Polyvinyl acetate (PVAc)

Key benefits:

• Thermoplastic and adhesive
• Very low odour
• Good compatibility with plasticisers
• Wide range of solvent solubilities
• Convenient ready-to-use solutions available

We produce a range of polyvinyl acetate homopolymers and copolymers for use as low-profile additives (LPAs) in polyester resin moulding. These thermoplastic polymers provide effective control of resin shrinkage during cure, achieving Class A surfaces in SMC and excellent dimensional stability in BMC and pultrusion.

Pultrusion is a high-volume process used for the production of continuous composite profiles such as rods, frames and tubes where dimensional stability and surface finish are important. Low to medium molecular weight PVAc homopolymer grades are used, with M30, M40 and M45, providing a range of solution viscosities for excellent resin flow and reinforcement wetting.

In highly filled bulk moulding compounds (BMC) Synthomer grades M40, M45 and M50 give medium viscosity solutions for easy compound addition and efficient low-profile properties. BMC for headlamps, electrical boxes and appliances are some typical applications where these LPAs will provide benefits.

Sheet moulding compound (SMC) formulations require a high-performance LPA system. The PVAc can be selected to not only achieve excellent surface quality but also controlled thickening of the resin sheet during maturation. Many SMC-produced components need a zero-shrink performance to meet the exacting requirements of Class A surfaces demanded in automotive and truck panels.

H302 is a carboxylated PVAc widely used for formulation in all types of SMC. On some SMC machines where a separate B side addition is made to carry pigment into the SMC resin, homopolymer grades M45 or M50 can be used to provide stable solution viscosity for pigment suspension. Where a lower viscosity solution is required, H301 is a lower molecular weight carboxylated PVAc which can be used alone or in combination with H302.

Resin transfer moulding (RTM) or vacuum infusion are low-pressure injection systems which use simpler tooling for shorter production runs. Low molecular weight products such as M30 and H301 can be used to achieve shrink control in tooling resins, boat hulls and panels. H356 is a specialised PVAc copolymer designed for RTM, offering excellent shrink control across a wide temperature range.

The polymer overcomes variable performance issues caused by:

• No external mould heating
• Variable resin thickness and exotherm
• Intricate mould design.

Synthomer M grade PVAc homopolymers are an excellent polymer base for solvent based adhesives.  They deliver excellent adhesion, penetration and drying properties for a wide range of substrates including paper, wood, metal and many plastics.

MCT5 combines the benefits of a carboxylic acid group as a reactive site with a thermoplastic backbone. This product has the added advantage that it can be delivered to the point of use either as a solid, an aqueous solution, a low VOC-containing solution or as a solvent-based system.

The cross-linking reactions that are possible with MCT5 can be exploited by the product formulator to provide increased toughness to films and adhesive layers, as well as reducing their rate of water up-take or solvent sensitivity.

These reactions are useful in application areas such as the adhesion of metallised security stampings on credit cards and bank notes, hot-stamping foil adhesives for decorative packaging and cross-linked coatings.

Polyvinyl acetate (PVAc) exhibits a visco-elastic nature between 0-50°C, the temperature bandwidth most suitable for sound damping. Synthomer M grade PVAc homopolymers and copolymers are known to have exceptionally high internal sound dampening characteristics. M30 and M50 grades specifically have proven performance in the production of sound damping foils for transport vehicles.

These foils are low weight, giving enhanced fuel economy to the vehicle as well as providing a very high level of passenger comfort, with low noise and vibration transfer to the internal cabin. Sheets formulated with these resins result in more effective sound damping performance over a broad range of temperatures. In comparison to competing resin technologies such as asphalt, PVAc is thinner, lighter, and non-toxic.

Synthomer solid M grades and solutions can be formulated into a wide variety of interior and exterior varnishes, sealers, primers and coatings where adhesion, good penetration and substrate stabilisation is required. Formulations incorporating PVAc resins exhibit excellent resistance to oil and grease, reduced water vapour permeability, and enhanced durability.

Synthomer’s M35/73 grade is commonly selected by coating formulators for use in stabilising primer formulations. Designed as a penetrative binder resin for dusty, chalky and weathered masonry or concrete surfaces, coatings exhibit excellent substrate wetting, impregnation, binding and drying behaviour.

Synthomer M solids and solutions are used alone or in combination with pigments or other resins to impregnate paper, board, felts, non-woven textiles and leather. These materials can then be thermoformed to provide stiffening for fabric items and glass fibre mats.

The high wet strength plus water and oil resistance imparted by Synthomer M grades ensures that these products are typically used as first choice resin in the manufacture of speciality papers for oil and air filtration.