1、AEROSPACE RECOMMENDED PRACTICE ARP5256 Issued 1997-03 Reaffirmed 2014-11 MIXING RESINS, ADHESIVES AND POTTING COMPOUNDSRATIONALE ARP5256 has been reaffirmed to comply with the SAE five-year review policy. _ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance
2、 the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every
3、 five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2014 SAE International All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by an
4、y means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.
5、org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/ARP5256 TABLE OF CONTENTS1. SCOPE.31.1 Purpose32. REFERENCES.32.1 Applicable Documents32.1.1 SAE Publications32.1.2 Applicable References33. GENERAL 34. HEALTH AND ENVIRONMENTA
6、L .44.1 Personal Protective Equipment 45. CONSUMABLE MATERIALS/EQUIPMENT .56. RESIN COMPOUNDS AND ADDITIVES76.1 Potting Compounds76.2 Paste Adhesives.76.3 Additives.76.3.1 Microballoons .86.3.2 Fumed Silica.86.3.3 Powdered Aluminum 86.3.4 Milled Fibers .96.3.5 Chopped Fibers96.3.6 Fire Retardant Add
7、itives .96.3.7 Resin Extenders .9TABLE OF CONTENTS (Continued)7. MIXING 97.1 Laminating Resin Quantity Determination.107.2 Adhesive Quantity Determination .117.3 Resin, Adhesive and Potting Compound Mixing Method 12SAE INTERNATIONAL ARP5256 Page 2 of 13_ 1. SCOPE:This SAE Aerospace Recommended Pract
8、ice (ARP) describes and gives general guidelines on useand applicability of the standard method for mixing resins, adhesives, and potting compounds.1.1 Purpose:The purpose of this document is to provide a standard method for mixing resins, adhesives, andpotting compounds that may be referenced in re
9、pair documents produced by airlines or airframeand engine manufacturers. It is intended that this document be one of a number of ARPs that willcover other aspects of the techniques required to perform composite repairs. This will provide asuite of available repair techniques that are acceptable for
10、use throughout the commercial aircraftindustry.2. REFERENCES:2.1 Applicable Documents:The following publications form a part of this document to the extent specified herein. The latestissue of SAE publications shall apply. The applicable issue of other publications shall be theissue in effect on the
11、 date of the purchase order. In the event of conflict between the text of thisdocument and references cited herein, the text of this document takes precedence. Nothing inthis document, however, supersedes applicable laws and regulations unless a specific exemptionhas been obtained.2.1.1 SAE Publicat
12、ions: Available from SAE, Commonwealth Drive, Warrendale, PA 15096-0001.ARP4916 Masking and Cleaning of Epoxy and Polyester Matrix Thermosetting CompositeMaterialsARP4977 Drying of Thermosetting Composite MaterialsAIR4844 Composites and Metal Bonding Glossary.2.1.2 Applicable References:Original Equ
13、ipment Manufacturers (OEM) ManualsEngineered Materials Handbook Volume 1 - Composites ASM International HandbookCommittee ISBN 0-87170-279-7 (v.1)Handbook of Composites edited by George Lubin Van Nostrand Reinhold3. GENERAL:Repairs cured below 212 F (100 C) usually require the use of two part lamina
14、ting resins,adhesives, and potting compounds. The two part systems are made up of a base resin and ahardener. The base resin and the hardener can be in paste or liquid form, and are always suppliedin separate air tight containers. To aid mixing, some resins and hardeners have different colors. Ahomo
15、geneous (uniform) mixture is an important factor for the quality of the bonding.SAE INTERNATIONAL ARP5256 Page 3 of 13_ 3. (Continued):The resin and hardener should be stored in a cool dry environment. The storage temperaturedepends on the specific type of material. Some can be stored at room temper
16、ature while othersrequire refrigeration at 40 F (4 C) or freezer storage at 0 F (-18 C). Refer to the manufacturersstorage instructions and the procurement specification for the appropriate storage conditions.Depending on the resin/adhesive viscosity and the application, a viscosity control additive
17、 might beneeded. The resin/adhesive should be mixed first with the hardener before adding the viscositycontrol additive to have a homogeneous (uniform) mixture.Some manufacturers have pre-measured kits such as sem-kits or blister packs. These offer theadvantage of not having to weigh each of the com
18、ponents, but the mixing procedure is just asimportant as non pre-measured kits. Several mixing machines are also available to assist in themixing. Follow the manufacturers directions for the mixing procedures. Mixing or blendingequipment should produce a smooth, workable mixture that is essentially
19、free from lumps andentrapped air.4. HEALTH AND ENVIRONMENTAL:General guidelines are given throughout this document regarding the hazards to the user and theenvironment of the materials and equipment listed. However, the user shall obtain the MaterialSafety Data Sheet (MSDS) from the supplier prior t
20、o using any of the materials. The relevantenvironmental health and safety organizations shall be consulted regarding safe use of thematerial. Material suppliers are also a good source of information in the safe use of their materials.4.1 Personal Protective Equipment:Personal protective equipment re
21、quired to handle a specific material safely is identified in thesuppliers Material Safety Data Sheet (MSDS).The areas of the body most likely to be affected when working with resins are the skin, eyes, andrespiratory tract. Guidance is given on the kinds of personal protective equipment that may ber
22、equired and typical uses.Before using any type of personal protective equipment, training shall be given to ensure that theequipment is used safely and correctly.a. Exhaust Systems: When mixing resins and adhesives in a shop environment, a fume cabinetwith local extraction should be used. Control of
23、 the emissions shall be in accordance withlocal and national regulations. Local exhaust systems shall be capable of providing a goodflow of fresh air to personnel. The system shall be air operated or use flameproof motors if itis to be used in areas where flammable vapors may be present. A local exh
24、aust system maybe used as a method of providing a safe environment keeping fume concentrations below theallowable limits in confined spaces where vapors may accumulate.SAE INTERNATIONAL ARP5256 Page 4 of 13_ 4.1 (Continued):b. Eye Wash: The eye wash facility shall conform to the local standards and
25、shall be capable ofhand free operation to allow the user to hold the eyelids open while operating the eye wash. Eye wash facilities shall be used if eyes are exposed to resin, hardener, fillers, milled fibers,cleaning materials, or solvents.c Gloves: The gloves shall allow full hand dexterity and sh
26、all not be coated with any materialthat may contaminate the repair materials or repair area.5. CONSUMABLE MATERIALS/EQUIPMENT:The basic consumable materials/equipment that are used for resin mixing are identified below. Since there is such a large selection of each of these items, only general guida
27、nce is given. Theuser needs to evaluate the application and determine the appropriate selection.a. Spatula: Clean spatulas are needed to transfer the resin and hardener to the mixing containerand to mix the resin in the container. Typically, a metal spatula or a wooden tongue depressoris used. Use s
28、eparate spatulas for each resin component to prevent cross contamination. Asingle tongue depressor can be split in half length wise to make a spatula with a sharp end toget into corners better (see Figure 1).FIGURE 1 - Tongue Depressor for SpatulaSAE INTERNATIONAL ARP5256 Page 5 of 13_ 5. (Continued
29、):b. Container: A clean container is needed to contain the resin during measuring and mixing. Therecommended containers are translucent High Density Polyethylene (HDPE), glass, metal,coated paper, PTFE or polypropylene with a height to diameter ratio of one. The split tonguedepressor shown in Figure
30、 1 can be used with a rounded bottom container or a straight bottomcontainer as shown in Figure 2. Make sure the spatula is able to scrape all unmixed resin fromthe sides and bottom of the container. The translucent sides allow the user to inspect for anyunmixed resin. Metal containers with rust on
31、the inside or wax coated paper should not beused.FIGURE 2 - Proper Positioning of Spatula When MixingCAUTION: Do not use waxed or coated containers. The coating may dissolve andcontaminate the material.c. Shallow Tray: A shallow tray may be used to maximize the pot life when using large portions ofm
32、ixed resin. The shallow tray must use the same material considerations as the mixingcontainer or may be covered in Mylar or Nylon film. The recommended maximum resin depth inthe tray is 0.25 in (6.35 mm).d. Spreader: (sometimes called a squeegee) A broad flexible spatula used to spread the mixedresi
33、n over a large area, for example to spread resin over fabric.SAE INTERNATIONAL ARP5256 Page 6 of 13_ 5. (Continued):e. Scale: A scale is required to weigh the resin components. The scale may be electronic, triplebeam or equal arm with a single beam. The accuracy must be better than 1% of the smalles
34、tamount being weighed, e.g., if the smallest amount of hardener to be weighed is 10 g, then theaccuracy of the scale shall be 0.1 g. Spring scales shall not be used. A tare feature is useful inminimizing weighing errors by allowing the balance to be rezeroed after the container and eachcomponent are
35、 added.6. RESIN COMPOUNDS AND ADDITIVES:6.1 Potting Compounds:Potting compounds are a combination of a resin or adhesive with an additive such as aluminumpowder, fumed silica or microballoons. They can be supplied premixed or can be preparedbefore use by mixing the additive with the mixed resin and
36、hardener. Potting compounds areused to fill dents or pits and to reinforce broken honeycomb core.The amount of additive is usually called out as a percentage of mixed resin weight. The baseresin and hardener should be mixed first before adding the additive to have a morehomogeneous (uniform) mixture
37、.The mixing techniques for the potting compounds are the same as for the resins as defined inSection 7.Note that some potting compounds can be purchased ready mixed and kept frozen so that nomixing is required by the user.6.2 Paste Adhesives:Paste adhesives are usually supplied in 2 part kits. The a
38、dhesive is filled, typically with a finealuminum powder. Paste adhesives are used for adhesive bonding particularly where the fit isuncertain and gap filling capability is required. They also have better strength at highertemperatures than their unfilled counterparts. In repair situations they may b
39、e used as a pottingcompound. The mixing techniques are the same as for the resins as defined in Section 7,however particular care to ensure thorough mixing is required as the components often have verydifferent viscosities6.3 Additives:The sections below describe some of the more widely used additiv
40、es that are added to epoxy andpolyester resins. Most of the additives are fine powders or fibers and require thorough mixing toform a homogeneous (uniform) product.Care should be taken to ensure that all additives are thoroughly dry before adding to the resinmixture. For small quantities a drying cy
41、cle of 12 h at 150 F (66 C) is sufficient. The additivescan then be kept dry by packaging in air tight sealed plastic containers.SAE INTERNATIONAL ARP5256 Page 7 of 13_ 6.3.1 Microballoons: Microballoons consist of small hollow spheres of glass, phenolic or ceramic witha typical diameter range of 6
42、to 200 m. The microballoons look like a fine powder with bulkdensities ranging from 4.4 to over 15.6 lb/ft3(70 to over 250 kg/m3) and a true or liquiddisplacement density range of 7.8 to 37.5 lb/ft3(125 to 600 kg/m3) depending on the grade.They are widely used for filling liquid epoxy resin systems
43、to make a lightweight paste orsyntactic potting compound that has a variety of uses. Typical applications are the edge fillingor local reinforcing of composite honeycomb panels, as a low temperature curing core spliceparticularly for repair applications and in the engine as a shroud material for the
44、 fan blades.Material used for making syntactic epoxies typically has an average diameter of 90 m and atrue density of 15.6 lb/ft3(250 kg/m3). The addition of approximately 20% by weight of thistypical filler gives a 40 lb/ft3(640 kg/m3) syntactic foam.6.3.2 Fumed Silica: Fumed silica sometimes known
45、 as colloidal silica consists of a very pureamorphous silicon dioxide in the form of three dimensional chains of approximately sphericalparticles (aggregates). The average aggregate length is 0.2 to 0.3 m. The bulk density is2.5 to 3.0 lb/ft3(40 to 50 kg/m3) with a true density of 137 lb/ft3(2200 kg
46、/m3).Fumed silica is added to liquid epoxy resins and paints to impart thixotropy. The shear stressdependent change in viscosity that is imparted allows the resin to be applied to vertical surfacesby brushing (the shearing action of the brushing reducing the viscosity). After application, theviscosi
47、ty increases, due to hydroxyl linking of the aggregates being reestablished, preventingsag or slump of the applied resin.The addition of up to 5% by weight of fumed silica usually imparts sufficient thixotropy for mostepoxy resins.NOTE: Not to be used as a filler, only to be used to control viscosity.6.3.3 Powdered Aluminum: The powdered aluminum usually comes in the form of a 45 to 90 mpowder of mostly spherical particles. Similar material is sold as a
