Rheology of PVAc–MMT–STAB

Journal of Thermoplastic Composite Materials

2011

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To improve the chemical, physical, mechanical and thermal properties of polyvinyl acetate (PVAc), N-hydroxymethyl acrylamide (NMA) was used to polymerize with vinyl acetate (VAc). During the emulsion polymerization of VAc using polyvinyl alcohol as protective colloid and ammonium persulfate as initiator, PVAc-NMA was prepared under the conventional conditions in laboratory. In the polymers, larger PVAc-NMA particles and other smaller NMA-NMA particles randomly dispersed together. Their dispersion was good. PVAc-NMA was a pseudo-plastic non-Newtonian fluid, also possessed the normal stress effect (or Weissenberg effect), the pole-climbing phenomenon. With the change of different synthesis processes and the increase in NMA content in the synthesis system, the molecular weight of PVAc-NMA increased. NMA could lower the glass transition temperature of PVAc, and then improved PVAc's low temperature resistance, so PVAc-NMA could be applied in more harsh or much lower temperature conditions. The static tensile of PVAc-NMA was better. PVAc and PVAc-NMA all had the cold crystallization. The pyrolysis of PVAc and PVAc-NMA was similar. It was found to consist of eight phases.

Section: Introductionmentioning

confidence: 99%

Development of Novel Polymers prepared by vinyl acetate and N-hydroxymethyl acrylamide

Journal of Thermoplastic Composite Materials

2011

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“…PDE, PDP, PCP, VE and PBA, have different effects on the viscosity of ECAs because of the different viscosities of their respective solutions; (2) these flexibilizers might not be dissolved completely such that some residues contain small particles to raise the viscosity; and (3) these flexibilizers generally do not react with the functional epoxy at RT, but some of them might undergo chemical reaction at high temperature to lengthen the polymer chain and raise the viscosity. It also can be seen that the viscosity of ECAs and FECAs decreases with increasing shear rate, indicating that they all are pseudo‐plastic non‐Newtonian fluids, also called the shear‐thinning fluids …”

Section: Resultsmentioning

confidence: 99%

Novel flexible electrically conductive adhesives from functional epoxy, flexibilizers, micro-silver flakes and nano-silver spheres for electronic packaging

Fan

2013

Polym. Int

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In this study, five different flexibilizers were added into a matrix resin to improve the flexibility of electrically conductive adhesives (ECAs). The flexible ECAs were fabricated from the matrix resin and electrically conductive fillers. Their curing was fixed at 150 °C for 30 min. Of the five flexibilizers, 1,3‐propanediol bis(4‐aminobenzoate) (PBA) had the best effect on the electrical, mechanical and thermal properties of the ECAs. During curing, PBA reacted with the functional epoxy in the matrix resin. The soft ether segments in PBA were grafted into the crosslinked epoxy network to form an orderly spaced mesh structure. This led to high‐temperature stability, with the pyrolysis temperature being above 350 °C. Flexible ECAs with a 10% weight ratio of PBA in the matrix resin had the best properties. Their viscosity and bulk resistivity were the lowest. Their flexibility and electrical conductivity were the highest. They also had low storage modulus which could effectively dissipate or reduce the residual shear stress generated by the mismatch of thermal expansion coefficient between chip and substrate. Their impact strength was the lowest, and the toughening effect was so significant that the improvement was about 48% compared to ECAs. © 2013 Society of Chemical Industry

“…Therefore, in this paper, to simplify the preparation process, PVAc-MMT was prepared under conventional conditions in the laboratory with no ultrasonic dispersion, no radiation and no other additives as main components. In our previous work, [14][15][16] MMT was often organically activated to obtain good exfoliated nanocomposites, while, here, original MMT was used. In the preparation, MMT was 2% of VAc.…”

Section: Introductionmentioning

confidence: 99%

Development of exfoliated nanocomposite prepared from vinyl acetate and montmorillonite

Plastics, Rubber and Composites

2012

To improve the chemical, physical, mechanical and thermal properties of polyvinyl acetate (PVAc), montmorillonite (MMT) was added and polymerised with vinyl acetate to prepare an exfoliated nanocomposite of PVAc-MMT. Linear macromolecular chains of PVAc were formed between MMT layers and they exfoliated MMT into layers or sheets of nanoparticles. Both PVAc and PVAc-MMT were pseudoplastic non-Newtonian fluids, and possessed the normal stress effect (or Weissenberg effect) that was the pole climbing phenomenon. PVAc-MMT's static tensile properties were better, and PVAc's glass transition temperature was lowered by MMT. Both PVAc and PVAc-MMT possessed cold crystallisation, and their pyrolysis were similar, because MMT had no obvious effect on pyrolysis temperatures but mainly delayed thermal degradation processes.