Role of wetting and adhesion in alternative of CSM (chopped strand mat) reinforcement

Fiberglass chopped strand mat (CSM) has been the workhorse reinforcement for many years within the composites business – comparatively additional in Asia Pacific & European Market compared to North America, for obvious reasons. CHOPPED STRAND MAT is actually a nonwoven cloth within which chopped fibers are held together to make a uniform multi-directional reinforcement. Either polyester powder (for powder CHOPPED STRAND MAT) or plasticized PVA (PVAc) emulsion (for emulsion CHOPPED STRAND MAT) is used because the binder to carry the chopped fibers to alter formation of the mat.
Modified bisphenol fumarate polyester is usually used as the binder for powder bonded CHOPPED STRAND MAT. in sight of the binder’s chemical nature, solubility in vinyl resin (present within the laminating resin) is incredibly fast and complete - the vinyl resin (though in certain form) being a virtual solvent for the powder binder. it's analogous to sugar syrup's ability to soak up and dissolve additional sugar. Bonding power is expounded to adhesion and also the glorious adhesion with powder CHOPPED STRAND MAT is owing to the actual fact that the polyester powder binder is additional polar than this plasticized PVAC emulsion. Higher polarity results in higher wetting (zero contact angle because it spreads o.k. on the optical fibre substrate) and thus higher adhesion. The speed of dissolution of the polyester powder binder by vinyl resin (in the laminating resin) is fast throughout impregnation, resulting in very fast wet-through.  The size used for the chop roving (at the fiber forming stage) usually incorporates a polyester-based film former that imparts superior wet-out characteristics within the powder CHOPPED STRAND MAT. it's this mix of wonderful wet-out and quick wet-through abilities (especially the former) that enables most contact space at the resin-glass fiber interface and contributes to raised mechanical properties (specifically interlaminar shear strength excluding flexural strength/modulus) of composites created with powder CHOPPED STRAND MAT vis-à-vis emulsion CHOPPED STRAND MAT.