Epoxy resin is usually the matrix for adhesives, coatings, composites, and other materials, widely used in construction, machinery, electronics, aerospace, and more. What makes epoxy so widely used is the result of these varied formulations. The curing agent especially matters: once the epoxy resin is fixed, the curing agent decisively determines the processing behavior of the epoxy composition and the final properties of the cured product.
Components of an epoxy resin composition and their roles
Classification of epoxy curing agents and their features:
By reactivity and chemical structure:
Aliphatic amine curing agents:
High activity, can cure at room temperature
Reacts vigorously with heat release, short pot life
Usually needs post-cure: 7 days at room temperature, then 2 h at 80–100°C
Cured product has low heat deflection temperature, usually 80–90°C
Cured product is brittle
High volatility and toxicity
Aromatic polyamine curing agents:
Cured product has good heat resistance; chemical resistance and mechanical strength are better than aliphatic polyamines
Low activity, mostly heat-cured
The benzene ring lowers electron cloud density on the nitrogen, weakening basicity, plus steric hindrance from the ring
Mostly solid, high melting point, poor processability
Can be liquefied by low-eutectic-point mixing, or by adding polyamines to monoglycidyl ethers
Modified amine curing agents:
Good compatibility with epoxy, not strict on stoichiometry
Cured product has a good toughening effect
Low exotherm, long pot life, lower heat resistance of cured product, HDT around 60°C
Anhydride curing agents:
Very slow reaction, can't form highly crosslinked products, generally not used as curing agents on their own
Low volatility, low toxicity, low irritation
Slow reaction, little heat release, long pot life
Cured product has low shrinkage and high heat resistance
Cured product has high mechanical strength and excellent electrical properties
Needs heat curing, long time
Common curing agent for epoxy, second only to polyamines
By curing temperature, curing agents fall into four types:
Low-temperature curing agents: cure below room temperature;
Loctite 352 UV adhesive specs
Loctite 352 UV adhesive (LOCTITE AA 352M) is a one-part, UV-curing modified acrylate adhesive, often called Loctite 352 glue in industrial selection. It's mainly used for bonding, coating, or sealing metals, glass, and similar materials, and after curing it has good resistance to vibration and impact. Here are the key parameters from the Loctite 352 TDS so users can quickly understand its performance and use conditions.
Product overview
Loctite 352 glue is a modified acrylate UV adhesive. It's a transparent, pale amber liquid, one-part, no mixing required, medium viscosity. It cures by UV light and can be secondarily cured with heat or an activator. Typical applications include bonding electronic devices, appliance parts, and decorative components, and it can also be used to bond, seal, or coat metal and glass parts.
Core features:
Chemical type: modified acrylate
Appearance: transparent pale amber liquid
Composition: one-part, no mixing
Cure: UV curing
Secondary cure: heat and activator
Advantage: fast production cure
Applications: bonding, coating, sealing
Parameter quick view
Item / Parameter
Product name: LOCTITE AA 352M / Loctite 352
Chemical type: modified acrylate
Appearance (uncured): transparent pale amber liquid
Composition: one-part, no mixing
Density @25°C: 1.06
Refractive index, ASTM D542: 1.48
Color, Gardner scale: ≤6
Viscosity, Brookfield RVT, 25°C: 15,000–26,000 mPa·s (spindle 6, 20 rpm)
Flash point: see MSDS
UV cure wavelength: 365 nm; full surface cure in air requires 250 nm
Heat cure: 30 minutes at 121°C
Activator cure: with LOCTITE 7075 activator, about 4 minutes to handling strength for small gaps, fully cured in 72 hours
Typical post-cure test: 30 seconds per side at 365 nm, 100 mW/cm², then 24 hours at 22°C
Material properties before cure
Before curing, Loctite 352 glue is a transparent pale amber liquid with density about 1.06 g/cm³, refractive index about 1.48, and Gardner color ≤6. Its Brookfield RVT viscosity at 25°C is 15,000–26,000 mPa·s, a medium-viscosity UV adhesive suitable for dispensing, coating, and sealing. For flash point, check the MSDS.
Cure method and speed
1) UV cure
Loctite 352 UV adhesive cures under 365 nm UV light. To fully cure surfaces exposed to air, 250 nm UV light is also needed. Cure speed depends on the UV intensity reaching the product surface.
Debonding time reference:
Light source / Condition / Debonding time
A quick intro: PET (Polyethylene Terephthalate) is one of the most common plastics in daily life, widely used in soft drinks, dairy, edible oil, condiments, alcohol, household chemicals, electronics, and more. The grade used for food and beverage packaging bottles and cans is called bottle-grade PET, also known as polyester bottle chips or bottle-grade polyester chips, with purified terephthalic acid (PTA) and ethylene glycol (MEG) as the main raw materials.
China is the world's largest supplier of bottle-grade PET. By the end of 2025, nominal capacity was 21.47 million tons per year, about 49% of global capacity, up 5.1% year on year. Yisheng Petrochemical, China Resources Chemical, Sanfangxiang, and Wankai New Materials together have about 17.2 million tons of capacity, giving the domestic industry a CR4 of 80.11%.
Mention Wankai New Materials and you can't avoid founder Shen Zhigang. Born in 1974 in Xiaoshan, Hangzhou, he worked as a machine repairman. In 1992, with 8,000 yuan he'd saved, he bought two second-hand shuttle looms, hired three workers, and started a business in a 30-square-meter workshop in Xiaoshan. By 1997 he had 32 looms, and no longer satisfied with just weaving fabric, he decided to move upstream and founded Hangzhou Shenda Chemical Fiber Co., Ltd. (the predecessor of Zhengkai Group).
In 2002, Zhengkai Group was born and gradually grew into a comprehensive private group integrating textiles, trade, real estate, and investment, with five subsidiaries, over 1,000 employees, and annual revenue exceeding 1 billion yuan. In 2008, Shen originally planned to land a new textile and chemical fiber project in Haining. But with uncertainty growing in the textile industry's prospects, after on-site research and careful assessment, he set his sights on the food packaging track and invested in founding Wankai New Materials, formally entering the PET materials industry.
After more than a decade of development, by the end of 2025, Wankai New Materials had a designed PET production capacity of 3 million tons per year, located in the chemical new materials park in Jianshan New District, Haining, and the Lingang Industrial Park in Fuling, Chongqing, forming an east-west layout. This creates differentiated competition against Yisheng Petrochemical's south (Hainan) and north (Dalian) layout, China Resources Chemical's east (Changzhou) and south (Zhuhai) layout, and Sanfangxiang's concentrated eastern (Jiangyin) layout.
In addition, Wankai New Materials has an annual ethylene glycol production capacity of 600,000 tons.
Sichuan Zhengdakai New Materials Co., Ltd., located in the Liuchi Industrial Park of the Puguang Economic Development Zone in Dazhou, Sichuan, reached full production and stable operation of its first phase in May 2025, mainly supplying the Chongqing base, achieving ethylene glycol-PET bottle chip integration and further strengthening the company's low-cost, high-efficiency operating advantages.
