Polypropylene–rubber blends: 2. The effect of the rubber content on the deformation and impact behaviour

The scratch behaviors of a broad range of polymers are investigated to understand how the material characteristics of a polymer affect the scratch resistance. A constant load scratch test and a progressive load scratch test are chosen for the present study. A scratch model proposed by Hamilton and Goodman is applied to correlate the mechanics and material parameters during the scratch process. An attempt is made to correlate the scratch behavior and basic material properties, such as the Young's modulus, yield stress, and tensile strength. A correlation between the scratch behavior and material surface characteristics, such as the friction coefficient, scratch hardness, and elastic recovery, under the current scratch tests are also made. Scratch subsurface damage in polymers is studied using optical microscopy. It is shown that shear yielding is the main cause of the plastic flow scratch pattern, while tensile tear on the surface and shear-induced fracture on the subsurface are the main damage mechanisms found in the fracture scratch pattern. The main causes for the susceptibility of thermoplastic polyolefins to scratch damage are discussed. Approaches for making scratch-resistant polymers are also addressed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 47–59, 2001

Scratch behavior and material property relationship in polymers

Polypropylene–rubber blends: 5. Deformation mechanism during fracture

Carbon nanomaterials including carbon black (CB), carbon nanotubes (CNTs) and graphene have attracted increasingly more interest in academia due to their fascinating properties. These nanomaterials can significantly improve the mechanical, electrical, thermal, barrier, and flame retardant properties of elastomers. The improvements are dependent on the molecular nature of the matrix, the intrinsic property, geometry and dispersion of the fillers, and the interface between the matrix and the fillers. In this article, we briefly described the fabrication processes of elastomer composites, illuminated the importance of keeping fillers at nanoscale in matrices, and critically reviewed the recent development of the elastomeric composites by incorporating CB, CNTs, and graphene and its derivatives. Attention has been paid to the mechanical properties and electrical and thermal conductivity. Challenges and further research are discussed at the end of the article.

https://iopscience.iop.org/article/10.1088/0957-4484/26/11/112001/pdf

Elastomeric composites based on carbon nanomaterials

Toughening of polypropylene by different elastomeric systems

An extensive fundamental investigation of the rheological properties and solid wall boundary condition shear stress of elastomers and elastomer–carbon black compounds has been carried out. The elastomers were an emulsion butadiene–styrene copolymer (SBR 1500) and a polybutadiene. Shear flow rheological properties were measured using a newly designed sandwich rheometer, in both constant shear rate and creep modes as well as in a capillary rheometer. A constant elongation rate rheometer for elastomers was developed. Stress relaxation measurements were also carried out in the sandwich rheometer. The shear viscosity of the gum elastomers exhibits a constant very high shear zero viscosity (8 × 108 Pa.s for SBR 1500 at 100°C) and decreases with increasing shear rate. The compounds exhibit yield values of similar magnitude to carbon black compounds of molten plastics. Only the SBR 1500 and its compounds were studied in the elongational flow mode. It was not possible to achieve a steady state in these experiments. An apparatus for measurement of shear stress as a function of velocity (shear rate) at a specified pressure was developed. The instrument, which we call a friction tester, was used not only to determine wall shear stress but to investigate the regime of flow and potentially determine conditions for the onset of slip. Evidence of changing flow regimes were found, and the implications discussed.

Rheological and solid wall boundary condition characterization of unvulcanized elastomers and their compounds

Fracture behavior of polypropylene (PP)/ethylene–propylene–rubber (EPR) blends containing small crystal in elastomeric phase was investigated. Various ethylene-α-olefin co-polymers (ECP) were used as crystal components and put into the elastomer phase of the blends. The crystallite size was controlled by changing the composition of the ECP. From thermal analysis and electron microscopic analysis, it was found that the ECP having a smaller crystal had better affinity to EPR and thus the crystal was finely dispersed in the elastomeric phase. The ECP with large crystallite size had poorer affinity to EPR and tended to segregate in the elastomeric phase. Scratch resistance and tensile elongation of blends were measured and it was found that the small crystal drastically improved the above properties while the large crystal deteriorated them. The dispersed small crystal was thought to act as a crosslinking point in the elastomeric phase. The reinforcement of the elastomeric phase by such quasi-crosslinking structure was the possible reason for the improvement of the mechanical properties of the blends. © 1995 John Wiley & Sons, Inc.

Characterization of microstructure and fracture behavior of polypropylene/elastomer blends containing small crystal in elastomeric phase

A thermoplastic resin composition comprising (a) modified polyolefin produced by graft-polymerizing a polyolefin with a glycidyl compound represented by the following general formula: ##STR1## wherein R is a hydrogen atom or an alkyl group having 1-6 carbon atoms, Ar is an aromatic hydrocarbon group having 6-20 carbon atoms and containing at least one glycidyloxy group, and n is an integer of 1-4; and (b) a matrix polymer resin such as polyamide, polyester, polycarbonate etc.

Modified polyolefin-containing thermoplastic resin composition

Blends of propylene–ethylene block copolymer (PEB) and propylene homopolymer (PP) were prepared to give various rubber contents (4–20 wt %). By diluting the PEB with PP with molecular weight equal to that of the PEB matrix, molecular characteristics of all the blends were kept constant. The rubber particle size and size distribution of all the blends were almost constant, so that the interparticle distance decreased with increased rubber content. According to the observation of the fracture behavior at −20°C, a brittle to ductile transition was found at the rubber content of 16 wt %. Microdeformation behavior of the blends was investigated in the region of brittle to ductile transition by using transmission electron microscopy. In the case of the brittle sample with low rubber content, crazing and voiding were observed. Whereas even in the ductile sample with high rubber content, crazing certainly took place before shear yielding. The origin of ductile fracture could possibly be attributed to the relaxation of strain constraint by the microvoids contained in the craze. © 1993 John Wiley & Sons, Inc.

Microdeformation mechanisms in propylene–ethylene block copolymer

A thermoplastic resin composition comprising (a) modified polyolefin produced by graft-polymerizing a polyolefin with a glycidyl compound represented by the following general formula: wherein R is a hydrogen atom or an alkyl group having 1-6 carbon atoms, Ar is an aromatic hydrocarbon group having 6-20 carbon atoms and containing at least one glycidyloxy group, and n is an integer of 1-4; and (b) a matrix polymer resin such as polyamide, polyester, polycarbonate etc.

Shigeyuki Toki

Papers

Rheological and solid wall boundary condition characterization of unvulcanized elastomers and their compounds

Characterization of microstructure and fracture behavior of polypropylene/elastomer blends containing small crystal in elastomeric phase

Modified polyolefin-containing thermoplastic resin composition

Microdeformation mechanisms in propylene–ethylene block copolymer

Modified polyolefincontaining thermoplastic resin composition