Name: China Manufacturer High Quality Best Price CYASORB UV-3638 CAS 18600-59-4
Brand: Wuhan Fortuna Chemical Co., Ltd.

Items	Specifications	Results
Appearance	off-white powder	Conforms
Assay	98%min	99.4%
Melting point	310℃min	318.6℃
Volatiles	0.5%max	0.2%
Ash	0.1%max	0.02%
Maximum absorption wavelength	453nm	453nm
Conclusion	The result conform with standard

Overview

CYASORB UV-3638 is a highly effective and widely used liquid benzotriazole-based ultraviolet (UV) light absorber. It is manufactured by Cytec Industries (now part of Solvay Group). Its primary function is to protect polymers (plastics, coatings, adhesives) from the degrading effects of UV radiation, thereby significantly extending their service life and maintaining their appearance and mechanical properties.

Key Characteristics

Chemical Name: 2-(2H-Benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol
CAS Number: [70321-86-7]
Appearance: Pale yellow viscous liquid
Molecular Weight: 449.6 g/mol
Chemical Family: Hydroxyphenyl Benzotriazole
Key Advantage: Its liquid state makes it exceptionally easy to handle and incorporate into various formulations, especially compared to powdered additives.

How It Works (Mechanism of Action)

CYASORB UV-3638 operates through a mechanism called reversible intramolecular proton transfer:

Absorption: The molecule absorbs high-energy UV radiation (particularly in the 290-400 nm range).
Energy Conversion: Instead of letting this energy break the polymer chains (which causes degradation, discoloration, and brittleness), the absorber converts the harmful UV energy into harmless low-grade heat.
Reversion: The molecule then reverts to its original ground state, ready to repeat the process. This makes it a long-term, sacrificial stabilizer.

This process effectively "sacrifices" the UV absorber to protect the polymer matrix, dramatically slowing down the photodegradation process.

Primary Applications

CYASORB UV-3638 is valued for its compatibility and performance in a wide range of materials, including:

Polyvinyl Chloride (PVC): Especially in flexible applications like roofing membranes, vinyl siding, and fencing.
Polyurethanes (PU): Used in coatings, adhesives, sealants, and elastomers (e.g., for protecting interior automotive dashboards and trim).
Unsaturated Polyester Resins: For gel coats and composites used in marine (boat hulls) and transportation applications.
Acrylics: In coatings and transparent sheets.
Adhesives and Sealants: To prevent yellowing and loss of strength upon outdoor exposure.
Wood Coatings: To protect the coating and the underlying wood from UV damage.

Advantages and Benefits

Excellent Compatibility: Its liquid form and chemical structure allow it to mix easily with many polymer systems and other additives without causing blooming or exudation.
High Efficacy: Provides strong UV screening across the critical UV-A and UV-B wavelengths.
Ease of Handling: As a liquid, it eliminates dusting issues associated with powders, simplifies metering, and disperses effortlessly during processing.
Color Stability: Very effective at preventing yellowing and discoloration in clear and lightly pigmented formulations.
Synergy: It works very well in combination with Hindered Amine Light Stabilizers (HALS). While the UV absorber (UVA) blocks incoming radiation, the HALS scavenges free radicals that are formed. This combination offers superior and more durable stabilization than either component alone.

Comparison to Other Common UV Absorbers

Feature	CYASORB UV-3638 (Liquid)	Tinuvin 326 (Solid Powder)	Tinuvin 1130 (Liquid)
Form	Liquid	Solid Powder	Liquid
Chemical Type	Benzotriazole	Benzotriazole	Benzotriazole
Primary Advantage	Easy handling, compatibility	Cost-effective, good performance	Good solubility, all-purpose
Best For	Liquid systems, PVC, PU, adhesives	Plastics processed at high temps	Coatings, acrylics, PVC

Summary

In essence, CYASORB UV-3638 is a premium liquid UV absorber chosen for applications where ease of processing, excellent compatibility, and high performance in demanding environments are critical. It is a key ingredient in formulating durable plastic products, protective coatings, and adhesives that must withstand long-term exposure to sunlight without failing or losing their aesthetic appeal.