ABS塑料与电镀层结合力差的原因分析及其控制

Causes for poor adhesion strength of electroplated coating to ABS

plastic and their controls:-

Abstract：The main reasons for blistering of deposit during

electroplating of Cu／Ni／Cr on ABS plastic and for fallin9—off of deposit in adhesion strength testing were analyzed. Including

unsatisfactory state of plastic substrate，unfavorably injection

molding parameters，improper pretreatment for electroplating

and insufficient surface activity of adjacent deposits．Some measures for improving the adhesion strength of electroplated

coating to ABS plastic were presented，such as selecting high—

quality electroplating-grade ABS plastics，controlling molding

process parameters，and improving the roughening process in pretreatment as well as the activating process in

electroplatin9．The importance of using correct method for

testing adhesion strength was emphasized．

Keywords：poly (Acrylonitrile—C0—butadiene—C0—styrene)

；plastic；electroplated coatin9； adhesion strength；moldin9； pretreatment；test method

Author’s address：Benli Plastic Plating Factory， Shenzhen

518105，China

1   ABS 前言

ABS plastic artifacts varieties more, injection manufacturers to

reduced cost, sometimes will selection quality poor of ABS

plastic stereotypes or used not stable of stereotypes process

injection, and plating process and to change plastic material

factors on plastic coating combines force of effects, this a problem

often to ABS plastic plating line operation personnel brings

plagued, also to coating surface quality management added many

trouble, directly effects user on products of satisfaction degree,

makes enterprise quality management and the production cost

increased. Based on years ' practical experience in ABS plastic

plating, coating and plastic parts of the difference in force

between a simple analysis of defect, from the choice of plastic,

control parameters, strengthen the management of plating

process and other aspects, and puts forward some

countermeasures.

2 ABS塑料电镀层结合力差的原因分析

In General, resulting in poor adhesion of ABS plastic plating layer

causes has 4 parts:

Plastic substrate in bad condition.

Poor parameters of injection molding, plastic stress

concentration.

Before plating is not reasonable.

Poor adjacent coating the surface activity. In addition, improper

test methods for adhesion or are likely to cause miscarriage

of Justice.

2．1 ABS塑料基体状态的影响

ABS plastic matrix form mainly refer to ABS plastic polymer

particles b 8 components in (butadiene) content of less than l8%

or greater than 23%, and their distribution is not uniform. In the

chemical roughening process, b particle is dissolved and AS

skeleton, basically not subject to corrosion, so the plastic surface

forming a dense microscopic pits, metal in these pits form

numerous small snaps and riveting effect. B low particle

concentration and particle size for large sparse or too much

content and too tight, causing plastic riveting effect of surface

coating, plating and plastic parts adhesion is poor. Choose

different brands of ABS plastic on the same condition of semi-

gloss chromium electroplating after hundreds of tests, and

referring to the ASTM d 3359-1997 rating results are shown in

table 1. Chromium Electroplating technology for half light: before

processing a copper surface metallization of a Coke (3 min) a

clean one activation and one half the cleaning light nickel (3~5

min) a clean one activation and one cleaning chrome (2~3 min).

Table l Adhesion strength of semi-bright chromium coatings to

ABS plastics of different designations under identical

electroplating conditions

Table 1 shows that different ABS plastic plating on adhesion vary

greatly, in ABS727 and ABS3001M prepared on plastic injection

molding, plating adhesion is better. In addition, if the ABS plastic

molded rear surface stress concentration, without releasing

direct plating, can also cause poor adhesion。

2．2 ABS塑料成型参数的影响

 Plastic molding, due higher melting temperature and slow down

the injection can help improve the adhesion between the plastic

parts with plating layer. ABS plastic T-700-727, HTF86T model 4

sets of process parameters of injection mobile shutter button,

and then, under the same conditions light chrome plating, coating

hundreds of cells obtained from test results are presented in

table 2.

Table 2 Effects of molding process parameters of ABS plastic on

adhesion strength of electroplated bright chromium coating

 

 

Table 2 shows that the high melting temperature, low injection

pressure, high temperature and slower injection, are conducive

to obtain good adhesion of the coating. However, injection mold

temperature higher than 90 degrees could easily lead to injection

molding shrinkage deformation, mould sticky mode; in addition,

injection speed should be appropriate, if the injection time longer

than 10 s, easy Weld lines, surfaces, and gloss difference.

Therefore, it is prudent to adjust the injection parameters. In

addition, ABS plastic part forming complex geometrical shape,

wall thickness of thin or uneven, even better, stability of the

injection molding process, it will be difficult to avoid stress

concentration. Plating, plastics and plating adhesion between the

layers in different sections of wall thickness are different. In

General, the thicker the plastic parts of the wall, better adhesion

[1]; surface stress of thin-walled plastic parts easy to

concentrate, poor adhesion of electroplated coatings。

2．3电镀前除油与粗化工序的影响

 Stripping agent on the surface of plastic parts or oil pollution, oil,

dirty, then roughing solution cannot be reached directly to

roughing it on the surface of plastic parts. After degreasing, the

ABS plastic parts, crude mixed with sulphuric acid in chromic

acid solution corrosion in excess, plastic surface decay, cannot

form regularly shaped pits. Therefore, coarse or excessively will

cause poor adhesion [2].

Causing roughening of the cause of adverse effects following

several points:

(1) Chemical roughening of chromic acid and sulphuric acid in

imbalance or low, coarsening of trivalent chromium in molten

high levels.

(2) The roughening of the time is too short or too long.

(3) The roughening temperature is too low or too high.

(4) Roughing solution from contamination. After prolonged use,

coarsening dissolved in butadiene rubber and its adsorption on

the surface of plastic parts prevent coarsening.

2．4电镀层之间表面状态的影响

 Activity on the surface of the plastic parts is key to adhesion,

especially surface activity between the coating and coating

demand higher. Surface activity, less tension between the coating

and coating, its good adhesion. Lead plating surface difference

between due to:

Electrolyses nickel acid-activated properly.

Between the copper and semi-bright nickel activation (micro

corrosion) is not enough.

Electric conductive bad arm leads to secondary discharge. 3

improving ABS plastic plating adhesion of measure

3.1 selecting high quality plating grade ABS plastic recommended

using ABS727 and 3001M. For bonding requirements product

can also use ABS747.

3.2 strict controls of process parameters of injection molding

Barrel melting temperature is 230~250℃, injection timing

control within 10 s, and appropriately raise mold temperature,

reduce internal stress of plastic parts.

The molding of plastic parts using glacial acetic acid soaking

30~60 s, cracks should be removed surface "hoar frost" should

be based on kamaboko for 4 h, release stress after plating.

Plastic parts uniform wall thickness of products in addition to

baking to remove stress, but also need to increase the thickness

of copper layers in the coating.

3．3加强镀前处理

Control of oil temperature is about 50 degrees, increasing

ultrasonic to enhance oil-removing effect.

Roughing solution of chromic acid and sulphuric acid should be

controlled in the ratio of 1:1 and trivalent chromium content of

no more than 15 g/l.

The roughening temperature is 62~68℃, 5~10 min. (4) after

roughing solution contamination, you should replace the one-third

bath and cleaning tank. Half one-third roughing solution should

be updated.

 

3．4改善镀层的活化方法

Electrolyses nickel 8~10 ml/L plastic parts after hydrochloric

acid activated.

After copper plating using ammonium per sulfate 5~10 g/l,

sulfate-containing activated 0.5~1.0 min 5~10 mL/L solution.

Always check that the electric conductive slot live under arm is

well; blackout should be removed, activated before use.

Even the parameters of injection molding and plating processes

are controlled in the best range, but when testing the adhesion of

irregular operation, can also cause miscarriage of Justice.

Specific performance:

Improper testing tools, territories or hundred knife sharp.

The hundred tests cut line width >0.2 mm.

paste the mishandling of the tape, as the cutter in the scratch

coating-(1 mm x l mmx100) using viscous adhesive paste with

her nails pressed to expel air from the inside with adhesive tape,

the easy the cutting plate raised and was tearing the coating falls

off. Thus, the uniform and strictly in accordance with ASTM d

3359-1997 test method standard operating, is very important.

Mainly pay attention to the following several points

：

according to the standard ASTM d 3359-1997, semi-gloss chrome

or plastic parts with thin wall product should meet the 3B class

(that is, table slightly off of the total area and total area

5%~L5%) or more, light chrome should be greater than 3B class.

With hundreds of knives or knife, and line width to <0.2 mln,

depth wear coating shall prevail.

Hundreds of ABS plastic parts coatings after you recommend

3M600 or 3M610 adhesive paste, vertical 90 ° tearing;

Paste adhesive paper should be with your thumbs gently

squeezing repeatedly and discharge air inside with adhesive

tape, not allowed to use nails pushed. Adhesion test, if the

coating off to complete a hundred layers of copper, then between

coating and coating of surfaces in bad condition if after shedding

plastic coating, you can determine a plastic substrate condition,

unreasonable or improper roughening process of injection

molding parameters.

References: [1] Chen Zhongyi. plastic coated parts quality and

relevant factors [j]. Electroplating and environment, l988,8 (2):

23.25.

[2] Chen Zhongyi. two crude method of plastic plating [j] plating

and finishing, l987,9 (2): 33-34.