Sinopec Styrene-Isoprene-Styrene Block Copolymer draws attention among specialty polymers. Chemists and materials experts often call it SIS. Its core structure comes from the careful arrangement of styrene and isoprene segments in a block sequence. The result is a thermoplastic elastomer with a reputation for flexibility and resilience. This copolymer gets produced through living anionic polymerization, which lets manufacturers control both the molecular weight and the balance of each block. That means the end properties, like strength, toughness, and elasticity, can be adjusted for different roles. The molecular formula of a standard SIS block copolymer often appears as (C8H8)m-(C5H8)n-(C8H8)p, which gives a nod to both styrene and isoprene repeating units. CAS Number 25038-32-8 sometimes shows up on technical sheets and Material Safety Data Sheets (MSDS).
SIS block copolymer from Sinopec generally shows up as translucent flakes, chunky powder, round pearls, or pressed solid bars. Sometimes, it shows up as straw-colored granules or small, glassy pellets. Its density sits around 0.92 grams per cubic centimeter, which feels surprisingly light when compared to standard plastics. Unlike rubber erasers or tires, SIS does not smell strong or stick to fingers. Touching a sample gives a faint, soft sensation with a little bounce. This copolymer melts cleanly, turning into a clear to slightly cloudy viscous liquid when heated to about 150–220°C, depending on its specific form. Some grades even stay transparent as thin films. No crystal grains or sharp edges turn up as the structure is primarily amorphous. Folks who handle lots of plastics notice how SIS stays easy to pour, scoop, or press into molds, avoiding static cling or stubborn dustiness. Bulk density stays consistent—this matters when loading mixers or hoppers in manufacturing plants, helping keep workflow predictable.
Sinopec SIS relies on styrene and isoprene as core raw materials. Styrene provides glassy segments, giving the polymer its structural backbone and clarity. Isoprene, derived from petrochemicals, supplies rubbery, soft segments. Chain polymerization brings these monomers together in an ordered pattern with styrene blocks anchoring each end and isoprene in the center. A polymer chain might appear as S-I-S, where the blocks line up neatly. Chemists can tweak how many repeat units build each section, which lets them dial in mechanical and thermal features for specific projects. The average molecular weight often lands between 100,000 and 300,000 g/mol. Polymers with higher styrene content display a stiffer, more transparent appearance, while higher isoprene ratios make it softer and more elastic. SIS copolymer resists many mild chemicals and stays stable under sunlight for daily use, although aggressive solvents can dissolve or swell the material. For this reason, SIS often gets blended with tackifying resins, paraffinic oils, or even other block copolymers to fit the needs of hot-melt adhesive tapes, nonwoven fabrics, or waterproofing membranes.
Industry buyers can find Sinopec SIS in grated flakes, compact powder, uniform pearls, clear solid blocks, and even pre-dissolved solution form for easy use. Flakes pack tight and pour without bridging. Powder disperses evenly in mixers. Pearls or granules cut down on airborne dust and static. Some factories prefer solid slabs, slicing only what’s needed. Liquid SIS, sometimes found in toluene or cyclohexane solution, makes coating or adhesive formulation as straightforward as mixing paint. Typical commercial batches guarantee styrene content from 14% to 40% and isoprene content from 60% to 86%, as measured by NMR. K-value, a common descriptor for molecular weight, helps users match the polymer to hot-melt processes or compounding equipment. The HS Code for import and export—39023010 for block copolymers in primary forms—shows up often in shipping documents. Volume and weight must be noted: 1 liter of solid SIS weighs about 0.92 kg, and bulk packages can weigh 25 kg per bag or bigger. Each form has pros and cons for transport, storage, and downstream use in industry or workshop settings.
Few copolymers combine flexibility, clarity, and process ease the way SIS does. Its melt viscosity and excellent compatibility with hydrocarbon resins let glue makers hit just the right balance between flow and tack for diapers, sanitary pads, or pressure-sensitive tapes. Film extruders appreciate the way SIS copolymer forms clear, tough layers that stretch and recover after repeated pulls, such as in athletic or medical bandages. Because of the friendly handling profile, operators rarely need special gloves or ventilation for routine work with SIS. Safety Data Sheets do require basic dust masks if high-speed mixing or pellet transfer raises airborne concentration. Storage advice stays practical: keep dry, store away from heat or direct sunlight, and avoid strong oxidizing agents. SIS qualifies as non-hazardous and non-toxic under normal federal guidelines and meets the test for food contact in many countries, but blending materials or application solvents may raise new safety considerations, so users check MSDS for each specific grade. The copolymer itself does not burn fiercely and leaves little ash, releasing only basic combustion products if exposed to open flame. End-of-life handling often follows municipal solid waste guidelines; some grades are recyclable with other elastomeric materials. SIS never enters the hazardous-waste stream in everyday industrial use, making it a more people-friendly choice in busy factories or school labs.
Few raw materials pop up in so many fields as fast as SIS block copolymer. Hot-melt adhesives and tapes, shoe soles, weatherproofing strips, and disposable hygiene products—these need that mix of softness and stick, paired with a safe touch and clean burn. SIS earns a place among workhorse materials because real users, from large manufacturers to local shop owners, seek reliable handling and clear supply chains. Tough, flexible gym tape, self-sealing medical wraps, quick-setting glues for packaging—these depend on the unique chemistry of block copolymers like SIS. My own experience in hands-on polymer development taught me that repeatable flow and bond strength matter more than glossy marketing. Suppliers such as Sinopec hold onto market trust by keeping documentation clear, batch tests up-to-date, and by providing steady technical support to help troubleshoot unusual process conditions. The more general the application, the more critical reliable structure and composition become. The genuine value of SIS comes from meeting these everyday performance demands while also keeping health, safety, and cost within reach for a broad range of users.
No material comes without its downside. SIS, like similar block copolymers, sits at the mercy of feedstock prices, especially for isoprene and styrene raw materials. Global price swings reach the workshop level over months. Supply chain disruptions create headaches for both procurement teams and small buyers. Some applications run into limits with thermal stability; SIS melts low and softens at high heat, which can affect products left in hot trunks or direct sun. Waste sorting at product end-of-life poses another issue, as municipal systems often lack categories for specialty copolymers. Cost-conscious manufacturers lean into solutions that mix SIS with recycled polyolefins or bio-based tackifiers, reducing virgin demand. Longer-term, process improvements and catalyst innovations could lower energy use in production, while end-user education pulls some weight in recycling and disposal. Funding for community recycling centers and updated waste policies may smooth the way for better handling of SIS and similar materials in the future. Responsibly sourced monomers, open safety evaluation, and transparent supply records help build long-term trust for anyone relying on SIS in their products or daily work. Even small changes, like switching to bag or pearl form to cut dust, improve practical safety and process efficiency. In industrial and small-batch environments, those incremental improvements matter for quality, compliance, and everyday success.
