选型表填了五页，量产还是天天粘模。TPE怎么选，漏一项工况，整批件都得返工。
TPE怎么选？五步法一句话概括
TPE 选型，说复杂很复杂，说简单就五步：硬度 → 包胶 → 耐温 → 介质 → 成本。
顺序不能乱。前两步定方向，后两步定生死，最后一步定去留：
| 步骤 | 问什么 | 定了什么 |
|---|
| 步骤一 硬度 | 这个件要多软多弹？ | 硬度区间、体系族 |
| 第二步 包胶 | 要不要包在别的材料上？ | 体系（SEBS/TPU/接枝TPE） |
| 第三步 耐温 | 最高/最低温度多少？ | 耐温等级、体系上限 |
| 第四步 介质 | 接触油/水/化学/食品吗？ | 配方方向、专用牌号 |
| 第五步 成本 | 良率后的单件成本多少？ | 性价比取舍 |
技术金句：硬度定方向，包胶定体系，温度定等级，介质定配方，成本定生死——五步，一步都不能跳。
为什么顺序不能乱？因为前一步的结果是后一步的输入。
先定硬度，才能筛体系；定了体系，才谈得上耐温和介质；耐温和介质过了，成本才有意义——倒过来走（先问价格），
是采购询价里最常见的弯路：便宜料买回来，前四步全部重来。
步骤一先定硬度？手感对标实物锚点
硬度是 TPE 的基础语言。Shore A 是主力刻度，0 到 100，每 10 度一档手感：
| Shore A | 实物锚点 | 常见件 |
|---|
| 0-10 | 果冻、软糖 | 凝胶垫、仿生皮肤 |
| 20-30 | 橡皮筋、鼠标垫 | 玩具、表带内衬 |
| 40-50 | 手机壳、轮胎胎面 | 护套、握把 |
| 60-70 | 牙刷柄、鞋底 | 工具手柄、密封件 |
| 70-80 | 轮胎、雨刮条 | 鞋底、脚轮 |
| 80-95 | 实心轮胎、擀面杖 | 脚轮、耐磨件 |
同样的 Shore A 70，SEBS 软糯、TPU 弹韧、TPV 近橡胶——硬度表盘只是起点，体系性格才是手感本体。定硬度，不是定一个数字，是定一个“要什么手感”。
Shore 00 这把刻度尺也得单独认：它管超软件。凝胶垫、仿生皮肤、减震内衬在 00-30A 之间，Shore 00 刻度比 A 更细，0-100 的 00 档手感从“豆腐”到“橡皮”。
要“果冻感”，去看 Shore 00；要“软糖感”，Shore 00 中高段或 A 个位数。
定硬度有个实操技巧：拿实物样品比。
带一个手感满意的样品（哪怕不是 TPE 的），让供应商对硬度、对体系、对配方——比看十个数字都直观。
硬度计一按，真假见一半；样品一捏，手感全知道。
硬度怎么测才准？
三个细节：温度——TPE 硬度随温度变化明显，25℃ 和 40℃ 能差 5-10 度，测试要在标准温度；厚度——试样太薄读数偏硬，标准要求一定厚度；
仪器——不同厂家的硬度计读数可能差 5 度，同体系对比要用同一台。
**硬度计一按，真假见一半；温度不对，读数骗人。
硬度计的选择也有讲究：常规软料用 Shore A，超软用 Shore 00，高硬度用 Shore D——用错刻度，读数毫无意义。
读数时还要注意读数时间：标准是 1 秒读数（A 型）或 15 秒（D 型），压久了读数会漂。测三点取平均，记录温度，这才是一组能用的硬度数据。
五步法到这里就走完了：硬度定手感，包胶定体系，耐温介质定生死，成本定去留，验证定成败。
每一步都有数字可依，每一关都有留样可查——这就是把选型从经验变成流程的意义。**
第二步再定包胶？基材决定体系
要包胶，先问基材：
| 基材 | 推荐体系 | 原因 |
|---|
| PP | SEBS 基（王） | 相容性好，粘接强 |
| ABS/PC | TPU、改性SEBS | 极性匹配 |
| PA/金属 | 接枝TPE、TPV | 化学键接枝 |
| PE | 难包，需专用处理 | 表面能低 |
包胶件最怕脱层。包胶脱层，先查基材清洁，再查温度匹配——料选对了，工艺接不住也白搭。
包胶的四个工艺要点，一次说清：
- 1. 基材必须清洁：脱模剂、油污是脱层的头号杀手，包胶前基材表面处理不能省。
- 2. 硬胶余温：双色注塑时硬胶带着余温进第二射，温度匹配好了，粘接强度上一个台阶。
- 3. 包胶厚度：一般 1.5-3mm，太薄粘不牢，太厚容易缩水变形。
4. 验证方法：剥离测试是标准动作——行业里公开的案例，比如电动工具手柄包胶，剥离强度做到 35N/cm 以上、-40℃~80℃ 冷热循环不开胶，才算过线。
包胶选错体系，脱层返工是必然结果——接枝型 TPE 包 PA 是“化学键”级别的结合，普通 SEBS 包 PA 是“表面贴皮”，一撕就开。
包胶验证三步：初粘测试（脱模后手动撕）→ 剥离强度测试（标准样条拉）→ 冷热循环（-40℃~80℃ 循环后看分层）。三步都过，包胶才算稳。
行业公开案例：电动工具手柄包胶，剥离强度做到 35N/cm 以上、冷热循环不开胶，就是按这三步验证出来的。
第三步耐温、第四步介质：一票否决项
耐温和介质是“一票否决”项，别指望调机救：
| 工况 | 最低要求 | 备注 |
|---|
| 常温室内 | SEBS 基即可 | ≤120℃ |
| 高温长期 120℃+ | TPV/TPEE | 密封件看 CS |
| 150℃ 长期 | TPEE/TPSIV | 工程级 |
| 耐油 | TPU/TPV | 先定耐油等级 |
| 耐水解 | TPEE 慎用/专用 | 长期水浸要实测 |
| 食品接触 | 食品级 SEBS | 带 GB/FDA 认证 |
| 阻燃 | UL94 V0/无卤 | 出口必查 |
温度超一档，寿命短一截；介质没对上，泡三天就废——这两项没有“差不多”，只有“过”和“不过”。
耐温怎么测才算数？热老化测试（如 1000h/70℃）和低温测试（如 -40℃ 弯折）都要做，别只看瞬时耐温。瞬时 150℃ 不化，和 1000 小时 150℃ 不掉性能，是两个概念。
行业公开的做法：TPE 材料商普遍提供老化曲线和压缩永久变形数据（70℃×22h 典型值），采购时要的就是这份数据，不是口头承诺。
介质怎么测？把实际接触的介质、温度、时长告诉供应商，让配方对上去。
油分矿物油、液压油、机油，各不一样；水分离子水、热水、消毒液。“耐油”两个字不够——耐什么油、多少度、多久，三个参数缺一不可。
介质测试清单可以做成一张表：介质名称、浓度、温度、浸泡时长、允许变化（体积/硬度/重量）。
测完留样，数据说话——口头“耐油”不算数，测试报告才算数。TPE 材料的介质数据，正规供应商都提供第三方或自有实验室报告。
第五步成本：算总账才算数
成本不是单价，是良率之后的单件成本：
单件成本 =（料价 + 加工费 + 报废分摊）÷ 良品数
便宜的料，贵在返工上：单价省三毛，良率掉十个点，账是亏的。反之，贵一档的体系如果让良率从 90% 到 98%，总账反而省。
算一笔实账（示例数据）：
| 方案 | 料价（元/kg） | 良率 | 每万件报废数 | 单件综合成本 |
|---|
| A 便宜料 | 18 | 88% | 1200 | 高 |
| B 贵一档 | 22 | 97% | 300 | 反而低 |
料价差四块钱，良率差九个点，总账差出三成——这就是为什么老采购都算单件成本，不算单价。
加工窗口也是成本的隐藏项：一个需要 200℃ 加工、另一个 170℃ 就能成型，能耗差一截；一个料易粘模、一个脱模顺畅，周期差几秒。
选型时把注塑参数窗口一并要来，成本账才算完整。
三个真实件的选型走一遍，五步法就活了：
工具手柄：要包 PP 基材、耐汗耐油、-20℃ 不断裂——步骤一硬度选 60A，步骤二包胶选 SEBS 基（极性相容），步骤三耐温 -20℃~60℃ 通过，步骤四介质是汗液和轻油，
步骤五按良率算总账。
工业密封圈：要耐液压油、长期受压——步骤一硬度 70A，步骤二不包胶，步骤三耐温 100℃ 长期，步骤四耐矿物油，体系直接锁定 TPV，
SEBS 基在耐油和压缩永久变形两项上就被否了。
充电桩电缆护套：要耐弯折、阻燃、耐候——步骤一硬度 85A 左右，步骤二不包胶，步骤三耐温 -40℃~70℃，步骤四户外耐候加阻燃，锁专用 SEBS 基牌号，
普通 SEBS 过不了弯折寿命。
三个件走完，同一个五步法，三条完全不同的路。
小批验证的流程，五步法之外的最后一道工序：
步骤一 索样：让供应商按五步表推荐 1-2 个牌号，同时要物性表和注塑参数建议。
步骤一 索样：让供应商按五步表推荐 1-2 个牌号，同时要物性表和注塑参数建议。
第二步 试模：用生产模具打小批，记录熔融温度、模温、成型周期、收缩率实际值。
第三步 测性能：硬度、拉伸、撕裂、压缩永久变形、耐温、耐介质，按工况清单逐项对。
第四步 老化验证：热老化 1000h、低温冲击、UV 老化，把“一年后还行不行”提前问完。
第五步 三批放行：连续三批批次一致，才允许批量供货。
这五步看着繁琐，其实每步都有现成的方法和标准——真正难的是坚持做完。跳一步，量产就多一分返工风险；走完全程的，后面基本是顺的。
五家报价怎么比？先筛三家材料方向对的，再按良率后的单件成本比，最后用同批次留样对数据。
科隆客户案例：耐磨不合格，定制牌号治本
武汉一家改性料应用厂做耐磨件，表面磨花快，客户投诉不断。科隆排查后发现：通用牌号的耐磨指标只到边缘值，工况里的砂粒环境比标准测试苛刻得多。
科隆配合定制耐油/耐温专用牌号，把耐磨等级提到工况实际需要的档位，小批验证后返工率降了一半。选型不是选“够用的”，是选“工况对得上的”——通用牌号解决不了的，专用牌号才是答案。
常见坑：选型漏项，量产找补
| 坑 | 后果 | 解法 |
|---|
| 只报硬度就下单 | 到手手感不对 | 先填五步表 |
| 漏写介质 | 泡油开裂 | 介质栏必填 |
| 不看加工窗口 | 粘模/缩水 | 要注塑参数 |
| 样品和批次混谈 | 批量漂移 | 三批留样 |
| 只看单价 | 良率打脸 | 算单件成本 |
选型五步表的最终形态，就是一张采购单：硬度档位、基材、温度范围、介质清单、目标良率、单件成本上限——**六栏填满，
发给谁报价都不会跑偏**。
这也是我们建议每个采购手里都留一张“选型五步决策卡”的原因：不是要背流程，是要把判断权握在自己手里。
再补三个细节坑：色粉体系——TPE 配色要用专用色母，普通色粉易析出；干燥——部分牌号不烘料会有银纹；存储——开封后吸潮，性能漂移。
坑不在深处，在细节里。
三个高频疑问，一并答了：
问：同一牌号，两家供应商报价差两成，怎么选？
答：先对物性数据（测试条件一致才有可比性），再要批次稳定性记录，最后小批试模。差价如果来自配方降档，试模时通常就露馅。
问：样品性能很好，量产就漂移，为什么？
答：八成是批次管控问题。要求供应商提供三批留样数据，把样品批次和供货批次对起来，漂移就能被抓住。
问：选型表填了，供应商说这个工况用不着那么严，听谁的？
答：听数据的。让供应商把建议的依据（测试数据、案例）拿出来，拿不出来的，按保守档走。
选型这件事，宁严勿松——严了最多贵一点，松了是返工和事故。
选型的最后一个动作是文档化：把五步表、牌号选择、测试结果、批次记录整理成一页纸，放进项目档案。
好处有三个——换人接得住（新工程师照着档案就能续选）、换供应商有依据（数据在手，不被报价单牵着走）、复盘有抓手（出了问题，
先看档案，再谈责任）。
很多公司的选型知识散在个人脑子里，人一走，经验就断——把选型文档化，是把个人经验变成公司资产的办法，成本只是一张表。
硬度还有一个容易忽略的联动：硬度变了，其他物性跟着变。
同一个体系，硬度升高，通常拉伸强度升、断裂伸长率降、压缩永久变形变好、手感变硬。
所以“先定硬度”不是孤立的——它同时预告了这批料的其他性能走势。
用硬度表盘做索引，用物性表做确认，两条线对上了，选型才算闭环。
小结
把本文的判据对照你的TPE，多数问题在纸面上就能先排除一半，这比价格表更重要。
五步走完，体系、牌号、工艺、成本全部落位。剩下的交给验证：小批试产、三批留样、批量放行。
The selection table took five pages to fill out, yet mass production still experiences daily mold sticking. How to choose TPE? If one operating condition is missed, the entire batch has to be reworked.
How to choose TPE? Summarized in one sentence with a five-step method
Choosing TPE, it's complicated when you look at it closely, but it can be simplified into five steps: hardness → coating → temperature resistance → medium → cost.
The order cannot be confused. The first two steps determine the direction, the next two steps determine life or death, and the final step decides whether to stay or leave:
| Step | Why ask | What have you decided? |
|---|
| Step One Hardness | How soft and bouncy should this piece be? | Hardness range, system family |
| Step 2: Encapsulation | Do you want to wrap it in other materials? | System (SEBS/TPU/Grafted TPE) |
| Step Three: Temperature Resistance | What is the highest/lowest temperature? | Temperature rating, system upper limit |
| Step 4 Medium | Does it come into contact with oil/water/chemicals/food? | Formulation direction, dedicated grade |
| Step Five: Cost | What is the unit cost after yield? | Cost-performance trade-off |
Technical Golden Saying: Hardness determines the direction, rubber coating determines the system, temperature determines the grade, medium determines the formulation, and cost determines life or death — five steps, not a single one can be skipped.
Why can't the order be messed up? Because the result of the previous step is the input for the next step.
You need to determine the hardness first before you can screen the system; once the system is determined, you can talk about temperature and medium resistance; only after passing temperature and medium resistance does the cost make sense—going in reverse (asking about the price first),
It's the most common pitfall in procurement inquiries: buying cheap materials, and then having to redo the first four steps all over again.
Step one: first determine the hardness? The feel is benchmarked against a physical reference point.
Hardness is the fundamental language of TPE. Shore A is the main scale, ranging from 0 to 100, with a tactile feel for every 10-degree increment:
| Shore A | Physical anchor | Common parts |
|---|
| 0-10 | Jelly, gummy candy | Gel pads, bionic skin |
| 20-30 | Rubber bands, mouse pad | Toys, watch strap lining |
| 40-50 | Phone case, tire tread | Sheath, handle |
| 60-70 | Toothbrush handle, shoe sole | Tool handle, seals |
| 70-80 | Tires, wiper blades | Soles, Casters |
| 80-95 | Solid tires, rolling pin | Casters, wear parts |
The same Shore A 70: SEBS is soft and sticky, TPU is elastic and tough, TPV is nearly rubber-like—the hardness dial is just the starting point; the system's characteristics are the essence of the feel. Setting hardness is not about setting a number, it's about deciding 'what kind of feel you want.'
Shore 00 This durometer must also be recognized separately: it measures ultra-soft materials. Gel pads, bionic skin, and shock-absorbing liners are between 00-30A. The Shore 00 scale is finer than the A scale, and the 0-100 range of the 00 scale feels like everything from 'tofu' to 'rubber'.
For a 'jelly feel', check out Shore 00; for a 'gummy feel', Shore 00 mid-to-high range or A single digits.
There is a practical technique for determining hardness: compare with a real sample.
Bring a sample with a satisfying feel (even if it’s not TPE), so the supplier can directly understand the hardness, the system, and the formula—it’s more intuitive than looking at ten numbers.
With a press of the hardness tester, half of the truth is revealed; with a squeeze of the sample, the whole feel is understood.
How can hardness be measured accurately?
Three details: Temperature — TPE hardness varies significantly with temperature; it can differ by 5-10 degrees between 25°C and 40°C, so testing should be done at the standard temperature; Thickness — if the sample is too thin, the reading will be harder; the standard requires a certain thickness.
Instruments—hardness readings from different manufacturers can differ by 5 degrees, so comparisons within the same system should use the same device.
**Press the hardness tester, and half the truth appears; if the temperature is wrong, the reading deceives.
The choice of durometer also has its nuances: Shore A is used for regular soft materials, Shore 00 for ultra-soft materials, and Shore D for high hardness—using the wrong scale renders the readings meaningless.
When reading the value, attention must also be paid to the reading time: the standard is 1 second for type A or 15 seconds for type D. If pressed for too long, the reading will drift. Measure three points and take the average, record the temperature, and then this is a set of usable hardness data.
The five-step method ends here: hardness determines the feel, rubber coating determines the system, temperature-resistant medium determines life and death, cost determines whether to keep or discard, and validation determines success or failure.
Every step has numbers to rely on, and every stage has samples to check — this is the significance of turning selection from experience into process.
Step two is to decide on the encapsulation? The substrate determines the system.
To coat with rubber, first ask about the substrate:
| Substrate | Recommendation system | Reason |
|---|
| PP | SEBS based (Wang) | Good compatibility, strong adhesion |
| ABS/PC | TPU, modified SEBS | Polarity matching |
| PA/Metal | Grafted TPE, TPV | Chemical bond grafting |
| PE | Difficult to contain, requires special handling | Low surface energy |
The biggest concern for coated parts is delamination. If the coating delaminates, first check the substrate cleanliness, then check the temperature compatibility—if the material is chosen correctly but the process can't handle it, it's all in vain.
The four key points of coating technology, explained in one go:
- 1. The substrate must be clean: mold release agents and oil are the number one killers of delamination. Surface treatment of the substrate before coating cannot be skipped.
- 2. Residual heat of the hard rubber: During two-color injection molding, the hard rubber carries residual heat into the second shot. If the temperature is well matched, the bonding strength improves to the next level.
- 3. Coating thickness: generally 1.5-3mm; too thin and it won't stick well, too thick and it is prone to shrinkage and deformation.
4. Verification method: The peel test is a standard procedure—the publicly known cases in the industry, such as the coating on electric tool handles, are considered passing only if the peel strength reaches above 35 N/cm and there is no delamination during thermal cycling from -40℃ to 80℃.
Choosing the wrong encapsulation system inevitably leads to delamination and rework—grafted TPE encapsulating PA forms a 'chemical bond' level connection, whereas ordinary SEBS encapsulating PA is just 'surface adhesion' and peels off easily.
Three steps for encapsulation verification: initial adhesion test (manually peel after demolding) → peel strength test (pull standard specimen) → thermal cycling (-40℃~80℃, check for delamination after cycling). Only if all three steps pass is the encapsulation considered stable.
Industry Public Case: For electric tool handle overmolding, achieving a peel strength of over 35N/cm and no delamination under hot and cold cycles was verified by following these three steps.
Step three: temperature resistance, step four: medium – veto items
Temperature resistance and medium compatibility are 'veto items,' don't expect adjustments to fix them.
| Operating condition | Minimum requirements | Remarks |
|---|
| room temperature | SEBS base is fine | ≤120°C |
| High temperature for a long time 120℃ | TPV/TPEE | Check the seals CS |
| 150℃ long-term | TPEE/TPSIV | Engineering grade |
| Oil-resistant | TPU/TPV | First determine the oil resistance grade |
| Hydrolysis-resistant | TPEE Use with Caution / Special Use | Long-term water immersion needs to be measured in practice |
| Food contact | Food-grade SEBS | With GB/FDA certification |
| Flame retardant | UL94 V0 / Halogen-free | Exports must be inspected |
If the temperature is one level higher, the lifespan is shortened; if the medium is not correct, it becomes useless after three days—these two things have no 'almost right,' only 'pass' or 'fail'.
How should temperature resistance be measured to be valid? Both heat aging tests (such as 1000h/70℃) and low-temperature tests (such as -40℃ bending) need to be conducted; don't just look at instantaneous temperature resistance. Not melting at 150℃ instantaneously and not losing performance at 150℃ for 1000 hours are two different concepts.
Common industry practice: TPE material suppliers generally provide aging curves and compression set data (typical value at 70°C × 22h). What you need when purchasing is this data, not a verbal promise.
How to measure the medium? Tell the supplier the actual medium in contact, temperature, and duration, so the formula can match.
Oil includes mineral oil, hydraulic oil, engine oil, all of which are different; water includes ionized water, hot water, disinfectant. The two words 'oil-resistant' are not enough—you need to specify which oil, at what temperature, and for how long; all three parameters are indispensable.
The medium test checklist can be made into a table: medium name, concentration, temperature, soaking duration, allowable changes (volume/hardness/weight).
After sampling and testing, the data speaks for itself—oral claims of 'oil resistance' don't count, only test reports matter. For the dielectric data of TPE materials, reputable suppliers provide reports from third-party or in-house laboratories.
Step Five Cost: Only by Calculating the Total Account Does It Count
The cost is not the unit price, but the cost per piece after yield rate:
Unit cost = (Material price + Processing fee + Scrap allocation) ÷ Number of good products
Cheap materials are costly because of rework: saving three cents per unit but dropping the yield by ten percentage points results in a loss. Conversely, a more expensive system that increases yield from 90% to 98% actually saves money in the overall account.
Calculate a real account (example data):
| Plan | Material Price (CNY/kg) | Yield | Number of scrap per ten thousand units | Unit Total Cost |
|---|
| A cheap material | Eighteen | 88% | One Thousand Two Hundred | Tall |
| B slightly higher tier | Twenty Two | 97% | Three Hundred | Rather low |
The material price differs by four yuan, the yield rate differs by nine points, and the overall cost differs by thirty percent — this is why experienced buyers calculate unit cost per piece, not unit price.
The processing window is also a hidden cost: one requires processing at 200°C, while another can be formed at 170°C, resulting in a significant difference in energy consumption; one material easily sticks to the mold, while another releases smoothly, leading to a difference of a few seconds in the cycle time.
When selecting the model, make sure to also get the injection molding parameter window; only then will the cost account be complete.
Go through the selection of three real items, and the five-step method comes alive:
Tool handle: The PP substrate needs to be coated, resistant to sweat and oil, and not crack at -20℃ — Step 1: choose a hardness of 60A, Step 2: use SEBS-based coating (polar compatible), Step 3: withstand temperatures from -20℃ to 60℃, Step 4: media are sweat and light oil.
Step five calculate the general ledger based on yield.
Industrial Seals: Must resist hydraulic oil and long-term pressure—Step 1: hardness 70A, Step 2: no overmolding, Step 3: long-term temperature resistance 100°C, Step 4: resistant to mineral oil, system directly locking TPV.
SEBS was rejected on both oil resistance and permanent compression deformation.
Charging pile cable sheath: must be bend-resistant, flame-retardant, and weather-resistant—Step one hardness around 85A, step two no rubber coating, step three temperature resistant -40℃~70℃, step four outdoor weather resistance plus flame retardancy, locking with dedicated SEBS base grade,
Ordinary SEBS cannot pass the bending fatigue life test.
Three pieces go through, the same five-step method, three completely different paths.
The process of small batch verification, the final step beyond the five-step method:
Step One Sample Request: Ask the supplier to recommend 1-2 grades according to the five-step table, and also provide the physical property table and injection molding parameter recommendations.
Step One Sample Request: Ask the supplier to recommend 1-2 grades according to the five-step table, and also provide the physical property table and injection molding parameter recommendations.
Step 2 Mold Trial: Use the production mold to produce a small batch, recording the actual values of melt temperature, mold temperature, molding cycle, and shrinkage rate.
Step 3: Test performance: hardness, tensile, tear, compression set, temperature resistance, medium resistance, check each item according to the working condition list.
Step 4 Aging Verification: Thermal aging 1000h, low-temperature impact, UV aging, ask in advance whether it will still be okay after one year.
Step 5: Release in three batches: Only when three consecutive batches are consistent is bulk supply allowed.
These five steps may seem complicated, but each step actually has ready-made methods and standards—the real difficulty is sticking with them until the end. Skip a step, and there's an extra risk of rework in mass production; if you go through the entire process, things generally go smoothly afterward.
How to compare quotes from five companies? First, narrow down to three companies with the correct material direction, then compare the unit cost after yield, and finally use samples from the same batch to compare the data.
Cologne Customer Case: Wear Resistance Fails, Custom Grades Provide a Fundamental Solution
A Wuhan factory applying modified materials to make wear-resistant parts experienced fast surface wear, leading to continuous customer complaints. After an investigation by Kolon, it was found that the wear resistance index of the general-grade material only reached the borderline value, and the sand particle environment in the working conditions was much harsher than the standard test.
Cologne collaborated to customize special grades resistant to oil and temperature, elevating the wear resistance level to the actual requirements of the working conditions. After small-batch validation, the rework rate dropped by half. Selection is not about choosing 'adequate,' but about choosing 'matching the working conditions'—general grades cannot solve the problem; only special grades are the answer.
Common pitfalls: missing items in selection, making up during mass production
| pit | Consequence | Solution |
|---|
| Place the order by only reporting the hardness | The feel in hand is not right | Fill in the Five-Step Form first |
| Omitted medium | Oil bubble cracking | Media field is required |
| Do not view the processing window | Sticking to the mold / Shrinkage | Need injection molding parameters |
| Mixing discussion of samples and batches | Batch Drift | Three batches of retained samples |
| Only look at the unit price | Yield slaps in the face | Calculate unit cost |
The final form of the five-step selection table is a purchase order: hardness grade, base material, temperature range, list of media, target yield, maximum unit cost — **six columns filled in,
No matter who you send the quote to, it won't go off track.
This is also why we recommend that every purchaser keep a 'Five-Step Selection Decision Card' on hand: it's not about memorizing the process, it's about keeping the decision-making power in your own hands.
Three more detailed pitfalls: Pigment system — TPE coloring requires special masterbatch, ordinary pigments tend to separate; Drying — some grades will have silver streaks if not dried; Storage — absorbs moisture after opening, leading to performance drift.
The pit is not in the depth, but in the details.
Three frequently asked questions, answered together:
Question: For the same grade, if two suppliers' quotes differ by 20%, how should one choose?
Answer: First, check the physical property data (comparability only exists if the test conditions are consistent), then review the batch stability records, and finally conduct a small batch trial molding. If the price difference comes from downgrading the formula, it usually becomes apparent during the trial molding.
Question: The sample performs very well, but it drifts during mass production. Why?
Answer: Eighty percent of the time it is a batch control issue. Require the supplier to provide data from three retained samples, match the sample batches with the supply batches, and the drift can be caught.
Q: The selection form has been filled out, but the supplier says this working condition doesn't need to be so strict. Whose advice should I follow?
Answer: Listen to the data. Ask the supplier to provide the basis for their recommendations (test data, cases). If they can't provide it, follow the conservative plan.
When it comes to selecting models, it's better to be strict than lenient—being strict might just cost a bit more, being lenient leads to rework and accidents.
The final step in the selection process is documentation: organize the five-step table, grade selection, test results, and batch records into one page and put it into the project file.
There are three benefits — replacing personnel is manageable (a new engineer can continue selection according to the files), changing suppliers has a basis (with data in hand, not being led by quotations), and review has a handle (if a problem occurs,
First look at the files, then talk about responsibility.
Many companies' selection knowledge is scattered in individuals' minds. When someone leaves, the experience is lost — documenting the selection process is a way to turn personal experience into company assets, and the cost is just a table.
There is another easily overlooked linkage with hardness: when hardness changes, other physical properties change along with it.
In the same system, as hardness increases, the tensile strength usually increases, the elongation at break decreases, the permanent compression deformation improves, and the feel becomes harder.
So 'setting the hardness first' is not isolated—it simultaneously predicts the trends of other properties of this batch of material.
Use the hardness dial for indexing, use the physical properties table for verification, and only when the two lines match can the selection be considered complete.
Summary
Compare the criteria in this article with your TPE; most problems can be screened out on paper first, which is more important than the price list.
Complete in five steps: system, grade, process, and cost all fall into place. Leave the rest to verification: small batch trial production, three-batch record samples, and mass release.
