Optimization of scratch resistance and mechanical properties in wollastonite-reinforced polypropylene copolymers

Abstract

The aim of this research was to establish a balance between scratch resistance and scratch damage visibility in the wollastonite-filled heterophasic polypropylene copolymers.The influences of various factors including the surface hardness, elasticity, friction coefficient, and combinations thereof on the scratch behavior (scratch resistance and scratch visibility) were elucidated. Using micro-scale and nano-scale scratch tests and image analysis techniques, the scratch hardness, scratch depth, and scratch visibility of the composites were characterized.It was found that the introduction of wollastonite in the polypropylene copolymer matrix contributes to ductile fracture behavior because of an induced crystallization alteration. Accordingly, the scratch resistance of reinforced composites revealed an increase as a result of higher stiffness of the wollastonite as well as contribution of new crystalline structure. The addition of siloxane to the composites improved the resistance to surface damage by lowering the surface friction coefficient originated from enhanced chain mobility. Simultaneous addition of high density polyethylene and siloxane induced a significant influence on the resistance to the scratch damage.

Mechanical properties of wollastonite reinforced thermoplastic composites: A review

“…The results of dynamic mechanical analysis with higher storage and loss modulus of PP composites supported the reinforcing ability of wollastonite. However, a different finding was obtained by Sobhani and Khorasani, where it is found the introduction of wollastonite into PP copolymer matrix contributed to ductile fracture behavior of the composites and leaded to enhancement in elongation at break up to 30%. The ductile fracture occurred in this study might due to the good interfacial interaction and formation of new crystalline structure in PP copolymer induced by wollastonite, which facilitated the stress transfer and allow occurring of plastic deformation in the polymer matrix.…”

“…Improvement in impact strength of the PP copolymer was observed when wollastonite was incorporated . Work of Hadi et al revealed that impact strength of both calcium carbonate‐ and wollastonite‐reinforced PP composites increased with the filler content but wollastonite contributed greater enhancement…”

The Potential of Functionalized Ceramic Particles in Coatings for Improved Scratch Resistance

“…Even a few scratches, though most of them are a few micrometers in depth, can deteriorate the original appearance [3] and in some cases, may even affect functionality by rendering them more vulnerable to other types of strain (flexion, impact, fatigue, etc.) [4]. Hence, scratch resistance and scratch visibility are very important factors for the top functional coatings in laminate floors.…”

“…When these flaws on the damaged surface are larger than the wavelength of visible light, the scratches become visible [7]. The scratch visibility is known to correlate well with parameters like scratch hardness, scratch depth, surface roughness on the scratch path [6], coefficient of friction of the surface, and filler-matrix interface strength as well as the elastic recovery characteristics of the polymer [4]. The damage caused by plastic flow generally has a lower impact on the scratch visibility than brittle damage due to less scattered light [8,9].…”

“…Alumina has successfully been used as reinforcement for organic coatings with improved scratch resistance in a number of previous studies, for example, when added to Nylon-11 [15], melamine films [18] or PTFE [19]. A further improvement in the scratch resistance can be obtained through the strengthening of the polymer/particle interface [4], which will improve the dispersion state of the particles within the polymer matrix [20] and reduce the stresses associated with polymerization shrinkage [21] among others. Silane coupling agents are commonly used for functionalization, along with amines, carboxilates, phosphonates, etc., [22] as they can act as chemical bridges between the particle and the polymer.…”