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Surface energy considerations for offset printing of coated paper and paperboard, TAPPI Journal November 2023

ABSTRACT: Offset printing of coated paper involves the complex interactions of ink with a surface that is characterized by three major properties: roughness, porosity, and related pore network structure and surface chemistry (related to surface free energy [SFE]). The effects of porosity and roughness are relatively well understood and are documented in the literature, whereas the influence of surface chemistry is much less studied and therefore the focus of this paper. The key results shown include: i) Coating porosity has a negligible effect on SFE determination by contact angle using two fluids. ii) The chemistry of the latex polymer in the coating formulation dominates the influence on SFE compared to pigment, with any surface energy differences present in the pigment being almost completely masked by latex. iii) Wetting agent and corona treatment can impact water absorption rate and surface spreading of water, resulting in small differences in printability. Increasing the concentration of the surfactant on a coated surface indicates switching orientation of the surfactant molecules, giving a “step wise” printing result. When looking to improve offset printability by selection of different pigments, the variation in SFE is less important than variation in either surface roughness or porosity.

Papermakers’ Top Issues on Docket for PaperCon 2020, Paper360º March/April 2020

Papermakers’ Top Issues on Docket for PaperCon 2020, Paper360º March/April 2020

2021 TAPPI/PIMA Awards: Rising to the Challenge, Paper360º May/June 2021

2021 TAPPI/PIMA Awards: Rising to the Challenge, Paper360º May/June 2021

Automation Update: What Does the Future Hold?, Paper360º March/April 2019

Automation Update: What Does the Future Hold?, Paper360º March/April 2019

It Turned into Nothing, Paper360º March/April 2022

It Turned into Nothing, Paper360º March/April 2022

Failure Isn’t Just an Option — It’s Unavoidable, Paper360º

Failure Isn’t Just an Option — It’s Unavoidable, Paper360º March/April 2017

Pulp and Paper: Industries with a Bright Future, Paper360º January/February 2019

Pulp and Paper: Industries with a Bright Future, Paper360º January/February 2019

Leading for Change: 2023 TAPPI Award Winners, Paper360º May/June 2023

Fixing Just One Link Doesn’t Strengthen a Chain, Paper360º September/October 2022

Use of kaolin clay in aqueous barrier coating applications, TAPPI Journal November 2023

ABSTRACT: Paper-based packaging with barrier effect, as opposed to single use plastics, is gaining more prominence for sustainability reasons. At the same time, latex- or biopolymer-based aqueous barrier coating dispersions are increasingly being adopted as a better alternative to the traditional barrier coating materials, such as wax, surface active chemicals, and polyethylene. In this work, studies were performed to determine the influence of different kaolin clays in latex binder-based aqueous coatings on barrier properties, namely, oil and grease, water resistance, and water vapor transmission rate, by applying coatings to solid bleached sulfate (SBS) paperboard substrate in the laboratory. The aim was to explore potential benefits of using kaolin clay to replace some of the latex binder in coating and improve or maintain various types of barrier performance and blocking without negatively influencing the other performance attributes, including heat seal. The delaminated clay with the highest shape factor provided improved barrier properties over the clays of low shape factor. The ultrafine and non-delaminated clays required significantly higher coat weights to reach satisfactory barrier properties. Coatings with different latex levels indicated that a considerably high proportion of coarse delaminated clay can be incorporated to replace latex binder, while still achieving exceptional barrier properties. Furthermore, a change in binder system was found to significantly alter the barrier properties and the role that a mineral pigment can play. The results indicate that a proper selection of binder systems for each barrier property would be required while considering the clay/latex coating systems.