Handbook of Nucleating Agents George Wypych, Editor Toronto 2016 Published by ChemTec Publishing 38 Earswick Drive, Toronto, Ontario M1E 1C6, Canada © ChemTec Publishing, 2016 ISBN 978-1-895198-93-5 (bound) ISBN 978-1-927885-12-3 (epub) Cover design: Anita Wypych All rights reserved. No part of this publication may be repro- duced, stored or transmitted in any form or by any means with- out written permission of copyright owner. No responsibility is assumed by the Author and the Publisher for any injury or/and damage to persons or properties as a matter of products liabil- ity, negligence, use, or operation of any methods, product ideas, or instructions published or suggested in this book. Library and Archives Canada Cataloguing in Publication Wypych, George Handbook of nucleating agents / George Wypych. -- First edition. Includes bibliographical references and index. Issued in print and electronic formats. ISBN 978-1-895198-93-5 (bound).--ISBN 978-1-927885-12-3 (epub) 1. Polymers--Additives--Handbooks, manuals, etc. 2. Crystallization. I. Title. TP1142.W956 2016 668.9 C2015-907781-8 C2015-907782-6 Printed in Australia, United States and United Kingdom 1 Introduction Nucleation is the initial process that occurs in the formation of a crystal from a solution, a liquid, or a vapor, in which a small number of ions, atoms, or molecules become arranged in a pattern characteristic of a crystalline solid, forming a site upon which additional parti- cles are deposited as the crystal grows.1 Phase transformation begins with formation of a new phase in the supersaturated old (mother) phase. The thermodynamic stability of the system requires continuity of the ther- modynamic functions during the phase transformation, the change in the thermodynamic potential occurring close to the transition point is by nature very small.2 Two possibilities exist: either an infinitely small amount of a new phase appears, having different properties than the old phase, or a new property appears.2 The first case is known as the first-order phase transition because first derivatives of the thermodynamic potential are changed, whereas the second case is known as the second-order phase transition because second derivatives of the thermodynamic potential are changed.2 Nucleation is a step in the phase and state transitions, involved in such processes as condensation, evaporation, crystallization, or melting, which are all the first-order transi- tions. The first-order transition begins with a need to overcome a free-energy barrier to create nucleus of the new phase on which additional elements of the system are deposited to grow a crystalline phase. Nucleation is either homogeneous or heterogeneous. Homogeneous nucleation is very rare since it requires specially designed experiments in system, which does not have any foreign elements. Although even in such cases, heterogeneous nucleation at container walls or free surface occurs (e.g., formation of bubbles in champagne poured into glass).3 In homogenous system, the formation of the new phase solely depends on fluctuations within the old phase. Assemblies of elements of the homogeneous system are formed in kinetic equilibrium with free liquid system and they are dissolved back into old phase. When temperature drops, more clusters are formed (metastable old phase becomes pres- ent) and finally stable nucleus is created on which other particles are deposited forming crystal. This means that the system needs to be brought into the metastable region to reduce the phase transition barrier until it becomes of the same order as the thermal energy, kT (where k is the Boltzmann constant and T is the absolute temperature).2 Heterogeneous nucleation occurs on the surface of impurities. These may exist in any system or special additives can be added to facilitate heterogeneous nucleation. Any interface with another material has potential importance for nucleation.3 Examples include a free surface, the wall of a container, embedded particle, an interphase boundary in a liq- uid or solid, and a grain or domain boundary in a solid.3 All such interfaces have positive free energies.3 Heterogeneous nucleation faces much smaller barrier towards phase transi- 2 Introduction tion. Rain, fog, ice and snow, salt crystallization by evaporation of sea water, and gas bub- ble formation in mineral water—in addition to polymer processing—begin with the nucleation of a new phase. Polymeric materials during their production must undergo phase changes to be formed into shapes required by their product design. For this reason, nucleation processes are very essential for the production technology, economy of the production, and product characteristics. This book discusses use of nucleating agents to increase the production rate, modify structure and morphology, and reduce haze of polymeric products with proper selection of nucleating agents (or the so-called clarifying agents). Handbook of Nucleating Agents brings analyses of important publications out of slightly less than 10,000 available today referring to various aspects of action of nucleating agents. Also many relevant patents are reviewed. Sufficient understanding for proper use of nucleation technology requires analyses of many aspect related to this subject. The book is divided into 14 chapters each of which concentrates on the essential performance of nucleating agents. Chemical origin and related properties of nucleating agents are analyzed in the general terms to highlight the differences in their properties and thus mode of their action. The specific agents are dis- cussed in Databook of Nucleating Agents which is published as a separate book to help in selection of products available in the commercial markets and to analyze properties of different products. Many theoretical principles help in proper application of nucleating agents. One of the important aspects is their effect on the rate and the degree of crystallization of poly- meric matrices into which they have been introduced. Critical processes occur here during crystallization process. Decrease of temperature alone already causes crystallization of polymers, usually with formation of α-crystals. Addition of nucleating agent contributes to formation of β-crystals which drive equilibrium of properties towards faster solidifica- tion (possibility of speeding process of removal of parts from forms) or to better organiza- tion of internal structure which translates to improved mechanical performance. Also, addition of well selected nucleating agents helps to produce sufficiently small spherulites that they do not interfere with light transmission thus help to produce materials having high clarity. Quality of contact between the nucleating agent and the matrix polymer affects effi- ciency of its action. This will depend on properties of a pair polymer-agent and distribu- tion of agent in the polymer matrix. Good wetting and absorption may lead to a complete removal of barrier to nucleation between both phases. Effect of concentration of nucleating agent and cooling rate are part of well designed system, which is able to produce expected results, and able to increase nucleation effi- ciency. Knowledge of the mechanisms of nucleation is also important aspect of selection of nucleating agents for particular tasks. Large segment of the book discusses use and selection of nucleating agents for dif- ferent processing methods, different polymers and specific products. These sections con- tain practical know-how on use of nucleating additives in different environments. Introduction 3 This part is followed by chapters discussing effect of nucleating agents on mechani- cal and physical properties of materials, important analytical methods used in their stud- ies, and health and safety information in the relationship to application of nucleating agents. Chemical origins of nucleating agents are discussed in the next chapter. There are 20 chemical groups of nucleating agents which are either currently used as commercially available additives or tried in experimental formulations. Each group is characterized by range of properties characteristic for representatives of the group. REFERENCES 1 Encyclopedia Britannica. 2 Nanev, C, The Theory of Nucleation, Handbook of Crystal Growth, 2nd Ed., Elsevier, 2015, pp. 315-58. 3 Kelton, K F; Greer, A L, Heterogeneous nucleation, Nucleation in Condensed Matter, Vol. 15, Elsevier, 2010, pp. 165-226. 2 Chemical Origin of Nucleating Agents Twenty chemical groups of inorganic and organic chemical are involved in production of nucleating agents. They include: • acids • amides • carbon nanotubes • graphene derivatives • hydrazides • inorganic materials boron nitride calcium carbonate hydroxides silica talc others • masterbatches • phosphate salts • polymeric materials • proprietary formulations • salts of carboxylic acids • sorbitol derivatives • xylan esters • others Each group is discussed in a separate section below. The main output includes a table containing properties of nucleating agents which belong to the particular group. The data come from 300 generic and commercial nucleating agents. The data show the range of properties which can be expected from products included in the group. To review data of individual nucleating agents used by industry, a separate publication entitled Databook of Nucleating Agents is available. 6 Chemical Origin of Nucleating Agents 2.1 ACIDS 2.1 Properties of acids GENERAL PROPERTIES Names: 2,5-Pyridine dicarboxylic acid; Glycine; L-Alanine; CAS #: 100-26-5; 56-40-6; Poly–DL–alanine; L-Aspartic acid; Polyglycine; Polyglycolide; 56-41-7; 56-84-8; 25281-63-4; Polylactide 25718-94-9; 26124-68-5; 26100-51-6 Synonims: isocinchomeronic acid; mixture of polycarbonic acids, inorganic carbonates, and fatty acid derivatives; aminoacetic acid; aminosuccinic acid; poly(glycolic acid); polyoxyacetyl; poly(L-lactic acid) IUPAC names: pyridine-2,5-dicarboxylic acid; poly[oxy(1-oxo-1,2-ethanediyl)] Purity, wt%: 98-98.5 PHYSICAL PROPERTIES State: solid Color: white to off-white Odor: odorless Melting point, oC: 232-270 Bulk density, kg/m3: 430-920 Density, g/cm3: 1.16-1.7 Volatility, wt%: 0.2% (105oC, 2h) Melt flow rate, g/10 min: 6-7 Solubility in water, wt%: soluble pH: 2.5-6.4 Solubility in solvents: methanol, acetone, acetic acid, ether HEALTH AND SAFETY Carcinogenicity: N (NTP, OSHA) Flash point, oC: 128.7 UN safety phrases: S22,S24/25 Oral rat, LD50, mg/kg: 7930 NFPA Flammability: 0-1 NFPA Health: 0-1 NFPA Reactivity: 0 USE Manufacturers: Endex; generic Outstanding properties: ice nucleation; biodegradable Recommended for polymer: PBA, PLA, iPS, PVA Processing methods: extrusion With decreasing cooling rate between 50 and 0.5 K s–1 the number of crystal nuclei increases which enhances cold-crystallization on subsequent heating, and which delays the formation and reduces the amount of additional nuclei during annealing of PLLA.1 The minimum half-time of crystallization is of the order of magnitude of few minutes and increases with increasing molar mass.1 The nucleation mechanism is independent of tem- perature in the range of 313 to 383K.2 REFERENCES 1 Androsch, R; Iqbal, N; Schick, C, Polymer, in press, 2015. 2 Androsch, R; Di Lorenzo, M L, Polymer, 54, 6882-85, 2013. 2.2 Amides 7 2.2 AMIDES 2.2 Properties of amides. GENERAL PROPERTIES Names: 1,3,5-Benzenetrisamide; Irgaclear; Light Amide; NJstar; CAS #: 51253-00-1; N,N'-Bis(2-stearamidoethyl)sebacamide; N,N’-Dicyclohexyl- 60768-10-7; 2,6-naphthalene dicarboxamide; N-Tallow-4-toluenesulfon- 153250-52-3; 160535-46-6 amide; Rikaclear; Uniplex Synonims: 1,3,5-benzene tricarboxamide; 1,3,5-tris (2, 2-dimethylpropanamide)-benzene; ethylene bis stearamide; N,N'-bis(2-stearamidoethyl)sebacamide; N,N'-dicyclohexyl-2,6-naphtha- lene dicarboxamide; (N,N',N''-tris[2-methylcyclohexyl]-1,2,3-propaneticarbooxamide) IUPAC names: 1,3,5-benzenetricarboxamide; N,N'-bis[2-(2-aminoethyl)octadecanoyl] decanediamide; 2-N,6-N-dicyclohexylnaphthalene-2,6-dicarboxamide; N-alkyl toluene sulfonamide Moisture content, %: 0.1-0.5 Purity, wt%: 99 PHYSICAL PROPERTIES State: solid Color: white, yellow Acid number, mg KOH/g: 15 Boiling point, oC: 456-700 Melting point, oC: 78->400 Refractive index: 1.483-1.649 Bulk density, kg/m3: 100-400 Density, g/cm3: 0.92-1.4 Solubility in water, wt%; insoluble Volatility, wt%: 0.5 Surface tension, mN/m: 48.0-76.6 Vapor pressure, kPa: 0.279 HEALTH AND SAFETY Flash point, oC: 200-248 REL/PEL, mg/m3: 5 (respirable fraction, OSHA), 15 (total dust, OSHA) USE Manufacturers: BASF, Recommended for polymer: PA, PBT, PET, PLA, iPP, PVDF Kyoeisha Chemical, New Japan Chemical, Unitex Outstanding properties: excellent thermal stability with chemical resistance, β-crystal nucleating agent, improves secondary processability, enhances shock resistance and heat resistance by lower- ing the melting point of PP resins; clarifying agent eliminates plateout during extrusion, improves the transparency, gloss, rigidity, flexural modulus, tensile strength Typical applications: sheet, profiles Concentration used, wt%: 0.0015-0.3 Processing methods: extrusion, injection molding Food contact: yes An aryl amide derivative (TMB-5) was used to nucleate the poly(l-lactide)/poly(d- lactide) (PLLA/PDLA) blend.1 The selective nucleation of stereocomplex (sc) crystals was observed.1 A sc crystal layer was found on the lateral surface of nucleating agent.1 REFERENCES 1 Xiong, Z; Zhang, X; Wang, R; de Vos, S; Wang, R; Joziasse, C A P; Wang, D, Polymer, 76, 98-114, 2015. 8 Chemical Origin of Nucleating Agents 2.3 CARBON NANOTUBES 2.3 Properties of carbon nanotubes. GENERAL PROPERTIES Names: CNT Regular; Nanocyl, Pyrograf CAS #: 1333-86-4 Synonims: single wall carbon nanotubes; multiwall carbon nanotubes Purity, wt%: 90 Product content: 70-99% carbon, 10-30% oxide, 0.14% sulfur, 0.94% iron PHYSICAL PROPERTIES State: solid Color: black Odor: odorless Particle size, μm: 0.45-100 (length, 0.3-150 nm (diameter) Melting point, oC: 3652-3697 Solubility in water, wt%: insoluble Bulk density, kg/m3: 40-870 Specific surface area, m2/g: 20-1000 Density, g/cm3: 1.3-2.1 Thermal conductivity, W/mK: 50-3500 HEALTH AND SAFETY Autoignition temperature, oC: 610 Oral rat, LD50, mg/kg: >2000->5000 NFPA Flammability: 1 NFPA Health: 1-2 NFPA Reactivity: 0 USE Manufacturers: Carbon Nano-material Technology; NanoLab; Applied Sciences Recommended for polymer: PE, PCL, PLA, PP Outstanding properties: a good nucleating agent as well as reinforcement, fast heterogeneous crystallization, high electrical conductivity Short chain branching in polyethylene decreases adsorbed polymer chain on the sur- face of carbon nanotubes.1 Simulation study shows that the carbon nanotube seems to increase more efficiently the polyethylene crystallinity in the case of the branched chains than in the linear ones.1 The presence of surface groups on carbon nanotubes reduced their ability to nucleate poly(L-lactic acid).2 At high supercooling, where homogeneous nucle- ation is prevalent, the addition of carbon nanotubes does not affect the crystallization rate of PCL. REFERENCES 1 Jeronimo, K; Cruz, V L; Ramos, J; Vega, J F; Trujillo, M; Mueller, A J; Martinez-Salazar, J, Eur. Polym. J., 56, 194-204, 2014. 2 Kiang, Y-Y; Xu, J-Z; Liu, X-Y; Zhong, G-L; Li, Z-M, Polymer, 54, 23, 6479-88, 2013. 3 Zhuravlev, E; Wurm, A; Poetschke, P; Androsch, R; Schmetzer, J W P; Schick, C, Eur. Polym. J., 52, 1-11, 2014. 2.4 Graphene derivatives 9 2.4 GRAPHENE DERIVATIVES 2.4 Properties of graphene derivatives. GENERAL PROPERTIES Names: Fullerene; GnP Purity, wt%: 99-99.95 Synonims: graphene, graphene oxide nanosheet Product content: C60 spherical allotrope of carbon, important property of C60 molecule is its high symmetry; nanoparticles consist short stacks of graphene sheets having a platelet shape PHYSICAL PROPERTIES State: solid Color: black Odor: odorless Specific surface area, m2/g: 750 Particle size, μm: 2 USE Manufacturers: Nano-C; XG Science Recommended for polymer: epoxy, PCBM, PLC, PLLA, PP Outstanding properties: increase in fracture toughness, epitaxial crystallization Typical applications: solar cells, medical applications, many industrial applications Processing methods: injection molding Concentration used, wt%: 0.01-0.25 The graphene nanosheets impede the movements of PCL chain and increase the sys- tem viscosity, resulting in an evident increase of crystallization activation energy.1 The nonisothermal cold crystallization behavior of PLLA was enhanced by the presence and amount of graphene oxide.2 REFERENCES 1 Lv, C; Wu, D; Qiu, Y; Chen, J; Yao, X; Ding, K; Wei, N, Thermochim. Acta, 612, 25-33, 2015. 2 Zhao, H; Bian, Y; Li, Y; Han, C; Dong, Q; Dong, L; Gao, Y, Thermochim. Acta, 588, 47-56, 2014.