I. Core Application Scenarios Where SBC Adhesives Need Polarity Modification 1. Bonding polar substrates: When bonding strong/medium polar substrates, the interface between non-polar SBC substrates and polar substrates (such as PET, BOPP corona film, nylon PA, PVC, paper, wood, metal, glass, concrete, and polar rubber) has the problem of excessive surface energy difference, and non-polar molecules cannot form hydrogen bonds and van der Waals forces with the polar groups of the substrate (-OH, -COOH, -COO-、-NH2, Cl-, etc.), resulting in interface bonding failure. It is necessary to improve the polarity of the adhesive to achieve interface polarity matching. 2. System contains polar fillers/additives: When polar fillers (such as calcium carbonate (activated/unactivated), talc, silica, titanium dioxide, carbon black) or polar functional additives (such as polar antioxidants, flame retardants, plasticizers) are introduced into the SBC adhesive formulation, the compatibility between the non-polar SBC base material and the polar filler is poor, and it is easy to cause packing agglomeration and uneven dispersion of the system, resulting in the appearance of the adhesive blooming, the decrease of initial adhesion/adhesion, and the deterioration of film formation. 3. Environmental resistance: The interface bonding of non-polar SBC adhesives is mainly based on physical adsorption, and in water, humidity, heat, and weakly polar chemical environments, water molecules are easy to invade the interface to destroy the adsorption force, resulting in bonding failure. The introduction of strong polar groups (such as -OH, -Si-O-、-COOH) through polar modification can form hydrogen bonds/chemical bonds at the interface, improve the stability of interface bonding, and enhance the resistance to water, moisture and heat, and weak chemicals. 4. Cross-material bonding of composite adhesives/laminates: For example, flexible packaging lamination (PET/PE, PA/PE, paper/plastic composite), building material lamination (PVC/polyolefin foam board) and other scenarios, involving polar-non-polar substrate composites, require adhesives with both polar and non-polar characteristics, and achieve bidirectional compatibility of transpolar interfaces through polarity regulation. 5. Solvent-free / water-based SBC adhesive system: Conventional SBC is an oil-soluble non-polar polymer, when preparing water-based SBC adhesive (emulsion/dispersion), its hydrophilicity (polarity) needs to be improved to achieve aqueous phase dispersion; When preparing solvent-free SBC adhesives, if polar oligomers (such as polyester polyols and polyether polyols) are compatible, it is necessary to adjust the compatibility of SBC polarity to improve polar oligomers to avoid phase separation of the system. II. Strategies for the synergistic use of various modification methods 1. Low-cost conventional polarity modification Application scenarios: non-grafting/blending equipment, universal bonding 2. Universal medium polarity modification Application scenarios: bonding PET/PVC/ paper 3. Medium to strong polarity modification Application scenario: bonding PA / metal 4. No additional process, fast bonding of polar substrates Application scenario: Direct adaptation with general-purpose SBC adhesives 5. Polar/hydrophilic modification of water-based SBC adhesives Application scenario: Bonding water-based substrates / high water resistance requirements 6. Polar modification of SEBS high-end weather-resistant adhesives Application scenario: Automotive/electronic adhesives, bonding metals/engineering plastics
The default non-polar characteristic of SBC adhesives serves as the basis for their compatibility with polyolefin substrates. When the application scenario goes beyond non-polar interface bonding or the compatibility range of purely non-polar systems, it is necessary to modify the polarity to address issues such as poor interfacial compatibility, low bonding strength, and insufficient system dispersibility. Specific scenarios are as follows:
In actual production, it is difficult for a single modification method to take into account polarity, elasticity, bonding strength, and process cost, and usually uses 2-3 methods for cooperative modification:
Reference Formulation: Pure SBC Compound + Non-Polar Tackifier Resin Compound (C5 Resin 30% + Rosin Ester 20%) + Titanate Coupling Agent (0.8%-1%)
Formula features: Completely rely on polar tackifying resin to provide body and interface polarity, coupling agent optimizes the compatibility of resin and SBC, without any chemical modification or blending equipment, suitable for the bonding needs of conventional polar substrates in small and medium-sized factories, and has the highest cost performance.
Reference Formulation: EVA blend (30%) + activated calcium carbonate filling (20%) + medium polar tackifier resin (rosin ester / C9 modified resin, 25%-30%) + titanate coupling agent (0.5%-0.8%)
Formula features: no chemical reaction, polar elastomers and viscosity resins to provide medium polarity of the body, coupling agent optimizes the compatibility of fillers and systems, slightly improves polarity while reinforcing the adhesive layer, reduces costs, and adapts to conventional medium polar substrates;
Reference formula: SIS, SBS grafted modified with MAH (grafting rate 5%) + strong polar tackifier resin (rosin modified phenolic resin, 10%-15%) + epoxy/aminosilane coupling agent (0.8%-1.2%)
Formula characteristics: body grafting introduces core polarity, strong polarity tackifying resin reinforces interface polarity, silane coupling agent builds chemical bonds between adhesive layer - metal / PA substrate to achieve double strengthening of body polarity + interface polarity, excellent water resistance;
Reference formulation: Conventional non-polar SBC adhesive + substrate corona treatment + medium-polar tackifying resin (terpene/rosin ester, 10%-20%) + silane coupling agent (0.5%-0.8%)
Formulation features: Does not change the adhesive formulation, provides interface polarity through substrate corona treatment, tackifying resin enhances adhesion between the adhesive layer and substrate, coupling agent extends the effective bonding period after corona treatment; polarity bonding is achieved solely through interface control, with zero process modifications.
Reference formulation: SIS grafted with AA (grafting rate 8%) + acrylic emulsion blend (30%) + polyester-based polar tackifying resin emulsion (20%-25%) + amino silane coupling agent (1%-1.5%, water-based)
Formulation features: Carboxyl grafting enhances hydrophilicity, acrylic emulsion + polyester tackifying resin emulsion reinforce the polarity of the aqueous system, water-based silane coupling agents strengthen the interface water resistance between the adhesive layer and polar substrates, achieving stable aqueous dispersion and meeting adhesion performance requirements.
Reference formulation: SEBS-g-MAH blend (20%) + phenol-modified terpene resin (25%-30%) + epoxy silane coupling agent (KH-560, 1%) + fumed silica (5%)
Formulation features: SEBS-g-MAH and phenol-modified terpene resin provide strong intrinsic polarity, silane coupling agent enhances interfacial bonding with polar substrates used in automotive/electronics, while coupling fumed silica balances polarity, weather resistance, and adhesive layer thixotropy, suitable for high-end precision bonding applications.