Nansha, Guangzhou, ChinaOwn plant since 2011
Neutral cure and acetoxy silicone sealants for weatherproofing, glazing, sanitary and general construction sealing — with the substrate, joint design and movement checks that decide which grade fits.
If the joint touches metal, mirrors, marble, natural stone or concrete, specify neutral cure. Everywhere else — glass-to-glass, glazed ceramic, plain sanitary work — acetoxy cure does the same job faster and costs less.
That one rule settles most enquiries. The reason behind it is what the sealant gives off while it cures: acetoxy silicone releases acetic acid, which corrodes metal, undercuts the reflective backing on mirrors, etches stone and reacts with alkaline concrete. Neutral cure releases nothing corrosive, which is why it is the default specification on almost every construction project.
Specifications and enquiries use these terms interchangeably. If yours uses one of the names on the left, you are asking for the product on the right.
| Also called | Is | Because |
|---|---|---|
| Non-acetic silicone · non-acid silicone · non-acetoxy silicone · oxime cure · alkoxy cure | Neutral cure | Cures without releasing acetic acid |
| Acetic silicone · acid cure silicone · acetoxysilane cure · vinegar silicone | Acetoxy cure | Releases acetic acid — hence the vinegar smell |
| Property | Neutral cure | Acetoxy cure |
|---|---|---|
| Cure byproduct | Alcohol or oxime — non-corrosive | Acetic acid — corrosive |
| Skin formation | 10–20 minutes | 5–10 minutes |
| Full depth cure | 2–3 mm per 24 h | 2–3 mm per 24 h |
| Movement capability | ±25% | ±20% |
| Service temperature | −40°C to +150°C | −40°C to +150°C |
| Odour while curing | Low | Strong vinegar |
| Relative cost | Higher | Lower |
| Standards | ASTM C920, EN 15651 | ASTM C920 |
| Typical use | Curtain wall, glazing, façade, perimeter, metal and stone | Glass-to-glass, aquaria, glazed ceramic, non-metallic sanitary |
Category-level reference values. Exact figures vary by grade — request the technical data sheet for the product you are evaluating.
This table is the whole selection problem in one view. Where acetoxy is marked unsuitable, the failure is not immediate — it appears weeks or months later as corrosion, staining or a bond that lets go, which is why it so often reaches the site before anyone catches it.
| Substrate | Neutral | Acetoxy | What goes wrong |
|---|---|---|---|
| Glass | Yes | Yes | — |
| Glazed ceramic | Yes | Yes | — |
| Aluminium, copper, brass, galvanised steel | Yes | No | Acetic acid corrodes the metal at the bond line |
| Mirrors | Yes | No | Attacks the silvered backing — black edges spread inward |
| Marble, granite, natural stone | Yes | No | Acid etches and stains the surface permanently |
| Concrete, mortar, cementitious board | Yes | No | Alkaline surface neutralises the acid; the bond never develops |
| Polycarbonate, acrylic, ABS | Test first | No | Stress cracking; always trial on the actual plastic |
| Powder-coated and anodised profiles | Yes | Test first | Adhesion depends on the coating, not the metal beneath |
Modulus is how hard the cured sealant pushes back as the joint moves. It is a separate question from cure system, and specifications frequently name it — "low modulus neutral cure silicone" is a request for both properties at once.
| Class | ISO 11600 designation | Specify it when |
|---|---|---|
| Low modulus (LM) | 25LM — ≤0.4 MPa secant modulus at 100% elongation | The joint moves a lot, or the substrate is weak — render, lightweight block, thin stone. A soft sealant moves instead of tearing the substrate away. |
| High modulus (HM) | 25HM — >0.4 MPa secant modulus at 100% elongation | The joint carries load or must resist deformation — structural glazing, and anywhere the seal is doing more than keeping water out. |
ISO 11600 also carries a use letter: F for façade joints andG for glazing. A full designation therefore reads likeISO 11600 F&G 25LM — a façade and glazing sealant, ±25% movement, low modulus. Ask for the class designation on the technical data sheet rather than the words "low modulus" alone; the letters are what a specifier can check.
A different question again, and one worth answering honestly: silicone is not the right product for every joint. Polyurethane sealant is a separate chemistry with its own advantages, and the two are commonly confused because both arrive in the same cartridge.
| Property | Silicone | Polyurethane |
|---|---|---|
| Paintable | No — paint will not adhere | Yes |
| UV and weathering | Excellent, 20+ years | Degrades under prolonged UV unless coated |
| Abrasion resistance | Low | High |
| Trafficked horizontal joints | Not suitable | Suitable |
| Adhesion without primer | Good on glass and metal | Often needs a primer |
| Temperature range | −40°C to +150°C | −30°C to +80°C |
The short version: silicone for glazing, façades and wet areas; polyurethane for joints that need painting or take foot and vehicle traffic. If the joint has to be painted to match the wall, no silicone will do it — that is a polyurethane job. Note that polyurethane sealant is a different product from theone-component PU foamused to fill gaps around openings; the two are frequently confused in enquiries.
"Neutral cure" covers more than one chemistry. Both common systems release no acetic acid, but they release different things and behave differently, so a specification or a sensitive substrate may need one rather than the other. Ask which system the TDS and SDS name.
| System | Releases while curing | Watch for |
|---|---|---|
| Oxime | An oxime, commonly MEKO (butanone oxime) | Can discolour or corrode copper and brass; noticeable odour. Its EU hazard classification has tightened, so some European specifications exclude oxime systems |
| Alkoxy | An alcohol, usually methanol | Lowest odour and no attack on copper or brass; usually cures more slowly, and grades differ in shelf life |
Our listed neutral grade is described as oxime/alkoxy at category level; the system for the grade you are quoted is on its SDS.
Choosing neutral cure removes the acid problem. It does not remove the need to check the sealant against the actual surface, and these are the substrates where that check matters most:
| Substrate | Risk | The check |
|---|---|---|
| Mirrors | Backing paints vary; some are attacked by components in the sealant | Use a grade the mirror maker approves, or one tested on that backing |
| Marble, limestone, porous stone | Plasticiser migrates into the stone and leaves a dark band along the joint | A grade tested as non-staining on that stone, for example to ASTM C1248 or ISO 16938 |
| Anodised and powder-coated aluminium | Adhesion depends on the coating, which varies by supplier | Peel-adhesion test on the actual profile; a primer where the TDS calls for one |
| Polycarbonate and acrylic sheet | Stress cracking in the plastic | Trial on the actual sheet under the stress it will carry |
| EPDM gaskets, bitumen, setting blocks | Incompatible materials discolour the sealant or lose adhesion | Compatibility test with the accessory materials, for example to ASTM C1087 |
| PE, PP, PTFE | Silicone does not bond to them | Use them as bond breakers, not as bonding surfaces |
| Painted surfaces | The bond is only as good as the paint | Adhesion test on the finished paint system |
A weatherseal keeps water and air out of a joint and moves with it; if it fails, the building leaks. A structural glazing sealant holds glass to its frame and carries wind load; if it fails, the glass can come away. The second is designed, tested and approved differently: sealants are qualified to standards such as ASTM C1184 or ETAG 002, adhesion and compatibility are tested on the project's own frames, glass and accessories, and approval is normally given project by project, often for two-component products.
The grades we list are weatherseals. If a joint carries load, send the project specification and we will tell you whether we can supply against it rather than offer a weatherseal in its place.
Datasheet figures are often read as if they were interchangeable. They are not:
| Figure | What it tells you | What it does not |
|---|---|---|
| Movement capability (e.g. ±25%) | How far the joint can repeatedly open and close, as a share of its width, in a cyclic test such as ISO 9047 or ASTM C719 | Anything about a single stretch to failure |
| Elongation at break (e.g. ≥400%) | How far a test piece stretches once before it tears | Durability under repeated movement — a high figure does not mean a high movement class |
| Modulus (ISO 11600 LM / HM) | How hard the cured sealant pulls on the joint edges as it stretches | Adhesion — a low-modulus sealant still needs a sound, clean substrate |
| Shore A hardness | Surface softness of the cured rubber | Modulus or movement capability; it correlates only loosely with either |
| Tensile strength | The strength of the rubber itself | The bond to the substrate, which is tested separately, for example by peel adhesion to ASTM C794 |
| Skin time and cure rate | When the surface can be touched, and how fast cure proceeds inward | When the joint can take movement — a 10 mm deep joint cures in days, not minutes |
More on reading datasheets in our specifications guide.
| Symptom | Likely cause | Check first |
|---|---|---|
| Stays soft or tacky | Expired or heat-damaged cartridges, very dry air, a section too deep, or contact with an incompatible material | Batch date and storage; joint depth; what the sealant touches |
| Tears down the middle | Movement beyond the sealant’s capability, joint too narrow, or three-sided adhesion | Joint width against expected movement; backer rod or bond breaker |
| Peels from one edge | Dust, moisture, release agent or old sealant on the surface; a coating that needs primer; bead not tooled into contact | Surface cleaning and priming against the TDS |
| Dark band on stone | Plasticiser migration into porous stone | Switch to a grade tested non-staining on that stone |
| Black edges spreading on a mirror | Acetoxy or an incompatible grade attacking the backing | Mirror-compatible neutral grade |
| Discoloured or yellowed sealant | Contact with incompatible gaskets or bitumen, cleaning chemicals, or dirt pick-up | Compatibility of adjacent materials |
| Corrosion at a metal edge | Acetoxy sealant on metal | Neutral cure for any joint touching metal |
| Mould in a wet-area joint | Grade without fungicide, standing water, or mould left behind old sealant | Mould-resistant grade; full removal and cleaning before resealing |
When you ask us to match a grade, tell us the joint use, the substrates on both sides and their finish, joint width and depth, expected movement, indoor or outdoor, and the class your specification names (for example ISO 11600 F 25LM or ASTM C920).
Silicone sealant is an elastomeric sealing compound based on polydimethylsiloxane (PDMS) polymer — a silicone-based material that cures at room temperature to form a flexible, waterproof, and weather-resistant rubber seal. Unlike organic sealants (polyurethane, acrylic, or butyl), silicone sealant maintains its properties across an exceptionally wide temperature range (-40°C to +150°C for standard grades, up to +250°C for high-temperature formulations), resists UV degradation for 20+ years, and does not shrink, crack, or harden over time. These characteristics make silicone sealant the preferred sealing material for construction, glazing, automotive, and industrial applications worldwide.
The curing mechanism of silicone sealant is moisture-activated: the sealant reacts with atmospheric humidity to crosslink from the outside surface inward, forming a durable elastomeric rubber. Skin formation (surface tack-free time) typically occurs within 10-20 minutes, while full depth cure proceeds at approximately 2-3 mm per 24 hours. The curing chemistry determines the sealant classification — neutral cure or acetoxy cure — each with distinct performance characteristics and substrate compatibility.
The tables above are the decision. This is the chemistry underneath them, for anyone who has to justify the choice to a specifier or a customer.
Neutral cure silicone uses an oxime or alkoxy crosslinking system that releases non-corrosive byproducts during curing. This is the critical difference from acetoxy silicone: neutral sealant will not corrode metals (copper, brass, aluminum, galvanized steel), will not damage mirrors (no black-edge effect), will not stain or etch marble and natural stone, and will not react adversely with concrete and cementitious substrates. For these reasons, neutral silicone sealant is the default specification for most construction and industrial sealing applications. PACT's neutral silicone sealant achieves tensile strength of ≥0.8 MPa, elongation at break of ≥400%, and movement capability of ±25%, meeting ASTM C920 and EN 15651 standards.
Acetoxy silicone sealant releases acetic acid during curing — identifiable by the strong vinegar smell. Acetoxy sealant cures faster than neutral (skin formation in 5-10 minutes vs. 10-20 minutes) and is generally less expensive to manufacture, making it a cost-effective choice for applications where its limitations are not a concern. Acetoxy sealant bonds well to glass, glazed ceramics, and non-porous surfaces, and is commonly used for aquarium sealing, glass-to-glass bonding, and simple bathroom sealing on non-metallic substrates. However, it must never be used on metals (causes corrosion), mirrors (dissolves reflective coating), marble or natural stone (acid etching), or concrete (reacts with alkaline surface).
Silicone sealant serves essential sealing functions across the construction and building maintenance sectors:
PACT produces silicone sealant in white, clear/transparent, black, grey, brown, and almond as standard stock colors. For projects requiring specific color integration with facade materials, window frames, or interior finishes, we offer custom RAL color matching with a minimum order of 3,000 cartridges. Custom color samples are produced and shipped for client approval before bulk production begins. Color pigments are UV-stable to resist fading over the sealant's service life.
Our sealant production facility in Guangzhou features automated cartridge filling lines, planetary mixer systems for consistent batch-to-batch quality, and in-house testing laboratories for quality verification. Every production batch is tested for application properties (skin time, extrusion rate, sag resistance), mechanical properties (tensile strength, elongation, hardness), and adhesion to standard substrates (glass, aluminum, concrete, ceramic). We produce silicone sealant in 280ml and 300ml cartridges (compatible with standard caulking guns), 590ml sausage packs, and 20L pails. Full OEM and private label services are available, including custom cartridge labels, branded carton packaging, and technical documentation in your required languages.
Neutral cure (oxime/alkoxy) silicone sealant suitable for a wide range of construction and industrial applications. Releases no acetic acid, so it does not corrode metals the way acetoxy does; mirror, stone and structural joints need a grade confirmed for that use.
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Fast-curing acetoxy (acetic cure) silicone sealant for glass, glazing and sanitary work. Highest tack and quickest skin-over of any silicone chemistry, at the cost of substrate compatibility.
View Details →Oxime cure — no acetic acid to corrode metal; mirror and stone joints still need a compatible grade.
Faster skin and lower cost, but releases acetic acid — wrong for metal and stone.
Cure chemistry, substrate limits, modulus and where each one fails.
Movement joints against gap filling — they are not interchangeable.
What façade and window fabricators specify, and the standards they test to.
Container quantities, heat stability and the documentation Gulf customs asks for.
ISO 9001, ISO 14001, REACH statements and SGS reports, and what each one covers.
Custom labels, cartons and formulation adjustments from our existing lines.
Why a container crossing the tropics at 60-70°C is the hardest storage condition your adhesive will see.
Non-acid silicone is neutral cure; liquid nails is grab adhesive. Fifty terms with their synonyms.
Substrate, volume and destination market are enough for us to price it.
Send the joint use, substrates, joint size and the class your specification names, and we will match a weatherproofing or sanitary grade — or tell you plainly when the job needs a structural glazing sealant we do not list.
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