How to Prepare SBS for Production of Adhesives?

Styrene-butadiene-styrene triblock copolymer (SBS) possesses features of both thermoplastics and vulcanized rubber owing to the solubility and thermoplasticity of polystyrene (PS) and the toughness and resilience of  polybutadiene (PB). The features result from the incompatibility of thermodynamics between the end of PS molecular chain and the middle of PB molecular chain. The end of PS molecular chain shows glassy state at room temperature, acting as a crosslinking point of rigid network, and displays viscous state at the temperature above viscous flow temperature, enabling plasticity because of the crosslinking destroyed. For this reason, SBS becomes the major material for the production of adhesives.

Solvent-based SBS adhesives have lower viscosity, which enables it to be used for producing adhesive agents with higher solid content and suitable for coating, saving solvent and the energy for solvent volatilization.

Linear SBS is more suitable for being used as the main material of adhesives. The structure of SBS is segmented into linear and radial. Linear SBS possesses low relative molecular weight, good solubility, low viscosity, and lower cohesive strength. Radial SBS has high relative molecular weight, high cohesive strength, high physical crosslinking density, and higher heat resistance and elastic modulus than linear SBS. But if the amount of radial SBS is too large, the shrinkage internal stress of adhesives will increase. The presence of internal stress in adhesive joints will reduce joint strength, resulting in poor toughness and great brittleness of adhesives after curing. In addition, adhesives and adherend molecules need to be made into a solid joint by interdiffusion. Radial SBS are less wettable than linear SBS, and cannot evenly and completely wet bonding materials when bonding.

Toluene, dichloroethane, carbon tetrachloride, vinyl acetate, and cyclohexane are good solvents, while n-hexane, heptane, petroleum ether, solvent gasoline, and acetone are poor solvents for SBS. Single solvent is difficult to meet SBS’s comprehensive requirements. Hence, binary or multi-component mixed solvents made of good solvents and poor solvents are generally used. Poor solvents in the mixed solvents must volatilize at a faster rate than good solvents. Otherwise, the surface of adhesive film will be rough, and its bonding strength will decrease.

 

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Technology and Applications of SBS-based Adhesives

SBS refers to styrene-butadiene-styrene triblock copolymer. It is a type of thermoplastic elastomer, generally called “thermoplastic styrene-butadiene rubber” and well-known as “the third generation of synthetic rubber”. SBS has both plastic and rubbery properties, showing plasticity at high temperature and elasticity at room temperature. It exhibits properties of thermoplastics without plasticating and properties of vulcanized rubber without vulcanization.

SBS has many advantages such as excellent solubility, the ability to melt at high temperature, low melt viscosity, ease of modification, and good compatibility with a lot of polymers. Thus, it is widely applied in the building decoration, printing and laminating, pressure-sensitive adhesives, woodwork, bags and suitcases, footwear, and other industries.

Currently, the type of building decorative adhesives mainly includes neoprene adhesives and SBS-based adhesives. Due to structural characteristics, SBS-based adhesives are inferior to neoprene adhesives in initial adhesion, bond strength (especially when bonding to polar materials), tack time, heat and weather resistance, and other aspects. This greatly restricts the use of SBS-based adhesives in the building decoration application.

The lack of polar groups in SBS macromolecules results in the failure of SBS-based adhesives to perfectly bond to polar substrates such as aluminum-plastic panels, fireproof boards, PVC panels. There are a lot of researches globally conducted on grafting modification, epoxidation and other aspects of SBS-based adhesives, to improve their bonding properties. However, this will undoubtedly require the increasing investment and industrial costs of adhesive manufacturers, and is difficult to put into operation because of the complicated technique.

 

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SBS Modification by PE / PP / PS

Why SBS needs to be modified by adding plastic products? This mainly results from its poor processing performance and product properties that can’t meet the practical application requirements. In general, SBS is rarely used in the finished products independently. To satisfy the special requirements of applications and reduce costs, SBS must be modified by adding additives, resins and others.

With excellent elasticity, SBS elastomers can be mixed with other polymer materials in the molten state, extruded and cut, then cooled to prepare the modified SBS thermoplastic elastomers. This improves SBS’s flowability and mechanical properties such as hardness, abrasion resistance and tear strength, and expands its application range. The major polyolefin plastic polymers used for SBS modification include PE, PP, PS, etc. They share common characteristic in the good compatibility with SBS, thus the modified SBS has excellent bonding property.

PE / PP: Both polyethylene (PE) and polypropylene (PP) have outstanding properties, including ease of processing, excellent electrical properties, excellent flexural strength, low temperature flexibility, excellent corrosion resistance, and low permeability. The use of PE and PP for SBS modification can improve the abrasion resistance, hardness, weatherability, tear strength and melt flow rate of SBS elastomers, while maintain high tensile strength and elongation at break.

PS: Polystyrene (PS) has the advantages such as easy molding, low shrinkage, low hygroscopicity, and good thermal performance. PS has good compatibility with SBS. Strong bonding force exists at the phase interface of two polymers, and increases as the rising number of styrene chain segments in SBS. The tensile strength and elongation at break of the SBS modified by PS will decrease as the increase of PS content, while the hardness will rise slightly.

SBS modified by plastics is mainly applied in footwear, wires and cables, automotive, household appliances, medical devices, and other sectors.

 

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Requirements for Ingredients in Production of SBS Granules for Shoe Soles

SBS, the major raw material for SBS-based TPR footwear, provides strength, elasticity and other performance for footwear. SBS grade YH-815,   SBS T171 are frequently used for production of SBS-based TPR footwear. However, the specific grades should be selected based on manufacturers’ requirements for footwear, including costs, performance, sole type, etc.

Softening Oil

Softening oil is mainly used for improving the flowability, reducing costs in the production of SBS granules for shoe soles. The flowability of SBS granules for shoe soles is generally measured by melt flow rate (MFR). The hardness of SBS granules for shoe soles can be reduced by adding softening oil.

The softening oil can be chosen based on two cases: a. The selected softening oil has good compatibility with polystyrene, the rigid phase in SBS; b. The selected softening oil has good compatibility with polybutadiene, the soft phase in SBS. The former one is not recommended.

Resin

Resin plays the role of improving performance and filling in the production of SBS granules for shoe soles. The selection of resin should consider the compatibility with SBS first, generally following the principle of “SBS is compatible with resin when their solubility parameters are approximate.” General-purpose polystyrene (GPPS) is the most common organic filler, which can enhance hardness and elasticity modulus of SBS granules for shoe soles with slight reduction of abrasion and tear resistance. The commonly used resins also include ethylene vinyl acetate copolymer (EVA) and polyethylene (PE). EVA can enhance weatherability, ozone resistance, aging resistance and solvent resistance.

Fillers

The addition of fillers in the production of SBS granules for shoe soles is to reduce costs.

 

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SBS rubber 185 – Styrene Butadiene Styrene block copolymer materials

SBS rubber 185 – Styrene Butadiene Styrene block copolymer materials

SBS rubber 185 DESCRIPTION

Thermoplastic elastomer SBS rubber 185 is oil-extended, radiation type, styrene-butadiene-styrene triblock copolymer. Its oil-filled rate is 31%, and styrene content is 32%. It can be injection moled directly due to its high fluidity. YH-185 and YH-815 are both radiation type oil-extended rubber. However the wear-resisting property and tensile strength of SBS polymer YH-185 have been significantly improved than YH-185.

SBS rubber 188

SBS rubber 185 APPLICATION

Adhesive / Shoes / Compounding

SBS-815+

CHEMICAL PROPERTIES

Structure: R

Styrene Content  (%) : 32

Oil Content  (%): 31

MFI  (g/10min) : 0.1-2.0

Shore A  (/): 60-70

Solution Viscosity  (25%,25℃,mPa.s) :  -

Tensile Strength  (Mpa) :  ≥15

Elongation  (%): -

Stress at 300%  (Mpa) : -

Ash  (%):  -

Volatility  (%):≤0.70

 

FORMULA

TPR Shoe (Parts by mass)

SBS(YH185): 130

Oil : 45

PS : 15

CaCO3 : 75

 

ALTERNATIVE GRADES

LCY 1485

 

MANUFACTURE

Sinopec

 

One-stop global sourcing

Competitive pricing and quality

Professional customized service

 

Certificate REACH SVHC ,EU,ROHS,PAHs, FDA,RAPIDS,VOC

Price: negotiable

 

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SBS rubber 165 – Styrene Butadiene Styrene block copolymer materials

SBS rubber 165 – Styrene Butadiene Styrene block copolymer materials

 

SBS rubber 165 DESCRIPTION

Thermoplastic elastomer SBS polymer 165 is non-oil-extended styrene-butadiene-polystyrene triblock copolymer rubber with linear structure and high transparency. The styrene content is 40%.

SBS rubber 188

SBS rubber 165 APPLICATION

Shoes / Compounding

SBS rubber 165 application

 

CHEMICAL PROPERTIES

Structure: L

Styrene Content  (%): 40

Oil Content  (%): 0

MFI  (g/10min) : 5.0-9.0

Shore A  (/): 86-92

Solution Viscosity  (25%,25℃,mPa.s) : -

Tensile Strength  (Mpa) : ≥28.0

Elongation  (%): -

Stress at 300%  (Mpa) : ≥5.5

Ash  (%): -

Volatility  (%) ≤0.70

 

ALTERNATIVE GRADES

Taipol 4202

Kraton 1155B

 

MANUFACTURE

Sinopec

 

One-stop global sourcing

Competitive pricing and quality

Professional customized service

 

Certificate REACH SVHC ,EU,ROHS,PAHs, FDA,RAPIDS,VOC

Price: negotiable

 

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SBS rubber T171 – Styrene Butadiene Styrene block copolymer materials

SBS rubber T171 DESCRIPTION

Thermoplastic elastomer SBS rubber T-171 is an oil-extended styrene-butadiene-styrene triplex block copolymer specially for shoes with high molecular weight and radiation type. Its oil-extended rate is 33%, and the styrene content of SBS polymer T-171 is 40%.

SBS rubber 188

SBS rubber T171 APPLICATION

Shoes / Compounding

SBS rubber 171 application

 

CHEMICAL PROPERTIES

Structure: R

Styrene Content  (%): 40

Oil Content  (%): 33

MFI  (g/10min) :  1.0-7.0

Shore A  (/): 60-80

Solution Viscosity  (25%,25℃,mPa.s) :  -

Tensile Strength  (Mpa) :  -

Elongation  (%):-

Stress at 300%  (Mpa) :-

Ash  (%):-

Volatility  (%): ≤1

 

FORMULA

Gum Outsole (Parts by mass)

SBS(T-171): 40

PS: 8

SiO2: 7

Naphthenic Oil: 7

K-resin:  3

 

ALTERNATIVE GRADES

LCY 1475

 

MANUFACTURE

Petrochina

 

One-stop global sourcing

Competitive pricing and quality

Professional customized service

 

Certificate REACH SVHC ,EU,ROHS,PAHs, FDA,RAPIDS,VOC

Price: negotiable

 

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