial tack and environmental friendliness. For instance, the EU and manufacturers have developed low-VOC formulations; BASF has launched flooring adhesives emphasizing “ultra-low VOC and zero odor” for carpet installation applications.

• Recyclable Carpet Design: With rising environmental demands, some manufacturers adopt single-material backings (e.g., all-polypropylene backing) or reversible bonding methods to facilitate recycling, replacing traditional multi-layer SBR-backed structures.

Suitable Application Scenarios and Development Trends

From the above analysis, different adhesives fit various carpet manufacturing needs:

• SBR Latex: Advantages include high bond strength, excellent wear resistance, and low cost, making it the mainstream choice for conventional carpet backing. It is suitable for products requiring robust adhesion and durability, such as wall-to-wall tufted carpets and broadloom woven carpets. However, its VOC emissions and obstacles to recycling may limit use in markets with strict environmental regulations. In the future, SBR usage is likely to be constrained by higher environmental standards.

• Acrylic Latex: With low VOC emissions, excellent weather resistance, and strong adhesion, acrylic latex is increasingly used for carpet backing, fiber bonding, and high-end carpets. It is ideal for applications requiring eco-friendliness, color stability, and installation convenience, especially in commercial or outdoor carpet products. Market trends indicate ongoing growth in acrylic latex, partially substituting SBR—particularly in applications that demand high filler loading and low-temperature curing.

• Natural Latex: Due to biodegradability and excellent softness, natural latex remains in use for certain high-end residential carpets (e.g., all-cotton or natural-fiber carpets) and underlays. Yet, its price volatility and allergenic properties limit its prospects in large-scale industrial carpet manufacturing. Its applications are confined to niches where sustainability and comfort are paramount.

• PU Adhesives: Thanks to exceptional bond strength and superior durability, PU adhesives occupy a niche in high-performance carpets and technical applications. They are well-suited for carpet tiles, outdoor commercial carpets, and products requiring water resistance and UV durability. Owing to higher cost, PU adhesives primarily target the high-end market. As waterborne PU technologies advance and processes mature, their use is expected to expand—particularly in projects emphasizing “green installation” and “ultra-low VOC” requirements.

Looking ahead, carpet-industry adhesive development will trending toward more environmentally friendly (low-VOC, solvent-free), high-performance (high adhesive strength, wear resistance, flexibility), and cost-effective formulations. Advances in polymer science—such as nano-modification, crosslinker optimization, and biodegradable blends—will drive adhesive performance. Simultaneously, circular economy principles will encourage manufacturers to design recyclable carpets using reversible or thermosensitive adhesives. In summary: SBR latex remains indispensable for its cost-effectiveness; acrylic latex and PU adhesives are rapidly growing due to performance advantages; natural latex maintains a presence in specific niche markets. Choosing the appropriate adhesive will depend on carpet end-use, cost constraints, and environmental requirements to balance performance and sustainability.

Lior

Email:[email protected]