上个月有个做连接器壳体的厂打电话过来，开口第一句就带着火气。
他说去年买的一批 PA66-GF30 出了事——打出来的壳体在客户端装配的时候，卡扣一掰就断，断了一整排。终端那边停线排查，损失按小时在走。
他怀疑买到假料了。
我隔着电话问了他两句话。
第一句：这批料有没有留样？
他说没有，用完了。
第二句：有没有留供应商给的那一包原始包装，上面的批号还在吗？
他说包装袋早就扔了。
这两句问完，我心里基本有数了：这批货大概率追不回来了。
后来的事情印证了这个判断——没法对比、没法复测、没法向任何一方主张。最后这笔损失是他们自己全额吃下的。
而在这一年里，我们遇到过好几次类似的电话，最后追查出来的结论，十有八九不是"假料"，是四种料的概念被混着谈了。
卖家说的是副牌，货是真副牌，价格也是副牌的价——但买家心里那个"副牌"，和实际到手的那种"副牌"，压根不是一回事。
这篇就把这四个词一次拆干净：正牌、副牌、水口、回料。
它们的价格能差一倍，风险能差一个量级。混着谈，是谈不出结果的。
一、四个词，四件不同的事
先把结论放在前面：
| 说法 | 从哪来 | 指标状态 | 核心风险 | 该用在哪 |
|---|
| 正牌料 | 原厂聚合产线，合格品 | 各项都在牌号 TDS 窗口内 | 价格高 | 关键件、认证件、量产件 |
| 副牌料 | 同一产线，被判为降级 | 某一项（或几项）偏出窗口 | 批次不一致 | 非关键件，且必须锁批号 |
| 水口料 | 注塑厂浇口、流道、废件 | 已成型过一次 | 性能衰减，掺比受控才可用 | 内部回用，掺比要写死在工艺里 |
| 回料 | 回收料重新造粒 | 分子链已断裂，聚合度下降 | 力学、耐热、抗老化全面下滑 | 非结构件；汽车、新能源、电子关键件坚决不碰 |
看到这张表的关键不是记，是理解一句话：
副牌是尺度偏了，水口是用剩的，回料是链断了。
这是三种性质完全不同的"不完美"。
打个比方：
副牌像一个尺寸加工偏了的零件——它材料没问题，只是某个尺寸出了公差带。只要这个尺寸在你的场合不重要，它完全能用
水口像一碗已经煮过一次的汤——没坏，但味道淡了一层
回料像一根断过又接起来的绳子——接上了还是能用，但受力的地方永远在最弱的那一段
把它们当一类货来谈价，就等于把三种风险按最低的那个来定价。
副牌料是怎么产生的
知道了"它是什么"，还得知道"它从哪来"——因为来源决定了它的风险长什么样。
副牌料不是"做坏了的料"，它通常是以下几种情况：
① 装置开停机的过渡段
聚合装置从停机到跑出稳定工况，需要一个过程。这段跑出来的料，各项指标可能都不太居中，就被划到副牌序列。
② 牌号切换的混料段
装置从 A 牌号切到 B 牌号，中间那段既不是 A 也不是 B。它是两个牌号之间的过渡产物，这类料常常表现出"黏度偏高"或"色相不稳"。
③ 某一项指标漂移出了窗口
最常见的是黏度（分子量）、含水率、色相、灰分。大概率只有一项偏，其余全在窗口内——这是副牌料的典型特征。
④ 仓储运输造成的次生问题
受潮、结块、外包装破损导致的污染变色。这类不是产线上的问题，但同样会被降级处理。
看明白这四条，你就懂了副牌料最要命的那个特点从哪来——因为它每次产生的机制可能都不一样，所以批次之间天然不一致。
二、最关键的一句：副牌 ≠ 回料
这两个词被当成同义词的次数最多，也最误事。
副牌料的本质是"分级"，不是"降质"。 它是同一套装置、同一批熔体出来的料，只是在黏度、色相、含水率、灰分这类指标上偏离了正牌窗口，所以被划到副牌序列。它的分子链是完整的。
回料的本质是"再生"。 分子链在生产、使用、再加工的过程中断过，聚合度下降。而聚合度这件事，任何添加剂都补不回来。
为什么补不回来
这句"补不回来"值得说透，因为它是整个区分的关键。
尼龙的力学性能，很大程度上取决于分子链有多长——链越长，分子之间缠绕得越紧，拉断它需要越大的力。这个长度的度量叫聚合度，实验室里通常用相对黏数来间接表达。
回料经历过成型、使用、粉碎、再造粒这一整圈，中间的高温、剪切、水分，每一次都在把链剪短一截。剪短了就是短了。
那市面上常说的"扩链剂"能补吗？
能接一部分，但接不回原样。扩链剂的作用是把断口重新接起来，它可以把一部分短链连成长链，但接出来的链长分布已经变了——有的接上了，有的没接上，长短参差不齐。
就像一根断了三处的绳子，你把三处都打了结，它还是完整的一根，但它的强度由最弱的那个结决定。
这就是为什么回料的典型表现不是"某一项指标低"，而是——
全面的、方向一致的下降：拉伸降、冲击降、耐热降、抗老化能力降
批次稳定性差：因为来料本身批次就不稳
外观上看不出来：这是最坑的一点，打出来的件颜色正常、尺寸合格
开篇那个连接器的故事就在这里：外观、尺寸全都合格，唯独卡扣一掰就断。
这个区别直接决定用法
副牌料可以"挑着用"——偏在哪一项，就避开对那一项敏感的场景
回料只能"限着用"——它的问题不是某一项，是整体的底子
所以当有人拿"副牌料"的价格卖给你一批回料时，问题不在于便宜不便宜，在于你以为你买到的是 A，实际拿到的是 B。
采购上的一条判断：我们经手的副牌料里，最常见的偏差项是黏度（分子量），其次是含水率；反而大家最担心的"强度不够"，排在后面。 这一条直接改掉采购的两个动作：该测的是黏数和水分，不是只盯拉伸强度；该问的是"这批和上批差在哪"，不是"强度够不够"。
注意这句里的反直觉之处：黏度偏了，往往比"强度略低"更麻烦。
因为黏度决定了加工窗口——同一台机器、同一套参数，换一批黏度偏低的料，可能就打不满、或者有披锋；而外观和尺寸合格的件，内在的强度可能已经悄悄走掉了。
三、五项现场判别（不用等实验室）
以下方法按"从快到慢"排，前三项现场就能做。
① 看颗粒
全新料的颗粒大小均匀、有光泽、切口整齐；回料的颗粒大小不一、发暗，常带杂质点。
现场怎么看：抓一把料摊在白纸上，凑到窗边自然光下。
看色泽一致性——同一批里有明显深浅不一的，说明来路杂
看形状——切粒机出来的应当是规整的圆柱状或椭圆状，大小接近
看碎屑和粉尘——袋底如果有一层明显的粉末，说明二次造粒次数多或者运输磨损严重
这一步的成本是零，三十秒能做完。它的作用不是定性，是决定要不要继续往下查。
② 烧一下闻
尼龙燃烧是蓝底黄焰、起泡滴落、有烧焦毛发的味道，离火能自熄。回料通常带刺鼻异味，烟更大。
为什么是烧焦毛发的味道：尼龙分子链上有酰胺基，含氮，燃烧时会产生含氮化合物，气味类似烧头发或烧羊毛。这是尼龙区别于聚乙烯（蜡烛味）、聚丙烯（柴油味）、ABS（甜腥味带浓黑烟）的一个非常实用的特征。
操作要点（注意通风、远离易燃物）：
用镊子夹一粒，打火机从下方靠近
观察火焰底部颜色、是否起泡、熔体是否滴落
离开火焰，看它能不能自熄
凑近闻时注意方法——用手扇着闻，不要直接凑上去
回料因为来源杂，常常混有别的塑料（PE、PP、甚至 PVC），表现为烟明显变大、气味刺鼻、离火不自熄。
③ 问批号，并且去核实
要原厂包装、原厂 COA（质检单），核对批号，必要时向原厂或授权渠道核实。
这一步能筛掉大部分问题货，成本最低、效果最好。
说白了——前面两项是"看起来对不对"，这一项是"根本上是谁的"。
并且一定要留样。开篇那个客户的教训就在这一步。
留样的规矩很简单：
每批留 500 克到 1 公斤，密封、避光、标注批号和到货日期
保留到这个批次用完以后至少半年
留样要和生产用料同一批次、同一包装，不要从第二批里再抓一把
留一公斤料的成本是几块钱。它换回来的，是出事的时候你有东西可以送检、有对象可以追溯。
④ 测跨批次熔指
注意是跨批次，不是单批。
单批熔指正常说明不了什么——副牌料的核心特征不在单点值，而在批次之间的波动。
为什么要跨批次看：假设你手上有三批料，熔指分别是 25、28、31 g/10min，每一批单独看可能都在一个可以接受的范围里。但把它们放在一起看，波动幅度已经很可观了——而这个波动，会直接翻译成注塑车间里的"这批料怎么和上次不一样"。
具体的影响是：
熔指偏高的批次 → 流动性过好 → 容易出披锋、物料控不好
熔指偏低的批次 → 打不满、需要提高压力和温度 → 反过来又增加了降解风险
所以跨批次测的意义，是提前知道你会不会被"调机"折腾。
⑤ 测相对黏数
乌氏粘度计，GB/T 1632.1 聚酰胺黏数测定。
这一项反映聚合度，掺混再生料会明显拉低。它是识别"副牌掺回料"最硬的一个指标。
结合第一节说的"为什么补不回来"，这条就很好理解了：能掺进去的再生料一定链短，链短一定拉低整体黏数。这是一道绕不过去的账。
再加一项：灰分
如果还要加一项，就加灰分（马弗炉灼烧称重，GB/T 9345.1）。
对增强料来说，灰分能直接反算出实际玻纤含量，专门用来对付"标称 30%、实到 15%"。
原理很简单：树脂烧完是气体飞走了，玻纤是无机物留在坩埚里。烧剩下的重量占比，就是玻纤含量的近似值。
这一项对玻纤增强料的采购尤其重要——因为玻纤是成本的大头，也是性能的主要来源。少一半玻纤，价格差得远。
四、它们各自该用在哪
判断标准只有一条：这个件坏了会怎样。
正牌料 → 认证件、安规件、安全件、主机厂配套件、量产周期长的件。这些位置省料钱是不划算的。
副牌料 → 内部非受力件、外观不敏感件、短周期件、试产件。用它有三个前提：锁定批号、明确用它做哪个件、先小批验证。
水口料 → 一般只在注塑厂内部回用，掺比写进工艺文件，且只掺在自己能追溯的那部分。外购水口料的风险比很多人想的大。
回料 → 对性能不敏感、不承力、不涉安规的场景。凡是要求"长期稳定"的位置，都不合适。
水口料的掺比，为什么不能往上加
这里多说一句，因为它是注塑厂天天在做、又最容易出事的一件事。
水口料每经过一次成型，都热水解了一点、都热降解了一点。所以掺比往上走，性能不是线性下降，是越往上掉得越快。
行业里常见的做法是：内部非外观、非受力的件，掺比控制在一个相对保守的水平；受力件、外观件直接不掺。而且这个掺比必须写进工艺文件——
关键是写进去。因为一旦只靠师傅的经验，就会出现"今天忘了一桶加多了""新人不知道该加多少"的情况，而这种情况导致的批次差异，比材料本身的差异还大。
五、用副牌料的三条纪律
第一，只用非关键件。
第二，锁定批号。
副牌料最大的风险不是指标低，是批次之间不一样。所以一次备够、锁死批号，比反复比价重要得多。换批号就要重新验证，这一条没有例外。
这里有个很现实的矛盾：副牌料的特点就是"一批一价、一批一况"，而它最需要的恰恰是"稳定"。所以在副牌料上反复比价、谁便宜买谁的，方向其实是反的——每一次为了便宜几毛钱换供应商，都在重新引入一次验证成本。
第三，先小批验证。
拿小批量试模、试装、试跑一个周期，再谈放量。这一步花的时间，比事后处理失效便宜得多。
结语
回到最开始那个电话。
后来我跟他说，这次追不回来的原因不是对方赖账，是我们这边没有留下任何可以比对的东西。
判断副牌料的正确问法，从来不是"偏没偏"，是"偏了什么、偏多少"。 前一个问题只能得到是或否，后一个问题才能得到判断。
而比问法更靠前的，是三件几乎不花钱的事：留样、留包装、留批号。
它们在一切顺利的时候完全没用，唯独在出事的那一天，它们是全部。
如果你手上正有一批料要定用途，把三样东西发过来：牌号与标称指标、实测的黏数或熔指、现在用在什么件上——我们给一份用不用、怎么用的判断。
总有人问：副牌料到底能不能用。
我们的回答一直没变——能用的地方很多，不能用的地方一处都不能碰。它和回料是两回事：一个是指标偏了，一个是分子链断了。
Last month, a factory that makes connector housings called, and the very first thing they said was full of anger.
He said that a batch of PA66-GF30 he bought last year had problems—the housings molded from it would break at the snap-fit clips during assembly at the client's side, breaking an entire row. The production line there stopped to investigate, and losses are being calculated by the hour.
He suspects that he bought counterfeit material.
I asked him two questions over the phone.
First sentence: Was a sample of this batch kept?
He said no, it's all used up.
Sentence two: Did you keep the original package provided by the supplier, and is the batch number still on it?
He said he had already thrown away the packaging bag.
After asking these two questions, I basically had a clear idea in my mind: this batch of goods is most likely not recoverable.
Later events confirmed this judgment — there was nothing to compare, nothing to retest, and no way to claim against any party. In the end, they bore the full loss themselves.
And during this year, we encountered several similar phone calls, and after investigation, the conclusion was that nine times out of ten it was not 'fake materials,' but rather a mix-up of the concepts of four different materials.
The seller is talking about a secondary brand, the goods are indeed a secondary brand, and the price is also that of a secondary brand—but in the buyer's mind, the 'secondary brand' and the 'secondary brand' they actually receive are not the same thing at all.
This article will break down these four words one by one: genuine brand, secondary brand, water mark, reclaimed material.
Their prices can differ by a factor of two, and the risks can differ by an order of magnitude. Mixing them together in discussion will not lead to any conclusions.
1. Four words, four different things
Let's put the conclusion first:
| statement | Where are you from? | Indicator Status | Core Risk | Where should this be used? |
|---|
| Genuine material | Original factory polymer production line, qualified products | All items are within the TDS window for the grade | High price | Key parts, certified parts, mass-produced parts |
| Secondary suit material | The same production line was judged to be downgraded. | One (or several) items are sticking out of the window | Batch inconsistency | Non-critical parts, and the batch number must be locked |
| Water inlet material | Injection molding factory gates, runners, and scrap | Has been molded once | Performance degradation, can be used only if the blending ratio is controlled | Internal reuse, the blending ratio must be fixed in the process |
| Return material | Recycled material re-pelletizing | The molecular chains have broken, and the degree of polymerization has decreased. | Comprehensive decline in mechanical properties, heat resistance, and aging resistance | Non-structural parts; absolutely avoid touching key parts of automobiles, new energy, and electronics |
The key to looking at this table is not to memorize it, but to understand one sentence:
The secondary cards are off-scale, the water inlet is leftover, and the recycled material comes from a broken chain.
These are three completely different kinds of 'imperfections'.
For example:
The auxiliary card is like a part with a processing deviation in its dimensions — the material is fine, it's just that one dimension is out of tolerance. As long as this dimension is not important for your situation, it can be used perfectly.
The water's mouth is like a bowl of soup that has already been cooked once—it hasn't gone bad, but the flavor is a layer weaker.
Recycled material is like a rope that has been broken and then tied back together—it can still be used once rejoined, but the part that bears the most force is always at its weakest section.
Treating them as the same type of goods when negotiating the price is equivalent to pricing three types of risks according to the lowest one.
How is secondary card material produced?
Knowing 'what it is' is not enough; you also need to know 'where it comes from'—because its origin determines what its risks look like.
By-product material is not 'material that has gone bad'; it usually falls into the following situations:
① Transition phase of equipment start-up and shutdown
The polymerization unit requires a process to reach stable operating conditions from a shutdown. During this ramp-up period, the material produced may have various indicators that are not very average, and it is assigned to the secondary grade sequence.
② Mixed material section for grade switching
When the equipment switches from grade A to grade B, the intermediate section is neither A nor B. It is a transitional product between the two grades, and this type of material often exhibits 'higher viscosity' or 'unstable color'.
③ A certain indicator drifted out of the window
The most common are viscosity (molecular weight), moisture content, color, and ash content. Most likely, only one of them deviates, while the rest are within the window — this is a typical feature of secondary-grade material.
④ Secondary problems caused by storage and transportation
Contamination and discoloration caused by dampness, caking, or damage to the outer packaging. This type is not an issue on the production line, but it will still be downgraded.
Once you understand these four points, you'll know where the most critical characteristic of secondary card material comes from — because the mechanism by which it is produced may be different each time, it is naturally inconsistent between batches.
2. The most crucial sentence: Secondary cards ≠ Reclaimed material
These two words are most often treated as synonyms, and it causes the most trouble.
The essence of off-grade material is 'grading,' not 'downgrading.' It comes from the same set of equipment and the same batch of melt; it just deviates from the main-grade window in terms of indicators like viscosity, color hue, moisture content, and ash content, so it is classified into the off-grade series. Its molecular chains are intact.
The essence of recycled material is 'regeneration.' The molecular chains are broken during production, use, and reprocessing, resulting in a decrease in polymerization degree. And the polymerization degree cannot be restored by any additives.
Why can't it be made up?
The phrase 'cannot make up for it' is worth explaining thoroughly, because it is the key to the entire distinction.
The mechanical properties of nylon largely depend on the length of its molecular chains—the longer the chains, the tighter the molecules are entangled, and the greater the force required to break them. This measure of length is called the degree of polymerization, which is usually indirectly expressed in laboratories using relative viscosity.
Recycled material goes through the whole cycle of molding, use, crushing, and re-pelletizing. In the process, the high temperature, shear, and moisture each time shorten the chains a bit. Once shortened, they are short.
Can the 'lengthening agent' commonly mentioned on the market help?
It can reconnect partially, but not restore it to its original state. The function of a chain extender is to reconnect the broken ends; it can turn some short chains into long ones, but the resulting chain length distribution has already changed—some are reconnected, some are not, and the lengths are uneven.
It's like a rope broken in three places; if you tie knots at all three points, it's still one complete rope, but its strength is determined by the weakest knot.
This is why the typical manifestation of recycled material is not 'a low value in a certain indicator,' but rather—
Comprehensive, directionally consistent decline: tensile strength decline, impact strength decline, heat resistance decline, aging resistance decline
Poor batch stability: because the incoming materials themselves are not stable from batch to batch
It can't be seen from the appearance: this is the most troublesome point, the produced parts look normal in color and meet the size requirements.
The story of that connector from the beginning goes like this: appearance and size are all up to standard, but the latch breaks as soon as you snap it.
This difference directly determines the usage
Secondary grade material can be "picked and used"—if you focus on any particular item, avoid the sensitive scenario
Recycled material can only be "limited to use"—the problem isn't just one item, but the overall foundation
So when someone sells you a batch of recycled material at the price of "secondary grade," the issue isn't whether it's cheap, but whether you think you're buying A and actually getting B.
One judgment in procurement: Among the secondary grade materials we handle, the most common deviation is viscosity (molecular weight), followed by moisture content; On the contrary, the biggest concern is "insufficient strength," which comes later. This one directly changes two procurement actions: the focus should be on viscosity and moisture, not just tensile strength; The question should be "What's the difference between this batch and the previous batch?" not "Is the strength sufficient?"
Note the counterintuitive part in this sentence: off-stick viscosity is often more troublesome than "slightly lower strength."
Because viscosity determines the processing window—the same machine and the same set of parameters, switching to a batch of material with lower viscosity may result in incomplete or sharp edge; while parts with qualified appearance and dimensions may have already lost their intrinsic strength.
Three, five on-site judgments (no need to wait for the lab)
The following methods are arranged "from fast to slow," and the first three can be done on site.
(1) Check the pellets
New material has uniform particle size, gloss, and neat cuts; Recycled material particle sizes vary, dark, and often contain impurity spots.
How to check on site: Take a handful of material and spread it on white paper, then place it by the window under natural light.
Check color consistency—if there are obvious differences in depth within the same batch, it means the source is impurities
Check the shape—the pellet should be regular cylindrical or oval, similar in size
Check the debris and dust—if there's a clear layer of powder at the bottom of the bag, it means there are many secondary pelletizing cycles or severe wear during transport
This step is zero cost, and it can be completed in thirty seconds. Its role is not to determine whether to investigate further.
(2) Burn and smell
Nylon burns with a blue background and yellow flame, foaming and dripping, and has a burnt hair smell. It can self-extinguish when taken out of the flame. Recycled material usually has a pungent odor and even greater smoke.
Why does it smell like burnt hair? Nylon has amide groups in its molecular chain and contains nitrogen. When burned, it produces nitrogen compounds, and its smell is similar to burning hair or wool. This is a very practical feature that distinguishes nylon from polyethylene (candle smell), polypropylene (diesel smell), and ABS (sweet, fishy smell with strong black smoke).
Operating Tips (Ensure ventilation, keep away from flammable materials):
pick up a pill with tweezers, use a lighter from below to observe the color of the flame bottom,
to observe if bubbles form or if melt drips
leave the flame and see if it can self-extinguish
When approaching for smelling, pay attention to the method—fan it with your hand, don't approach it directly
Because the material comes from various sources, often mixed with other plastics (PE, PP, even PVC), this manifests as noticeably larger smoke, a pungent smell, and the material does not extinguish when removed from the flame.
(3) Ask for the batch number, and verify
for original factory packaging and original COA (quality inspection form), verify the batch number, and if necessary, verify with the original manufacturer or authorized channels.
This step can filter out most problematic goods, with the lowest cost and best results.
To put it plainly—the first two are "does it look right?" This one is "whose is it ?"
And always keep samples. The lesson from the customer at the beginning is right here.
The rules for keeping samples are simple:
Keep 500g to 1kg per batch, sealed, protected from light, marked with batch number and arrival date
Keep samples for at least half a year after this batch is used
Samples must be in the same batch and packaging as production materials, don't grab another batch from the second batch
How much does it cost to keep one kilogram of material? It's replaced, so when something happens, you can send it for inspection and trace the object.
(4) Measure melting index across batches
Note: It's cross-batch, not single batch.
A single batch melting index doesn't mean much—the core feature of secondary grades isn't the single point value, but the fluctuations between batches.
Why look across batches: Suppose you have three batches, with melt fingers of 25, 28, and 31 g/10min, each batch alone might be within an acceptable range. But when viewed together, the fluctuation is already quite significant—and this fluctuation translates directly into the injection molding workshop saying, "Why is this batch different from last time?"
The specific impact is:
batches with a relatively high melting index → excessive fluidity → prone to distortion and poor material control .
batches with a relatively low melting index → insufficient filling, requiring increased pressure and temperature, → which in turn increases the risk of degradation
So the purpose of cross-batch testing is to know in advance whether you will be "adjusted up" by the machine.
(5) Measure relative viscosity
Uhl's viscometer, GB/T 1632.1 polyamide viscosity determination.
This item reflects the degree of polymerization; mixing recycled material significantly lowers the profile. It is the strongest indicator for identifying "secondary brand remixed materials."
Combining the first section's question about "why can't it be replenished," this point is easy to understand: the recycled material that can be mixed in must have short chains, and a short chain will lower the overall viscosity. This is an unavoidable issue.
Add one more item: ash content
If you want to add another item, add ash (muffle furnace calcination weighing, GB/T 9345.1).
For reinforcements, ash content can directly calculate the actual glass fiber content, specifically to deal with "nominal 30%, actual 15%."
The principle is simple: when resin burns, the gas escapes; the fiberglass is inorganic and remains in the crucible. The proportion of weight left after burning is an approximate value of the fiberglass content.
This is especially important for purchasing fiberglass reinforcement—because fiberglass is the main source of cost and performance. Half the cost is reduced, and the price difference is huge.
4. Where should each be used
There is only one criterion for judging this: what happens if this part breaks?
Genuine Materials → Certified parts, safety parts, safety parts, OEM parts, parts with long mass production cycles. Saving material costs in these areas is not cost-effective.
Sub-brand Material → Internal non-stress-bearing parts, non-sensitive parts, short-cycle parts, trial production parts. There are three prerequisites for using it: lock the batch number, clearly specify which part to use, and first verify in small batches.
Sprue material → is generally only reused internally in injection molding plants, mixed into process documents, and only in the traceable parts. The risks of purchasing sprue material are greater than many people think.
Reuse → Scenarios that are not sensitive to performance, do not bear load, and do not comply with safety regulations. Any location requiring "long-term stability" is not suitable.
Why can't the sprue material adulteration be increased?
Here, one more thing: because it is something injection molding plants do every day and is most prone to problems.
Each time sprue material is molded, it undergoes some thermal hydrolysis and degradation a bit. So as you go up the blending ratio, performance doesn't decrease linearly—it drops faster the higher you go.
A common practice in the industry is: for internal non-exterior and non-load-bearing parts, the doping ratio is kept at a relatively conservative level; For load-bearing and exterior parts, no adulteration is done at all. And this doping ratio must be written into the process document—
The key is to write it down. Because if we rely solely on the master's experience, situations like "forgot an extra bucket today" or "newcomers don't know how much to add" will occur, and the batch-to-batch differences caused by such situations are even greater than the differences in the materials themselves.
5. Three disciplines for using secondary-brand materials
First, only use them for non-critical components.
Second, lock the batch number.
The biggest risk with secondary-brand materials is not that the specifications are lower, but that batches differ from each other. Therefore, preparing enough at once and locking the batch number is far more important than repeatedly comparing prices. Changing the batch number requires re-validation; there are no exceptions to this.
There is a very practical contradiction here: the characteristic of secondary-brand materials is "one batch, one price, one batch, one situation," while what they most need is "stability." So repeatedly comparing prices and buying the cheapest supplier is actually the wrong approach — each time we switch suppliers to save a few cents, we reintroduce the cost of validation.
Third, validate with a small batch first.
Test the mold, assembly, and run for one cycle with a small batch before discussing mass production. The time spent on this step is far cheaper than dealing with failures afterward.
Conclusion
Returning to that initial phone call.
Later I told him that the reason we couldn't recover this time was not that the other party defaulted, but that we hadn't left behind anything for comparison.
The correct question when judging secondary-brand materials is never "Is it off-spec?" but "What is off-spec, and by how much?" The former can only give a yes or no answer, while the latter allows for a proper judgment.
Even more fundamental than the question are three things that cost almost nothing: keep samples, keep packaging, keep batch numbers.
They are completely useless when everything goes smoothly, but on the day something goes wrong, they are everything.
If you currently have a batch of material to allocate, send over these three things: grade and nominal specifications, measured viscosity or melt index, and what components it is currently used in — we can provide a judgment on whether and how to use it.
Some people always ask: can secondary-brand materials actually be used?
Our answer has never changed — there are many places where they can be used, and not a single place where they can’t touch. It is different from recycled material: one has off-spec performance, the other has broken molecular chains.
